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FUR DYEING AND FUR DRESSING




                  PRINCIPLES AND PRACTICE
                            OF
                FUR DRESSING AND FUR DYEING


                            BY
                  WILLIAM E. AUSTIN, B.S.
          CONSULTING CHEMIST TO THE FUR INDUSTRY


                       _ILLUSTRATED_


                      [Illustration]


                         NEW YORK
                  D. VAN NOSTRAND COMPANY
                    EIGHT WARREN STREET
                           1922


                    Copyright, 1922, by
                  D. VAN NOSTRAND COMPANY


  All rights reserved, including that of translation into
       foreign languages, including the Scandinavian


          PRINTED IN THE UNITED STATES OF AMERICA




PREFACE


The great increase in the use of furs during the past few decades has
caused the fur dressing and dyeing industry to rise from relative
insignificance to considerable importance as a branch of applied
chemistry. The past eight years, moreover, have witnessed the virtual
transference of the leadership in the dressing and dyeing of furs from
Europe to America, and in the quality and variety of products, the
domestic industry is now in every way the equal of, and in many respects
superior to the foreign. The great bulk of American furs which formerly
were sent to Leipzig, Paris or London to be dressed and dyed, are now
being dressed and dyed in this country.

In spite of these facts, very little is generally known about the nature
and manner of the work constituting the dressing and dyeing of furs.
Even among members of other branches of the fur trade, there is very
little accurate information on the subject. Real knowledge concerning fur
dressing and dyeing is possessed only by those actually engaged in the
industry. The interest and efforts of scientists and technologists have
been enlisted to only a small extent in the technical development of the
industry. The reason for this may be attributed to two related causes:
first, the almost monastic seclusion in which fur dressers and dyers,
particularly the latter, conducted their operations, and even to-day the
heavy cloud of mystery is being dispelled but very slowly; and second,
as a consequence of the first, the lack of any reliable literature on
the subject. Of the few books which have been written on the industry
of fur dressing and fur dyeing (all of them either German or French),
most are hopelessly out of date, or contain no trustworthy data; or,
if they do have real merit, they cannot be obtained. Numerous articles
in the technical journals are of interest, but they contain very little
information of value.

This work is intended for a two-fold purpose: first, that it may serve as
a text-book for those who expect to make fur dressing and dyeing their
vocation. The fundamental principles upon which the industry is based
are discussed in the light of the most recent chemical and technical
developments, and the most important operations are treated fully and
systematically, and are illustrated with practical examples.

Secondly, as a practical handbook for the worker in the fur dressing and
dyeing plant. The latest factory processes and methods are described, and
numerous working formulas given. The formulas are all such as have been
successfully used on a large scale, and give satisfactory results when
applied under the proper conditions.

In addition, it is believed that the book will prove of interest to
chemists and other students of industrial chemistry, since it will be an
introduction into a field of applied chemistry, about which very little
is known to those outside of the industry.

Thanks are due to Dr. L. A. Hausman, of Cornell University, for material
used in Chapter II; to Dr. E. Lesser of the American Dyewood Company,
for information and assistance on the subject of Vegetable Dyes; to the
Gaskill Chemical Corp., American Aniline Products, Inc., the Cassella
Company, and the Franklin Import & Export Co., for information about
their products in connection with the chapter on Oxidation Colors; to F.
Blattner, Fletcher Works, Inc., S. M. Jacoby Co., Proctor & Schwartz,
Inc., Reliable Machine Works, Seneca Machine & Tool Co., Inc., and the
Turner Tanning Machinery Co., for the use of the cuts of the various
machines.

                                                      WILLIAM E. AUSTIN.

NEW YORK, May, 1922.




TABLE OF CONTENTS


  CHAPTER                                                         PAGE

  PREFACE

     I. FURS AND THEIR CHARACTERISTICS                               1

          Introductory. Knowledge of furs essential. Definitions.
        Differences in furs of various animals. Effect of climate
        on furs. Effect of age and season on furs. Durability and
        relative weights of furs. Description of important furs.


    II. STRUCTURE OF FUR                                            21

          The skin. The hair. Under-hair and top-hair. Chemical
        composition of furs. Action of chemicals on the skin.
        Action of chemicals on the hair.


   III.  FUR DRESSING: INTRODUCTORY AND HISTORICAL                  29

          Objects of fur dressing. Origin of fur dressing. Use
        of fats. Use of salt and alum. Use of the tannins. Early
        organizations of the fur workers. Modern organizations
        of the fur dressing industry.


    IV.  FUR DRESSING: PRELIMINARY OPERATIONS                       36

          Flat skins and cased skins. Herbivorous and carnivorous
        fur animals. Beaming or scraping. Softening the skins.
        Cleaning; hydro-extracting. Fleshing.


     V. FUR DRESSING: TANNING METHODS                               45

          Nature of the tanning process. Chief tanning methods.
        Comparison of the tanning methods. Effect of dyeing
        operations on the dressing.


    VI. FUR DRESSING: DRYING AND FINISHING                          71

          Importance of the drying process. Methods of drying.
        A modern type of drying device. Oiling. Staking or
        stretching. Beating and combing. Drum-cleaning. Unhairing
        and shearing.


   VII. WATER IN FUR DRESSING AND DYEING                            85

          Importance of water in dressing and dyeing. Water
        suitable for dressing and dyeing. Soft water and hard
        water. Effects of hardness in water.


  VIII. FUR DYEING: INTRODUCTORY AND HISTORICAL                     90

          Purposes of fur dyeing. Improvement of furs faulty in
        color. Production of a uniform shade on furs. Dyeing furs
        to obtain novel effects. Imitation of valuable furs on
        cheaper skins. Difficulties due to the hair. Difficulties
        due to the leather.


    IX. FUR DYEING: GENERAL METHODS                                 98

          Two methods of dyeing furs. Development of the dyeing
        methods. The brush process. The dip process. Blending.
        Drying and finishing the dyed furs.


     X. FUR DYEING: KILLING THE FURS                               106

          Nature of the killing process. Old killing formulas.
        Modern killing agents. Procedure of killing. Killing with
        soda. Killing with lime. Killing with caustic soda.


    XI. FUR DYEING: MORDANTS                                       114

          Nature of mordanting. Purposes of mordanting. Theory
        of mordants. Procedure of mordanting. Aluminum mordants.
        Iron mordants. Copper mordants. Chromium mordants. Tin
        mordants. Alkaline mordants.


   XII. FUR DYEING: MINERAL COLORS USED ON FURS                    125

          Mineral chemicals as fur dyes. Lead dyes. Potassium
        permanganate as a dye. Other mineral dyes.


  XIII. FUR DYEING: VEGETABLE DYES                                 128

          Wood dyes. Old dye formulas. The vegetable dye
        materials. The tannin substances. Logwood. Fustic.
        Brazilwood. Other vegetable dyes. Characteristics of the
        wood dyes. Application of the vegetable dyes. Application
        by the brush process. Application by the dip process.
        Production of shades other than black.


   XIV. FUR DYEING: ANILINE BLACK                                  144

          Dyeing of seal. Nature and history of Aniline Black.
        Chemistry of the Aniline Black process. Three stages
        in the formation of Aniline Black. Methods of applying
        Aniline Black. One-bath Aniline Black. Oxidation Aniline
        Black. Diphenyl Black. Aniline Black by Green’s process.
        Aniline Black by the dip method.


    XV. FUR DYEING: OXIDATION COLORS                               155

          The original patents. The first Oxidation fur dyes.
        Early difficulties. Solution of the difficulties.
        Progress with the Oxidation dyes. Para-phenylene-diamine:
        a typical Oxidation color. Range of shades obtainable.
        Mordants. Procedure in dyeing. Typical formulas.
        Combination of Oxidation colors with other dyes.


   XVI. FUR DYEING: COAL TAR DYES                                  171

          Use of coal tar dyes. Basic colors. Acid colors; dyeing
        at higher temperatures. Chrome colors. Vat dyes.


  XVII. BLEACHING OF FURS                                          179

          Purpose of bleaching. Steps in the bleaching process.
        Methods of bleaching. Bleaching materials with reducing
        action. Bleaching materials with oxidizing action.
        Blueing.


  BIBLIOGRAPHY                                                     185




FUR DRESSING AND FUR DYEING




CHAPTER I

FURS AND THEIR CHARACTERISTICS


Furs have in general two uses: as the goods which constitute the basis of
the furrier’s art, and as the source of material for the hat manufacturer.
In the latter case, only the hair part of the fur is utilized in the hat
trade for the production of felt, the skin being either made into leather,
or used as the raw material for making high-grade glue and gelatine. It
is the furrier, therefore, who uses the great bulk of furs, and requires
them to be dressed and dyed.

In discussing the dressing and the dyeing of furs, there are, broadly
speaking, two fundamental subjects to be considered: first, the raw
materials employed, which are, of course, the skins or pelts as they
come from the trapper. (Other substances used in fur dressing and dyeing
are accessories, and will be studied in connection with the processes.)
Second, all those operations, physical and chemical, manual and
mechanical, to which the raw skins have to be subjected in order to obtain
the finished fur, ready for use by the furrier.

Next to the inherent qualities of the fur skin, the future value of a
fur in a manufactured garment depends largely on the dressing and dyeing
it receives. It is in these operations that the beauty of the fur can
be brought out to its fullest degree, and if possible, enhanced, or the
attractive features can be marred or destroyed, and the fur rendered
quite worthless. Therefore, it is quite essential for the fur dresser
and the fur dyer in addition to the technical knowledge and experience
which are the fundamental requisites of the industry, also to have more
than a superficial familiarity with the various kinds of furs. In fact,
an accurate knowledge of the nature and chief characteristics of furs
in general, and of the individual classes, in particular, is almost
indispensable to obtain the best results. The habits and habitats of
the various fur-bearing animals are factors which largely determine the
constitution of the fur, and the nature of the skin. There are as many
different kinds of fur hair, with as many different kinds of skin bearing
the hair, as there are classes of furs. The methods of dressing, and
often, if the furs are to be dyed, the manner of dyeing, are determined
by the nature of these component parts of furs. Various chemicals affect
furs in widely different ways. The divergence with regard to the physical
and chemical properties of the classes of furs is such as to make almost
imperative a detailed knowledge of the typical members of the many groups
of commercial furs.

To be sure, there are many engaged in the dressing and dyeing of furs,
who never made a formal study of this phase of the industry, but acquired
their knowledge empirically, and are apparently quite successful. It
must not be denied, that practise and experience, as in every field of
enterprise, are essential to obtaining the best results. But the time and
cost of acquiring this precious experience can be considerably reduced by
systematically studying the important characteristics and properties of
furs. These will be treated briefly, but in sufficient detail to form a
basis for discussing the operations of dressing and dyeing.

Fur-bearing animals are mammals whose skins are used in the manufacture of
fur garments and other fur wearing apparel. The skin, when it is removed
from the animal is called a pelt, or sometimes, in the case of large
animals, a hide. The pelt, after having been dressed and dyed, is called
a fur, the skin part being referred to as the leather, and the hair as the
pelage. However, this terminology is not strictly adhered to in practise,
and the various terms are often employed interchangeably.

The various fur-bearing animals differ considerably in the characteristics
of the furs they yield. With few exceptions, notably beaver and Alaska red
fox, the depth of shade increases as the habitat of the animal species is
nearer the equatorial regions. There seems to be a direct relationship
between the intensity of color of the pelt, and the distance from, or
proximity to the polar, or the torrid regions. Thus, white mammals, such
as polar bear, ermine, white or Siberian hare, are found only in the
northern lands. An exception is the sheep, which, due to its domestic
nature, can be found in almost all parts of the civilized world. Tropical
animals on transportation to colder climates, have been known to become
lighter-haired when adapted to their new environment. The skins of animals
living in dense woods or forests, are generally of a deeper color than
in animals living in more open territory. As a general rule, fur-bearing
animals have darker hair on the back than on the sides and belly. The
badger, hamster, ratel and panda are exceptions having the darker hair on
the belly and sides, and the lighter hair on the back. With regard to the
intensity of color, the skunk has the blackest fur, although some domestic
cats are also quite black. Other animals whose fur is nearly black, are
the black bear, and the black fox, which is a variety of the silver fox,
but the color is often of a brownish shade. The colors which predominate
among animals of the fur-bearing variety, are white, black, brown, and
grey. Less common are yellow shades, and those known as blue.

The quality of the fur on all mammals improves with cold, and animals
living at greater altitudes, with correspondingly lower temperatures,
have thicker and finer hair than those living nearer sea-level. A cold
winter generally produces fur of high quality and fine color, a mild
winter may cause the hair to be inferior. In all climates, animals found
in dense woods, have fur which is deeper, silkier, thicker, and glossier
than that of animals living in the open. Animals inhabiting inland lakes
and rivers, have finer and softer hair than those living near the coast
or land exposed to sea winds. In general, the hair of animals of the cold
regions is short, fine, soft, and downy, while the hair of animals of
warmer lands, is longer, stiffer, and harder.

Both the quality and color of the fur vary with the age of the animal.
The young usually have a thicker coat of fur than adults, but the hair is
too soft, and the skin generally too tender to be fit for use. In certain
cases, particularly the baby lambs, very young skins are especially
prized, and eagerly sought, but extraordinary care has to be exercised in
working with them. Fur is at its best when the animal is between one and
two years old. After this age, the fur becomes coarse and scraggy. The
animal attains its fullest growth of hair usually in the height of winter,
and the fur is best between then and very early spring. Before mid-winter
the hair is short and thin, and in the spring it begins to shed, and will
continue to fall out even in the dressed fur. The color of the hair also
becomes lighter with age, and the new growth which generally comes in the
fall is darker than the old coat.

Different members of the same species, will, other factors such as age
and season being equal, vary as to color and quality. There may even be
several different color phases of the same species of animal, such as the
cross fox and the silver fox, both of which are of the same genus as the
red fox; black muskrats are of the same class as the brown variety, etc.
The individual pelt likewise presents many variations in color and nature
of the hair. In some parts, the hair is thicker and softer than others,
and the color varies in intensity and shade throughout the different
sections of the skin.

Furs do not have differences confined to the hair part only; the leather
also presents considerable variation among the different fur-bearing
animals, especially in regard to the weight and thickness. The durability
of furs, relatively considered under similar conditions of wear, also
varies widely. In the following table the relative durability of dressed
furs, and in certain instances also dyed furs, otter being taken as
standard, is given, as well as the weight in ounces per square foot of
skin of these furs.

           _Name of Fur_             _Durability_    _Wt. in oz.
                                     _Otter = 100_   per sq. ft._
  Astrachan                                10           3
  Bear, brown or black                     94           7
  Beaver, natural                          90           4
  Beaver, plucked                          85           3-7/8
  Chinchilla                               15           1-1/2
  Civet cat                                40           2-3/4
  Coney                                    20           3
  Ermine                                   25           1-1/4
  Fox, natural                             40           3
  Fox, dyed black                          25           3
  Genet                                    35           2-3/4
  Goat                                     15           4-1/8
  Hare                                     05           2-1/4
  Krimmer                                  60           3
  Kolinsky                                 25           3
  Leopard                                  75           4
  Lynx                                     25           2-3/4
  Marten, Baum natural                     65           2-3/4
  Marten, Baum blended                     45           2-3/4
  Marten, Stone natural                    45           2-7/8
  Marten, Stone dyed                       35           2-7/8
  Mink, natural                            70           3-1/4
  Mink, dyed                               35           3-1/4
  Mink, Jap                                20           3
  Mole                                     07           1-3/4
  Muskrat                                  45           3-1/4
  Nutria, plucked                          25           3-1/4
  Opossum, natural                         37           3
  Opossum, dyed                            20           3
  Opossum, Australian                      40           3-1/2
  Otter, land                             100           4-1/2
  Otter, sea                              100           4-1/2
  Persian lamb                             65           3-1/4
  Pony, Russian                            35           3-1/2
  Rabbit                                   05           2-1/4
  Raccoon, natural                         65           2-1/4
  Raccoon, dyed                            50           2-1/2
  Sable                                    60           2-1/2
  Sable, blended                           45           2-1/2
  Seal, fur                                80           3-1/2
  Seal, fur dyed                           70           3-1/8
  Skunk, tipped                            50           2-7/8
  Squirrel, grey                           20–25        1-3/4
  Wolf, natural                            50           6-1/2
  Wolverine                               100           7

In estimating the value of a fur, many factors have to be considered.
There is no one standard by which the skins are judged, each kind of
fur having its own criterion. However, the general points by which raw
furs are graded are, color, size, origin, quality and quantity of hair,
condition of leather, date or season of trapping, methods of handling,
etc. Beaver, for example, is graded as large, medium, small and cubs.
Red foxes, first, into Alaska, Labrador, and Nova Scotia, and then these
divisions are classed as large, medium and small. Skunks are graded
according to the amount of white on the skin, the less white, the more
valuable the fur.

The qualities which make a fur desired depend first of all on the nature
of the fur itself. Pretty color, luster, thickness, softness, length,
uniformity and regular fall of the hair are the chief points to be
considered. While the leather part of the fur is of secondary importance
in the evaluation of a fur, it must possess strength, lightness of weight,
and when properly dressed, should be supple and have a certain firmness or
‘feel.’ The abundance or scarcity of a fur-bearing animal also determines
the value of the fur. Furs which are always comparatively rare, such as
silver fox, Russian sable, chinchilla, etc., are always highly prized.
In this connection, circumstances which tend to decrease the number of
available pelts of any particular animal, such as pestilences, gradual
extermination due to excessive trapping, prevention of trapping, by
protective laws, also affect the value of a fur. A third factor which has
an influence on the value of furs, is the prevailing style or fashion.
Many kinds of furs which are both beautiful and rare, such as Russian
sable or chinchilla, are practically unaffected by the whims of fashion.
But a fur of ordinary value may at times become so popular, that the
demand for it will cause its price to be greatly increased. Similarly, a
fur which has enjoyed a considerable vogue, may pass out of demand for a
time and consequently depreciate in value.

A detailed description of the various furs used in commerce is not within
the scope of this work, because such an account rightly belongs in a book
on zoölogy. However, it is desirable that the reader who is interested
in the dressing and dyeing of furs should have at least a passing
acquaintance with the chief furs used in commerce, together with such of
their individual characteristics as are of importance. The figures given
are for the average dressed skin.[1]

  [1] Descriptions after W. S. Parker, Deputy Chairman, Fur Section of
      London Chamber of Commerce, in Encyclopedia Britannica, 11th Ed.

~Astrachan~, see Lambs.

~Badger.~--2 × 1 ft. This is one of the few animals whose fur is darker
on the belly than on the back. The American sorts have coarse, thick
under-hair of a pale fawn or stone color, with a growth of longer black
and white hairs 3–4 inches long. The Japanese varieties are usually dyed
for imitation skunk. The American kind is also dyed occasionally but is
mostly used natural. Badger hair is very extensively used for ‘pointing.’

~Bear, Black.~--6 × 3 ft. Has fine, dark brown under-hair, with bright,
flowing black top-hair 4 inches long. The fur of cubs is nearly as long,
although the skins are much smaller, and the hair is finer, softer, and
lighter-pelted. The best skins are from Canada.

~Bear, Brown.~--6 × 3 ft. Similar to the Black Bear, but more limited in
number. The color ranges from a light yellow to a rich dark brown. The
best and most valuable sorts come from the Hudson Bay territory, inferior
skins coming from Europe and Asia.

~Bear, White.~--10 × 5 ft. This is the largest of the bears. The hair is
short and close except on the flanks, while the color ranges from white
to yellow. The best skins come from Greenland, the whitest being the most
valuable.

~Beaver.~--3 × 2 ft. This is the largest of the rodents, and is very
widely used; formerly to a great extent in the hat trade. The under-hair
is close and of a bluish-brown hue, and nearly an inch deep. The over-hair
is coarse, bright black or reddish-brown in color, and is usually plucked
out, as the under-hair is the attractive part of the fur. The darkest
skins are the most valuable. Formerly beaver was used to dye in imitation
of seal, but more suitable furs are now used.

~Broadtail~, see Lambs.

~Caracul~, see Lambs.

~Cat, Civet.~--9 × 4-1/2 inches, with short, thick and dark under-hair,
and silky, black top-hair with irregular white markings. It is similar
to the skunk, but is lighter, softer, less full, and has no disagreeable
odor.

~Cat, House.~--18 × 9 inches. Is mostly black and dark brown, the best
skins coming from Holland. The hair is weak, coming out with the friction
of wear. In the trade, the black variety is known as genet.

~Chinchilla.~--12 × 7 inches. This is one of the rarest and most beautiful
furs. It comes from Bolivia and Peru, where, due to the uncontrolled
trapping of the animal, it is becoming scarce, and this compelled the
governments to enact laws prohibiting the taking of chinchilla for a
certain period. The fur is of a delicate blue-grey, with black shadings,
the fur being 1–1-1/4 inches deep. Unfortunately, the skin is quite
perishable.

~Chinchilla, La Plata.~--9 × 4 inches. Incorrectly called “bastard
chinchilla” in the trade. It is a similar species to the Bolivian
chinchilla, but due to the lower altitude and warmer climate of its
habitat, is smaller, with shorter and less pretty hair, the color of the
under-hair being darker, and of the top-hair less pure. It is quite as
undurable as true chinchilla.

~Chinchillone.~--13 × 8 inches. Is also from South America. The fur is
longer, weaker, poorer and yellower than real chinchilla, but the skins
are often dyed in shades closely resembling the natural chinchilla.

~Ermine.~--12 × 2-1/2 inches. The under-hair is short and even, with the
top-hair slightly longer. The leather is light, close in texture, and
quite durable. In mid-winter the color is pure white, except the tip of
the tail, which is usually quite black. The best skins are from Siberia.

~Fisher.~--30 × 12 inches, with tail 12–18 inches long. It is the largest
of the marten family. The under-hair is deep, and of a dark shade, with
a fine dark, glossy and strong top-hair, 2 or more inches long. The best
skins are from Canada. The fur is something like a dark silky raccoon,
while the tail, which is very highly prized, is almost black.

~Fitch.~--12 × 3 inches. It is of the marten species, and its common name
is polecat. The under-hair is yellow and 1/3 of an inch deep. The top-hair
is black, 1-1/2–1-3/4 inches long, very fine and open in growth, and not
so close as the martens. The largest and best skins are from Denmark,
Holland and Germany. The Russian skins are smaller, silkier, and are
usually dyed as a substitute for sable.

~Fox, Blue.~--24 × 8 inches. The under-hair is thick and long, while the
top-hair is fine and not so plentiful as in other foxes. It is found in
Alaska, Hudson Bay Territory, Greenland and Archangel. Although called
blue, the color is really of a slaty or drab shade. The skins from
Archangel are more silky and of a smoky bluish color, and being scarce are
most valuable. The white foxes which are dyed a smoky blue are brilliant
and quite unlike the browner shades of the blue-fox.

~Fox, Cross.~--20 × 7 inches. The skins generally have a pale yellow or
orange tone, with some silver points, and a darkish cross marking on the
shoulders, on account of which the animal got its name. Some are very
similar to the pale red foxes of Northwest America. The darkest and best
skins are from Labrador and Hudson Bay, those from lower latitudes being
inferior.

~Fox, Grey.~--27 × 10 inches. Has a close dark drab under-hair, with
coarse regular, yellowish, grizzly-grey top-hair. The majority of the
skins come from Virginia and southwestern U. S. A. Those from the west
are larger and brighter-toned.

~Fox, Kit.~--20 × 6 inches. The under-hair is short and soft, as is also
the top-hair, which is a very pale grey mixed with some yellowish-white
hairs. It is the smallest of the foxes, and is found in Canada and
northern United States.

~Fox, Red.~--24 × 8 inches, although some kinds are larger. The under-hair
is long and soft, and the top-hair is plentiful and strong. The colors
range from pale yellow to a dark red, some being very brilliant. It
is widely found in northern America, China, Japan, and Australia. The
Kamchatka foxes are exceptionally fine and rich in quality. Farther north,
near the open sea, the fur is coarse. The skins have an extensive use,
both natural and dyed. They are dyed black in imitation of the black
fox, or these when pointed with badger or other white hair to imitate the
silver fox.

~Fox, Silver.~--30 × 10 inches. The under-hair is close and fine, and the
top-hair, which is black to silvery, is 3 inches long. The fur on the neck
usually runs almost black, and in some cases the black extends over half
the length of the skin. When all black, it is a natural black fox, and
is exceedingly rare and high-priced. The silver fox is very valuable, the
finest wild skins coming from Labrador. The tail is always tipped white.
The majority of the silver fox pelts that reach the market today are bred
on ranches in Canada and the United States.

~Fox, White.~--20 × 7 inches. It is usually small and inhabits the extreme
northern sections of Hudson Bay, Labrador, Greenland, and Siberia. The
Canadian are silky-haired and inclined to a creamy color, while the
Siberian are whiter and more woolly. The under-hair is generally of a
bluish-grey tone, but the top-hair in winter is usually full enough
to hide such a variation. Those skins which have under-hair that is
quite white are rare and much more expensive than the others. In summer
specimens of these species have slightly discolored coats, the shades
resembling those of the blue fox. The skins which are not perfectly white
are bleached, or if they cannot be bleached sufficiently white they are
dyed various shades of smoke color, blue-greys and also imitation blue
fox.

~Goat.~--The size varies greatly. The European, Arabian and East Indian
varieties are used mainly for leather and wool. Many from Russia are dyed
black for rugs. The hair is brittle, with poor under-hair, and is not
durable. The Chinese export many skins in grey, black and white, made into
rugs of two skins each. Frequently the skins are dyed black or brown in
imitation of bear.

~Hamster.~--8 × 3-1/2 inches. A destructive rodent found largely in Russia
and Germany. The fur is very flat and poor, of a yellowish-brown color,
with a little marking of black. On account of its lightness it is used
for linings; occasionally it is dyed.

~Hare.~--24 × 9 inches. The common hare of Europe is used mostly for the
hatters’ trade. The white hares of Russia, Siberia, and other northern
regions are the ones mainly used for furs. It is whitest in mid-winter,
and the fur on the flanks is longer than that on the back. The hair is
brittle and not durable, and the leather is quite as bad. Yet the skins
are used to dye imitations of more than a dozen different furs. The North
American hares are also dyed black and brown.

~Kangaroo.~--The sizes vary greatly, the larger kinds being generally
used for making leather. The sorts used for fur are, blue kangaroo, bush
kangaroo, wallaroo, rock wallaby, swamp wallaby, and short-tailed wallaby.
Many of the swamp wallabies are dyed imitation skunk, and look quite
attractive. The colors are generally yellowish or brown, some in the swamp
variety being dark brown. The skins are quite strong. The rock wallabies
are soft and woolly, and often have a bluish tone. They are used for rugs.

~Kolinsky.~--12 × 2-1/2 inches. It is of the marten family. The under-hair
is short and rather weak, but regular, as is also the top-hair. The color
is usually a uniform yellow. They are generally dyed in imitation of other
members of the marten family. It is very light in weight, and the best
skins are obtained from Siberia. The tails are used for artists’ “sable”
brushes.

~Lambs.~--Those of commercial interest are from South Russia, Persia,
and Afghanistan, and include Persian Lamb, Broadtail, Astrachan, Shiraz,
Bokhara, Caracul, and Krimmers.

The _Persians_ are 18 × 9 inches, and are the finest and best. When
properly dressed and dyed they should have regular, close, bright curls,
varying from small to very large and if of equal size, regularity,
tightness and brightness, their value is inestimable.

All the above lambs, except krimmer, are naturally a rusty black or brown,
and are in most cases dyed a jet black. Luster cannot be imparted where
naturally lacking.

_Broadtails_, 10 × 5 inches, are the young of the Persians, killed
before the wool has had time to develop beyond the flat wavy state. They
are naturally of exceedingly light weight, and when of an even pattern
possessing a lustrous sheen are costly. The pelt, however, is too delicate
to resist hard wear.

_Astrachan_, _Shiraz_, and _Bokhara_ lambs, 22 × 9 inches, are of
a coarser and looser curl. Caracul lambs are the very young of the
astrachan, and the finest skins are almost as effective as the broadtails,
although not so fine in texture.

_Krimmers_, 24 × 10 inches are grey lambs obtained from Crimea. They are
of a similar nature to the caraculs, but looser in curl, and ranging in
color from a very light to a dark grey, the best being pale bluish-greys.

_Slink lambs_ come from South America and China. The South American are
very small, and generally those are still-born. They have a particularly
thin pelt, with very close wool of minute curls. The Chinese sorts are
much larger.

~Leopard.~--3 × 6 feet long. There are several kinds, the chief being the
snow leopard or ounce, Chinese, Bengal, Persian, East Indian, and African.
The first variety inhabits the Himalayas, and has a deep, soft fur, quite
long as compared with the Bengal sort. The colors are pale orange and
white with dark markings. The Chinese are of a medium orange-brown color
and full in fur. The East Indian are less full and not so dark; the Bengal
are dark and medium in color with short, hard hair. The African are small,
with pale lemon-colored ground, and very closely marked with black spots.

~Lynx.~--45 × 20 inches. The under-hair is thinner than in the fox, but
the top-hair is fine, silky and flowing, 4 inches long, of a pale grey,
slightly mottled with fine streaks and dark spots. The fur on the flank
is longer, and white, with very pronounced markings of dark spots, and
this part of the skin is generally worked separately. Skins with a bluish
tone are more valuable than those with a sandy or reddish hue. The lynx
inhabits North America as far south as California. The best skins come
from Hudson Bay, and also Sweden. They are generally dyed black or brown,
similar to dyed fox.

~Marmot.~--18 × 12 inches. A rodent found largely in the south of
Germany. The fur is yellowish-brown, rather harsh and brittle, and without
under-hair. Also found in North America, China, and the best skins come
from Russia. It is dyed brown in imitation of mink or sable, the stripes
usually being put on in the completed garment.

~Marten, Baum.~--16 × 5 inches. Also called Pine Marten, and is found in
the woods and mountains of Russia, Norway, Germany and Switzerland. It
has a thick under-hair with strong top-hair, and ranges from a pale to a
dark bluish-brown. The best are from Norway, are very durable and of good
appearance, and a good substitute for the American sable.

~Marten, Japanese.~--16 × 5 inches. It is of a woolly nature with rather
coarse top-hair, and quite yellow in color. It is dyed, but it is not an
attractive fur, lacking a silky, bright and fresh appearance.

~Marten, Stone.~--Size and quality similar to the baum marten. The color
of the under-hair is stony white, and the top-hair is a very dark brown,
almost black. Skins of a pale bluish tone are used natural, while less
clear colored ones are dyed, usually in Russian sable shades. They are
found in Russia, Bosnia, Turkey, Greece, Germany, and France, the best
coming from Bosnia and France.

~Mink.~--16 × 5 inches. Is of the amphibious class, and is found
throughout North America, as well as in Russia, China and Japan. The
under-hair is short, close and even, as is also the top-hair, which is
very strong. The best skins are very dark, and come from Nova Scotia. In
the central states the color is a good brown, but in the northwest and
southwest, the fur is coarse and pale. It is very durable and an economic
substitute for sable. The Russian species is dark, but poor and flat in
quality, and the Chinese and Japanese sorts are so pale that they are
always dyed.

~Mole.~--3-1/2 × 2-1/2 inches. Is plentiful in the British Isles and
Europe, and is much in demand on account of its velvety fur of a pretty
bluish shade. Although the skins are comparatively cheap, the cost of
dressing is high on account of the considerable amount of labor involved.
The pelt is very light in weight, but does not resist well the friction
of wear.

~Monkey, Black.~--18 × 10 inches. The species usually found on the west
coast of Africa, is the one of interest to the fur trade. The hair is very
long, very black and bright, with no under-hair, and the white pelt is
very noticeable by contrast.

~Muskrat, Brown, Black, Russian.~--12 × 8 inches. A very prolific rodent
of the amphibious class, obtained in Canada and the United States. It has
a fairly thick and even brownish under-hair, and a rather strong, dark
top-hair of medium density. It is a durable and not too heavy fur. It
is used natural, but recently the plucked, sheared and dyed skins have
found a very extensive use as Hudson seal, an imitation of real seal. The
so-called black variety of muskrat is found in New Jersey and Delaware,
but only in comparatively small numbers. The Russian is also very small
and limited in numbers. It is of a pretty silvery-blue shade with even
under-hair, with very little silky top-hair, and silvery-white sides,
presenting altogether a marked effect.

~Nutria.~--20 × 12 inches. Is a rodent about half the size of the beaver,
and when plucked, has only about half the depth of fur, which is not so
close. It is often dyed a seal color, but its woolly nature renders it
less effective than the dyed muskrat. The skins are obtained from northern
South America.

~Opossum, American.~--18 × 10 inches. Is a marsupial, the only one of
its class found outside of Australia. The under-hair is of a very close
frizzy nature, and nearly white, with long bluish-grey top-hair mixed with
some black. It is found in central sections of the United States, and is
frequently dyed imitation skunk.

~Opossum, Australian.~--16 × 8 inches. Is of a totally different nature
from the American. Although it has fur-hair and top-hair, the latter is
sparse and fine, so that the fur coat may be considered one of close even
under-hair. The color varies according to the district of origin, from
blue-grey to yellow with reddish tones.

Those from near Sidney are a light clear blue, while those from Victoria
are a dark iron-grey, and stronger in the fur-hair. The most pleasing
shade of grey comes from Adelaide. The reddest are the cheapest. The
ring-tailed opossum, 7 × 4 inches, has a very short, close and dark grey
under-fur, some almost black, but the skins are not used extensively.
The Tasmanian opossum, grey and black, 20 × 10 inches, is of a similar
description, but larger, darker, and stronger in the under-hair.

~Otter, River.~--The size varies considerably, as does also the length of
the fur, according to the origin. It is found in greatest numbers in the
coldest northern regions, and with the best under-hair, the top-hair being
unimportant, as it is plucked out. Most of the best river otters come
from Canada and the United States, and average 36 × 18 inches. The skins
from Germany and China are smaller and shorter furred. The colors of the
under-hair vary from very dark brown to almost yellow. Both the fur and
the leather are extremely strong, and many skins are dyed imitation seal
after plucking.

~Otter, Sea.~--50 × 25 inches. Is one of the most beautiful of furs.
The under-hair is of a rich, dense, silky nature, with short and soft
top-hair, which is not plucked. The colors range from a pale grey-brown
to a rich black, and many skins have a sprinkling of white or silver-white
hairs. The blacker the under-hair, and the more regular the silver points,
the more valuable is the skin.

~Pony, Russian.~--This is a comparatively cheap, but very serviceable
fur, and possesses some very desirable qualities. It has a thin leather,
but is also scantily haired. Young pelts have a design on them somewhat
similar to broadtail lambs, or moire astrachans, but this design is lost
to a considerable degree by dyeing the furs. The hair, which is very
glossy, is generally dyed black, although the natural pelts are also worn
extensively.

~Rabbit.~--10 × 16 inches. The fur is thick and fine, but the pelt is very
weak. It is a native of central Europe, Asia, North and South America,
New Zealand and Australia. The color ranges from white to black. France,
Belgium and Australia are the greatest producers of rabbits suitable for
dyeing black, the so-called French seal, for which they are mostly used.
At the present time the dyeing of rabbits constitutes a considerable
percentage of the total fur-dyeing operations in this country. The most
varied shades are produced on rabbit, and it probably is the basis of
the greatest number of dyed imitations of better furs. In addition to the
French seal, or sealine, rabbit is dyed in imitation of beaver, mole, etc.

~Raccoon.~--20 × 12 inches. Varies considerably in size, quality and color
of the fur, according to the part of North America in which it is found.
The under-hair is 1–1-1/2 inches deep, pale brown, with long top-hair
of a dark and silvery-grey mixture of a grizzly type, the best having a
bluish tone, and the cheapest a yellowish or reddish-brown. The best skins
come from the northern part of the United States. The skins have a wide
use natural, but are also dyed dark blue, or imitation skunk, the latter
being a very effective and attractive substitute, and extensively used.
Sometimes the skins are plucked, and if the under-hair is good, the effect
is similar to a beaver.

~Sable, American and Canadian.~--17 × 5 inches. The skins are sold in the
trade as martens, but since many of the skins are of a very dark color,
and almost as silky as Russian sable, they have come to be known as sable.
The prevailing color is a medium brown, while many are quite yellow. These
pale skins have been dyed so well that they can cheaply substitute Russian
sable. The finest skins are from the Eskimo Bay and Hudson Bay districts,
the poorest from Alaska.

~Sable, Russian.~--15 × 5 inches. Belongs to a species of marten similar
to the European and American, but much more silky in the texture of the
fur. The under-hair is close, fine and very soft, the top-hair is regular,
fine and flowing, and silky, ranging from 1-1/2 to 2-1/2 inches in depth.
In color they vary from a pale stony or yellowish shade to a rich, almost
black, dark brown, with a bluish tone. The leather is exceedingly close
and fine in texture, very light in weight, and very durable. The Yakutsk,
Okhotsk, and Kamchatka sorts are good, the last being the largest and
fullest-furred, but of less color density than the others. The most
valuable, are the darkest from Yakutsk in Siberia, particularly those
having silvery hairs evenly distributed over the skin, but these furs are
very rare.

The Amur skins are paler, but often of a pretty, bluish tone, with many
interspersed silvery hairs. The fur is not so close or deep, but is very
effective nevertheless. The paler skins from all districts are now tipped,
the tips of the hair being stained dark, the fastest dyes being used, and
only an expert can detect them as differing from the natural shades.

~Seal, Fur.~--The sizes range from 24 × 15 inches to 15 × 25 inches,
the width being the widest part of the skin after dressing. The most
useful skins are the pups 42 inches long, the quality being very good and
uniform. The largest skins, known as wigs, and ranging up to 8 feet in
length, are uneven and weak in the fur. The supply of the best sort is
chiefly from the northern Pacific, Pribilof Islands, Alaska, northwest
coast of America, Aleutian Islands, and Japan. Other kinds are taken from
the south Pacific regions. The dressing and dyeing of seal takes longer
than for any other fur, but when finished, it has a fine, rich effect,
and is very durable.

~Seal, Hair.~--This is chiefly used for its oil and leather, and not for
its fur. It has coarse, rigid hair, and no under-hair.

~Skunk, or “Black Marten.”~--15 × 8 inches. The under-hair is full, and
fairly close, with glossy, flowing top-hair about 2-1/2 inches long. The
majority of the skins have two stripes of white hair extending the whole
length of the skin. These were formerly cut out, but more recently are
dyed the same color as the rest of the skin. They are widely found in
North and South America. The best are from Ohio and New York. The skunk
is naturally the blackest fur, is silky and very durable.

~Squirrel.~--10 × 5 inches. This size refers to the Russian and Siberian
types, which are practically the only kind imported for fur, other species
having too poor a fur to be of great commercial interest. The back of the
Russian squirrel has an even, close fur, varying from a clear bluish-grey
to a reddish-brown, the bellies in the former being of a flat quality and
white, in the latter, yellowish. The backs are worked up separately from
the bellies. The pelts, though light in weight, are tough and durable.
The tails are dark and very small, and considerably used.

~Tiger.~--The size varies, the largest measuring about 10 feet from the
nose to the root of the tail. It is found throughout India, Turkestan,
China, Mongolia, and the East Indies. Coats of the Bengal variety are
short and of a dark orange-brown with black stripes. Those from other
parts of India are similar-colored, but longer in hair, while those
from the north and China are not only large in size, but have very long
soft hair of a delicate orange-brown, with very white flanks, and marked
generally, with the blackest of stripes.

~Wolf.~--50 × 25 inches. Is closely allied to the dog family, and very
widely distributed over the world. The best are the full-furred skins
of a very pale bluish-grey with fine, flowing black top-hair, from the
Hudson Bay district. Those from the United States and Asia are harsher and
browner. The Siberian is smaller than the North American, and the Russian
still smaller. A large number of prairie-dogs, or dog-wolves, is also used
for cheaper furs.

~Wolverine.~--16 × 18 inches. Is a native of America, Siberia, Russia, and
Scandinavia, and is of the general nature of the bear. The under-hair is
full and thick, with strong, bright top-hair about 2-1/2 inches long. The
color is of two or three different shades of brown on one skin, the center
being dark, and presenting the general appearance of an oval saddle,
bordered with a rather pale shade of brown, and merging to a darker shade
towards the flanks. This peculiar character stamps it as a distinguished
fur. It is expensive, and quite valuable on account of its excellent
qualities.

~Wombat, Koala or Australian Bear.~--20 × 12 inches. It has a light grey
or brown, close, thick under-hair 1/2 inch deep, and no top-hair, with a
rather thick, spongy pelt. It is cheap, and well suited for rough wear.




CHAPTER II

STRUCTURE OF FUR


Fur is made up of two main components, the hair and the skin, and each of
these has a very complex structure.

In the living animal the skin serves as a protective covering, and also
constitutes an organ of secretion and of feeling; consequently it is
of a highly complicated nature. The skin of all fur-bearing animals is
essentially the same in structure, although varying considerably as to
thickness and texture. It consists of two principal layers, which are
entirely different in structure and purpose, and correspondingly different
in both physical and chemical respects: the epidermis, epithelium or
cuticle, which is the outer layer, and the dermis or corium, which is the
true skin. (Fig. 1A).

The epidermis is very thin as compared with the corium. Its outer layer
consists of a tissue of cells, somewhat analogous to the horny matter
of nails and hair. The inner surface, called the ‘rete malpighi,’ rests
on the true skin, and is a soft, mucous layer of cells. These cells are
spherical when first formed, but as they approach the surface become
flattened, and dry up, forming the horny outer layer of the epidermis,
which is constantly throwing off the dead scales, and which is constantly
being renewed from below. It is from this inner layer of the epidermis
that the hair, the sweat-glands, and the fat-glands are developed.

The corium, or true skin, consists essentially of white, interlacing
fibres of the kind known as connective tissue. These fibres are themselves
made up of extremely fine smaller fibres, or fibrils, cemented together by
a substance of a somewhat different nature from the fibres, the coriin.
Towards the center of the skin, the texture of the interweaving fibres
is looser, becoming much more compact at the surface just beneath the
inner layer of the epidermis. This part of the corium is so exceedingly
close that the fibrils are scarcely recognizable. It is in this part that
the fat-glands are situated, while the hair-roots and sweat-glands pass
through it into the looser texture of the corium. The surface next to the
flesh is also closer in structure than the middle portions of the skin,
and has somewhat of a membranous character due to the fibres running
almost parallel to the surface of the skin. The skin is joined to the body
proper by a network of connective tissue, frequently full of fat-cells.
This layer, together with portions of the flesh which may adhere to it,
is removed by the process called ‘fleshing,’ and this side of the skin
is known as the flesh side. The corium also contains a small proportion
of yellow fibres, known as ‘elastic fibres,’ which differ physically and
chemically from the rest of the skin substance.

During the course of the development of the embryo animal, a small group
of cells forms like a bulb on the inner side of the epidermis, above a
knot of very fine blood-vessels in the corium. This group of cells grows
downward into the true skin, and the hair-root which is formed within it,
surrounds the capillary blood-vessels, drawing nourishment from them, and
thus forming the papilla. (Fig. 1A). Smaller projections also form on the
bulb, and the fat-glands are gradually developed. The sweat-glands are
formed in a manner similar to the development of hair.

The individual hair fibre is quite as complicated in structure as the
skin, and is made up of four distinct parts. (Fig. 1B).[2]

  [2] Descriptions and figures taken from “Mammal Fur Under the
      Microscope,” by Dr. L. A. Hausman, in _Natural History_,
      Sept.–Oct., 1920.

The medulla, or pith, is the innermost portion of the hair, and is
composed of many shrunken cells, often connected by a network which may
fill the medullary column partially or wholly.

Surrounding the medulla is the cortex, which is made up of spindle-shaped
cells fused into a horny, almost homogeneous, transparent mass, and
forming a large proportion of the hair shaft.

In the majority of the fur-bearing animals, there is distributed within
and among the cells of the cortex a pigment in the form of granules or
minute particles, arranged in the different hairs in fairly definite and
characteristic patterns. It is to these pigment granules that the color
of the hair is due primarily. In some cases the coloring matter of the
shaft is uniformly diffused and not granular.

[Illustration: FIG. 1

_A._ STRUCTURE OF SKIN.

_B._ STRUCTURE OF HAIR.]

The outermost coat of the hair, or cuticle, is composed of thin,
colorless, transparent scales of varying forms and sizes, and arranged
in series like the shingles of a roof. It is on these scales that the
lustre or gloss of the hair depends. Since lustre is due to the unbroken
reflection of light from the surface of the hair, the smoother the
surface, the glossier it will appear. When the scales of the cuticle are
irregular and uneven, the surface of the hair will not be uniform and
smooth, and the light reflected from it will be broken and scattered, and
consequently the hair will not possess a high degree of lustre. As a rule,
the stiff, straight hairs have the most regular and uniform arrangement
of the scales of the cuticle, and hence are the smoothest and glossiest.

Fur hairs are in general either circular or elliptical in cross-section,
those which are circular being straight or only slightly curved, while
those which are elliptical in cross-section are curly like the hair of
the various kinds of lambs.

Most fur-bearing animals have two different kinds of hair on their bodies.
Nearest to the skin is a coat of short, thick, soft and fine hair, usually
of a woolly nature, and called the under-hair, under-wool, or fur-hair.
Overlying the fur-hair is a protective layer of hair, longer and coarser
than the under-hair, and usually straight, hard, smooth and glossy. This
is called the top-hair, over-hair, guard-hair or protective hair. In some
furs, the top-hair constitutes one of the chief elements of their beauty,
while in others, the top-hairs are removed, so as better to display the
attractive features of the under-hair. The roots of the top-hair are
generally deeper in the skin than those of the fur-hair, and in some
instances where the top-hair is removed, as in the seal, the roots are
destroyed by the action of chemicals applied to the skin side, the roots
of the fur-hair being wholly unaffected by this treatment.

The fur-hair and the top-hair in the same animal have different
medullary and cuticular structures, and these characteristics may be
used to distinguish the two kinds of hair. Figs. 2A and B illustrate
these differences. In each case, the two large hairs on the left of the
illustration are the guard-hairs, showing respectively the cuticular
scales and the medulla. On the right are the two fur-hairs showing the
scales and the medulla.

Although composed of many different kinds of tissues, and varying so
greatly in physical structure, both the skin and the hair belong to
the same class of chemical compounds, namely the proteins. These are
highly complex substances, forming the basis of all animal and vegetable
tissues. There are many different kinds of proteins, varying somewhat in
their constitutions, but all show, on analysis the following approximate
composition of chemical elements:

  Carbon                                50–55%
  Hydrogen                              6.5–7.3%
  Nitrogen                              15–17.6%
  Oxygen                                19–24%
  Sulphur                               0.3–5%

The principal kinds of proteins found in the various fur structures
are albumins, keratin, collagen, and mucines. Albumins, of which the
white of egg is the most familiar variety, occurs to some extent in the
corium as serum in the blood-vessels, and also as the liquid filling
the connective tissues, known as the lymph. They are soluble in cold
water, but when heated to about 70° C., they coagulate and are then
insoluble. Concentrated mineral acids and strong alcohol will also effect
coagulation.

[Illustration: FIG. 2

_A._ HAIR OF EUROPEAN BEAVER.

_a._ TOP-HAIR. _b._ UNDER-HAIR.

_B._ HAIR OF SKUNK.

_a._ TOP-HAIR. _b._ UNDER-HAIR.]

Keratin is the chief substance of which all horny parts of the animal
body are composed, such as the hair, nails or hoofs. It is the principal
constituent of the hair, the epidermis, and the walls of the cells of
the inner layer of the epidermis, or the ‘rete malpighi.’ Keratin is
particularly rich in sulphur, and is quite insoluble in cold water.
Caustic alkalies attack keratin-containing parts.

The collagens are the principal proteins of the skin, forming largely the
substance of the connective tissue fibres, and consequently the framework
of the skin. They are insoluble in cold water, dilute acids and salt
solutions, and are only very slowly attacked by dilute alkalies. Dilute
acids and alkalies cause collagen to swell; concentrated acids, vegetable
tanning materials, basic chrome or iron salts cause it to shrink. By
boiling with water, dilute acids or dilute alkalies, collagen is split up
into gelatin or glutin.

The mucines of the skin, intercellular material or coriin, are soluble
in dilute acids, in dilute solutions of alkalies and of alkaline earths
such as lime, and in 10% salt solution, but insoluble in water, and in
salt solutions of greater or less concentration than 10%. On drying the
skin, the mucines cement the connective tissue fibres, causing the skin to
become stiff, horny and translucent. The mucines are also constituents of
the cells of the ‘rete malpighi.’ The solubility of the mucines in dilute
solutions of alkalies and of alkaline earths causes the epidermis to be
loosened from the corium, when the skins are treated with such solutions
for some time.

When raw skins are boiled with water, the greater part goes into solution,
the residue consisting chiefly of the keratins of the hair and epidermis
cells. On cooling, the solution solidifies to a jelly of gelatine. It
combines with both acids and alkalies. A property of the skin which is
of importance in the tanning operation of fur-dressing, and a quality
which also characterizes gelatine, is the capacity to absorb liquids
and swell up, without changing chemically. Raw pelts swell up easily
in pure cold water, but much more easily in solutions of dilute acids
or dilute alkalies, only a little of the skin material being dissolved.
In stronger solutions, the skins swell up less, while more of the skin
substance dissolves, and by prolonged action of strong acids or alkalies,
an almost complete solution of the skin is obtained, without, however,
any of the material decomposing. With very strong alkalies or acids,
the skin substance is broken up into simpler compounds, such as various
amines and ammonia. The swelling action of acids or of alkalies increases
with the increase in concentration of the acid or alkali, but only up
to a certain point, after which further increase in the strength of the
acid or alkaline solution causes a reduction in the swelling, and even
produces shrinkage. In the presence of neutral salts, like common table
salt, sodium chloride, the swelling action of acids, is reduced, but the
action of alkalies remains practically unaffected.

When treated with the various chemicals, fur hair acts in a manner quite
similar to wool. If it be remembered that certain classes of furs are
derived from animals of the sheep family, such furs as Persian lamb,
krimmer, etc., it becomes apparent why chemicals should affect furs in
nearly the same way as wool. The great majority of furs differ from those
of the sheep family, in possessing much greater resistance to the action
of chemicals. The range is a wide one however, and no exact criterion can
be adopted. As a general rule, the reactions are most marked with fur-hair
of a woolly nature, so this may be taken as a standard of reference.

Acids have relatively little action on the hair, when applied in dilute
solutions. The scales of the cuticle or epithelium are somewhat opened,
the fibre becoming slightly roughened thereby. Even at high temperatures,
the hair is quite resistant to the action of dilute acids. Concentrated
acids destroy the hair with the liberation or formation of ammonia,
hydrogen sulphide, and various amino acids. When treated with dilute
acids, the hair, especially if it is of a very woolly nature, retains
considerable quantities of acid, this phenomenon being probably due to
the fixation of the acid by the basic groups in the hair. Nitric acid
produces a yellow coloration when applied in dilute solution for a short
time. Sulphurous acid, the acid formed by the burning of sulphur, has a
bleaching action on the hair.

Alkalies attack the hair, even in dilute solutions, and by longer action
complete decomposition sets in, with formation of ammonia and amino-acids.
Ammonium carbonate, soap, and borax are practically harmless in their
effect on the hair. Sodium and potassium carbonates roughen the hair on
prolonged action, even in dilute solutions. Calcium hydroxide on continued
action removes sulphur from the hair, causing it to become brittle.

Salts of alkalies and alkaline earths do not affect the hair at all.
Salts of the heavy metals on the other hand, are absorbed in appreciable
quantities. From a dilute solution of alum, aluminum hydroxide is absorbed
by the hair, the potassium sulphate remaining in solution. Similarly with
copper, iron, and chromium salts, the metal oxides are fixed by the fibre.




CHAPTER III

FUR DRESSING

INTRODUCTORY AND HISTORICAL


Fur dressing has a twofold purpose. First of all, the putrefactive
processes must be permanently stopped, so that the skin may be
preserved as such, or worked up as some fur garment, without danger of
decomposition. Having taken measures to assure the endurance or relative
permanency of the pelt, the prime consideration is, of course, the
appearance of the hair. The hair must be so treated that all its inherent
beauty is brought out to the fullest extent. It must be made clean and
soft, and all the natural gloss must be preserved, and if possible,
enhanced. The appearance of the leather is relatively unimportant, since
it is not seen after the furs are made into garments. There are, however,
certain qualities which it is essential for the leather to possess after
being dressed, and these are, softness, lightness of weight, elasticity or
stretch, and a certain firmness or ‘feel.’ In other words the important
considerations in fur dressing are the employment of means, and the
exercise of care to preserve or even improve those characteristics of the
pelt which make it valuable.

The dressing of furs has many features in common with the manufacture
of leather, which is a kindred art. But whereas in fur dressing the
prime consideration is the appearance of the hair, and the leather is of
secondary importance, in the production of leather, the hair plays no part
at all, since it is entirely removed from the pelt. The fundamental points
of resemblance between leather manufacture and fur dressing are in those
processes and operations which are concerned with the preservation of the
leather, and rendering it in the proper condition for use.

Both leather dressing and fur dressing have an origin which may be
regarded as identical, and which dates back to the haziest periods of
antiquity. In the course of satisfying his needs, primitive man killed
the animals about him, and thus obtained his food. The killed animal also
furnished a skin, which after undergoing certain manipulations and other
treatments, could serve as a protective covering, ornament, or defensive
weapon. Since the skin in its natural state was hardly fit for use because
of its easy tendency to putrefaction, it is evident that man had to find
some means of preventing this decay in a more or less permanent fashion,
and moreover had to treat the skin so that it would be suitable for use,
by rendering it soft and flexible. The discovery of means to accomplish
these purposes was probably one of the first great steps forward on the
path of progress and civilization.

There are evidences of the use of animal skins in the earliest periods
of antiquity, in fact it is a usage which may be literally regarded as
“old as the hills.” One of the earliest written records of the employment
of the skins of animals as garments, is in the Old Testament, where it
states, “Unto Adam and to his wife did the Lord God make coats of skins,
and clothed them.” Numerous other biblical references indicate the use
of animal skins for various purposes, sometimes prepared as leather,
with the hair removed. Among the Egyptians tanning seems to have been
a common occupation. The particularly attractive skins, like those of
the leopard or panther, were especially prized, and were made up as furs
for ornamental wear, rugs and decorations. The less valuable skins were
unhaired and made into leather. Although the tanning or leather-producing
processes of the Egyptians are quite unknown, numerous figures engraved in
stone afford an indication to some of the manipulatory operations, such
as soaking the skins, fleshing, softening with stones, stretching over
a three-legged wooden “horse,” etc. Many articles, made of leather, have
been found in the various Egyptian sarcophagi, and all are in a splendid
state of preservation, after forty centuries, thereby indicating a very
efficient method of dressing animal skins. Likewise, the presence in the
museums of various articles, leather and fur, of Assyrian, Phoenician
and Persian origin, tends to show that these peoples also possessed a
considerable degree of proficiency in tanning. Frequent references in the
Greek literature show that leopard and lion skins were worn as war cloaks,
and they undoubtedly were properly made. In the _Iliad_ is described an
operation for the preparation of skins for use as garments, and the method
seems to be a sort of chamois dressing.

The first method of tanning skins was, in all probability, that of rubbing
into the skins various fatty materials found close at hand, such as parts
of the animal, fat, brains, milk, excrement, etc., such an operation
constituting the basis of what is now known as the chamois dressing. One
of the reasons for believing that it was the first process to be used by
primitive man, is the fact that certain undeveloped tribes and races of
the present day still dress skins by it. The American Indians, even to
this day prepare skins by rubbing in, on the flesh side, the brains of
the animals which furnished the skins. The Eskimos dress skins by rubbing
in animal fats or fish-oil, and subsequently softening and stretching
the skins with their teeth in place of, or for want of other implements.
Usually, however, variously shaped stones or bones of animals are used
to obtain the proper degree of softness and flexibility. It is true, too,
that some of the skins dressed in this primitive fashion can scarcely be
excelled by any dressed with more modern processes and tanning methods.

The next step forward in the preparation of animal skins for use was
undoubtedly the utilization of substances found in the earth. Common
salt, sodium chloride, was the most universally used substance of mineral
origin, just as it is today. Our prehistoric ancestors eventually
discovered the preservative action of salt, and applied it to skins.
While it was effective, it was not sufficiently permanent, so another
mineral, also of very common and wide occurrence was used in combination
with the salt, and the result proved quite satisfactory. This second
common mineral was alum. The use of alum, which is the basis of numerous
tanning processes to this day, seems to have been quite a popular method
of ancient times. Artemidorus, a Greco-Roman writer, mentions the use
of alum by the Greeks, and the Romans are known to have prepared a soft,
flexible leather called aluta (alum leather), by using it. In view of the
fact that Egypt had extensive deposits of alum, it is believed that the
alum-salt process was employed also by the Egyptians in the preparation
of leather. However, the evidence on this point is not conclusive.

One of the most important methods of producing leather, either as such
or on furs, was with the aid of certain vegetable extracts, known as the
tannins, from which the process of tanning gets its name. The discovery
of the value of these materials for converting the decaying raw skin
into a leather which could be preserved for an almost indefinite length
of time, and which was flexible and soft as desired, was of far-reaching
importance. For it is only in very recent times that these tannins have
been superseded in part by new tanning substances whose use is simpler
and more time-saving. Yet there are unmistakable indications that the
tannins were employed for tanning at a period which reaches back to the
dawn of history. Although it is scarcely probable that the people who
used these materials could have known of the existence or the nature
of the particular substances in the vegetable extracts which actually
effect the tanning action, experience taught them to employ these plants
which possessed the highest content of active ingredients, and which,
consequently, were most effective in use. Tychios, of Boetius, a Greek
supposed to have lived about 900 B.C. and mentioned in the _Iliad_, is
considered the oldest known tanner, and was regarded by Pliny, a Roman
writer, as the discoverer of tanning, and of the use of the various
vegetable tanning materials. At any rate, the Greeks used the leaves of
a so-called tanning-tree, which was probably the sumach. The Egyptians
worked with the acacia, while the Romans used as tanning materials the
barks of the pine, alder and pomegranate trees, also nut-galls, sumach and
acorns. The Romans were quick to employ methods used by the peoples whom
they conquered, and it is in this way that they learned the use of many
of the plants mentioned, for tanning purposes.

Many other ancient peoples had various processes of tanning, the methods
probably differing in each country. Thus the Chinese, Syrians, and much
later, the Moors, were each known for proficiency in a certain class
of leather tanning. It has been said that in general, even up to modern
times, tanning with nut-galls was the characteristic method of the Orient;
with oak-tan, that of the Occident, while the use of alum is regarded as
the method peculiar to the Saracens.

In prehistoric times and the early centuries of civilization, skins or
pelts were prepared for use by the individual, the work usually being
done by the housewife and daughters, while the masculine members of the
family were engaged in hunting the animals and obtaining the skins. At a
later period, when people had advanced to the point where they lived in
cities, the preparing or dressing of skins became centered in the hands
of a comparatively small number of people, and thus the work took on the
aspects of a trade. The workers in fur were at first the same people who
made leather out of the skin, for the two kinds of work were very closely
associated. During the period of the Roman supremacy, historical records
show that the furriers, who did all the work connected with furs, from
purchasing the raw skins, dressing them, making them into garments, to
selling the latter, were organized into associations together with the
leather workers. After the fall of the Roman empire, and throughout the
centuries known as the Dark Ages, all traces of the furriers seem to
have been lost, but in the beginning of the Renaissance period in the
fourteenth and fifteenth centuries, we again find records of the furriers,
who were now all members of the furriers’ guilds, also in association
with the leather workers. As formerly, all the work connected with the
production of fur apparel from the raw furs, was done by the master
furrier and his apprentices. The methods and the implements used, were
essentially the same as in Roman times, and in fact, up to a very recent
period there was very little change in either.

With the advent of the great industrial era at the beginning of the
nineteenth century, the guild system became ineffective, but the
furriers continued their work as heretofore. Up to about the middle of
the nineteenth century, the furrier continued to be the only factor of
any importance in the fur trade. There was no need for speed in his
work, for the demands of the trade were not so urgent. The fact that
the dressing of furs often occupied two to four weeks was no deterring
factor in his business. However, with the great expansion of the fur trade
about this time, it became impossible for the individual furrier to do
everything himself, and keep up with the requirements of his customers.
Specialization commenced, and establishments were set up solely for fur
dressing. The traditional time- and labor-consuming processes were still
used, but the efficiency of work on a large scale enabled the fur dressers
successfully to fill their orders. But the fur trade continued to grow by
leaps and bounds, and very soon the fur dressers were no longer able to
meet the demands of the trade. It was then that the science of chemistry
came to the aid of the fur dresser, and helped him meet the exigency. By
devising dressing processes which were cheap and efficient, and which only
required several hours, or at the most one or two days, as compared with
as many weeks, the chemist brought the fur dresser out of his dilemma.
And with the adoption of mechanical time- and labor-saving devices, the
fur dressing industry has made wonderful progress.




CHAPTER IV

FUR DRESSING

PRELIMINARY OPERATIONS


The fur dresser receives the skins in one of two shapes, flat or cased,
depending on the manner in which they were removed from the animal. Flat
skins, as for example, beaver, are obtained by cutting on the under side
of the animal from the root of the tail to the chin, and along the inner
side of the legs from the foot to the first cut. The skins are either
fastened to boards or attached to wooden hoops slightly larger than the
skins, so as to stretch them, and are then carefully dried, avoiding
direct sunshine or artificial heat, as it is very easy to overheat the
skins and thereby ruin them. The great majority of skins, however, are
cased. The pelts are cut on the under side of the tail, and along the
hind legs across the body, the skin being then removed by pulling it
over the head off the body like a glove, trimming carefully about the
ears and nose. The skin is thus obtained inside out, and is drawn over a
stretching board or wire stretcher of suitable shape and dimensions, so
as to allow the skin to dry without wrinkling. The pelts, after drying
in a dry, airy place, are removed from the stretchers and are ready for
the market. With some furs, as foxes, the skins are turned hair-side out
while still somewhat moist, and then put on the stretcher again till fully
dried. In most cases, however, skins are sold flesh-side out. Throughout
the various dressing operations cased skins are kept intact, being turned
flesh-side out or hair-side out according as the processes are directed
to the respective sides. The pelts are only cut open if they have to be
dyed, or after the manufacturer receives them, when they have to be worked
into manufactured garments.

A distinction which is made by fur dressers and dyers, and also by the fur
trade in general, divides furs into those derived from domestic animals,
particularly the various kinds of sheep, including also the goat species,
and those obtained from other animals by trapping. In fact, at one time,
and to a certain extent even to-day, dressers were divided into two groups
based on this distinction, one class dealing only with furs obtained
from the sheep family, and the other working with other kinds of furs.
This differentiation is not a simple arbitrary one, but has a rational
justification. As mentioned before, the manner and habit of living of the
animal are important factors in determining the nature and constitution of
its skin, both leather and hair. The structure of the body being dependent
primarily upon the nature of the food absorbed by the animal, it is only
natural that herbivorous or vegetable-eating animals such as sheep and
goats, should possess fur of a different sort from that of the carnivorous
or meat-eating animals, such as the majority of fur-bearers are. It also
seems clear that furs differing in their character and constitution should
require somewhat different treatments, and accordingly the methods are
modified when furs like lambs or goats are dressed. To a great extent,
however, the fundamental operations are similar for all furs, regardless
of nature or origin, and these will be discussed briefly.

Inasmuch as the first great purpose of fur dressing is to render the
skins more or less permanently immune from the processes of decay, it
is necessary to prepare the pelts so as to be most fit to receive the
preserving treatment. The skins as they are delivered to the fur dresser
have, in the majority of cases, been stretched and dried to preserve
them temporarily, while in some instances, especially with the larger
furs like bears and seals, they are salted and kept moist. The flesh-side
of the pelt still has considerable fleshy and fatty tissues adhering to
it, and the hair is generally soiled and occasionally blood-stained. In
order to get the pelts into such a condition that they can be worked
and manipulated, they first have to be made soft and flexible. Very
greasy skins are scraped raw in order to remove as much as possible of
the attached fat, the operation being known as beaming or scraping. The
typical beam, shown in Fig. 3, consists of a sloping table usually made
of some hard wood, and placed at an angle of about 45°. It is generally
flat, although in some instances convex beams are also used, about a yard
long, 8 to 10 inches wide, and firmly supported at the upper end. The skin
is placed on the beam, flesh-side up, and is scraped with a two-handled
knife (Fig. 4), always in a downward direction.

[Illustration: FIG. 3. BEAM.]

[Illustration: FIG. 4. KNIVES USED IN FUR DRESSING.]

The first step in softening the skins is to get them thoroughly moistened,
and this is variously done, depending on the nature of the skin. Lambs,
for example, require the gentlest means of wetting them, while rabbits
can stand soaking in water for several days. The manner and duration
of moistening must be adjusted to the character of the pelt. For the
putrefactive processes which were stopped by stretching and drying the
skins, continue as soon as the pelt is again moistened. The progress
of decay causes the evolution of certain gases, the simplest of which
is ammonia, and eventually, if permitted to proceed, brings about the
complete disintegration of the skin tissue. It has been found that a
certain amount of gas formation is necessary to loosen up the fibres in
order to get the best quality of leather after tanning. This process must
be interrupted at the proper time and not allowed to proceed too far.

Skins which have been preserved fresh by salting, require only a
comparatively short time (about 2 hours) to become softened by soaking
in clean, soft water. Most dried skins need a longer treatment before
they are sufficiently flexible. The addition of certain substances to the
water facilitates and accelerates the softening. In some instances salt
water is used for soaking the pelts, the preservative action of the salt
tending to prevent any loosening of the hair. A solution of 1/4% borax
is very effective in rendering the skins soft, and clean as well. Borax
has an exceedingly mild alkaline action, and causes a slight swelling of
the skin tissue, which then absorbs the water more readily. Being also
preservative and antiseptic, borax tends to prevent decomposition of the
skin tissue. Another chemical of a different nature, but equally effective
is formic acid, used in the proportion of 1.5–2.5 parts per 1000 parts of
water. Formic acid also induces a swelling of the skin, the pelts being
soaked in a short time, and the antiseptic action of the acid obviates the
possibility of the hair becoming loose. The water used should be fresh and
clean, and the soaking must be stopped as soon as the skins have become
soft and flexible. Sometimes the skins are allowed to soak overnight in
water, while in other cases, the pelts are just moistened by dipping in
water until thoroughly wet, and then laying them in a pile for several
hours, or overnight. Another method which is practised with certain types
of skins is the use of wet sawdust or of sawdust moistened with salt
water. The fur skins are either embedded in the sawdust or drummed with
it for several hours, or until sufficient moisture has been absorbed
to render them flexible. By this means there is no danger of the skins
being over-soaked, or of the hair being loosened. When the skins have
been properly wetted, they are drawn with the flesh-side across the edge
of a dull knife-blade, in order to help loosen the texture of the skin.
They are then put into a tramping machine and worked until completely
softened. In the case of large or heavy skins, the moistened pelts are
worked on the beam with a dull beaming knife to impart thorough softness
and flexibility.

The pelts are then cleaned with particular reference to the hair. With
some furs this is accomplished simply by drumming for several hours with
dry sawdust, whereby the oil and dirt are removed from the hair, and the
hair is then freed from the sawdust by caging. Other skins are washed,
being passed through a weak soap solution for a short time, the dirty
spots being brushed. Occasionally an extract of soap-bark is used in
place of the soap, being even more effective. The cleansed skins are then
thoroughly rinsed to remove any of the cleaning material, which would
affect the gloss of the hair if allowed to remain on the skins. Then in
order to eliminate as much as possible of the water in the skins, they
are hydro-extracted, a centrifugal machine of the type shown in Fig. 5
being used. The basis of its action depends on the utilization of the
principle of centrifugal force. The machine consists essentially of a
perforated metal basket generally made of copper, capable of being rotated
at a high speed. Surrounding the basket is an iron framework, polished or
enamelled on the inside. The wet skins are placed in the rotating basket,
fur side toward the perforations, and the water which is thrown off from
the skins passes through the little holes, and is caught up on the walls
of the outside frame, from where it is led off through suitable ducts.
The centrifugal device is properly equipped with balancing and regulating
attachments, as well as with a brake. The power may be applied by the
over-drive or the under-drive as is most desirable in the particular case.
The inner surface of the basket can also be enamelled or otherwise made
resistant to the action of acids or other chemicals.

[Illustration: FIG. 5. CENTRIFUGAL MACHINE.

(_Fletcher Works, Inc., Philadelphia_)]

When the skin is removed from the animal, as much as possible of the
adhering fat and flesh is scraped off, but in spite of this, and in
spite of subsequent beaming by the fur dresser, there is always a thin
layer of flesh and fatty material remaining and this must be removed so
as to expose the corium, enabling the efficient action of the chemicals
used in the tanning processes. The process of removing this undesirable
layer from the flesh-side is known as fleshing. It is a rather delicate
operation, requiring considerable experience and dexterity on the part of
the worker, for it is exceedingly easy to cut into the skin and damage
the fur. A fleshing knife of the type commonly used is shown in Fig. 6.
It consists of a sharp blade fastened at a slight angle from the vertical,
with the cutting edge away from the workman, who straddles the bench, and
by drawing the skins back and forth across the edge of the blade, removes
all flesh and fat, leaving the corium free and clean. Large skins cannot
conveniently be fleshed in this fashion. They are placed on the beam, and
fleshed with a fleshing or skiving knife similar to the beaming knife, but
consisting of a slightly curved, sharp two-edged blade having handles at
both ends. Frequent attempts have been made to use suitable machines to
do this work. A type of machine which has met with considerable success
is depicted in Fig. 7. It is fashioned after the models used for the
fleshing of hides for leather manufacture, and has special adjustments
and regulating devices which afford protection for the hair part of the
fur. From time to time other fleshing machines are put on the market, yet
none of them seems to enjoy any great popularity, for fleshing is still
largely a manual operation. With some classes of pelts, fleshing presents
some difficulties, and chemical means have to be resorted to in order to
loosen the flesh sufficiently to enable proper fleshing. In the case of
large furs like bears, leopards, and the like, which while of no great
importance in the fur trade, are occasionally met by the fur dresser,
the skins after being soaked, and washed with soap-water, are partially
dried; then the flesh-side is treated with technical butter or oil, which
is tramped in. A mixture of salt water and bran is then applied to the
skins, thereby causing a swelling action to set in, and the flesh becomes
loosened, and is easily removed by fleshing on the beam. Seals receive a
special treatment which makes them soft, and gives them greater stretch
after they are tanned. A paste made by mixing a very dilute solution of
caustic soda with an inert substance like French chalk, china clay, etc.,
is applied to the corium after the skins have been fleshed, then the
pelts are folded up, and allowed to lie for several hours. They are then
entered into a dilute solution of calcium chloride and left overnight.
After being washed in a paddle or drum, first with fresh water, and then
in water containing lactic or formic acid to remove the lime, the skins
are ready for tanning.

[Illustration: FIG. 6. FLESHING KNIFE ON BENCH.]

[Illustration: FIG. 7. FLESHING MACHINE.

(_Turner Tanning Machinery Co., Peabody, Mass._)]




CHAPTER V

FUR DRESSING

TANNING METHODS


After the pelts have gone through the preliminary operations of softening,
washing and fleshing, they are ready to receive the treatment which
will convert the easily decomposing skin into leather of more or less
permanency, depending on the method used.

During the past century, considerable study has been made both by
scientific and technical people, of the problem of leather formation.
Numerous theories as to the nature of the process have been evolved, but
even to this day, no satisfactory explanation has been given which would
account for all the facts as they are now known, so the matter is still a
subject of considerable controversy. Procter, who is one of the leading
authorities on leather today discusses the development of the tanning
theories as follows:

“The cause of the horny nature of dried skin is that the gelatinous and
swollen fibres of which it is composed not merely stiffen on drying but
adhere to a homogeneous mass, as is evidenced by its translucence. If
in some way we can prevent the adhesion of the fibres while drying we
shall have made a step in the desired direction, and this will be the
more effective the more perfectly we have split the fibre-bundles into
their constituent fine fibrils, and removed the substance which cements
them. The separation of the fibres can be partially attained by purely
mechanical means.... Knapp, to whom we owe our first intelligible theories
of the tanning process, showed that by physical means the separation and
drying of the fibres could be so far effected as to produce without any
tanning agent a substance with all the outward characteristics of leather,
although on soaking it returned completely to the raw hide state. He
soaked the prepared pelt in absolute alcohol, which penetrated between,
and separated the fibres and at the same time dried them by its strong
affinity for water. More recently, Meunier has obtained a similar result
by the use of a concentrated solution of potassium carbonate which is even
more strongly dehydrating.

“Knapp made a further step by adding to his alcohol a small quantity
of stearic acid which, as the alcohol evaporated, left a thin fatty
covering on the fibres which completely prevented their adhesion, and
reduced their tendency to absorb water; and he so produced a very soft and
white leather. Somewhat similar are the principles of the many primitive
methods which apply fatty and albuminous matters, grease, butter, milk, or
brains to the wet skin, and by mechanical kneading and stretching, aided
by capillarity, work these matters in between the fibres as the water
evaporates. Such methods are still used, and enter into many processes in
which other tanning agents are also employed.

“Building upon these facts, Prof. Knapp advanced the theory that the
effect of all tanning processes was not to cause a change in the fibres
themselves, chemical or otherwise, but merely to isolate and coat them
with water-resisting materials which prevented their subsequent swelling
and adhesion. True as this theory undoubtedly is in many cases, it can
hardly be accepted as the whole truth, and it seems incontestable that
frequently the fibres themselves undergo actual chemical changes which
render them insoluble and nonadhesive.

“Before Knapp’s work, the prevalent theory, at least as regards vegetable
tannage, had been a chemical one, started by Sir Humphrey Davy. If a
solution of gelatine be mixed in proper proportion with one of tannin,
both unite to form a voluminous curdy precipitate; and, according to
Davy’s ideas, this was amorphous leather. Against this, it was urged
that even the supposed ‘tannate of gelatine’ itself could not be a
true chemical compound, since the proportions of its constituents were
considerably varied by changes in the strength of the solutions, or by
washing the precipitate with hot water; and further, that in chemical
compounds, the form was changed, and no trace of the original constituents
appeared in the compound; while in leather apart from some change of color
and properties, the original fibrous structure remained unaltered.

“This reasoning appears much less conclusive now than it did in Knapp’s
day. Against the last objection guncotton may be quoted as an instance
of profound chemical change with no alteration in outside appearance;
and it is recognized that, especially among complex organic substances,
chemical reactions are rarely complete, but that stable positions are
reached, so-called ‘equilibria,’ in which the proportion of changed and
unchanged substance is dependent on concentration or other conditions;
and that therefore such a precipitate might well be a mixture of gelatine
with a true gelatine tannate from which further portions of tannin might
be dissociated by water.

“With the clearing up of old difficulties, however, the conflict between
chemical and physical theories has, as is usually the case, merely
passed into a new phase. Years ago, it was shown by Linder and Picton and
others, that liquids could be obtained which were not really solutions
of ions or molecules, but merely suspensions like that of clay in water,
or butter-fat in milk; but so finely divided as to appear clear and
transparent, and pass through filters like true solutions. Later, by
means of the ultra-microscope their discrete particles have actually
been made visible, each of them consisting of many molecules of the
suspended substance. Nevertheless, these particles have many molecular
properties, possessing plus or minus electrical charges; behaving like
large ions under the influence of an electrical current; and mutually
precipitating and neutralizing each other when positive and negative
are brought together. Such solutions are called ‘colloid,’ and those of
gelatine and tannin are of the class, so that it is now often said that
the precipitation of gelatine by tannin, and the fixation of tannin by
gelatinous fibre are merely ‘colloidal’ and ‘physical,’ and not ‘chemical’
phenomena. Admitting the facts, the question still arises whether the
distinction between chemical and physical is not here one without a
difference; and whether between the purely ionized dilute solution of a
salt and the coarsely granular clay suspension there is any point where a
definite line of demarcation can be drawn. The writer inclines to the view
that there is not; and that ionic and colloidal combinations are extreme
cases of the same laws, both physical, and both chemical.”

There are several methods which are used in tanning furs, each having
its peculiar characteristics and qualities, and possessing individual
advantages and disadvantages. In order to be able to judge the merits of
the various processes, it is necessary to have a criterion which can serve
as a basis of reference. Fahrion, a recognized authority and investigator
in this field, gives a definition of leather which is usually accepted
as a standard for comparison. He says: “Leather is animal skin, which on
soaking in water and subsequent drying does not become hard and tinny, but
remains soft and flexible; which does not decay in the presence of cold
water; and which does not yield any gelatine on boiling with water.” While
the requirements set forth in this statement are essential for leather,
and a compliance with them would also be desirable for tanned furs, a
somewhat less rigorous standard of conditions to fulfil is satisfactory
for the general needs and purposes of furs. The chief qualities which
tanned furs must possess, with particular reference to the leather side of
the pelt, are retention of softness and flexibility after being moistened
by the furrier for manufacturing purposes, and subsequent drying; and
freedom from a tendency to decay during this operation and thereafter. If
the furs are to be dyed, the effect of the dyeing must also be considered,
and the tanning must be such as to enable the dyed furs to possess the
above qualities.

The most important tanning processes employed for furs are the following:

  1. Salt-acid tan, or pickle.
  2. Mineral tans.
  3. Chamois tan.
  4. Formaldehyde and similar tans.
  5. Combination tans.
  6. Vegetable tan.


1. SALT-ACID TAN, OR PICKLE

This is one of the most extensively used methods for tanning furs, and is
also very cheap and easily applied. A typical formula for this tan is the
following: A solution of salt is prepared containing about 10% of common
salt, sodium chloride, and to this is added 1/2–3/4 ounce of sulphuric
acid for each gallon of tanning liquor. The proportions may be varied
within certain limits, but the figures here given are those which have
proven successful in practise. The solution should be made in a wooden
or earthenware container, free from any metal, as it would be attacked
by the acid. The liquor is then applied to the flesh-side of the fleshed
skins by means of a brush, making sure to touch all parts of the pelt.
They are then placed in a pile and allowed to remain thus until tanned, an
operation which occupies a time ranging from a few hours to two or three
days depending on the thickness of the skins. When the corium has lost its
translucence and has become of a milky-white color throughout the entire
thickness of the skin, as can be seen by viewing a cross-section, the skin
may be considered tanned. In some instances, where the hair of the fur can
stand immersion without injury, the skins are entered into the pickling
solution and allowed to remain for 12 to 24 hours, which is generally a
sufficient time to tan them in this manner.

The acid of the pickle causes the skin to swell, the salt then penetrating
between the fibres of the corium, and at the same time reducing the
swelling of the skin. The acid also neutralizes the alkaline products
of decomposition which may form, while the salt acts as a deterrent to
the progress of the putrefactive processes. When the skin is dried after
tanning, and stretched and finished, a soft white leather is obtained
which is permanent as long as it is kept dry. It is the salt which causes
the fibres of the skin to be completely differentiated and thus prevents
their adhesion.

It is interesting to note that other acids besides sulphuric can be
used for the pickle, organic as well as mineral, formic acid in 1/4%
solution being especially effective and giving excellent results, but
is more expensive than the mineral acid. A method, which in principle
is identical with the pickle, but carried out in an entirely different
manner, is the lactic acid fermentation process, or “Schrot-beize” as it
is called in German. The procedure is in general as follows: “The fleshed
skins are placed on tables, flesh-side up, and covered with a layer of
bruised barley grains, or a mixture of 3 parts of wheat bran and 2 parts
of rye flour. Then the head, tail and legs are turned inward, and the
skins rolled up in little cushions, hair-side out, and placed in a vat.
When this is filled with the skins a solution of common salt is poured
over them, and they are allowed to remain thus in a moderately cool place
for 24 hours. After this time, the skins are carefully unrolled, so as
not to remove any of the adhering solid materials, and turning the skins
hair-side inward, they are laid flat together in pairs and placed in an
empty vat. After another 24 hours they are again unpacked and replaced in
another vat, care being taken each time to keep all the solid particles
adhering to the flesh-side. This operation is continued and repeated until
the skins are properly tanned, which takes from 10 to 14 days, depending
on the weather and the temperature. The skins are then removed, rinsed
free of the tanning substances, pressed, dried and finished.” A somewhat
modified form of this process is the so-called Russian tan, which is
usually done in the following manner: 5 parts of bruised barley grains
are mixed with ten parts of luke-warm water in a vat, which is then
covered up. A small quantity of brewers’ yeast is also added to aid in the
fermentation. As soon as the mixture develops a slight heat, one part of
fresh whey is added, and the fleshed skins entered into the tanning liquor
in which they remain for about 12 hours. They are then tramped in the
mixture so as to effect greater penetration, and left until the tanning
process is complete. Whey is the milk fluid left after the casein and most
of the fat have been removed from the milk by coagulation, and consists
practically of a solution of all the milk-sugar or lactose, and the lactic
acid of the milk, together with a small percentage of mineral salts, and
a slight amount of fat. By fermentation, the milk-sugar is converted into
lactic acid, which helps to effect the tan by swelling the skin.

The effectiveness of the fermentation processes depends to a considerable
degree on the action of certain bacteria and yeasts. Bacteria are
one-celled organisms belonging to the vegetable kingdom, and some are so
small as to be scarcely visible under a microscope, while some indeed
cannot be seen by any means, their existence being inferred from their
effects. As they vary in size, bacteria also vary in shape, some being
spherical, others in the form of long, thin rods, while still others are
of a spiral shape; another common form is the dumb-bell shaped bacterium.
Some types are provided with what are known as flagella, which resemble
fine hairs attached to the body of the organism, and which enable it to
move about actively in liquids. The food of bacteria is always in liquid
form, as only in this condition can it be absorbed. However, some kinds of
bacteria attack solid substances from which they obtain their nourishment,
but this is done in an indirect way, by secreting certain fluids known as
enzymes, which dissolve or digest the material and convert it into a form
that can easily be absorbed by the bacteria. The enzymes are non-living
chemical substances, which possess the peculiar property of bringing
about the chemical change of an almost indefinite amount of material
upon which they act, without themselves being in any way changed. Yeasts
also act in a manner similar to the bacteria in causing various chemical
changes, particularly inducing fementations. In the simple “Schrot-beize,”
the starch contained in the bran or barley grains is first converted to
a soluble sugar by means of enzymes secreted by the bacteria which are
always present. This sugar then undergoes an acid fermentation, with
the formation of lactic and acetic acids, due in this case to organisms
known as the _bacterium furfuris A_ and _B_. The action of the Russian
tan is similar, but quicker. In this case, the sugar is already present
in soluble form, and the yeast cells cause its fermentation with the
production of lactic acid. In both cases, the acids as they form swell
and loosen up the skin fibres slowly, the salt penetrating between them,
and keeping them separated on drying. Both methods give results which
are equally good, but by the Russian tan the skins acquire a disagreeable
odor, which makes this method of dressing objectionable.

The lactic acid fermentation processes have an advantage over the pickle,
in that the slow formation of weak organic acids with their gradual action
produce a softer leather, with a gentler ‘feel,’ the presence of the flour
and the grains of the tan, aside from their tanning action, contributing
to the fullness and softness of the leather. There is also less likelihood
of the leather being subsequently affected by the presence of the acid
in it, as lactic and acetic acids are much less injurious than sulphuric
acid to leather. These disadvantages of the pickle can to a large degree,
be overcome without any great difficulty. On the other hand, the matter
of the length of time of the tanning process, shows the acid pickle at
a great advantage, and so, especially for furs other than those obtained
from sheep and goats, the pickle is in most cases used as the principle
method of tanning. In Austria, Russia, and to a certain extent in Germany
also, the “Schrot-beize” is still considerably employed, chiefly for
dressing sheep and lamb skins. The dressing of the various kinds of
Persian lambs, caraculs, astrachans, etc., in the native center of the
industry in Buchara and surrounding districts, is also a “Schrot-beize,”
barley, rice flour or rye flour, and salt water being used to prepare the
skins, the manipulations being essentially the same as those described
above, although carried out in cruder and more primitive fashion.


2. MINERAL TANS

The basis of the tanning of furs by means of solutions of mineral
compounds is the fact that the basic salts of certain metals are capable
of producing leather. It has been found that compounds of aluminum such as
alum or aluminum sulphate, or any other soluble neutral salt of aluminum,
possess tanning powers. Other metals which are capable of forming salts
of the same type are also endowed with the quality of converting skin
to leather under suitable conditions, chromium and iron being the most
important metals in this connection. Chemically these metals all belong
to the same group, and have properties which are very similar in many
respects, the characteristic of most importance for tanning purposes
being the quality of forming soluble basic salts by the addition of
alkalies or alkaline carbonates to solutions of their neutral salts, or
in certain instances simply by the action of water upon these neutral
salts. By neutral salts are meant those in which the metallic content is
combined with the normal proportion of acid; while basic salts are those
in which the acidic portion is present in less than the normal ratio,
being partially replaced by a hydroxide group. When the acid part of
the salt has been entirely replaced in this way, the compound is called
a hydroxide or hydrate of the metal. Between the neutral salt and the
hydroxide several different basic salts are possible, some being soluble,
while others are insoluble. If into a solution containing a basic salt of
either aluminum, iron or chromium a skin be entered, a part of the basic
salt will be precipitated on it in insoluble form. Inasmuch as neutral
salts of these metals when dissolved in water split up to a small degree,
into free acid and soluble basic salt, a skin immersed in such a solution
will also absorb the basic salt in an insoluble form. Upon these facts in
general, depends the action of the mineral tans used in tanning furs.


A. _Alum Tan_

The alum tan is one of the oldest methods of producing leather, being
employed by the Romans about two thousand years ago, and it is believed,
by the Egyptians at a much earlier period. Its extensive use in Europe,
however, dates from the time of the conquest of Spain by the Moors, who
introduced the process.

At the present time, rabbits and moles are tanned by this process, as are
also at times other furs such as muskrats, squirrels, sables, martens,
etc., when a better tan is desired than that produced by the pickle.
Ordinary alum, which is a double sulphate of aluminum and potassium, and
aluminum sulphate are the chief compounds used for this tan. In recent
years, the aluminum sulphate has to a considerable degree replaced the
alum for tanning, inasmuch as it can be cheaply obtained in a sufficiently
pure form, and contains about one and one-half times as much active
aluminum compound as does alum.

While the aluminum salt can be used alone for tanning, it produces a
stiff, imperfect leather, so salt is always added. The ratio of the salt
to the aluminum sulphate or alum can vary within rather wide limits, the
mixtures used in practise ranging from one part of salt to four parts
of the aluminum compound, up to equal parts of both, or even in some
formulas, a greater proportion of salt than of the other constituent.
Ratios which are most common are four of alum to three of salt, or two of
alum to one of salt.

When aluminum sulphate is dissolved in water, a small part of it splits
up into a soluble basic salt and an equivalent amount of free acid. The
reaction may be shown as follows:

  Al₂(SO₄)₃ + 2H₂O = Al₂(SO₄)₂(OH)₂ + H₂SO₄
  aluminum    water  basic aluminum  sulphuric
  sulphate              sulphate       acid

When a skin is entered into such a solution, the free acid is absorbed,
causing a swelling of the pelt. While this is taking place, a further
quantity of the neutral aluminum salt splits up into more basic salt and
free acid. At the same time the basic aluminum sulphate is also taken
up by the skin, probably attaching itself to some of the acidic groups
contained in the skin substance, in a manner analogous to the combination
of the acid with the basic groups of the skin substance. A point is
reached, however, when the skin is no longer able to take up more of the
basic salt, for the presence of the acid undoubtedly acts as a deterrent.
The skin, if dried after such a treatment contains a small amount of
aluminum, which is insufficient to tan the pelt properly, and as a result
this comes out in an undesirable and quite useless condition. If to the
solution of the aluminum sulphate salt is added, a different result is
obtained. To a certain extent the salt acts here as in the pickle. The
skin on absorbing the free acid of the solution naturally swells, but the
salt reduces this swelling, and at the same time, by penetrating between
the fibres and dehydrating them, produces a leather as in the pickle.
In addition, the presence of the salt enables a greater amount of basic
aluminum sulphate to be formed, and thus a greater quantity is taken up
by the skin. On drying and stretching after such a treatment, a soft,
flexible and stretchable leather is obtained.

The number of formulas for tanning furs by this process is legion, the
principle being the same in every instance, and mixtures of salt and alum
or aluminum sulphate form the basis of the various tans. Following are a
few typical formulas, which have been found to be of practical value:

A solution is prepared by dissolving 7.5 lbs. of alum and 3 lbs. of
common salt in 20 gallons of water. When cool, the clean, fleshed skins
are entered, being paddled or drummed for a short time and then allowed
to remain until tanned. By this method the hair also takes up some of the
alum, and if the skins are to be dyed, unevenness may result. In order to
avoid this, the tanning may be effected by brushing a stronger solution
on the pelt. A mixture of 4 lbs. of alum and 3 lbs. of salt, dissolved
in 8 gallons of water, and made into a paste by the addition of 4 lbs. of
flour, is applied to the flesh-side of the skins. These are then placed in
pairs, flesh-side together, and allowed to remain in a pile until tanned.
Sometimes a second application is given. The flour may be omitted, but it
serves to cause the tanning mixture to adhere better to the skins.

Still another method is the following: Into the flesh of the moist,
fleshed skins is rubbed a mixture of two parts of dry powdered alum with
one part of salt. After allowing time for it to be absorbed, another
application is given, rubbing in well, and especially treating the thick
parts. The pelts are then folded up, or rolled together, flesh-side in,
and placed in a vat or tub, which is covered up to prevent drying. They
are left so until tanned, as shown by examination and test. They are then
rinsed, hydro-extracted and dried, and after stretching and finishing, a
soft, white, pliable leather is obtained.


B. _Chrome Tan_

By using chrome alum instead of ordinary alum, together with salt, skins
can be tanned, but the leather formed is not altogether satisfactory.
The basic principle here is the same as in the alum tan, depending on the
formation of soluble basic chrome sulphates in the solution of a neutral
sulphate. The method employed at the present time, the so-called one-bath
process as distinct from the two-bath process, which cannot be applied
for tanning furs, involves the production of the basic chrome sulphate by
the addition of an alkali or an alkaline carbonate to the solution of the
neutral salt. It was Prof. Knapp who first published this process as early
as 1858; but it was not until 1893 that it was shown to be of practical
value, and was then patented in this country by Martin Dennis. Since that
time it has been in general use with but slight modifications.

The chrome tan is used only to a limited extent in the tanning of furs,
the method requiring very careful treatment and accurate supervision
during the various stages of the process, and the leather coming out
colored a pale-blue-green tint, which for some purposes is objectionable.
In some plants ponies and rabbits are tanned with chrome; and when the
skins are to be dyed by means of certain coal tar dyes, they have to
receive a chrome tannage. The leather produced by a chrome tan is very
durable, and possesses great resistance to the action of water.

Any salt of chromium, with either mineral or organic acids, can be used,
but chrome alum is the one most commonly employed. If a skin is entered
directly into a solution of a chrome salt made basic with an alkali, the
precipitation of the insoluble basic salt will take place very rapidly,
and the tanning will be only superficial. The procedure is therefore
first to treat the skins with a chrome solution which forms only small
quantities of the basic salt. After the skins are impregnated with the
solution, this is made basic, so that the real tan will take place within
the skin tissues among the fibres of the corium. A common formula is the
following: 5 lbs. of chrome alum are dissolved in 10 gallons of water.
The skins are entered into the solution at about 70° F. and paddled for
about 2 hours, or drummed for one hour. Then a solution of three pounds
of washing soda is added slowly to the liquor which is then stirred up
well, and the skins drummed or paddled again for an hour or two, and then
left in the liquor for 12 to 24 hours till completely tanned. The skins
are rinsed, and washed in 1/2% solution containing 2/3% of the weight
of the skins of borax. The pelts are then well washed in clean water,
hydro-extracted and dried.


C. _Iron Tan_

Tanning by means of iron salts has thus far been merely a matter of
scientific interest and has not found any practical use. The principle
involved is identical with that of the preceding mineral processes.


3. CHAMOIS TAN

The chamois dressing, as previously noted, is undoubtedly the oldest
method of preparing leather from skin, the various fat-containing
substances derived from animals, fish, birds, etc., being used for the
purpose. The chief object of the fat was to coat the fibres of the skin,
thus preventing their adhesion, and at the same time rendering them
resistant to water. In the true chamois tan, the fat seems to have also
a chemical function in contradistinction to the other which is merely
physical or mechanical. For, if skins tanned by the chamois process
be treated with a weak solution of an alkali, all the fatty materials
should be removed thereby, but this happens only to a small extent, the
pelt retaining its softness and pliability, and the other characteristic
qualities of leather, indicating that the fat is combined intimately with
the skin substance in a permanent fashion.

In tanning furs, various oils and fats are used, but not all are capable
of producing a chamois tan. Among the fatty materials are mineral oils,
and vegetable and animal oils and fats. Mineral oils are the distillation
products of petroleum, partially liquid, and partially solid. Being
inert substances, they have no tanning effect, but serve merely as
water-proofing or fattening materials. Except for their oily nature they
have nothing in common with fats, being quite unaffected by solutions of
alkalies or of acids.

Vegetable and animal fats and oils are, when pure, neutral substances
formed by the combination of fatty acids with glycerine. They possess
the property of saponification, that is, of forming a soap when treated
with an alkali, the soap being the alkaline salt of the fatty acid.
Under certain conditions, the fat can be split up into free fatty acid
and glycerine by the action of acids, or even water alone. Some fats
on long standing, split up in this way spontaneously in the presence of
moist air. As a general rule, those fats which exhibit this property to a
marked degree are affected by contact with the air, due to the absorption
of oxygen which reacts chemically with the fats, forming what are known
as oxy-fatty acids, usually less soluble, and having a higher melting
point than the original fats. Vegetable and animal fatty materials are
classified on the basis of this phenomenon of absorbing oxygen from the
air, those possessing this quality to a great degree being called “drying
oils,” others being “partially drying,” or “non-drying.” Olive oil,
castor oil, cocoanut oil and cottonseed oil are examples of non-drying
or partially-drying vegetable oils, linseed oil being the most important
drying-oil in this class. Tallow, lard, butter-fat, neats-foot oil are
non-drying animal fats, the drying oils being seal oil, whale oil, and
cod-liver oil.

[Illustration: FIG. 8. TRAMPING MACHINE OR “KICKER.”

(_F. Blattner, Brooklyn, New York._)]

For tanning purposes, this property of absorbing oxygen is important,
because only with drying oils can a true chamois tan be obtained,
non-drying oils acting like mineral oils only as water-proofing materials.
The details of the chamois process are not quite clear, there being
considerable difference of opinion on the matter. But all the studies
on the subject tend to prove that there are at least two phases to the
process: first, the mechanical covering of the fibres with the fat, this
property being common to all fats or oils which may be used; and second,
the combination of the fat with the skin in some chemical way, as a result
of the oxidation of the fat, a characteristic found only in the drying
oils. During the oxidation of the fats, the glycerine in them is converted
to acrolein or acryl-aldehyde, which also aids the tanning. It was at one
time supposed that the tanning action was due to this aldehyde alone,
but a chamois tan can be made with fatty substances from which all the
glycerine has been removed. The evidence on this question, however, is
not quite conclusive.

In general, the procedure of the chamois tan is as follows: The
hydro-extracted, fleshed skins are rubbed on the flesh-side with a good
quality of seal-oil. They are then folded up, and put into a ‘kicker,’
where they are tramped for two or three hours to work in the oil. The
kicker is a machine such as shown in Fig. 8 consisting of a receptacle for
the skins, and two wooden hammers which work up and down mechanically,
turning and pounding the skins. (As many as 1000–1500 skins of the size
of musk-rats can be worked at one time in such a machine.) The pelts are
then taken out and hung up in a warm room for several hours, considerable
oxidation taking place. Another coat of oil is then applied, which is
again tramped in, and the skins are hung up once more and exposed to the
air to cause the oil to oxidize. After the skins are sufficiently tanned
they are rinsed in a weak soda solution to remove the excess oil, washed
and dried. When skins with fine hair such as marten, sable, mink, etc.,
receive a chamois tan, they are not tramped in kickers as the delicate
top-hair will be broken, and the value of the skin thereby reduced.
Instead they are placed in small drums, together with metal balls of
varying sizes and weights depending on the particular fur treated, and the
oil is worked in by rotating the drum. Such a ball-drum, as it is called,
is shown in Fig. 9.

[Illustration: FIG. 9. BALL DRUM.

(_F. Blattner, Brooklyn, New York._)]

In conjunction with the chamois tan may be discussed the process of
oiling, inasmuch as the method of application and the effect are both
similar to the chamois tan up to a certain point. It is customary to
treat skins tanned by any other method but the chamois process, with
some oil in order to render them more impervious to water. The greatest
variety of oils and fats can be used, the action in most cases being
simply the mechanical isolation of the skin fibres by such a substance,
thus corresponding to the first or physical phase of the chamois tan.
The chemical phase, if it takes place at all, is usually slight, and
is merely incidental. Oiling is generally applied either before drying
after tanning, or after drying, the oiled skins being placed in a kicker
and tramped to cause the oil to penetrate. In some instances the oiling
material is put in the same mixture as the tanning chemicals, and the
tanning and oiling are effected simultaneously.

Among fatty substances used for oiling are mineral oils, such as paraffine
oil, and vaseline; animal fats, like train oils, butter, egg-yolk,
glycerine, neats-foot oil; vegetable oils, like olive oil, castor oil,
cottonseed oil; also sulphonated castor oil and sulphonated neats-foot
oil. These may be used singly or in various mixtures, an emulsion of an
oil and a soft soap also being frequently employed.


4. FORMALDEHYDE TANS

Formaldehyde has proven to be of great value in the tanning of furs,
usually in conjunction with other processes. Formaldehyde is a gas with
a strong, irritating odor, and its 40% solution, which is the customary
commercial form, also possesses this quality. When skins are treated for
several hours with a very dilute solution of the commercial product, a
leather is obtained which combines the properties of the alum tan and
the chamois tan. Moreover, in the majority of observed cases, where furs
have been tanned with formaldehyde, the skins seem to acquire a certain
immunity to the attacks of vermin and moths. Although the skins do
not in any way retain the odor of the formaldehyde, nevertheless these
destructive agents seem to be repelled.

Numerous processes have been devised which use formaldehyde in connection
with other substances for tanning. Thus in a German patent is described
a method involving the alternate or simultaneous treatment of pelts
with solutions of formaldehyde and alpha or beta naphthol. Both the
formaldehyde and the naphthol exercise tanning actions, but the process
is not used in practise.

In 1911, Stiasny, a well-known leather chemist produced a synthetic
substance by the condensation of formaldehyde with a sulphonated phenol,
forming an artificial tannin. This chemical, called “Neradol D,” exhibits
many of the properties characteristic of true tannins, although in no way
related by structure and composition. By the use of “Neradol D” a soft,
white and flexible leather is obtained, and it is therefore a suitable
tanning material for furs.


5. COMBINATION TANS

In many instances more than one method is employed in tanning the furs,
and in this way what is known as a combination tan is produced. While the
various individual processes described give more or less satisfactory
results by themselves, they generally possess some features, which
for certain purposes may be undesirable, and which can be eliminated
or considerably reduced by using other processes at the same time or
subsequently. Some of the combination methods are, pickle with chrome
tan, alum tan with chrome tan, and formaldehyde tan with pickle, mineral
tan or chamois tan. By means of such combinations various qualities of
tanned furs can be obtained, and if it is desired to produce a pelt having
certain special characteristics, this can be brought about by combining
two or more standard methods.

Some illustrations of combined tannages are the following: Alum-chrome
tan. The skins are tanned by the regular alum process, then the
constituents of the chrome tan are dissolved directly in the same bath,
and the chrome tan is effected as usual. Chrome-formaldehyde tan. To the
regular chrome tan solution is added 1/2 lb. of formaldehyde for every 10
gallons of chrome liquor. The rest of the process is as ordinarily.


6. VEGETABLE TANS

In practise, the vegetable tanning matters are not used for furs, although
in some special instances gambier cutch may be employed occasionally
with some other tan. However, many of these tannins also have dyeing
properties, and are used in dyeing the furs. In this connection it must
be mentioned that furs dyed with these materials also receive a vegetable
tan, which improves the quality of the leather to a considerable extent.


Comparison of The Various Tanning Methods

In choosing a method for tanning any particular kind of fur, several
factors must be considered. The nature of the pelt, insofar as it is weak
or strong; the time, labor and cost of materials required by the tanning
process; the effect on the leather of the different dyes and chemicals
used in dyeing, if the skin is to be dyed, are a few of the points
requiring attention and consideration.

For furs which are only to be dressed, a simple tan like the pickle will
suffice in most cases. Special instances, such as the rabbit and mole
already mentioned, and a few other furs are tanned by the alum method. The
pickle is undoubtedly the cheapest and simplest method of tanning skins,
and yields a soft, white leather which is permanent as long as it is kept
dry. If it is put into water, about 25% of the salt contained within
the pelt dissolves out, and the acid present swells up the tissues. If
the skin is dried in this condition, it will come out hard and brittle,
tending to crack very easily. By treating the leather before drying with a
strong salt solution, a good deal of the extracted salt will be replaced,
and on drying and stretching, it will work out soft. Skins tanned by
the “Schrot-beize” are affected by water in quite the same manner as the
pickled skins.

The alum tan gives a leather similar to that produced by the pickle, but
with the advantage that the skins possess greater stretch and flexibility.
In its resistance to water, the alum-tanned pelt is quite as susceptible
as the other. As a general rule, the skin absorbs about 6% of its weight
of alum from the tanning solution, but gives up three-quarters of this
when it is soaked in water, producing on drying, a hard, stiff leather.
The chrome tan is especially impervious to water, easily resisting
temperatures of 80° C., and even boiling water. It is employed to only
a limited extent on account of the special effort and care required
to obtain satisfactory results, also because the pelt acquires a pale
blue-green color which is not desired on dressed skins. The chamois
tan, and some of the combinations of the formaldehyde tan with the other
methods, give very soft, flexible leathers which possess a sufficiently
great resistance to the effects of water and heat.

In tests made to determine the best working temperatures for dyeing
skins dressed by the salt-acid tan, and for skins dressed by the chamois
process, some very interesting facts were brought out. These two tans
were chosen because they represent opposite extremes, the salt-acid tan
usually giving the poorest results, and the chamois tan giving the best
results in practise in dyeing. Other methods, except the chrome, range
between these two. The procedure in these experiments was to treat the
skins at ordinary temperatures in water, or dilute solutions of the
various chemicals and dyes usually employed in dyeing, and then heat these
solutions until the leather just began to shrink and shrivel up. This
point, called the shrinking point (S.P.), gave the temperature to which
the skins could be subjected in the given solution without danger to the
pelt. (The experiments and observations were made by Erich Schlottauer,
while director of a large German fur dressing and dyeing plant).

The first observation made was that different furs tanned by the same
process were affected differently in the same solutions. Thus in plain
water, three furs, all tanned by the acid-salt tan, had shrinking points
varying by several degrees; similarly with two different furs tanned by
the chamois process, there was a variation in the shrinking point of two
degrees. The explanation of this discrepancy among the different skins may
be that there was a slight difference in the conditions under which they
were tanned, experiments showing that a maximum difference of 4° C. may
exist among skins tanned by the same process, but not under the same or
identical circumstances. Another reason for the variation may be the fact,
that some skins are more greasy than others, and are thus more resistant
to the effects of water or of some chemicals. The furs with the higher
shrinking points in water were those which naturally are more greasy than
the others.

Weak solutions of acids tend slightly to lower the shrinking point, while
weak solutions of alkalies appreciably raise it, in both chamois-tanned
and salt-acid-tanned skins. Solutions of dyes and mordants as a general
rule increase the resistance of the skin to heat, varying quantities of
these substances having no, or little different effects on the shrinking
points. Previous treatment of the leather with some oil considerably
raises the shrinking point of the pelt. Formaldehyde effects a great
increase of the resistance of the skins to heat, especially with
chamois-tanned furs. The experiments in this case were made by first
treating the skins in the weak formaldehyde solution, and then determining
the shrinking point in plain water.

Two skins, both dressed by the “Schrot-beize,” a Persian lamb and an
astrachan, after dyeing had shrinking points almost 10 degrees higher than
when undyed. The extra tannage which the skins received from the tannins
used in the dye mixtures for these furs, accounts for this increased
resistance to heat.

The following tables give the observed figures in the different
experiments:

                  TABLE I
  +-------------------+------+------+------+
  |                   |  A   |  B   |  C   |
  |                   | S.P. | S.P. | S.P. |
  +-------------------+------+------+------+
  |_Salt-acid Tan_    |  C.  |  C.  |  C.  |
  |Australian Opossum |  46° |  58° |  45° |
  |Marmot             |  45° |  50° |  42° |
  |Skunk              |  47° |  56° |  43° |
  |                   |      |      |      |
  |_Chamois Tan_      |      |      |      |
  |Mink               |  52° |  61° |  45° |
  |Muskrat            |  50° |  58° |  42° |
  +-------------------+------+------+------+
    A--Water
    B--Water plus 1% Ammonia (s.g. 0.910)
    C--Water plus 1% Sulphuric acid (66°
        Beaumé)

                  TABLE II
  +-------------------+------+------+------+
  |                   |  A   |  B   |  C   |
  |                   | S.P. | S.P. | S.P. |
  +-------------------+------+------+------+
  |_Salt-acid Tan_    |  C.  |  C.  |  C.  |
  |Australian Opossum |  53° |  52° | 54°  |
  |                   |      |      |      |
  |_Chamois Tan_      |      |      |      |
  |Mink               |  59° |  59° |  59° |
  +-------------------+------+------+------+
    A--1000 c.c. water plus 40 c.c.
        Peroxide plus 5 c.c. ammonia
    B--500 c.c. water plus 2 grams Ursol D
        (Para-phenylene-diamine)
    C--500 c.c. water plus 5 grams Ursol D

                      TABLE III
  +-------------------+------+------+------+------+
  |                   |  A   |  B   |  C   |  D   |
  |                   | S.P. | S.P. | S.P. | S.P. |
  +-------------------+------+------+------+------+
  |_Salt-acid Tan_    |  C.  |  C.  |  C.  |  C.  |
  |Australian Opossum |  51° |  51° |  53° |  56° |
  |                   |      |      |      |      |
  |_Chamois_          |      |      |      |      |
  |Mink               |  59° |  59° |  61° |  62° |
  +-------------------+------+------+------+------+
    A--500 c.c. water plus 5 grams ground
        nut-galls
    B--300 c.c. water plus 2 grams pyrogallic
        acid
    C--500 c.c. water plus 2 grams potassium
        bichromate
    D--Water, after treating leather with
        rapeseed oil

                      TABLE IV
  +-------------------+------+------+------+------+
  |                   |  A   |  B   |  C   |  D   |
  |                   | S.P. | S.P. | S.P. | S.P. |
  +-------------------+------+------+------+------+
  |_Salt-acid Tan_    |  C.  |  C.  |  C.  |  C.  |
  |Australian Opossum |  49° |  49° |  55° |  50° |
  |                   |      |      |      |      |
  |_Chamois Tan_      |      |      |      |      |
  |Mink               |  59° |  67° |  69° |  70° |
  +-------------------+------+------+------+------+
    A--500 c.c. water plus 5 c.c. formaldehyde
        for 1 hour
    B--500 c.c. water plus 5 c.c. formaldehyde
        for 12 hours
    C--500 c.c. water plus 10 c.c. formaldehyde
        for 3 hours
    D--As in C, but treated with 500 c.c. water
        plus 5 c.c. ammonia, instead of water
        alone.

            TABLE V
  +-------------+------+------+
  |             |  A   |  B   |
  |             | S.P. | S.P. |
  +-------------+------+------+
  |             |  C.  |  C.  |
  |Persian Lamb |  44° |  54° |
  |Astrachan    |  47° |  55° |
  +-------------+------+------+
    A--Before dyeing
    B--After dyeing

As a result of these experiments it may be concluded that the maximum
temperature for drying salt-acid tanned skins should be 40° C., while
for chamois tanned skins the temperature may be permitted to reach 45° C.
without any danger of the leather being affected. Moreover, in the case
of pickled skins, the matter of extraction of the tanning agent, as well
as that of the leather becoming “burned” may be effectively counteracted
by brushing some oil or fat on to the leather side before dyeing the pelt.

The shrinking points of skins dressed by the various tanning methods are
constant within certain limits, depending on the nature of the skin and on
the conditions of tanning, and it is possible by observing the shrinking
point, in conjunction with other characteristics of a given pelt, to
determine what method of tanning was used.




CHAPTER VI

FUR DRESSING

DRYING AND FINISHING


One of the most important operations of all the fur dressing processes is
the drying of the skins. For even when all the previous steps have been
successfully completed, there is still a great possibility of the skin
being injured if the drying is not properly and carefully carried out.

The essential requirements for good drying are proper temperature,
uniformity and rapidity. The leather part of the fur cannot, in the
moist state, resist temperatures exceeding about 45° centigrade, for when
dried, the skin turns out hard and stiff, and cracks easily. The furs must
therefore be dried at an initial temperature of 25° to 30° centigrade, and
as the moisture is gradually removed, the temperature may be raised, for
the less water that remains in the pelt, the less is the leather affected
by the heat, and the more difficult is the removal of its aqueous content.

If the drying process is not a uniform one, that is, if all the skins
in a lot are not subjected to the same drying conditions, then after the
drying has proceeded for a certain time, some skins may be quite dry while
others are not, or there may be as many different degrees of dryness as
there are skins drying. There is also the possibility of great variation
in the amount of moisture removed from different parts of the same skin.
Such a state of affairs requires an extra expenditure of time, labor
and heat power in order to get the whole lot of furs into a more or less
uniform condition. Moreover in some kinds of furs, especially those with
thick skins, when the drying is not even, there is danger of the epidermal
layer drying away from the corium, and subsequently peeling and cracking.
Uniformity of drying requires the maintenance of a reasonably constant
temperature equally distributed throughout all parts of the space where
the drying is done, so that all the furs may be dried under the same
conditions.

Rapidity of drying is desirable not only because it is beneficial to
the condition of the pelt, but also from the point of view of practical
business economy. The space occupied by the drying should be as small
as possible compatible with the volume of work, and with the efficiency
of operation. Slow drying involves the use of much space to take care of
all the skins to be dried, or an accumulation of pelts ready to be dried,
neither of which conditions is efficient or desirable.

It was formerly the general custom, still practised in some
establishments, to dry the skins by hanging them up, leather-side out on
lines in a large room or loft, the heat being usually supplied by steam
pipes. Such a procedure occupied often as long as two or three days to
get complete drying, involved a great deal of labor, and the results were
far from uniform. In fact, in order to get the skins more nearly equable,
it was necessary to subject them to an additional operation. This usually
consisted of rotating the skins in a closed drum for several hours, the
constant intermingling of the pelts in contact with each other causing
any moisture left in them to be evenly distributed throughout the whole
lot. The skins, by this process also are rendered somewhat softer and more
flexible, but by drying under proper conditions the entire extra operation
can be dispensed with, the furs coming out quite as soft and flexible
without the drumming.

A great improvement was the adoption of large fans to circulate the heated
air in the loft, thereby approaching more nearly an even temperature.
More modern devices have, however, been developed, whereby drying can be
effected in the most uniform manner, with perfect control of temperature,
and requiring the least possible consumption of space, time, labor and
power. A typical arrangement consists of a large closed chamber, generally
constructed of steel, and divided into several compartments each of which
may be operated independently of the others. Air, heated over suitably
located steam pipes to the required temperature, is forced through the
various compartments by means of fans operated by power. The conditions
may be varied in each compartment, as to temperature or humidity, both
of which can easily be regulated, or all the compartments may be used
together as one unit. The skins are hung up on rods or lines in the
compartments, or on special frames for the purpose, which are then entered
into the compartments and the doors shut. The dry, heated air is forced
to pass over the skins, and takes up their moisture. At the further end
of the drying chamber is another fan which removes the moisture-laden air
after it has done its work. The drying is effected in from 6 to 24 hours,
and all skins are obtained in the same condition, for the process is quite
uniform and regular.

Within recent years there has been evolved a highly efficient and
economical drying equipment, based on a somewhat different principle
than underlies any of the foregoing methods. The conveyor type of dryer,
as it is called, is admirably suited to the needs of the fur dressing
and dyeing industry, and is undoubtedly superior to any of the previous
systems of drying furs, in that it affords an enormous saving of space,
time, labor and power, and gives greater uniformity and presents better
working conditions.

[Illustration: FIG. 10. DIAGRAMMATIC VIEWS OF CONVEYOR DRYER. _a._ SIDE
VIEW; _b._ END VIEW.

(_Proctor & Schwartz, Inc., Philadelphia._)]

The conveyor dryer consists essentially of a steel enclosure, through
which the skins pass on horizontal conveyors. Where special insulation
is necessary, asbestos panels are used to line the enclosure, making the
dryer absolutely fireproof, and enabling the maximum utilization of heat.
In the middle of the dryer are located the steam coils which furnish
the heat, and in many instances exhaust steam can be used as the source
of heat. Figure 10 shows diagrammatically the arrangement and operation
of the conveyor type of dryer. The enclosure is divided into several
compartments, in each of which a different condition of temperature and
humidity is maintained, the temperature being closely and accurately
regulated by an automatic control, and once the dryer has been set for
any condition, all skins will be dried exactly the same, regardless of
weather or season.

[Illustration: FIG. 11. CONVEYOR DRYER.

(_Proctor & Schwartz, Inc., Philadelphia._)]

The skins to be dried are placed on poles which in turn are set on
the horizontal conveyors as in Fig. 11. As the skins pass through the
compartments, large volumes of air, heated to the required temperature
over the steam coils, are circulated among the skins by means of the fans.
Exhaust fans, properly placed, remove a certain quantity of moisture-laden
air when it has accomplished its full measure of work. When the skins on
the conveyors have passed the full length of the dryer, they are entirely
dry, and are then removed from the poles. (Fig. 12). The time required
for drying varies according to the nature of the fur from 1–2 hours to 6–8
hours. In tests made to determine the relative efficiency of the conveyor
type of dryer as against the old “loft” method, it was found that there
was a saving of over 50% in power, and of 85% in floor space, as well as
a great saving of labor, when the conveyor system was used, the number
of skins dried in a given period of time being the same in both cases.
The advantages of the new method are easily apparent, and the saving
is sufficiently great with large lots of furs, to make an appreciable
difference in the final cost of dressing.

If the skins have been dried by a modern drying system they all come out
in a uniform condition, and are ready to go on immediately to the next
operation. If, however, a form of the “loft” method of drying has been
used, it is customary to subject the skins to an additional process. The
dried pelts are put in drums with damp sawdust, and drummed for a short
time in order to get them into the proper condition. The drumming is
essential for the purpose of equalizing the condition of the pelts, some
being drier than others, and as a consequence of the contact with the
moist sawdust, they are all brought to the same degree of dryness. As a
result of this operation also, the skins become considerably softened.

[Illustration: FIG. 12. DELIVERY END OF CONVEYOR DRYER.

(_Proctor & Schwartz, Inc., Philadelphia._)]

Then if the pelts have not been previously oiled during the tanning
process, or prior to the drying, they receive this treatment now. The oil
or fat is applied to the leather side of the furs, which are then placed
in the tramping machine for a short time in order to cause the oil to be
forced into the skin. The fibres of the corium thus become coated with a
thin layer of fatty material, which contributes greatly to the softness
and flexibility of the pelt, and increases its resistance to the action of
water, and also, in certain instances a partial chamois tan is produced,
thereby improving the quality of the leather.

[Illustration: FIG. 13. STRETCHING MACHINE FOR CASED SKINS.

(_Reliable Machine Works, Evergreen, L. I._)]

The skins are now returned to the work bench, and subjected to the
stretching or “staking” process. This consists in drawing the skin in all
directions over the edge of a dull blade, which is usually fixed upright
in a post with the edge up. Or, the stretching may be done on the fleshing
bench, substituting a dull blade for the fleshing knife. Recently staking
machines are being used in the larger establishments, the work being
done much more quickly and efficiently. As a result of this operation,
the leather becomes very soft and flexible, every bit of hardness and
stiffness being eliminated, and the skins receive their maximum stretch,
thereby giving the greatest possible surface to the pelage. This not only
helps to bring out the beauty of the hair, but is also a decided advantage
from the economic point of view, as a considerable saving of material
is effected in this way, sometimes even to the extent of twenty-five per
cent. Cased skins are stretched in a somewhat different manner, by means
of stretching irons. These consist of two long iron rods joined by a pivot
at one end. The skins are slipped on to the irons, which are then spread
apart, and in this way the skins are stretched and softened. A machine
which does this work very efficiently is shown in Fig. 13. The skin is
drawn onto the stretching arms, in this case made of bronze, which are
then forced apart by pressing on a pedal. When properly stretched to the
maximum width in all directions possible, and thus thoroughly softened,
the skin can easily be reversed, that is, turned hair-side out. As many as
6000 skins can be stretched, or 4000 to 5000 skins stretched and reversed
by one man in one day on such a machine.

[Illustration: FIG. 14. FUR BEATING MACHINE.

(_S. M. Jacoby Co., New York._)]

The pelts are then combed and beaten. In smaller plants these operations
are done by hand, but suitable machines are being employed. In order to
straighten out the hair, it is combed or brushed. Then in order to loosen
up the hair, and to cause it to display its fullness, the furs are beaten.
This process is also done by hand in some establishments, but up-to-date
places use mechanical devices for this purpose. A type of machine which
has proven very successful, and is enjoying considerable popularity
is shown in Fig. 14. These machines are also made with special suction
attachments which remove all dust as it comes out of the beaten skin,
thereby making this formerly unhealthful operation thoroughly sanitary
and hygienic.

The final process is drum-cleaning. This operation is intended
specifically for the benefit of the hair part of the fur, and is very
important inasmuch as the attractive appearance of the fur depends largely
upon it. The drum, such as is shown in Fig. 15 is generally made of wood,
or sometimes of wood covered with galvanized iron. The skins together with
fine hardwood sawdust are tumbled for 2 to 4 hours, or sometimes longer.
Occasionally a little asbestos or soapstone is added to the sawdust; for
white, or very light-colored skins, gypsum or white sand is used, either
alone, or in admixture with the sawdust; and for darker skins, graphite or
fine charcoal is sometimes added in small quantities. The drum-cleaning
process polishes the hair, giving it its full gloss and lustre, and at
the same time absorbing any oil or other undesirable matter which may be
adhering to the hair as a result of the washing and tanning processes.
Any soap, or traces of mordant are wiped off and so removed, and by using
heated sawdust, or heating the drum while rotating, the fur acquires a
fullness and play of the hair which are great desiderata in furs. The
sawdust must then be shaken out of the furs. This is done by cageing. In
some instances, the drum itself can be converted into a cage, by replacing
the solid door with one made of a wire screen. (Fig. 16.) Usually,
however, the skins are removed from the drum and put in a separate cage,
which is built like the drum, but has a wire net all around it, through
which the sawdust falls, while the skins are held back. The cages are
generally enclosed in compartments in order to prevent the sawdust from
flying about and forming a dust which would be injurious to the health of
the workers. In large establishments, the drum-cleaning machinery occupies
a large section of the plant, many drums and cages being used, and special
arrangements being made to take care of the sawdust which can be used over
again several times, until it becomes quite dirty.

[Illustration: FIG. 15. DRUM. (COMBINATION DRUM AND CAGE AS A DRUM.)

(_F. Blattner, Brooklyn, New York._)]

[Illustration: FIG. 16. CAGE. (COMBINATION DRUM AND CAGE AS A CAGE.)

(_F. Blattner, Brooklyn, New York._)]

With this operation ends the ordinary procedure of fur dressing. But
there are several additional processes required in the treatment of
certain furs, which are generally undertaken by the dresser, and chief
among these are shearing and unhairing. Sometimes this work is done in
separate establishments organized solely for this business. Certain kinds
of furs, among them being seal, beaver and nutria, possess top-hair which
may detract from the beauty of the fur, the true attractiveness being in
the fur-hair. The top-hairs are therefore removed, and for this purpose
machines are now being used. Formerly this work was all done by hand, and
on the more expensive furs like seal and beaver, unhairing is now done on
a machine operated by hand. The principle of the process is as follows:
The skins are placed on a platform and the hair blown apart by means of
a bellows. The stiff top-hairs remain standing up, and sharp knives are
brought down mechanically to the desired depth, and the hair is cut off
at that point. The skin is then moved forward a short distance, and the
process repeated until all the top-hairs have thus been cut out. With
muskrats, or other pelts which do not require such very careful attention,
the whole process is done automatically on a machine. The fur-hair is
brushed apart by means of brushes and a comb, and at regular intervals,
sharp knives cut off the top-hairs. Several hundred skins can be unhaired
in a day on such a machine requiring the attention of only one man. A
machine for unhairing skins is shown in Fig. 17.

[Illustration: FIG. 17. UNHAIRING MACHINE.

(_Seneca Machine & Tool Co., Inc., Brooklyn, N. Y._)]

With other furs, such as rabbits, hares, etc., where the trouble of
unhairing would be too great commensurate with its advantages, the hair
is sheared instead. The top hair is cut down to the same length as the
under-hair by means of shearing machines which can be regulated to cut to
any desired length of hair. A typical device for shearing furs is shown
in Fig. 18.

[Illustration: FIG. 18. FUR-SHEARING MACHINE.

(_Seneca Machine & Tool Co., Inc., Brooklyn, N. Y._)]




CHAPTER VII

WATER IN FUR DRESSING AND DYEING


The assertion has often been made, although its absurdity is now quite
generally realized, that the success of the European fur dressers and
dyers, particularly in Leipzig, is due to the peculiar nature of the
water used, which is supposed to be especially suited for their needs.
The achievements in this country in the fur dressing and dyeing industry
during the past few years are ample and sufficient answers to the claim of
foreign superiority in this field no matter what reason may be given, and
particularly when the quality of the water used is advanced as a leading
argument. For the water employed by the establishments in and about New
York, as well as in other sections of the country is surely not the same
as the water of Leipzig, yet the work done here is in every respect the
equal of, if not better than the foreign products.

It is interesting to note that similar rumors were current here in the
early period of the development of the American coal-tar industry since
1914. Our efforts to establish an independent dyestuff industry were
doomed to failure, according to those who circulated the stories, because
we did not have the water, which they claimed was responsible for the
German success. The present status of the American dye business, in its
capacity satisfactorily to supply most of the needs of this country and
of others as well, speaks for itself.

However, as is often the case with such erroneous assertions, there
is just enough of an element of truth in the statement regarding the
peculiar qualities of certain kinds of water, to make the matter worthy
of consideration. Water is certainly a factor of great importance in fur
dressing and dyeing, and it is not every sort of water that is suitable
for use. This fact was recognized by the early masters of the art, for
they invariably used rain-water as the medium for their tanning and dyeing
materials, and their choice must be regarded as an exceedingly wise one.
While the necessity for giving consideration to the quality of the water
for fur dressing purposes is great, it is in fur dyeing that the effects
of using the wrong water are largely evident, and so extra care must be
exercised in the selection of water for this purpose.

The essential requirements for a water suitable for the needs of the
fur dressing and dyeing industry, are: first, a sufficient, constant
and uniform supply; and second, the absence of certain deleterious
ingredients. Chemically pure water is simply the product of the
combination of two parts by volume of hydrogen with one part by volume
of oxygen. Such water can only be made in the laboratory, and is of no
importance in industry. For practical purposes, distilled water may be
regarded as the standard of pure water. Here, too, the cost and trouble
involved in the production of distilled water on a large scale is
warranted only in a certain few industrial operations. A natural source
of water which in its character most nearly approaches distilled water
is rain. In fact, rain-water is a distilled water, for the sun’s heat
vaporizes the water from the surface of the earth forming clouds, which
on cooling, are condensed and come down as rain. Rain-water is usually
regarded as the purest form of natural water. Exclusive of the first
rain after a dry period, rain-water is quite free of impurities, except
possibly for a small percentage of dissolved atmospheric gases, which
are practically harmless, and which can usually be readily eliminated
by heating the water. Moreover, rain-water is quite uniform in its
composition throughout the year in the same locality, and it possesses
all the desirable qualities of a water suited for fur dressing and dyeing
purposes. Formerly when the quantity of water used in the industry
was comparatively small, the supply from rain was sufficient to meet
all the requirements. But now, when tremendous quantities of water are
used constantly, rain-water is no longer a feasible source, and other
supplies must be utilized, although in a sense, all water may be traced
to rain-water as its origin.

When rain-water falls on the earth it either sinks into the ground until
it reaches an impervious layer, where it collects as a subterranean
pool, forming a well, or continues to flow underground until it finally
emerges at the surface as a spring; or on the other hand the rain-water
may sink but a short distance below the surface, draining off as ponds,
lakes or rivers. In the first case the water is called ground water, in
the latter it is known as surface water. Ground water usually contains
metallic salts in solution, and relatively little suspended matter. If
the water has percolated through igneous rocks, like granite, it may be
quite free even of dissolved salts, and such water is considered “soft.”
If, however, the rocky formations over which, or through which, the water
has passed contain limestone or sandstone, or the like, salts of calcium
and magnesium will be dissolved by the water. The presence of the lime
and magnesia salts, as well as salts of aluminum and iron, in the water,
causes it to be what is termed “hard.” Surface water is more likely to
contain suspended matter, with very little of dissolved substances.
Suspended matter, like mud, contains much objectionable matter such
as putrefactive organisms and iron, but most of these materials can be
removed by filtration or sedimentation, and seldom cause any difficulties.

Hardness in water is generally the chief source of trouble when the water
is at fault. Hardness may be of two kinds, either permanent, or temporary,
or sometimes both are found together. Water which is permanently hard
usually contains the lime and magnesia combined as sulphates. Temporary
hardness, on the other hand, is due to the presence of lime and magnesia
in the form of bicarbonates, the carbon dioxide contained in the water
having dissolved the practically insoluble carbonates:

    CaCO₃  +  CO₂  +  H₂O  =  Ca(HCO₃)₂
   calcium   carbon  water     calcium
  carbonate  dioxide         bicarbonate

Temporary hardness can be eliminated by heating the water, the carbon
dioxide being expelled and the carbonates of lime and magnesia being
precipitated and then filtered off. Both permanently and temporarily hard
waters can be softened by the addition of the proper chemical, such as
an alkaline carbonate like sodium carbonate. This precipitates insoluble
carbonates of the lime, magnesia, iron and aluminum, leaving a harmless
salt of sodium in solution in the water. The sludge is allowed to settle
in tanks before the water is used.

In fur dressing and dyeing, water is employed for soaking and washing the
skins, dissolving chemicals, extracts and dye materials, and also for
steam boilers. A small amount of hardness in the water is not harmful,
and up to 10 parts of solid matter per 100,000, may be disregarded.
Permanent hardness is particularly objectionable in water for boiler
purposes, as it forms scale. The effect of the impurities of the water
depends on the nature of the chemicals and dyes used. Where acids are
used in solution compounds of magnesium, lime and aluminum will generally
not interfere. Hard water must not be used for soap solutions, as sticky
insoluble precipitates are formed with the soap by the metals, this
compound adhering to the hair, and being difficult to remove, will cause
considerable trouble in subsequent dyeing. An appreciable loss of soap
also results, as one part of lime, calculated as carbonate will render
useless twelve parts of soap. In tanning or mordanting, where salts of
tin, aluminum or iron are employed, hard water should not be used, as lime
and magnesia will form precipitates with them. Bichromates will be reduced
to neutral salts, and cream of tartar will also be neutralized. With dyes
also, hard water has a deleterious effect. Basic dyes are precipitated by
this kind of water, rendering part of the dye useless, and also causing
uneven and streaky dyeings. Sometimes the shades of the dyeings are
modified or unfavorably affected. Considerable quantities of lime and
magnesia in the water will cause duller shades with logwood and fustic
dyeings. The presence of iron, even in very slight quantities generally
alters the shade, darkening and dulling the color.

These facts were apparently all recognized and understood by the fur
dressers and dyers of an earlier period, for instead of utilizing the
water of lakes and streams near at hand, which afforded a more constant
supply, but which contained harmful impurities, they collected the
rain-water, which was always soft. Whether they realized the nature
and character of the substances that make water hard is uncertain,
but they were always careful to avoid such water. At the present time
establishments located in and about large cities like New York, where
the majority of American fur dressing and dyeing plants are situated,
have no trouble about the water. The cities supply water which is soft,
suitable alike for drinking and industrial purposes. Other plants, not
so fortunately situated, often have to employ chemical means to treat the
water so as to make it suitable for use.




CHAPTER VIII

FUR DYEING

INTRODUCTORY AND HISTORICAL


In discussing fur dyeing, the question naturally arises, “Why dye furs at
all? Are not furs most attractive in their natural colors, and therefore
more desirable than those which acquire their color through the artifices
of man?” The answer cannot be given simply. Natural furs of the more
valuable kinds are indeed above comparison with the majority of dyed furs.
Yet there are several reasons which fully justify and explain the need
for fur dyeing, for at the present time, this branch of the fur industry
is almost as important and indispensable as the dressing of furs.

The first application of dyeing to furs, had for its purpose the
improvement of skins which were poor or faulty in color; or rather, the
object was to hide such defects. As nearly as can be ascertained, this
practise was instituted at some time during or before the fourteenth
century, for fur dyeing seems to have been common during that period, as
is apparent from the verses of a well-known German satirist, Sebastian
Brant, who lived in the latter part of the fourteenth century:

    “Man kann jetzt alles Pelzwerk färben,
    Und tut es auf das schlechste gerben.”

However, at a later period, there was a general condemnation of the dyeing
of furs, and among the list of members of the furrier’s guilds, none can
be found who are described as dyers. There is a record of a decree issued
by a prince in a German city in the sixteenth century, prohibiting the
practise of fur dyeing. Inasmuch as furs were worn only by the nobility
and certain other privileged classes, and also were very costly, there
was great profit to be had by dyeing inferior skins so as to disguise the
poor color, and then selling such furs at the price of superior quality
skins. This was undoubtedly the reason for the prohibitory decree, but
there were some who continued to practise the forbidden art in secret,
using secluded and out-of-the-way places for their workshops, and mixing
their carefully-guarded recipes with as much mystery as the witches did
their magic potions. These circumstances probably account for the great
amount of mystery which has been, and still is to a considerable degree,
attached to fur dyeing, and also explains the opprobrium and distrust with
which fur dyers were formerly regarded.

Even at the present time, dyeing is often employed to improve furs which
are faulty in color. It frequently happens, that in a lot of skins there
are some which are considerably off shade, or in which the color is such
as to appreciably reduce their value below the average, the hair being
usually too light a shade, or of uneven coloring. By carefully dyeing
these skins of inferior color, they can be made to match very closely
the best colored skins of the particular lot of furs, and consequently
increase their value. With most of the cheaper kinds of furs, the trouble
and cost of improvement by dyeing would not be worth while today; but with
some of the more valuable furs, and especially such as are very highly
prized, like the Russian sable, or marten, or chinchilla, the darkening
of light skins by the skillful application of fast dyes to the extreme
tips of the hair, will increase their value sufficiently to warrant the
expense. This dyeing or “blending” as it is called in such cases, is done
in such a clever and artistic manner that only experts can distinguish
them from the natural. Dyeing used for such purposes is not objectionable,
provided the skins are sold as dyed or “blended.”

There are certain kinds of furs, such as the various lambs, Persian,
Astrachan, Caracul, etc., which are never used in their natural color,
because it is usually of a rusty brownish-black. These are furs possessing
valuable qualities otherwise, so they are dyed a pretty shade of black,
which brings out the beauty of the fur to the fullest extent. Sealskins
are also dyed always. Formerly they were dyed a deep, rich dark brown,
resembling the finest shades of the natural color, but now the seals are
dyed black with a brownish undertone, a color quite different from the
natural. While these two instances cannot be said to be cases of dyeing
to disguise faulty color, they are examples of improvement of color by
dyeing.

Closely associated with the use of dyes to increase the value of a fur
by improving its color, is the dyeing of skins of a certain lot of furs
to produce a uniform shade, thereby facilitating or to a considerable
degree eliminating the task of matching the skins by the furrier. This is
usually done only on skins which are quite small, of which a great many
are needed in the manufacture of fur garments, because the matching of
several hundred skins would entail too much time and labor commensurate
with the value of the fur. The most notable instance of the use of dyes to
produce a uniform shade on furs is the case of the moleskin. Occasionally,
furs are dyed after being made into garments, by careful application of
dyes, in order to obtain certain harmonious effects, such as uniformity
of stripe, or to produce a desired gradation of shade among the different
skins comprising the garment.

Not infrequently, the great variety of shades and color schemes which
Nature provides in the different furs, becomes insufficient to satisfy the
desire of the fur-wearing public for something new. The whims of fashion
always require some novel effect, even though it be for only one season.
To meet this demand for novelty, fantasy or mode shades are produced on
suitable furs,--colors which do not imitate those of any animal at all,
but which, nevertheless, strike the popular fancy. It often happens that
such a color becomes quite popular, and enjoys a considerable vogue, to
the great profit of those who introduced the particular color effect. The
best ones, however, meet with only a comparatively short-lived demand,
being soon superseded by different color novelties.

The basis, though, of the greatest proportion of fur dyeing at the present
time, is the imitation of the more valuable furs on cheaper or inferior
skins. With the gradual popularization of furs as wearing apparel since
the beginning of the last century, the demand for furs of all kinds
has increased enormously. The supply of furs, on the other hand, and
especially of the rarer kinds, has had difficulty in keeping pace with
the requirements, and as a result there is a shortage. A very effective
means of relieving this shortage, to a great degree, at any rate, is
the dyeing of imitations of the scarcer furs on cheaper skins. There
are many animals among the more common, and more easily obtainable ones,
whose skins are admirably suited as the basis of imitations of the more
costly furs. Some of the furs which are adapted for purposes of dyeing
imitations are marmot, red fox, rabbit, hare, muskrat, squirrel, opossum,
raccoon, and many others, and the imitations made are those of mink,
sable, marten, skunk, seal, chinchilla, etc., and indeed, there are very
few valuable furs, which have not been dyed in imitation on cheaper pelts.
On account of the general mystery which formerly surrounded fur dyeing
establishments, and which has persisted to this day, although to a lesser
degree, many peculiar notions were held, even by those in the fur trade,
concerning the production of imitations. The idea that in order to “make”
a certain fur out of a cheaper skin, it was necessary to use the blood
of the animal imitated, is typical of the conceptions of fur dyeing held
not so long ago. To-day, while the knowledge generally possessed about
this branch of the fur industry is meagre and vague, the air of mystery
and secrecy has become somewhat clarified, and such ideas as are current
about fur dyeing are more rational than formerly.

The dyeing of imitations is quite an artistic kind of work, and indeed
fur dyeing ought to be classed among the finest of industrial arts. Some
of the reproductions achieved by dyers on a commercial scale are truly
admirable. The possibility of imitating the finer furs on cheaper skins
naturally led to abuse, the dyed furs being passed off frequently on the
unsuspecting and uninformed buyer as the genuine original. In fact, this
practise became so flagrant that in England laws were enacted to remedy
the evil. At the present time, dyed furs are all sold as such, although
there always may be some unscrupulous merchants who seek to profit by
deception. Some of the imitations and the names of the furs for which they
were sold, are as follows:

  Muskrat, dyed and plucked        sold as seal
  Nutria, plucked and dyed         sold as seal
  Nutria, plucked and natural      sold as beaver
  Rabbit, sheared and dyed         sold as seal or electric seal
  Otter, plucked and dyed          sold as seal
  Marmot, dyed                     sold as mink or sable
  Fitch, dyed                      sold as sable
  Rabbit, dyed                     sold as sable
  Rabbit, dyed and sheared         sold as beaver
  Muskrat, dyed                    sold as mink or sable
  Hare, dyed                       sold as sable, fox, or lynx
  Wallaby, dyed                    sold as skunk
  White rabbit, natural            sold as ermine
  White rabbit, dyed               sold as chinchilla
  White hare, dyed or natural      sold as foxes, etc.
  Goat, dyed                       sold as bear, leopard, etc.

This list serves to indicate but a few of the great number of
possibilities which are available for the fur dyer to produce imitations
of the better classes of furs. Needless to say, these imitations cannot,
as a general rule, equal the originals, because while the color is one
of the most important features in judging the fur, the nature of the
hair, gloss, waviness, thickness, and also the durability are essential
considerations, and it is only in certain instances that skins used
for imitations approach the originals in these respects. However, for
the purposes and desires of the majority of people who wear furs, the
imitations are deemed quite satisfactory, and they also have the advantage
of being cheaper than the natural originals.

For whichever reason furs are dyed, there is no doubt that the art of fur
dyeing is one of the most difficult kinds of application of dye materials.
In the dyeing of the various textiles, either as skein or woven fabric,
the material is of a uniform nature, and therefore the dye is absorbed
evenly by the fibres. Moreover, textiles are dyed at, or near the boil,
the dyestuff being more uniformly and permanently taken up from solution
by the fibre at elevated temperatures.

How different is the case with furs! Far from being homogeneous, furs
present the greatest possible diversity of fibres to be dyed. As already
noted elsewhere, fur consists of two principal parts, the hair and the
leather, differing widely in their actions toward dyes. As a general
rule, the leather absorbs dyestuffs much more readily than the pelage,
and inasmuch as fur dyeing is intended mainly and primarily to apply to
the hair, there is usually an appreciable loss of dye material due to its
being absorbed by the leather, and thereby rendered unavailable for dyeing
the hair. This fact must be taken into account in the dyeing of furs, and
the methods must be adapted accordingly.

With reference to the hair itself, not only has each class of furs
hair of a different kind, but even in the same group there is always a
considerable divergence in the properties of the hair. The fur-hair, being
more or less of a woolly nature, takes up the dye with comparative ease,
while the top-hair is quite resistant to the action of all dye materials.
As pointed out in the discussion of the nature of fur, on different parts
of the same pelt the hair varies in its capacity for absorbing coloring
matters. The color of the hair, also frequently presents a great variety
throughout the skin, both in fur-hair and top-hair. Yet with all this lack
of uniformity and homogeneity, the dyed fur must be of an even color,
closely approaching the natural, gently graded and without any harsh or
unduly contrasted effects. The natural gloss of the hair, one of the most
valuable qualities of the fur, must be preserved. This is by no means
a simple matter, for the luster is affected by dyes and chemicals with
comparative ease, and especially careful treatment is necessary to prevent
any diminution of the gloss.

When the leather part of the fur is exposed to solutions of a temperature
exceeding 40°–50° centigrade, it soon shrivels up or shrinks, and on
drying the pelt, becomes hard and brittle, and therefore quite useless.
Methods of fur dyeing have to take into consideration this fact, and the
temperature of the dyebath must not be greater than 35°–40° centigrade. To
be sure, certain dressings make furs capable of withstanding much higher
temperatures, but their applicability is not universal, being suited only
for a very limited special class of dyestuffs. (V. Fur Dressing). The
necessity for employing comparatively low temperatures, coupled with the
great resistance of the hair to the absorption of dye, even at much higher
temperatures, makes fur-dyeing a very difficult operation indeed. Another
obstacle which must be surmounted, is the possibility of extraction by
the dye solution, of those materials, chemical or otherwise, which are
contained in the leather, and which are the basis of its permanence,
softness and flexibility. For in the majority of dressing processes, the
action of the ingredients is a preservative one, and when these are wholly
or partially removed from the leather during the dyeing, it becomes, on
drying, hard and horny, like the original undressed pelt. In cases where
furs are to be dyed, special dye-resisting dressings must be used, or the
dyed skins must receive an additional dressing before drying.

Dyeings on furs, to have any value, must possess great fastness to light,
rubbing and wear, and must not change color in time, either when the furs
are stored, or when made up into garments. The necessity for fur dyeings
to have these properties, together with the difficulties outlined above,
has greatly limited the field of available dyeing materials, as well as
the methods of application. These will now be taken up in detail.




CHAPTER IX

FUR DYEING

GENERAL METHODS


Before the furs can be dyed, they have to undergo certain preparatory
processes: first, killing, which renders the hair more susceptible to the
absorption of the dye; and second, mordanting, which consists in treating
the killed fur with chemicals which help the dye to be fixed on the hair.
Then the skins are ready to be dyed.

There are two principal methods by which dyes are applied to furs in
practise: the brush process, whereby only the tips or the upper part
of the hair are colored; and the dip process, whereby the entire fur,
including the leather is dyed. All other procedures in fur dyeing
are modifications or combinations of these two. Killing solutions and
mordanting solutions are also applied by one of these methods, usually
the dip process, although very frequently combinations of the brush and
dip methods are used.

Chronologically the brush method of dyeing came first. The early masters
of the art were extremely fearful about employing any means by which
there was a possibility of the leather being in any way affected. They
naturally had to devise such methods as would give the desired effect
in a satisfactory manner, and as would be confined solely to the hair
part of the fur, leaving the leather untouched. By applying the dye
or other material to be used, in the form of a paste with a brush, the
upper portion of the hair only was treated. For different kinds of furs
different sorts of brushes were used, and the depth to which the hair was
colored could be controlled by skillful manipulation of the brushes. It
was frequently necessary to give a ground color to the hair, the lower
part being dyed a different shade from the tips. This was accomplished
by spreading the dye paste over the hair with a broad brush, and then
beating the color in with a specially adapted beating brush. With larger
furs, two skins were placed hair to hair after the dye had been brushed
on, and the color forced to the bottom of the hair by a workman tramping
on the skins. The dyeing of seal was a typical illustration of these
procedures. First the tips of the hair were dyed. The color was brushed
on, allowed to dry, then the excess beaten out with rods. These operations
were repeated until the proper depth of shade was obtained, often as many
as a dozen or more applications of the dye being necessary. Then the base
color was spread over the hair, and beaten or tramped in until the lower
parts of the hair were penetrated. This process also required drying and
beating out of the excess dye, as well as numerous applications of the
dye to impart the desired color to the hair. Prior to the dyeing, the furs
were killed, by brushing on a paste containing the essential ingredients,
drying and beating and brushing the fur, just the same as in dyeing. It
will be readily seen that such methods were exceedingly laborious, and in
some cases the dyeing took many weeks, and even months.

It was quite a step forward when a certain fur dyer, possessing a little
more courage, or perhaps, experimenting spirit than the others, attempted
to dye furs by dipping them entirely into a bath containing a solution
of the dye instead of applying a paste as formerly. The advantages to be
gained by such a method of dyeing were many. A large number of skins could
be treated thus at one time, and this was a very important consideration
in view of the great increase in the demand for dyed furs. By allowing the
furs to remain in the dye solution until the proper shade was obtained,
the time and labor of applying many coats of dye by brush was considerably
reduced, and in addition, there was a greater probability of the products
coming out all alike, uniformly dyed. The results as far as the hair
was concerned, were indeed highly gratifying, but the condition of the
leather after dyeing was not so encouraging. This difficulty has to a
considerable degree been overcome, although there are frequent instances
of the leather being affected by the dyeing process even with modern
methods. However, the remedy in such cases, or rather the preventative
is the proper dressing of the skins prior to the dyeing. The dip method
of dyeing has acquired great importance, and is being employed in dyeing
operations involving the handling of millions of skins annually. In
certain instances, nevertheless, the brush method is of prime significance
as in the dyeing of seal, and seal imitations on muskrat and coney,
enormous quantities of furs being dyed in this fashion. In the majority
of imitations dyed, both the brush and the dip methods must be used.

Figure 19 illustrates the various types of brushes which are used at the
present time for the application of the dye by the brush method. Each
brush has a specific purpose and use. The procedure in brush dyeing is
somewhat as follows. The skins, after being properly treated, that is,
killed, and mordanted, are placed on a table, or work-bench, hair-side up.
Then by means of a brush which is adapted to the nature and requirements
of the particular fur, the solution is brushed on in the direction of
the fall of the hair, occasionally beating gently with the brush so as to
cause the dye to penetrate to the desired depth. Considerable skill and
care must be exercised in this operation as it is rather easy to force
the dye down further than is wanted, and in some cases the leather or the
roots of the hair may be affected. The skin having received its coat of
dye, is then dried and finished, if no other dyeing processes are to be
applied. Frequently, with certain types of dyes, several applications of
color are necessary, and these are brushed on as the first one, drying
each time. Then, on the other hand, the skin may receive a dyeing in the
bath by dipping, and for this also, the fur is first dried after the brush
dyeing.

[Illustration: FIG. 19. BRUSHES USED IN FUR DYEING BY THE BRUSH METHOD.]

Quite recently, owing to the great quantities of furs which are being
dyed as seal imitations, chiefly by the brush method, although the dip
method is used in conjunction with it, machines have been invented to
replace the hand brush, and the dye is now applied mechanically. Machines
for this purpose are by no means new, there being records of inventions
almost a score of years past, but they did not achieve much success.
Brush-dyeing machines, to be efficient, must be designed to suit the
needs of the particular type of fur to be dyed, otherwise there will be
a great lack of uniformity in the dyed skins, a condition which cannot
occur when the dye is brushed on by hand brushes. Figure 20A and B shows
diagrammatically, machines invented within the past few years, which are
used to dye mechanically furs by the brush process.

[Illustration: FIG. 20. TYPES OF MACHINES FOR DYEING FURS BY THE BRUSH
METHOD.

_A._ (U. S. Patent 1,225,447.) _B._ (U. S. Patent 1,343,355.)]

[Illustration: FIG. 21. DRUM FOR WORKING WITH LIQUIDS.

(_Turner Tanning Machinery Co., Peabody, Mass._)]

For the dipping process, the dye solution is prepared in vats, or
liquid-tight drums, or in some instances in paddle arrangements. The
skins are placed in the dye-bath, and the dyeing operation proceeds
without any difficulty. After the proper shade is obtained, the furs
are removed, washed free of excess dye, dried and finished. The dipping
method is employed where a single shade is to be dyed on the fur, as the
production of blacks on lambs. But in most cases, the dyeing in the bath
is supplemented by the application of a coat of dye by the brush to the
upper part of the hair, the color being usually a darker shade than the
ground dyeing. Thus, for example, in the dyeing of imitation sable on
kolinsky or a similar fur, the skins are first dyed the relatively light
color of the under-hair by the dip process, then the dark stripe effect
is brushed on.

The blending of sables, martens, chinchillas or other rare furs, is not
done in the same manner as with other furs, because each skin requires
individual attention and a long and careful treatment. The dye solution
is applied by means of very fine brushes or sometimes feathers, to the
extreme tips of the hair, until the proper degree of color intensity is
obtained. The time, labor, and skill necessary for this sort of work are
warranted only in the case of the highest-priced furs, and the blendings
are so excellent as to defy detection, except by experts.

[Illustration: FIG. 22. DEVICE FOR CONVEYING SKINS.

(_Turner Tanning Machinery Co., Peabody, Mass._)]

After the furs have gone through all the operations required by the
processes of killing, mordanting, dyeing and washing, they are ready to
be dried and finished. The procedure is quite similar to that employed in
fur dressing. Sometimes the leather side of the skins is brushed with a
strong salt solution before drying, in order to replace some of the salt
which was extracted during the dyeing processes. In other instances, a
light coat of some oily substance is brushed on, to render the leather
soft and flexible after drying, where there is a possibility of the skins
turning out otherwise. Great care must be exercised in the handling of
the dyed skins to avoid the formation of stains or spots on the hair,
which might ruin the dyeing. As little handling of the furs as is feasible
will reduce any trouble from this source. In conveying the wet skins
from one part of the plant to another it is desirable to use a device
such as is shown in Fig. 22. For drying, the same machines as described
under Fur Dressing can be used, and similar care must be taken to avoid
overheating or irregularity of drying. Drum-cleaning constitutes a very
important operation in the finishing of the skins, the hair receiving
a polish, and the full lustre and brilliancy of the dye being thereby
brought out. Then after caging to remove the sawdust or sand, the skins
are passed over the staking knife, or are treated in a machine suited
for the purpose, to stretch them and to render them thoroughly soft and
flexible. And therewith is concluded the work of the fur dyer proper, and
the skins are ready to return to the furrier, in whose hands they undergo
the metamorphosis into the fur garments to be worn chiefly by the feminine
portion of humanity.




CHAPTER X

FUR DYEING

“KILLING” THE FURS


If dressed furs are treated with a paste or solution of a dye properly
prepared, and at the right temperature, the hair will show very little
tendency to absorb the coloring matter. Even after prolonged treatment
with the dye, only a small amount will be taken up by the hair, and in a
very irregular fashion. Soft, woolly hair, like that of lambs and goats
will be colored more easily than that of furs with harder hair, and the
under-hair of a fur will generally have a greater affinity for the dye
than the harder and stiffer top-hair. Moreover, in some parts of the same
fur, the hair will absorb more color than in other parts. In other words,
the hair of furs resists the action of dye materials to a greater or less
degree, depending upon the character of the fur, and also upon the part
of the pelt. In order to overcome this resistance of the hair, and to
render it uniformly receptive to the coloring substances, the furs are
treated with certain chemical agents, the process being known technically
as “killing.”

The origin of the term is obscure, but it is interesting to note that
in the fur dyeing countries other than the United States and England,
the corresponding expression is used: in Germany, “töten,” and in France
“tuer.” The explanation of the process is as follows: The surface of the
hair is covered with a fine coat of fatty material which renders the hair
more or less impervious to dye solutions and solutions of other substances
which may be used for dyeing purposes. This fatty coating of the hair
cannot be removed by mechanical means, otherwise the hair would have
been freed of it during the dressing operations. Chemical solvents must
therefore be resorted to, and naturally alkaline materials are used, these
being usually cheapest and also most effective in their dissolving action
on fatty substances. Alcohol, ether, benzine, and other similar liquids
also serve as killing agents on furs, since they too, are fat solvents.
In all these cases, the fatty substance on the hair is dissolved away,
and the protective coat which previously rendered the hair impervious
to the dye, is now removed. There are certain chemicals however, which
normally do not dissolve substances of a fatty nature, but are strongly
oxidizing, such as peroxide of hydrogen, hypochlorites, permanganates,
perborates, nitric acid, etc., and exert a killing action when they are
applied to the hair, in that the hair is made capable of taking up the
dye from its solutions. In this case the killing can hardly be said to
be due to a degreasing process. The fact that killing can be brought
about with other substances than alkalies or fat solvents, has led to
the belief on the part of some investigators in this field that killing
is more than a degreasing operation, although the removal of the fatty
material of the hair undoubtedly takes place. Some authorities consider
that the killing process changes the pigment of the hair, which thereby
becomes more receptive to the dye. It is quite possible that some such
change in the structure of the hair fibre does take place, the surface
of the hair becoming slightly roughened, and therefore more capable of
fixing the coloring matter. The question is still an open one, and since
no conclusive researches have been made as yet, it will be assumed that
killing is simply a degreasing process, inasmuch as the modern practise
is based on this supposition, and very satisfactory results are obtained.

An account of the historical development of the killing process brings
out many interesting and enlightening facts, so it will be given here
briefly. One of the first substances used for killing, or degreasing the
hair of furs, was decomposing urine. Urine contains about 2% of urea which
gradually changes to salts of ammonia, and in the presence of the air,
largely to ammonium carbonate. This substance has a weak alkaline action,
but sufficiently effective to be used for killing the hair of certain
types of furs. Woolly furs, such as those derived from the various kinds
of sheep and goats, were degreased with stale urine, the skins being
washed in this, and then rinsed in water. The fat was emulsified by the
ammonium carbonate present, and could thus be easily removed. For other
furs, a stronger mixture was necessary. An example of a killing formula
used on wolf, skunk and raccoon, which were to be dyed black, is the
following:

  350 grams beechwood ashes
  200 grams unslaked lime
  150 grams copper vitriol
  100 grams litharge
   60 grams salammoniac
   40 grams crystallized verdigris
  3.5 liters rain water

Beechwood ashes were a very important constituent of the old killing
formulas. The reason for that lies in the fact that beechwood contains
a comparatively high percentage of potassium, which occurs in the ashes
of the burned wood as potassium carbonate, or potash. The ashes alone
were frequently used, being applied in the form of a paste, which in
some instances had an advantage over a solution, in that the killing
could be limited to certain parts of the skin where it was more desired
than in other parts. By extracting the wood ashes with hot water, and
evaporating the clear solution to dryness, potash could be obtained, which
was considerably stronger than the original ashes. Next in importance
for the killing was unslaked lime. This substance was also often used by
itself, being first slaked with water, and using the milk of lime thus
formed, after cooling. Salammoniac, although a salt, and consequently
without any killing action, in contact with the beechwood ashes or the
lime in solution or paste, liberated ammonia slowly, and so also acted
as a degreasing agent. The other chemicals in the formula took no part
in the actual killing of the hair, but acted either as mordant materials
or as mineral dyes. The copper salts, in this mixture present in two
forms, as sulphate in copper vitriol, and as acetate in the verdigris,
were important constituents of the dye formula, being essential to the
production of the proper shade. These substances properly had no place
in the killing formula. The litharge, also was not a killing agent, but
in the presence of the alkaline materials of the killing mixture, it
gradually combined with the sulphur contained in the hair, forming lead
sulphide, and thereby darkening the color of the hair. In this case,
the metallic compound acted, not as a mordant, but as a mineral dye. The
mixture was applied to the hair by means of a brush, the skins let lie for
some time, then dried, brushed and beaten. Many applications were usually
necessary to sufficiently degrease the hair. Inasmuch as the killing paste
was prepared by mixing the constituents together, and then was brushed
on at the comparatively low temperatures which the proper protection of
the hair required, it is questionable whether some of the metal compounds
were even enabled to act as described above as mordant or dye. In spite of
the trouble and considerable time required in working with such a killing
formula to obtain the hair in the desired condition for dyeing, the use
of such a mixture nevertheless possessed the advantage that the hair was
only very slowly and gradually acted upon, and so the gloss was preserved.
The action of strong alkaline substances acting quickly is more or less
detrimental to keeping the gloss of the hair, while the slow action of
the weak alkaline paste of the old formulas, and the gradual formation
of a protective metal film on the surface of the hair, rendered the hair
suitably receptive to the dye which was subsequently applied, without in
any measure affecting the lustre of the hair.

It would be needless to describe or discuss any more of the old killing
formulas, for the principle involved was the same in all cases, there
being usually a slight variation in the content of metallic salts,
beechwood ashes and unslaked lime being constituents of the great majority
of the mixtures used. Modern killing processes employ substances quite
similar to those of the old formulas, the operations, however, being much
less laborious and less time-consuming, and the cheap, pure products
which chemical science has been able to develop being used in place of
the crude products crudely obtained from natural sources. The chemicals
used at the present time for killing furs, are chiefly ammonia, soda ash,
caustic soda, and caustic lime. The choice of the killing agent depends
upon the nature of the fur, the hair of some furs being sufficiently
killed by treatment with weak alkalies, while in other furs the hair may
require stronger treatment. The ability of the hair of a particular fur to
withstand the action of the different alkaline substances must be taken
into consideration, there being a great divergence in this regard among
the different classes of furs. Raccoon, for example, is not appreciably
affected by a solution of caustic soda of 5 degrees Beaumé, while some
wolf hair cannot withstand the action of a solution of soda ash of less
than 1 degree Beaumé. Frequently much stronger alkalies are necessary to
kill the top-hair than the under-hair, so this accomplished by treating
the skins in a solution which is suited to kill the under-hair, and
subsequently the top-hair is treated with a stronger solution, this being
applied by the brush method.

Uniformity of action of the killing material on all parts of the skin,
and on all the skins of a given lot, is absolutely essential to obtaining
satisfactory results in dyeing. And it is by no means a simple matter
to get such uniformity, considering the numerous factors that must be
taken into account. Any operation involving the immersion of the skins
in solutions or even in water alone, has an effect on the leather side of
the skin, inasmuch as some of the tanning materials may be extracted. The
application of some substance of a fatty nature to a great degree prevents
this, and the skin can be killed, mordanted and dyed, and then come out
soft and flexible. But the great majority of substances of a fatty nature
are affected by alkalies, and so when the skins are being killed, the
action of the alkaline materials would be upon the fat contained in the
leather as well as that upon the hair. As a result the hair may not be
sufficiently killed, and so give uneven dyeings subsequently. Either a
certain excess of the killing chemical must be used, and it would be very
difficult to ascertain what quantity would suffice, or the killing action
must be prolonged; but best of all, in oiling the skins, an inert mineral
oil should be used, since it is wholly unaffected by alkalies.

Skins may be killed by the brush process or the dip process, or by both.
For brush killing, the stronger alkalies like lime and caustic soda are
used, the solution being applied to the top-hair with a suitable brush,
and the skins allowed to remain hair to hair for the necessary length
of time, after which they are treated further as skins killed by the dip
process. By this latter process, the furs are immersed in a solution of
the desired killing agent in a vat, or drum, or other appropriate device
which will permit of uniform action of the alkali on the hair of all the
skins. After remaining in the solution the required length of time, the
skins are drained, and rinsed in fresh water, and then entered into a weak
solution of an acid in order to neutralize any remaining alkali, it being
easier to wash out acid than alkali. The furs are then washed thoroughly
in clear water, preferably running water, to remove the last traces of
acid. The skins are then drained and hydro-extracted, or pressed, and are
then ready for the subsequent operations of mordanting and dyeing.


KILLING WITH SODA

Soda is sodium carbonate, which is produced commercially in a very pure
state in several different forms, the chief being sal soda, which is
crystallized sodium carbonate, containing about 37% of actual soda; and
soda ash, or calcined soda, which is anhydrous sodium carbonate. The
latter is the variety most commonly used.

  10 grams soda ash are dissolved in
   1 liter of water at 25°–30° C.

The skins are immersed for 2–3 hours, after which they are rinsed and
treated with

  10 grams acetic acid dissolved in
   1 liter of water.

The skins are again thoroughly washed, and then hydro-extracted.


KILLING WITH LIME

Lime, calcium oxide, forms a white, amorphous, porous substance, which
readily takes up water, giving calcium hydroxide, or slaked lime. Only the
best grades of lime should be used, as it is very frequently contaminated
with calcium carbonate and other inert materials.

  10 grams of lime are dissolved in
   1 liter of water.

The skins are entered, and allowed to remain for a period of time which
varies according to the nature of the fur. During the killing, the
solution must be agitated, in order to evenly distribute the milk of lime,
which has a tendency to settle out. After rinsing, the skins are “soured,”
by treating with weak acetic acid solution, then thoroughly washed, and
drained.


KILLING WITH CAUSTIC SODA

Caustic soda is used only on furs the hair of which is very hard and
resistant to killing. Usually it is applied by the brush process, but in
some instances, the dip method must be used. In order to reduce as far
as possible, the action of the caustic soda on the leather, the weakest
permissible solutions are used, increasing the time of treatment, if
necessary. Caustic soda is a white, crystalline substance, occurring
in commerce in lumps, but more conveniently in a solution of 40 degrees
Beaumé, containing 35% of caustic soda. Various quantities, ranging from
4 to 25 grams of this solution per liter of water are taken, according to
the character of the fur, and the skins treated for 2–3 hours, although
weaker solutions may be used, and increasing the duration of the killing.
By keeping the solution in motion, by means of a stirrer or any other
method of agitation, the best results are obtained. After the skins are
sufficiently killed, they are soured, and washed as by the other killing
methods.

Where the nature of the hair of the fur is such that the top-hair and
the under-hair require different killing treatments, the skins are first
killed by the dip process, with an alkali suited to kill the under-hair,
then a brush killing with a stronger alkali is applied to the top-hair.
The subsequent treatments are the same as for usual dip-killing methods.




CHAPTER XI

FUR DYEING

MORDANTS


The hair of furs has the peculiar quality of fixing the oxides or
hydroxides of certain metals from dilute solutions of their salts.
Advantage is taken of this property to mordant the furs, that is, to cause
a certain amount of the metallic oxide or hydroxide to be permanently
absorbed by the fibres. The term mordant comes from the French word
“mordre,” meaning to bite, it being formerly considered that the purpose
of a mordant was to attack the surface of the hair in such a way as to
permit the dye to be more easily absorbed. In fact, killing mixtures,
which were intended for this same object, used to contain the various
chemicals which have a mordanting action, in addition to the alkaline
constituents. The mordants were not applied as such, but always as
killing materials. It was later realized, however, that the mordant was
instrumental in the production of the color itself.

Mordanting may be considered as having a two-fold object: first, to help
fix the dye on the fibre in a more permanent fashion, thus rendering the
dyeings faster; and secondly, to help obtain certain shades of color, as
the various mordants produce different shades with any given dye. Some
classes of dyes can be applied to furs without the use of mordants, but
other types are taken up only in a very loose manner, being easily washed
out from the hair with water, and it is only when such dyes are brought on
to the hair in the form of a metallic compound, producing what is known as
a “lake,” that really fast dyeings are obtained with them. The substances
which are used for mordanting the hair are certain metallic compounds,
but not all metallic salts which are used in dyeing are mordants.
Sometimes such a compound is employed to develop the color of the dyeing
by after-treatment, as in the case of after-chroming, the action of the
metallic salt being directed only to the dye, and is not fixed by the
fibre as a mordant must be. In order for a metallic compound to act as a
true mordant, it must be fixed by the hair, and it must combine with the
dye, thus forming a sort of connecting link between the dye and the hair.
It is not absolutely essential that the mordant be applied first, although
this is the customary and commonest practise. There are three ways by
which the mordants can be fixed on the fur hair: First, by the absorption
of the metallic oxide or hydroxide from a solution of the mordant prior to
the dyeing; second, the mordant may be fixed on the fibre at the same time
as the dye; and third, the mordant may be applied after the fur has been
treated with the dye. The last two methods will be discussed in connection
with the dyes, as they are special cases.

The salts of metals which are comparatively easily dissociated in water,
with the formation of insoluble oxides or hydroxides, are most applicable
as mordants for furs, and among them are compounds of aluminum, iron,
chromium, copper and tin. The constituents of the hair seem to bring
about the dissociation of the metallic salt, and the oxide or hydroxide
as the case may be, is absorbed and firmly fixed by the hair. Just what
the manner and nature of this fixation are, is still uncertain. It is
supposed that chemical combination takes place between the hair and the
metal. The course of this process may, as far as is known, be described
as follows, taking, for example, the case of chromium sulphate: In dilute
solution, this compound gradually dissociates first into its basic salts,
and finally into the hydroxide, the breaking up of the neutral salt being
induced by the presence of the fur-hair.

  Cr₂(SO₄)₃ + 2H₂O = Cr₂(SO₄)₂(OH)₂ + H₂SO₄
  chromium    water   first basic    sulphuric
  sulphate            chrome salt      acid

  Cr₂(SO₄)₂(OH)₂ + 2H₂O = Cr₂(SO₄)(OH)₄ + H₂SO₄
                          second basic
                          chrome salt

  Cr₂(SO₄)(OH)₄ + 2H₂O = Cr₂(OH)₆ + H₂SO₄
                         chromium
                         hydroxide

These reactions take place within the fibre, after the hair has been
impregnated with the solution of the neutral salt, and when the compound
has been rendered completely basic, in other words has reached the form of
the hydroxide, it is supposed to combine with the acid groups contained
in the hair substance, forming thus some complex, insoluble organic
compound of the metal within the hair. According to some authorities the
mordant is supposed to be present in the hair simply as the hydroxide,
being tenaciously held by some physical means. The facts seem to indicate,
however, that the metal is actually combined in some chemical way with the
hair. For, if the mordant were present as hydroxide, then on white hair it
would show the color of the hydroxide, which it does not. The same facts
obtain with regard to other metals.

In order for the hair to be properly mordanted, it is necessary that
the metallic compound which is taken up by the hair be held in such a
manner that the mordant cannot be removed by water or even dilute acids
or alkalies. Salts which dissociate too readily produce mordants which
are only superficially precipitated on the hair and subsequently come
off. Usually some substance is added to the solution of the salt to
cause slower and more even dissociation of the salt, so that the hair
substance can be quite saturated with the metallic compound before any
insoluble precipitate is formed. Dilute sulphuric acid, organic acids like
acetic and lactic, and cream of tartar are used to facilitate the uniform
absorption of the mordant salt by the hair.

When the skins are mordanted before dyeing, they are immersed for 6 to
24 hours in a solution containing 1 to 20 grams of the metallic salts per
liter of water, together with the corresponding quantity of the assistant
chemical. The skins should be so entered into the mordant solution that
the hair is uniformly in contact with the solution, and all the skins
so that they are acted upon alike. Machinery such as is used for killing
is suitable for mordanting also. The duration of the mordanting, and the
concentration of the solutions are varied according to the depth of shade
required, and also according to the nature of the dye to be employed. By
suitably combining several mordants a considerable range of colors can be
obtained with a single dye.

The various chemicals used as mordants are essentially the same no matter
for which class of dyes they are used, there being only slight differences
in the concentrations of the solutions, the manner of application of
the mordants being practically the same. It is interesting to note that
with the exception of chromium compounds, which are of comparatively
recent adoption as mordants, all the chemicals now used for mordants
were employed by the earliest masters of the art of fur dyeing. While
some of the formulas used by those dyers display a lack of appreciation
of the true action and function of the mordanting chemicals, yet it is
quite remarkable that they chose, in spite of their limited knowledge of
chemical processes and phenomena, just those materials which do act as
mordants if properly applied. The most important metallic compounds for
mordanting furs at the present time are salts of aluminum, iron (ferrous),
copper, tin and chromium (as well as chromates and bichromates). The
compounds of the metals with organic acids such as acetic acid are
preferable, being more easily dissociated, and also leaving in solution
an acid which is less injurious to the fur than a mineral acid. However,
sulphates and other salts of the metals are also used extensively,
inasmuch as they are cheaper than the organic salts.


ALUMINUM MORDANTS

Chief among the aluminum mordants are the various kinds of alum, which is
a double sulphate of aluminum and an alkali such as sodium, potassium or
ammonium. All these salts except that of sodium, form large, colorless,
octahedral crystals, and are soluble in about 10 parts of cold water,
and 1/4 part of hot water. Sodium alum is even more easily soluble, but
on account of the difficulty of obtaining it in crystalline form, it
is little used. The common commercial alum is the potassium aluminum
sulphate.

Recently, aluminum sulphate has to a large extent replaced alum for
mordanting purposes, because it can be obtained very cheaply in pure form,
and it contains a greater amount of active aluminum compound than does
alum. Only the iron-free salt, however, may be used for the needs of fur
dyeing.

Aluminum acetate also finds extensive application as a mordant in fur
dyeing, and while somewhat more expensive than the alum or aluminum
sulphate, it has the advantage over these compounds of being combined
with an organic acid, which is preferable when the action on the hair and
leather is considered. Aluminum acetate can be obtained in the market in
the form of a solution of 10 degrees Beaumé, but can also be prepared very
easily as follows:

   665 grams pure aluminum sulphate, or
   948 grams potassium alum, are dissolved in
     1 liter of hot water.
  1137 grams of lead acetate (sugar of lead) are also dissolved in
     1 liter of hot water.

The two solutions are mixed, and thoroughly stirred. A heavy white
precipitate forms, which is filtered off, and discarded after the solution
has cooled. The aluminum acetate is contained in the filtrate, and the
solution is brought to a density of 10 degrees Beaumé by the addition of
water, if necessary, and is preserved for use in this form.


IRON MORDANTS

Ferrous sulphate, iron vitriol, or copperas, as it is commonly known,
forms pale green crystals, which on exposure to air lose water, and
crumble down to a white powder. It is very soluble in both cold and
hot water, but the solutions oxidize very rapidly, turning yellowish,
and should therefore be used immediately. Care must be taken that a
good quality of iron vitriol be used for the mordant, otherwise very
unsatisfactory results will be obtained.

Ferrous acetate is prepared in a manner similar to the aluminum acetate,
and is occasionally employed instead of the ferrous sulphate. Inasmuch,
however, as the solution of ferrous acetate is very easily oxidizable
when exposed to the air, a more stable form is used, and this comes on
the market as iron pyrolignite or iron liquor. This can be prepared by
dissolving iron in crude acetic or pyroligneous acid, or by treating a
solution of iron sulphate with calcium pyrolignite. Iron liquor is really
a solution of ferrous acetate that contains certain organic impurities
which prevent, or rather, considerably retard the oxidation of the iron
salt, but which in no way interfere with its mordanting properties. The
commercial product can be had in various concentrations, but 10 degrees
Beaumé is the most usual and most convenient.


COPPER MORDANTS

The most important copper salts used in fur dyeing processes are copper
sulphate, or blue vitriol, occurring in large blue crystals, very soluble
in cold and in hot water; and copper acetate, which is formed by treating
a solution of copper sulphate with a solution of the requisite quantity
of lead acetate. Copper acetate can also be obtained in the form of
blue-green crystals, very soluble in water, the solution becoming turbid
on prolonged heating, due to the formation of a greenish basic copper
acetate. This insoluble compound is known commonly as verdigris, although
it is not usually produced in the manner mentioned. Numerous fur dyeing
formulas contain verdigris, but inasmuch as the basic copper acetate is
insoluble and thus incapable of reacting with any of the substances used
in dyeing, it is assumed that the soluble normal copper acetate was meant,
for this compound is also sometimes called verdigris.

In addition, there must be mentioned here a compound which formerly found
extensive use in fur dyeing. This is a double salt of copper and iron,
analogous to alum, ferrous copper sulphate, known as blue salt. It is very
seldom used at the present time, being more effectively replaced by other
substances.


CHROMIUM MORDANTS

The typical chromium mordant is chrome alum, which is a potassium or
ammonium chromium sulphate, constituted just like the aluminum alums, and
forming crystals like these. More frequently used, nevertheless, than the
chrome alum, is chromium acetate, which is prepared from it, either by
treating a solution of the chrome alum with a solution of lead acetate,
or in the following manner:

   50 grams of chrome alum are dissolved in
  500 cubic centimeters of boiling water. To this is added
   15 grams of 20% ammonia, diluted with 15 grams of water.

The precipitate which forms is filtered off, and preserved, the filtrate
being discarded. After thoroughly washing the residue on the filter it is
dissolved in dilute acetic acid, heating if necessary, to effect solution.

Other chromium compounds of an entirely different type are also used in
fur dyeing, these being chromates and bichromates, the latter finding
greater application than the former. Sodium bichromate is the salt most
usually employed. This forms orange-red crystals which are very soluble
in water, and in addition to its use as a mordant it also serves as an
oxidizing agent for developing or fixing certain dyes on furs.


TIN MORDANTS

Compounds of tin find only limited application in fur-dyeing, the only one
of importance being tin salts, stannous chloride, which occurs in the form
of white, hygroscopic crystals, which must be preserved in closed vessels.
It is very soluble, but in dilute solutions it readily forms a basic salt,
so stannous chloride is usually used in very concentrated solutions.


ALKALINE MORDANTS

After the furs have been treated with the solution of some alkali for the
purpose of killing the hair, they are always passed through a slightly
acidulated bath to remove any alkali which may still be adhering. This
operation must always be gone through before the skins can be mordanted
or dyed, for if it were neglected, very uneven and uncertain results
would be obtained. This process, however, entails the expenditure of
no small amount of time, labor and chemicals when large lots of skins
are being handled. In order to eliminate this extra step of “souring”
between killing and mordanting or dyeing, it has been proposed to use
alkaline mordants which combine the killing and mordanting functions,
and accomplish these two processes at the same time. The advantages of
employing such mordants are easily apparent. Cumbersome manipulation and
handling of the skins, with the attendant consumption of much time and
labor are reduced to a minimum, and besides there is no needless waste of
chemicals as is the case in the ordinary methods of killing the furs.

The principle of alkaline mordants is not a strictly new one. If it
be remembered that the old killing formulas used by the fur dyers of
an earlier age, contained metallic salts with mordanting properties in
addition to the alkaline substances, which alone were effective as killing
agents, it would seem that the suggested alkaline mordants were merely a
revival in modified form of the old processes. This is undoubtedly true
in a large measure, for the killing mixtures which the old masters used
certainly embodied the fundamental principle of simultaneous killing and
mordanting, although it was not recognized at that time.

Modern alkaline mordants have therefore been devised which can be employed
for killing and mordanting furs at the same time. They are prepared as
follows:


ALKALINE ALUMINUM MORDANT

  250 grams of potassium alum are dissolved in
    1 liter of boiling water. To this solution is added
  300 grams of soda ash, previously dissolved in
  750 c.c. of water, and the resulting precipitate is filtered off,
      washed and pressed, and then dissolved in a solution of 65 grams
      of caustic soda in 1 liter of water.


ALKALINE CHROMIUM MORDANT

  250 c.c. of chrome acetate mordant of 20 degrees Beaumé
  320 c.c. of caustic soda solution of 38 degrees Beaumé (32.5%)
   10 c.c. of glycerine 30 degrees Beaumé (95%)

The solution of these substances is brought up to a volume of 1 liter by
the addition of 420 c.c. of water.


ALKALINE IRON MORDANT

   138 grams ferrous sulphate are dissolved in
   362 c.c. of warm water. Cool and add
    25 c.c. of glycerine. Then slowly and carefully add
  25.5 c.c. of concentrated ammonia, taking care that no precipitate
       forms.

While these alkaline mordants seem to have much in their favor, there
are certain possible objectionable features which must be considered.
The solutions of the mordants are generally very alkaline, and not every
fur can withstand more than a limited quantity of alkaline substance
for longer than a comparatively short time. Suitable mordanting usually
requires a longer time than killing does, so with the use of the alkaline
mordant, if the skins remain in the solution until sufficiently killed,
they may be insufficiently mordanted, while if the furs are treated long
enough to be properly mordanted, the hair may have been over-killed.
However, the idea of the alkaline mordant is a good one, and it is
only a matter of time and patient, scientific experimentation when the
difficulties of the method will be eliminated, and a much-desired process
will become a practical realization.

The general methods for applying the various mordants of all sorts follow
closely the procedure adopted for the killing formulas, and similar
precautions must be observed, in order to obtain consistently uniform
results. With the exercise of care, there is little reason for the
mordanting operations to go wrong.

After proper treatment of the skins in the mordants, they are removed and
drained off, then rinsed lightly in running water to remove the excess
of mordant liquor, after which they can be directly entered into the
dye bath. If it is not feasible to dye the mordanted skins at once, as
is often the case, the skins are kept moist, and under no circumstances
allowed to dry.




CHAPTER XII

FUR DYEING

MINERAL COLORS USED ON FURS


Before the introduction of the fur dyes now used, certain inorganic
chemical substances were employed in addition to the vegetable dyes,
for the production of colors on furs. Even to this day such materials
are used to obtain certain effects in special instances. The idea of
employing mineral chemicals undoubtedly originated in the textile-dyeing
industry, which at one time was dependent to an appreciable extent on
mineral substances for the production of certain fast shades. Compounds
of iron, lead, manganese, also of copper, cobalt and nickel were all used
for dyeing, either singly or in various combinations. In the application
on furs, the brush method was the only one practicable, as the skins would
have been ruined by dipping them into solutions of these chemicals in the
concentrations necessary for dyeing.

The dyeing of furs with mineral colors involves the precipitation on
the fibre in a more or less permanent form of the sulphide, oxide or
other insoluble compound of a metal, and can be brought about in several
ways. By what is known as double decomposition, that is, by the use
of two solutions successively applied, the ingredient of one causing a
precipitate to form when in contact with the constituent of the second,
the color is produced on the hair. Another method is to use solutions of
chemicals which decompose on contact with the hair, forming an insoluble
compound. In the first method the hair is alternately treated with the
two solutions of the requisite chemicals, drying between each brushing,
the process being repeated until the desired shade is obtained. The second
method merely requires the solution of the chemical to be applied to the
hair, which is then dried, the color forming by itself.

One of the most important of the mineral dyes, and which is occasionally
used to this day, is lead sulphide, formed by the double decomposition
method by precipitating a soluble lead salt with ammonium sulphide, or any
other alkaline sulphide. By simply brushing an aqueous solution of lead
acetate, also known as sugar of lead, on a white fur such as white hare or
rabbit, a light, brownish coloration is obtained due to the combination of
the lead with the sulphur of the hair. If the lead solution is carefully
applied several times on this type of fur, until a sufficiently dark
color is produced, it is possible to get a fairly good imitation of the
stone marten. The brown color is very fast, being actually formed within
the hair. In most cases, however, for dyeing lead sulphide shades it is
necessary to use the two solutions. Thus the pale greyish or slightly
brownish-grey shades of the lynx can be reproduced on white rabbit or
hare by this process. A solution containing 60 grams of lead acetate per
liter of water is brushed on to the hair of the fur which has previously
been killed in the usual manner, and the hair is then dried. A solution
of 50 grams of ammonium sulphide per liter of water is next brushed on,
and the fur again dried. Care must be exercised in handling the ammonium
sulphide as it is a very malodorous liquid, the fumes of which are
poisonous when inhaled. The alternate brushings are repeated until the
desired depth of shade is obtained. A very dark brown, approaching a black
can be obtained in this way. This color can be used for the production of
certain attractive effects. By brushing over the tips of the hair, which
has previously been dyed a dark brown by means of the lead sulphide color,
with a dilute solution of hydrochloric acid, or with peroxide of hydrogen,
the hair will become white in the parts so treated, due to the formation
of lead chloride or lead sulphate, respectively. Thus white tipped furs
can be obtained, but the process is applicable only when the furs have
been dyed by the lead sulphide method.

Potassium permanganate is occasionally used to produce dyeings of a
brown shade on furs. Considerable care has to be taken in applying this
substance, as it is possible to affect the hair. The strength of the
solution must be varied according as the hair to be dyed is weak or
strong. A cold solution of 10 to 20 grams of potassium permanganate per
liter of water is brushed on to the hair, which is then dried. A brown
precipitate of manganese is formed on the hair after a short time, and
the process is repeated until the required shade is obtained. For furs
with harder hair, stronger solutions can be used. The dyeing is very
fast, but it is seldom used, cheaper and better shades being obtained in
other ways. Spotted white effects can be produced on the brown dyeing with
permanganate of potash by applying a solution of sodium bisulphite, the
brown color being dissolved by this chemical.

The compounds of other metals, such as iron, copper, cobalt and nickel
are not used in practise as the dyeings are not fast, and can be better
produced in other ways.




CHAPTER XIII

FUR DYEING

VEGETABLE DYES


With the exception of the few shades which could be produced solely by
means of coloring matters of a chemical character, all dyeings on furs up
to about thirty years ago were made with dye substances obtained from the
vegetable kingdom, either alone, or in conjunction with the aforementioned
mineral colors. The colors of vegetable origin used in comparatively
recent times were mainly extracts of the wood of certain trees; so the
name “wood dyes” has come to be applied generally to the dyes of this
class. The use of the vegetable or natural dyes on furs dates back to
quite ancient times, as frequent allusions and descriptions in Biblical
and other contemporaneous literature testify. There are numerous pictures
on monuments and tablets illustrating the dyeing of furs among the ancient
Egyptians, the evidence indicating that the juice of certain berries, and
extracts of certain leaves were used for the purpose. At a later period,
in the Roman era, henna, which was used over two thousand years ago as
to-day for the beautification of the hair of women, was also used to
color fur skins. The instances cited here are merely of scientific and
historical interest, and are not of practical importance as far as fur
dyeing methods are concerned.

It was not until many centuries later that the dyeing of furs took on
the aspects of a commercial art, and the substances then employed were
chiefly tannin-containing materials such as gall-nuts and sumach, which
in conjunction with certain metallic salts, particularly those of iron,
were capable of producing dark shades. The use of iron compounds to form
dark grey or black colors on leather tanned by means of the tannins, had
been common for a long time, and it was natural that fur dyers should
try to produce such shades on furs in a similar fashion. The use of the
iron-tannin compound as a dye proved to be very effective, and to this day
the production of blacks by means of the vegetable coloring matters has as
a basis an iron-tannate. A formula in common use in the latter seventeenth
and the eighteenth centuries for producing black shades on furs, is the
following:

  Lime water                1117 parts
  Gall-nuts                 1500   „
  Litharge                   500   „
  Salammoniac                 65   „
  Alum                       128   „
  Verdigris                   64   „
  Antimony                    64   „
  Minium                      32   „
  Iron filings               128   „
  Green copperas             384   „

All these substances except the gall-nuts, the copperas and half the lime
water were boiled up in a cauldron; then the gall-nuts and the copperas
were placed in a bucket and the contents of the cauldron poured in, and
the rest of the lime water added. The mixture was stirred up, allowed to
settle for an hour, and when cool, was ready to be applied by the brush
method. For dyeing by the dip process, a similar mixture was used, only
considerably diluted with water. A study of the formula discloses the
fact that in it are combined killing and mordanting substances as well
as dyeing materials. The lime water, in conjunction with the salammoniac
serves as a killing agent, the verdigris, copperas and alum are mordants,
while the litharge and the minium, both compounds of lead, could possibly
act as mineral dyes, and the iron filings and the antimony took virtually
no part at all in the dyeing, except, perhaps to act in a mechanical way.

The formulas for other shades were made up along similar lines, the chief
constituent of vegetable nature being either gall-nuts, sumach, or both.
A mixture for a chestnut brown, for example, contained gall-nuts, sumach,
and the various other mineral constituents as in the black dye, litharge,
alum, copperas, verdigris, salammoniac, antimony, and in addition, red
lead and white lead. It is evident in both these instances that the shade
obtained was as much the result of mineral dyeing as of vegetable dyeing.

The discovery of America introduced into Europe many new dye substances,
chiefly wood extracts such as logwood and Brazilwood, but it was not until
the nineteenth century that these materials found their way into the
dye formulas of the fur dyer. Most of the processes used in the dyeing
of furs were adaptations of methods employed in silk dyeing, the silk
fibre being considered as most nearly approaching fur-hair in nature and
characteristics. By devious and circuitous paths the formulas of the silk
dyers reached the fur people, and so, in the middle of the nineteenth
century, dye mixtures containing the various dyewoods as well as the
tannin-containing substances were in general use for the dyeing of furs.
The following is a typical recipe of that time for the production of black
on furs like wolf, skunk, raccoon, etc.:

  Roasted gall-nuts         1000 parts
  Sumach                     200   „
  Iron mordant               200   „
  Copper vitriol             100   „
  Litharge                    80   „
  Alum                        60   „
  Salammoniac                 50   „
  Crystallized verdigris      40   „
  French logwood extract      30   „
  Rain water                7000   „

The mixture was boiled up, and after cooling was ready for application by
the brush method, the skins being first killed by a killing mixture also
applied by the brush. The dye substances in this case are the gall-nuts,
sumach and the logwood extract, with the iron mordant, copper vitriol, and
alum as mordants. For brown shades a similar formula was used containing
Pernambuco wood extract, logwood extract, quercitron bark, gall-nuts and
dragonblood, together with iron, copper and alum mordants.

Formulas such as the above were mainly empirical, that is, they
were compounded as a result of trial of various combinations of the
constituents, without considering the nature and quantitative character
of the reactions, as long as the desired shades could be obtained. Such
dye mixtures were frequently found to yield results varying from those
expected or originally obtained, because the effectiveness of the formulas
depended upon the exact duplication in every detail, of conditions which
had given satisfactory results previously, and it was not always possible
to attain such an accurate reproduction of circumstances, especially
when the fur dyers were quite ignorant of the scientific relationships
of the materials used. So when more light had been shed on the nature
and chemical characteristics of the vegetable dye substances, formulas
like those described were no longer employed, although the essential
ingredients were the same in the new processes. Unnecessary constituents
were eliminated, and proper ones substituted where it was required, and
the quantities of the materials used were made to conform to the chemical
laws governing the reactions. Since these new formulas were based on a
rational understanding of the constituents and their reactions, it is
desirable to study the latter briefly, before further discussing the
formulas themselves.

The substances of vegetable origin used in modern fur dyeing may be
grouped into two classes, one, the tannin-containing materials, and
the other, the dyewoods proper. The most important of the tannins are
gall-nuts, sumach and chestnut extract. Cutch, which also comes under
this class, is more frequently used for the production of brown shades,
so it is grouped with the dyewoods. Among the latter are logwood, fustic,
Brazilwood, quercitron, turmeric, and several others of less significance.


1. _Tannin Materials_

First and foremost under this heading are the nutgalls. These are
ball-shaped excrescences produced on certain plants by the punctures
of insects in depositing their eggs. There are two chief varieties, the
European, and the Chinese. The European galls are formed by the female
gall-wasp which drops an egg in the rind of young branches of certain
oaks. A swelling (the nutgall) is produced, in which the young insect
develops, and from which it finally escapes by piercing a hole through
the shell. Those galls which are not pierced have a fresh bluish or green
color, are heavy and contain most tannic acid. After the insect has gone
out, the galls are of a lighter, yellowish color, and also of inferior
quality. The best oak-galls are the Aleppo, and the Turkish or Levant
galls, containing 55–60% of tannic acid, and about 4% of gallic acid. The
Chinese galls are produced by the puncture of a plant-louse on the leaves
and leaf-stalks of a species of sumach, and not on oaks. The galls are
very light, and very rich in tannic acid, containing often as much as 80%.
For dyeing purposes, nutgalls are usually ground to a powder, and in some
instances they are even roasted first and then ground.

Sumach consists of the leaves and sometimes of the small twigs and stems
of a species of sumach plant known as the Rhus coriaria. The Sicilian
variety is the finest commercial quality, with the Virginian ranking next.
It is sold as a powder, but also in the form of the whole or crushed
leaves. The best sumach contains 15–25% of tannin. Extracts are also
manufactured, a liquid extract of 52 degrees Twaddell, which forms a dark
brown, thick paste; and a solid extract, formed by evaporating the liquid
extract to dryness.

Chestnut extract is prepared from the wood of the chestnut oak, which
contains 8–10% of tannin. The solid extract has a bright, black color,
while the liquid extract is a dark brown paste with a smell like that of
burnt sugar.

The tannins all give greyish to black shades with iron salts, and it is
this fact which renders them important for fur dyeing.


2. _Wood dyes_

One of the most important of all the natural dye substances, especially
for the production of blacks, is logwood. The color is really a red, but
with the common mordants it forms blue, violet or black shades. Logwood,
or campeachy wood, as it is sometimes called, is the product of a large
tree growing in the West Indies, and Central and South America. When
freshly cut, the wood is practically without color, but when exposed to
the air it soon becomes a dark reddish-brown on the surface. The coloring
principle of logwood is called hematoxylin, which is a colorless substance
when pure, and is of itself incapable of dyeing; but when it is exposed
to the air, especially when moist and in the presence of some alkaline
substance, it is converted into hematein, which is the real coloring
matter of logwood. To prepare the wood for use, the logs are chipped or
rasped, the chips being heaped up and moistened with water. Fermentation
occurs, and the heaps are frequently turned to allow free access of air to
the wood, and to prevent overheating. As a result of this process, a great
part of the hematoxylin is converted to the hematein. The logwood may
be used for dyeing in this state as chips, but logwood extracts can now
be obtained of a high degree of purity and are easier to work with. The
commercial forms of the extract, are the liquid of 51 degrees Twaddell,
and the solid extract. Hematein crystals can also be obtained. All these
extracts contain mainly hematein, together with a small percentage of
hematoxylin which is converted to the former during the dyeing process.
Logwood is never used as a direct dye, but is used to form color lakes
with the various mordants, the following colors being produced:

  Iron mordants give grey to black shades
  Copper mordants give green-blue to black shades
  Chrome mordants give blue to black shades
  Aluminum mordants give violet shades
  Tin mordants give purple shades

By combining several of the mordants, any desired shade of black can be
obtained, and if other dyewoods are used in conjunction with the logwood,
the range can be further increased.

Fustic, yellow-wood, or Cuba wood, as it is variously called, is obtained
from a tree also growing in the West Indies, Central and South America.
It is used either as wood chips, or as a paste extract of 51 degrees
Twaddell, and occasionally as solid extract. Fustic contains two coloring
matters, morintannic acid, possessing the characteristics of a tannin, and
which is quite soluble in water, and morin, which is rather insoluble, and
which settles out from the liquid extract. Fustic is the most important of
the yellow dyes of natural origin, and is used considerably in fur dyeing
with logwood for shading the blacks, or for producing compound shades.
With the usual mordants fustic gives the following colors:

  With iron salts           dark olive
  With copper salts         olive
  With chrome salts         olive-yellow to brownish-yellow
  With aluminum salts       yellow
  With tin salts            bright yellow to orange-yellow

Brazilwood, or redwood, is the product of a tree found in Brazil, and
exists in several varieties, such as peach wood, Sapan wood, Lima wood,
and Pernambuco wood. They all yield similar shades with the various
mordants, and all seem to contain the same coloring principle, brasilin,
which, like the hematoxylin, has no dyeing power, but by fermentation and
oxidation it is converted to brasilein, corresponding to the formation
of hematein. Brazilwood and the related woods are used either as chips or
extract, but seldom alone, usually in conjunction with other dyewoods. By
combining logwood, fustic and Brazilwood in various proportions, and by
employing suitable mordants, all the shades required by the fur dyer can
easily be produced.

Quercitron is the inner bark of a species of oak (Quercus tinctoria) found
in the United States. It contains two coloring principles, quercetrin and
quercetin. The fresh decoction of quercitron bark is a transparent dull
orange-red which soon becomes turbid and deposits a yellow crystalline
mass. It is generally used in conjunction with other dyes.

Cutch is the dried extract obtained from a species of acacia, the
principal varieties being Bombay, Bengal, and Gambier cutch. It contains
two coloring principles, catechin and catechu-tannic acid. Cutch acts as
a tannin, and like other tannins discussed above, can be used for the
production of grey or black shades with iron mordants. It is employed
chiefly, however, for dyeing browns. Aluminum salts give with cutch
a yellowish-brown, tin salts give a lighter yellow, copperas gives a
brownish-grey, and chrome and copper salts give brown shades.

Turmeric is the underground stem of the Curcuma tinctoria, the coloring
principle being called curcumin. It may be used as a direct dye, but
usually a mordant is used. Turmeric is sometimes used in place of fustic.

While the tannins can be used alone with an iron mordant for producing
greyish to black shades, the dyewoods alone yield colors which would be
too bright to be suitable for dyeing furs. In order to tone down this
brightness, and to give to the dyeings that greyish undertone which is
characteristic of the natural furs, and which can only be imitated by
means of the iron-tannin compound, it is customary to combine the tannins
with the wood dyes. The iron-tannate constitutes the foundation of the
color which gets its intensity, and necessary brilliancy and bloom from
the wood dyes. Moreover, the presence of the iron-tannin compound helps
considerably to increase the fastness of the dyeing. Furs dyed with the
combination of the tannins and the wood dyes obtain an additional tanning
treatment which materially improves the quality of the leather, for not
only do the tannin substances exert this tanning action, but the dyewoods
as well, for they are themselves either of the nature of tannins, or
contain a coloring principle which is a tannin. It is to the combined
effects of the tannin substances and the dyewoods that furs dyed with
vegetable dyes owe their beauty of color, lustre, naturalness of shade,
permanence of the dyeing, and durability of the leather. Wood dyeings
on furs have for this reason acquired a just renown, but owing to the
introduction of the new kinds of fur dyes, the use of the vegetable dye
substances has been greatly reduced.

The dyes of vegetable origin can be applied to furs by either the brush
method or the dip method, or both, and since mordants are required
with the dyes of this class, they are applied in one of the three ways
mentioned in a previous chapter: first, by mordanting before dyeing;
second, by applying mordant and dye simultaneously; and third, by
mordanting after the skins have been treated with the dye.


I. DYEING WITH VEGETABLE DYES BY THE BRUSH METHOD

The use of the brush method in applying the natural dyes to furs is
limited to a comparatively few kinds of dyeing, namely to produce
special effects on furs, or to give to the upper-hair of furs a coat
of dye different from the base color. In a quite recent German patent
is described a process for blending a red fox as a silver fox and
the procedure affords a good example of brush dyeing with preliminary
mordanting. The specification is as follows: “D. R. P. 310, 425 (1918).
A process for dyeing red fox as silver fox. The tanned and dressed skin
is first superficially decolorized by applying a dilute mixture of milk
of lime, iron vitriol and alum, with a soft brush so as only to penetrate
the top-hair. Allow to remain for 4–6 hours, dry, and beat out the dust.
A dilute solution of iron vitriol is brushed on so as only to wet the
top-hair, and the skin is thus allowed to remain moist for 12–24 hours.
Then without drying, a solution of iron vitriol, salammoniac, litharge,
red argol and wood ashes is brushed on cold with a hard brush so as
to penetrate all the hair down to very near the skin. The skin has now
completely lost its red color, and has become a pale yellow. It is now
ready to be dyed. An infusion of roasted nutgalls, which have been boiled
for 3–4 hours with water, is applied cold with a soft brush to the upper
hair. Allow to remain so for 2–3 hours, and without drying, apply a weaker
solution of the roasted nutgalls with a hard brush so as to saturate the
hair thoroughly. Dry and beat out. According to the concentration of the
solution applied, the hair will be colored blue-grey to black, and the
shade can be varied by varying the strength of the solutions used. The
different parts of the skin, or those parts of different shades can be
dyed accordingly.”

In this patent all the operations, including killing, mordanting and
dyeing are done by the brush method, and the process, from this point
of view is quite similar to one which might have been employed a century
previous. It is evident that the time and effort required to carry out the
details as described in the patent would only be warranted in exceptional
cases, where the value of the dyed fur would be considerably greater than
that of the natural skin.

An example of the application at the same time of dye and mordant by the
brush method is the original French Seal dye, which is still employed to
a limited extent to produce a brilliant, deep, lustrous black topping on
furs which have already been dyed by the dip process. A typical formula
for the old French Seal dye is the following:

  Green copperas             10 parts
  Alum                       10   „
  Verdigris                  10   „
  Gall-nuts                  80   „
  Logwood extract
    (15 degrees Twaddell)   150   „
  Water                    1000   „

This mixture is applied to the top of the hair of the furs, after previous
killing, and the skins allowed to remain moist for several hours, and
also exposed to the air. The skins are then dried, and beaten out, and if
necessary a second coat of dye is brushed on. In dyeing seal-imitation
on muskrat, or skunk-imitation on opossum, for example, the black color
required on the top-hair, or the upper part of the hair when the furs are
sheared, can be produced by applying a mixture similar to the above, to
the furs after they have received their base color by the dip process with
natural dyes or with the Oxidation Colors. Occasionally, the dyeing is
given an after-treatment with a dilute solution of sodium bichromate to
help develop the color, the action in this case being that of an oxidizing
agent, and not of a mordant.

As far as the third method of mordanting is concerned, that of first
applying the dye, and then the mordant, it is rarely practised with
the brush method. The procedure, however, consists in first brushing
on a solution of the desired dye, then drying and brushing on a mordant
solution. These operations are repeated perhaps two or three times until
the proper shade is obtained, exposing the furs to the air for the color
to be developed.


II. DYEING WITH VEGETABLE DYES BY THE DIP METHOD

It was in the application to furs by the dip process that the use of the
vegetable dyes attained great importance, and although at the present
time, natural organic dyes have largely been superseded by the Oxidation
Colors and Aniline Black dyes, yet for certain purposes, and especially
for the production of blacks, the wood dyes still are able to hold their
own.

The dyeing of black formerly constituted probably the most important
branch of the fur dyeing industry, and was undoubtedly the most difficult
one. For it is possible to obtain as many different kinds of black
as there are dyers of this color, but only a few certain shades are
desirable. The division of the classes of furs into those derived from
the various kinds of sheep, and those obtained from other animals is
particularly marked in the dyeing of black, and both the composition of
the dye formulas and the methods of dyeing are somewhat different for
the two groups. For the dyeing of black on Persian lambs, broadtails,
caraculs, etc., a combination of logwood and nutgalls with the requisite
mordants is used, while on hares, Chinese sheep, foxes, raccoons, opossum,
etc., a mixture of logwood and turmeric or fustic, with the proper
mordants is used.

The general procedure is as follows: The dye substances to be used are
ground up to a powder in a mill constructed for the purpose, after which
they are boiled with water in a copper-lined kettle or cauldron, heated
from the outside by steam. The customary arrangement is to have a jacketed
kettle, supported on a stand, and having taps and valves to enable the
liquor to be drawn off, or pivoted, so that the kettle can be tilted,
and the contents poured out. The use of the copper-lined vessel is to be
preferred, as it is unaffected by any of the dye substances, and so cannot
cause any rust stains. After the dyes have gone into solution and have
cooled, the mordant chemicals, previously dissolved in water, are added,
and the mixture stirred up. The dyeing in this instance is effected by the
simultaneous application of dye and mordant. The dye mixture is now run
off, or poured out in the proper quantity into a number of small vats of
25–30 gallon capacity, or into a paddle vat, which can be closed, while
the paddle is rotating. The latter device is to be preferred because it
permits the dye to retain its temperature better and for a longer period
of time, but when lambs are being dyed only the open vats are used. The
temperature of the dye mixture is between 40° and 45° C., for only at
this temperature can the hair absorb the dye properly without injuring the
leather. The killed skins are immersed in the dyebath for a time, usually
overnight, after which they are removed, drained and hung up, with the
hair-side exposed to the air, so as to permit the dye to develop, which
takes place with the aid of the atmospheric oxygen. The dyebath is again
brought to the proper temperature, and the skins are again entered, to go
through the same process as often as is necessary to obtain the desired
depth of shade. The dyed skins are thoroughly washed to remove excess dye,
then dried and finished. The following are a few dye formulas used in the
production of blacks:

  Logwood extract       100 grams
  Chestnut extract       14 c.c.
  Turmeric               38 grams
  Iron acetate 6° Bé.    50 c.c.
  Water                1200 c.c.

or,

  Cutch                  15 grams
  Soda                   14 grams
  Logwood extract       120 grams
  Verdigris              19 grams
  Iron acetate 5° Bé.    16 c.c.
  Water                1200 c.c.

A recently published formula for dyeing China goat skins black, is the
following:

Dissolve 50 lbs. of dark turmeric and 45 lbs. of logwood extract and
make up to 300 gallons of solution, at 95° F. Enter the killed skins and
leave them in the liquor until they rise to the surface. Then take them
out and add 25 lbs. of logwood extract, 10 lbs. of sumach, 10 lbs. of
blue vitriol, 5 lbs. of fustic extract, and about 60 lbs. of iron acetate
liquor. Stir up well, and immerse the skins for 18 hours. Draw them up,
and expose to the air for 12 hours. Heat the liquor again to 95° F. and
put the skins back for 12 hours. Draw out, hang up in the air for a time,
then wash thoroughly, hydro-extract, dry and finish.

In a German patent, D. R. P. 107,717 (1898), is described a method for
dyeing lambs black, consisting in treating the skins for 24 hours in a
logwood bath, then rinsing in cold water, and mordanting for 15 hours in
a solution of bichromate of potash. The skins are then washed and treated
with a solution of iron salt, then dried. This process, while of not much
practical importance, is an illustration of mordanting subsequent to the
dyeing treatment.

As far as the production of other shades is concerned, the procedure is
quite similar to the regular black method. For a dark brown, for example,
the skins are dyed in a mixture containing

  Gall-nuts                  40 parts
  Verdigris                  10   „
  Alum                       10   „
  Copperas                    5   „
  Brazilwood extract
    (15° Twaddell)          150   „
  Water                    1000   „

employing operations just as in the case of the black.

Greyish-blue shades on white hares, lambs, kids, etc., can be obtained by
treating the skins successively in the following baths:

  1. Logwood extract  100 grams
     Water              1 liter
  2. Indigotine        10 grams
     Alum              10 grams
     Water              1 liter

Bluish-grey tones on the same furs can be produced by treating with

  1. Logwood extract  200 grams
     Indigotine        15 grams
     Water              1 liter
  2. Alum             150 grams
     Salammoniac       12 grams
     Water              1 liter

Similar grey shades can be produced by mordanting the skins with an iron
salt, and then dyeing in a weak bath containing gall-nuts, sumach and iron
vitriol. This method is very effective for making Alaska or silver fox
imitations.




CHAPTER XIV

FUR DYEING

ANILINE BLACK


Fur seal for a long time has been a fur of distinction and importance in
the fur industry, and consequently the dyeing of seal has constituted an
important, though not very extensive branch of the art of fur dyeing.
In quite recent times the popularity of seal has become so great that
imitations have had to be produced to help supply the demand, and as a
result, French seal, or seal-dyed rabbit, and the so-called Hudson seal,
which is seal-dyed muskrat, have acquired a great vogue. Occasionally
opossum, nutria and other furs are also used for the purpose of producing
seal imitations. While the supply of real seals is relatively small, and
the demand large, the production of seal imitations has assumed large
proportions, and as a result, the dyeing of seal and its imitations or
substitutes has come to be a great branch of the fur dyeing industry.

During the past thirty years, the long and tedious processes of dyeing
seal and seal imitations, involving the use of dyes of vegetable origin,
have largely been superseded by what is known as the Aniline Black dye.
It was the French who first worked out successfully the application of
Aniline Black to furs, and the method has attained much importance and
extensive use in the fur dyeing industry.

Aniline Black is the name given to an insoluble black dyestuff produced
by the oxidation of aniline in an acid medium. As a finished product it
cannot be used in fur dyeing, but if the hair of the furs be impregnated
with a suitable preparation of aniline and then treated with certain
oxidizing agents, the color will be formed on the hair, being firmly
fixed and giving a fast black, resistant to light, washing and rubbing.
The basis of the dye, aniline, is an oily liquid, possessing a peculiar
fishy odor, colorless when pure, but rapidly turning brown when exposed to
the air. It is obtained from benzol, which is distilled from coal-tar, by
treating with nitric acid, forming nitrobenzol, which when subjected to
the action of reducing chemicals is converted into aniline. The process
may be shown schematically as follows:

Coal--coal-tar--benzol--nitrobenzol--aniline oil--Aniline Black. Aniline
Black was by no means a new dye when the French succeeded in producing it
on furs. It had been used for a long time previous on textiles, chiefly
cotton. The history of the development of the Aniline Black process
throws considerable light on its nature and constitution, and so presents
many features of interest. As early as 1834, the chemist Runge observed
the formation of a dark green color when heated aniline nitrate in the
presence of cupric chloride. Fritsche, in 1840, noticed that when chromic
acid was added to solutions of aniline salt, a dark green, and sometimes a
blue-black precipitate was produced, and later the same chemist obtained
a deep blue by the action of potassium chlorate on aniline salt. It is
interesting to note that Perkin, in 1856, conducting similar experiments
on the oxidation of aniline with chromic acid, obtained a blue-black
product from which he extracted the first synthetic coal-tar dye, mauve.
Thus far, all the experiments on the oxidation of aniline proved to be
merely of scientific interest, but in 1862, Lightfoot patented a process
for the practical application of colors formed by the oxidation of aniline
on the fibre, a greenish shade being obtained by that method, to which the
name emeraldine was given, and by subsequent treatment with bichromate
of potash, the green was changed to a deep blue color. Since that time,
the methods for producing and applying Aniline Black have been developed
and improved, although all the processes were based on the principles
incorporated in Lightfoot’s original patent. However, it was not until the
last decade of the nineteenth century that the dyeing of furs by means of
the Aniline Black method was successfully attempted.

A knowledge of the nature and the manner of the chemical changes which
take place in the production of Aniline Black is a valuable aid in
obtaining satisfactory results in practise; and although Aniline Black
was extensively used before the true character of the reaction was
understood, since the successful determination of the constitution of
Aniline Black and the discovery of the real nature of the process by
Green and his collaborators in 1913, the methods have been considerably
improved and simplified, with correspondingly better results in dyeing.
As a consequence, the methods of dyeing furs with Aniline Black have also
become simpler and more efficient.

A discussion of the chemical changes which occur in the Aniline Black
process, is out of place here on account of the highly involved and
complicated character of the reactions, to understand which requires a
considerable knowledge of specialized organic chemistry. But the essential
features of practical importance in the production of Aniline Black are
the following: As already noted, one of the characteristic properties of
aniline is its tendency to turn from a colorless to a dark-brown liquid in
the presence of the air. This change is due, together with certain other
causes, to an oxidation brought about by atmospheric oxygen. By employing
oxidizing agents, this oxidation can be accelerated and carried further,
and eventually the Aniline Black is obtained. Among the substances which
may be used to bring about the conversion of aniline to the insoluble
black dye are manganese dioxide, lead peroxide, hydrogen peroxide, chromic
acid, ferric salts, potassium permanganate, chloric acid and chlorates
in the presence of certain metallic salts, particularly those of vanadium
and copper. Chlorates, especially sodium chlorate and potassium chlorate,
are the most commonly employed oxidizing agents, bichromate of soda or
of potash being used, in addition, to complete the oxidation. When using
chlorates it is necessary to have present in the dye mixture a small
quantity of a metallic salt, which, while not entering into the reaction
itself, is nevertheless indispensable as an oxygen carrier. Vanadium
compounds have proved to be the most effective for this purpose, and
according to an authority, one part of vanadium salt is sufficient to
cause the conversion of 270,000 parts of aniline to Aniline Black, the
necessary amount of a chlorate being present of course. Salts of copper,
cerium, and iron are also extensively used, but they are not quite so
efficient as vanadium.

The formation of the Aniline Black in practise takes place in three
well-defined steps, which it is important to be able to recognize and
distinguish in order to obtain the best results. The first stage of the
oxidizing process produces what is called emeraldine, which in the acid
medium of the aniline bath is of a dark green, while in the free state it
is of a blue color. As the oxidation proceeds, the second stage develops,
the emeraldine being converted to a compound called nigraniline. This in
acid solution is blue, and the free base is a dark-blue, almost black.
It was formerly considered that the nigraniline was the Aniline Black
proper, and so when this stage of the oxidation was reached, the process
was often interrupted and not carried to the limit. This can account for
the fact that Aniline Black dyeings usually turned green after a short
time. The reason for this is that nigraniline, when treated with weak
reducing agents, as, for example, sulphurous acid, is at once changed
to emeraldine, with its dark green color. Since there is usually a small
amount of sulphurous acid in the air, especially in places where coal or
gas is burned, an Aniline Black dyeing which has not been carried beyond
the nigraniline stage will be reduced in time to the emeraldine, and cause
the dyeing to become green. The last step in the oxidation changes the
nigraniline into what is properly called the ungreenable Aniline Black.
Weak reducing substances like sulphurous acid do not change this compound
to emeraldine, and stronger reducing agents only convert it to a brownish
compound, which changes back to the black when exposed to the air. It is
quite evident that in order to obtain a black which will not change to
green in time, the oxidation of the aniline must be carried to the last
stage. By making tests during the dyeing of the furs, it can easily be
determined whether the oxidation has proceeded far enough.

In the dyeing of textiles with Aniline Black, it is customary to carry
out the operation at comparatively high temperatures, approaching 100°
centigrade. With furs such temperatures are out of the question, so it is
necessary to repeat the dyeing several times in order to obtain the proper
depth of shade working in the cold. Only the brush method can be used in
applying the Aniline Black dye to furs, on account of the strong acidity
of the dye mixture, which would ruin the leather, if the dyeing were done
in a bath. Indeed, great care must be exercised even by the brush method
to avoid too great penetration of the dye liquid, otherwise the roots
of the hair will be attacked, and the leather may be “burned” from the
hair side. Furs dyed with Aniline Black are frequently after-dyed by the
dip-process with logwood or some other similar dye, in order to add to
the brilliancy of the dyeing. Combined with intensity of color, Aniline
Black on furs is the only dye which will also give fast, lustrous shades,
and leave the hair soft and smooth.

There are several methods of applying Aniline Black on furs, the most
important being

  1. One-bath Aniline Black
  2. Oxidation Aniline Black
  3. Diphenyl Black
  4. Aniline Black by Green’s Process


1. _One-bath Aniline Black_

A typical formula for this method is the following given by Beltzer:

  Aniline salt            10 kg.
  Sodium chlorate        1.5 kg.
  Copper sulphate        0.7 kg.
  Vanadate of ammonia     10 gr.

All these substances are dissolved hot in 50 liters of water, and allowed
to cool, forming solution A. Aniline salt is aniline oil which has been
neutralized with the exact quantity of hydrochloric acid to form the
hydrochloride. It forms white or greyish crystalline lumps very easily
soluble in water. The sodium chlorate is the oxidizing agent, and the
copper sulphate and the vanadate of ammonia are the oxygen carriers.

15 kg. of sodium bichromate are also dissolved in 50 liters of water,
forming solution B. The bichromate is also an oxidizing agent and serves
to complete the oxidation of the aniline to the black.

Immediately before using, solutions A and B are mixed together, both being
cool. In general practise it is customary to mix only small quantities
at a time, as a considerable precipitate forms when the whole batch
is mixed at once, the precipitate being so much waste dye substance.
Usually a liter of A and a liter of B are mixed at a time, and the furs
brushed with the mixture. The brushing must be varied according as the
hair is hard and stiff, or soft and tender. The hair must be thoroughly
impregnated in all directions, and the penetration must not be too deep
to affect the leather. With experience and dexterity satisfactory results
can easily be achieved. After the skins have been properly treated, they
are dried at a temperature of about 35 degrees centigrade. When dry, they
are returned to the dye bench, where they receive another application
of the dye mixture, and are again dried. This operation may be repeated
as often as six or seven times before a sufficiently intense black is
obtained. Another way of producing the desired depth of shade with fewer
applications is by using more concentrated dye mixtures. Each method
has its disadvantages, the greater number of brushings requiring the
expenditure of more time and labor, and the greater concentration of
the bath resulting in a considerable loss of dye substance due to the
formation of a large precipitate when the two solutions are mixed, and
moreover, not all furs can be treated with concentrated mixtures. The best
results with this method usually require the application of six coats of
a mixture of moderate concentration.


2. _Oxidation Aniline Black_

In order to overcome the difficulty of employing very concentrated dye
mixtures, or of making many applications of the dye, a method was devised
whereby the two solutions of the previous process, instead of being mixed
together, are applied successively to the hair of the furs, the following
formula, also by Beltzer, being an example:

  Aniline oil                     10 liters
  Nitric acid 36° Beaumé, or
  Hydrochloric acid 22° Beaumé    20 liters
  Cold water                      20 liters

This is solution A, and is merely a solution of aniline hydrochloride,
or nitrate, depending on which acid has been used. Nitric acid, although
more costly than the hydrochloric acid, is to be preferred, because it
is an oxidizing acid, and so assists in the oxidation of the aniline, and
besides, has a more beneficial effect on the hair than the hydrochloric,
in the matter of softness and luster.

  Sodium chlorate          4 kg.
  Copper sulphate          1 kg.
  Vanadate of ammonia     10 gr.
  Water                   50 liters

This is solution B, containing the oxidizing agent, and the oxygen
carriers. Just before using, equal quantities of A and B are mixed, and
the skins brushed with the mixture. The skins are then dried at 35–45°
centigrade, at which temperature the color begins to develop. When almost,
but not entirely dried, the skins are subjected to the action of warm
vapor, which is allowed to enter the drying chamber, so as to keep the
temperature about 40° centigrade, the color developing better in this
way. This operation may be repeated, or the skins are directly treated
with a solution of 25 kg. of sodium bichromate in 100 liters of water,
to complete the oxidation. The moist skins are exposed to the air for a
time, and then dried at 35° C.

This method of dyeing has several advantages over the One-bath Aniline
Black. It requires fewer brushings, and enables the complete utilization
of the dye solutions without loss. With three applications of the dye
mixture by the Oxidation process, as deep and intense a black can be
obtained as with six brushings by the One-bath method. The dyeings, too,
are nearly, but not fully as brilliant and even as in the latter case.
The greater the number of coats of dye that are applied the more regular
will the dyeing be.


3. _Diphenyl Black_

In 1902, the Farbwerke Hoechst, a large German producer of coal tar
intermediates and dyes, invented an Aniline Black process to which they
gave the name Diphenyl Black. The chief departure from the previous
Aniline Black methods was the replacing of part of the aniline oil of the
dye mixture by Diphenyl Black Base I, which is para-aminodiphenylamine.
This base has the property of being oxidized to Aniline Black, just like
aniline oil, and the advantage claimed for the Diphenyl Black is that it
produces an absolutely ungreenable black. The method of application is
practically the same as for the other Aniline Black processes, chlorates
being used as the oxidizing agents, in the presence of oxygen carriers
such as salts of copper and vanadium. The use of bichromates is dispensed
with. On account of the comparatively high cost of the Diphenyl Black
Base I, this method has not found very extensive application, especially
as highly satisfactory ungreenable blacks can now be produced by other
methods.


4. _Aniline Black by Green’s Process_

In 1907, Green, who has done much work in the direction of elucidating the
character of the Aniline Black process, obtained a patent for a method
of applying Aniline Black in a manner which was different from all the
previously known formulas. The invention created great interest, and
although in its original form it did not find a wide application, many of
the methods used at the present time are in one way or another derived
from the idea of Green. A resumé of the patent will therefore be given
here: “The invention relates to the production of an Aniline Black, the
new process differing from all other known processes by the fact that
the oxidation of aniline is effected solely or mainly by the oxygen of
air. The possibility of dispensing with an oxidizing agent depends on the
discovery that the addition of a small quantity of a para-diamine, or of
a para-amido-phenol to a mixture containing aniline and a suitable oxygen
carrier, such as a salt of copper, greatly accelerates the oxidation of
the aniline by the atmospheric oxygen. Further, whereas in the ordinary
processes of Aniline Black, the quantity of mineral acid employed cannot
be materially reduced below the proportion of one equivalent to one
equivalent of the base, under the new conditions the mineral acid may
be wholly or partially replaced by an organic acid such as formic acid,
without the quality of the black being materially affected. As suitable
oxygen carriers the chlorides of copper have been found to give the best
results, it being preferrable to use the copper in the form of a cuprous
salt. This is effected by adding to the dye mixture cupric chloride,
together with a sulphite or bisulphite in sufficient quantity to reduce
the cupric salt to the cuprous state, and a sufficient quantity of a
soluble chloride to keep the cuprous chloride in solution. Among the
compounds suitable for the production of this black in conjunction with
aniline are, para-phenylene-diamine, dimethyl-para-phenylene-diamine,
para-amido-diphenylamine, para-amido-phenol, etc.”

This method may be used alone as the other Aniline Blacks, or the dyed
skins may be after-dyed in a bath containing a logwood dye, or it may be
used in conjunction with mineral dyes, or with the Oxidation Colors (see
next chapter). A typical formula for the black by Green’s process is the
following:

  Para-amido-phenol            0.5 kg.
  Aniline oil                   10 liters
  Hydrochloric acid 22° Bé.     10 liters
  Acetic acid 40%                5 liters
  Cold water                    25 liters

This is solution A. Solution B is prepared by dissolving

  Copper sulphate       2 kg.
  Salammoniac          10 kg.
  Cold water           50 liters

A and B are mixed, and the mixture applied to the hair of the furs several
times, drying each time at 35°–40° C. After three coats of dye have
been applied, a pretty and fairly intense black shade is obtained, which
is developed further by treating with a solution of 25 grams of sodium
bichromate per liter of water. The skins are then allowed to dry in air,
and then if desired, an after-dyeing is made with some other dye.

On account of its extreme fastness, Aniline Black, produced by any of
the methods outlined above, has attained a justifiable popularity for
the dyeing of furs, in spite of the necessity of using the more or less
cumbersome brush method of applying the dye. Very recently there was
issued to a German company a patent in which is described a method whereby
furs can be dyed with Aniline Black by the dip process. An abstract of
the patent (D. R. P. 33402) is as follows: “As is known, aniline salt,
and similar salts, together with oxidizing agents like bichromates,
chlorates, etc., cannot be used for dyeing furs by the dip process,
because the strongly dissociated mineral acid is injurious to the leather.
The dissociation of the acid can be reduced by adding neutral salts, like
common salt, or Glauber’s salt, so that good results can be obtained by
dyeing in a bath of the dye mixture, the leather retaining its softness.”

Thus far there have been no reports of the successful practical
application of this patent, so its value cannot be discussed. It is
extremely doubtful, however, that furs will ever be dyed in the dyebath
with the present type of Aniline Black formulas, no matter what substances
are added to prevent the leather from being affected.




CHAPTER XV

FUR DYEING

OXIDATION COLORS


The year 1888 may be considered the beginning of a new era in the
history of fur dyeing; the commencement of a period which was to see
the time-honored, traditional methods of the masters of the art give way
to newer methods of an entirely different character; and moreover, the
initiation of an age when science with its basis of fact and logic, was
to undertake the rationalization of an industry which had hitherto worked
upon a more or less irrational, empirical and uncertain comprehension
of the fundamental principles involved. It was not the work of a single
day, or even of a year which brought about the virtual revolution in the
dyeing of furs, but the result of long, patient, systematic effort. About
this time, the German coal tar industry was attaining its real stride
along the path of progress and achievement, and had already succeeded in
reaching, to an appreciable degree at any rate, most users of coloring
matters, with the consequence that the natural dyes, with their time and
labor-consuming processes of application were gradually being superseded
by the new synthetic dyestuffs which could be simply and quickly applied.
It was now the turn of the fur dyeing industry to receive the attention of
the scientists and technologists responsible for the growth of the coal
tar dye industry, and so there appeared in the above-mentioned year, the
following patents, taken out by a German chemist named Erdmann:


D. R. P. 47349

A Process for Dyeing Hair and Feathers

If white hair or feathers are soaked in an aqueous or alcoholic solution
of para-phenylene-diamine, and then exposed to the slow oxidation of
the air, or are treated in a second solution with some oxidizing agent,
then the hair or feathers will be dyed. According to the oxidizing agent
chosen, and the concentration of the solution used, the color obtained
will be light or dark, varying from the palest blond to the deepest
blue-black. Particularly suitable as oxidizing substances are ferric
chloride, permanganates, chlorates, hypochlorites, bichromates, and
hydrogen peroxide. The dyeings are fast, that is, they do not come off,
and the color cannot be removed by washing. Following examples may serve
to make the process clear:

20 grams pure para-phenylene-diamine and 14 grams caustic soda are
dissolved in a liter of water. The hair, previously degreased, is soaked
thoroughly in this solution, and while moist is entered into a three per
cent solution of peroxide of hydrogen. The action is not instantaneous,
but after a day, the hair is dyed a dark shade; by repetition of these
operations a blue-black is obtained.

The para-phenylene-diamine can be replaced in this process by other
similar bases, such as dimethyl-para-phenylene-diamine, as well as the
naphthylene-diamines. Since the substances which can be applied by this
process are uninjurious, the method described can be used to dye human
hair on the head or beard, and so seems suited to replace for the dyeing
of hair, the metallic salts and various pyrogallic solutions which are on
the market, and which are harmful to the health.


D. R. P. 51073 Supplement to 47349; Process for Dyeing Hair

This patent was an extension of the original patent to include certain oxy
and amido-oxy compounds, the method being essentially the same otherwise
as in the original patent. An illustration of the process is as follows:

73 grams para-amido phenol hydrochloride are dissolved with 40 grams
caustic soda in a liter of water. The solution dyes hair a golden-yellow,
which on subsequent treatment with a solution of ferric chloride turns to
a red-brown.

In these two patents is to be found the basis of the modern fur dyes
and fur dyeing methods. It is interesting to note that furs were not
mentioned at all in connection with the process, which was intended
mainly for dyeing hair, especially on the human head. It was only several
years later that the value of the method for dyeing furs was realized.
So about 1894, the Aktien Gesellschaft für Anilinfabrikation put upon
the market three fur dyes under the trade name Ursol, Ursol D, giving
dark-brown to black shades; Ursol P, giving red-brown colors; and Ursol
C, giving a yellowish-brown shade. Pyrogallic acid had been previously
used as a hair dye, and also to a slight extent as a fur dye, so it was
used in conjunction with the Ursol dyes for shading purposes. The new fur
dyes were not dyes in the ordinarily accepted sense of the term. They
were really coal-tar intermediates, substances similar in character to
aniline, and their dyeing property depended on the fact that they could
be oxidized either by atmospheric oxygen, or by means of oxidizing agents,
forming colored insoluble products. When the oxidation of the intermediate
was caused to take place on the hair the colored product formed on and
in the hair fibre, and remained fast. The reactions bringing about the
conversion of the intermediate to the colored insoluble compound are quite
analogous to those of the Aniline Black process, though possibly not so
complicated, with the important difference, however, that, while in the
production of Aniline Black acid is essential, in the present instance the
oxidation can be carried on in neutral or even alkaline medium. On account
of the character of the method used in applying the new fur dyes, the
name Oxidation Colors has been given to them. Strictly speaking, Aniline
Black is also an Oxidation dye, but it is usually considered in a class
by itself. The methods used at first in the application of the Ursol dyes
to furs followed closely the process as described in the patents. The furs
were first killed, usually by brushing on a lime mixture, drying, and then
beating out the dust. This operation was repeated, if necessary. Then a
solution of the desired dye, mixed with an equal volume of 3% peroxide of
hydrogen was brushed on and the fur allowed to lie exposed to the air. The
dyeing could also be done by the dip process, less concentrated solutions
being used. By varying the concentration of the solution, and prolonging
or shortening the time of action, the shades could be varied from very
light to very dark, and by combining two or more of the Oxidation Colors,
many different color effects could be produced. Soon other fur dyes were
developed and put on the market; for example, Ursol DB, giving blue to
blue-black shades, and Ursol 2G, yielding yellowish tones suitable for
mixing with the other colors. Ursol C was discarded shortly after its
introduction. The dyeings obtained with the Oxidation Colors seemed to be
very fast, resisting successfully the action of cold or hot water, or even
hot soap solution. Moreover, a dyed hair examined under the microscope
appeared to be colored through the epidermis to the medulla, and no
individual particles of dye could be discerned.

The new fur dyes had many evident advantages over the coloring matters
in general use at the time. The simplicity of the dyeing operations,
the short duration of the process, the great tinctorial power of the
new products, were facts which strongly recommended themselves to the
progressive fur dyer. The cost of the dyes was higher than that of the
vegetable dyes, but this consideration was largely overbalanced by the
saving in time and labor in using them. And yet, the Ursol dyes found
only a comparatively small market. The majority of fur dyers, always
conservative and reluctant to turn from the traditional ways of the
industry were skeptical of, and even hostile towards the new dyes and
the new methods of dyeing. In a sense, this opposition was justifiable.
It was not an easy task to relinquish all at once methods which had
been successfully applied for generations back, and with which they
were thoroughly experienced, in favor of processes which were radically
different, and with which they had no experience at all. But some
enterprising spirits among the fur dyers undertook to try out the new
products and it was not long before the skeptics had good cause for
condemning the work and achievements of the chemists as far as fur dyeing
was concerned. The new type of dyes did possess some of the advantages
claimed for them, but they also possessed many highly objectionable
features, which had never been manifest with the vegetable dyes. First
of all, the dyeings were not so fast as had at first appeared, for the
color came off the hair when the furs were rubbed, brushed or beaten.
Then it was observed that after a short time some of the dyeings changed
color, and at the same time the hair lost its gloss and became brittle.
The condition of the leather after dyeing was anything but satisfactory.
Most serious of all, however, was the appearance among the workers in
the dyeing establishments, and also among the furriers who worked with
the dyed skins, of certain pathological conditions which had hitherto
been unknown. Various skin diseases, eczemas, inflammation of the
eyes, asthmatic affections and intestinal irritations were some of the
afflictions which were directly attributable to the use of fur dyes of
the Ursol type. Medical science was at a loss to know how to treat these
ailments, because their nature was not understood.

Here indeed, were obstacles threatening to destroy all the hopes which
the discovery of the new class of dyes had aroused, and to check at the
outset the possibility of rational progress in the fur dyeing industry.
But the men of science were not content to let the matter drop thus.
Difficult problems had been solved before, and surely there must be
some way of overcoming the objections and deleterious features of a
system of fur dyeing which had so much potential merit. Where hindrances
sprang up in the path of progress, it was the duty of the chemist to
remove them, and when difficulties arose, it was up to him to resolve
them, as far as was humanly possible. So the chemists who had been
responsible for the introduction of the Oxidation Colors set themselves
to the task of eliminating the undesirable or injurious qualities. It
was many years before the results of painstaking effort and persistent
study cleared up the causes of all the objectionable aspects of the fur
dyes, and suggested means of overcoming them satisfactorily. The work
had been directed to the improvement of the dyes and of the methods of
dyeing with them. Purer intermediates were produced, and more easily
soluble ones, so that there would be no possibility of ultra-microscopic
particles of the dye being deposited on the surface of the hair from the
dye solution, instead of being taken up within the hair fibre. It was
this superficial deposition of minute crystals of the dye or of the only
partially oxidized intermediate, on the hair, crystals so fine as to be
invisible in the ordinary high-power microscope, which caused the color
to come off when the furs were brushed or beaten, giving rise to a dust
which was frequently very injurious to the health. Then, mordants were
adopted to help fix the dyes, compounds of copper, iron, and chromium
being used as formerly with the vegetable dyes, and the range of shades
was also increased thereby. Certain of the Oxidation Colors had a tendency
to sublime off the hair, so the dyed hair was chemically after-treated
in such cases to prevent this. The causes of the pathological aspects of
dyeing with the Oxidation fur dyes were not so readily disposed of. But
the adoption of devices to prevent the formation and circulation of dust
during the handling of the dye, the employment of adequate protection
against contact with the dye or its solutions, the use of the most dilute
solutions possible in dyeing, the thorough washing of the dyed skins to
remove any excess of the coloring matter, the prevention of dust formation
in the drying of the skins, and the rigid observance of, and adherence to
hygienic laws, were all factors in the elimination of the health-impairing
phases of dyeing with the Oxidation Colors.

It was only after all these improvements had been accomplished that the
fur dye intermediates began to acquire a degree of popularity among fur
dyers, and strange as it may seem, there was a more ready market for
these dyes in America, than in Germany where they were manufactured. Other
manufacturers of coal-tar intermediates also began to produce fur dyes,
and so, in addition to the Ursols, there were the Nako brand, the Furrol
brand, the Furrein brand, and one or two others. New dyes were invented,
until the whole range of colors suitable for fur dyeing had been produced.
The black dye, however, presented some difficulty. A black dye which would
rival logwood blacks could not be attained. Ursol DB in conjunction with
Ursol D was being used to produce bluish-blacks, but the dyeings were not
fast, turning reddish after a time. In 1909, a patent was taken out for
a dye mixture, which was made up like the DB brand, but instead of using
toluylene diamine with para-phenylene-diamine, the new dye was made up of
a methoxy, or ethoxy-diamine with para-phenylene-diamine, and it yielded
brilliant bluish-blacks, which were fast, and which very nearly approached
the logwood black in luster, intensity, and bloom. For some purposes,
however, the production of a black color is still dependent on the use of
the logwood dye.

When the Great War cut off to a large degree the importation of skins
dyed in Europe, the American fur dyeing industry developed tremendously,
and in a comparatively short time was able satisfactorily to accomplish
in the way of dyeing furs, what had taken foreign dyers a much longer
period to attain. It had been previously considered that furs could be
dyed properly only by European fur dyers, but the achievements in this
direction by Americans fully dispelled this belief. But the success of
the fur dyers in America might not have been so marked or rapid, had it
not been for the work of the American chemists. The war had also shut off
the supply of German dyes, upon which the dyeing industries of America
had formerly been dependent, so enterprising chemists in this country
undertook to fill the need, and in a surprisingly short time, American fur
dyes, in every respect the equal of the foreign product were offered to
the American fur dyers, and at the present time, the requirements of the
fur dyeing industry in this country are being adequately met by domestic
producers. Among the brands on the market are the Rodol, Furamine,
Furol, and several others. The Oxidation Colors are now being offered
in a high state of purity, and easily soluble, free from any poisonous
constituents, and there is absolutely no reason for the appearance of
any pathological conditions among workers on dyed furs, or users of such
furs, provided the necessary precautions have been taken in the dyeing
process. The occurrence of any affection which can be traced to dyed fur,
cannot possibly be due to the dye itself, but to gross carelessness and
negligence in dyeing, and in any such event, the dyer responsible should
be brought to account.

In order to get a better understanding of the nature and action of the
Oxidation Colors, a typical one will be studied in some detail. The most
important one in this class is para-phenylene-diamine, usually designated
by the letter D in all commercial brands of this fur dye, while its
chemical formula is represented as C₆H₄(NH₂)₂. When pure it occurs in
colorless, crystalline lumps, which rapidly turn brown when exposed to
the air; the technical product of commerce is of a dark-brown color.
It dissolves readily in hot water when pure, and also in acids. At one
time the hydrochloride was used instead of the free base, on account
of its greater solubility, but now a base is made which is sufficiently
pure to be very soluble in water. There are several methods of preparing
para-phenylene-diamine: first, by the reduction of amido-azobenzol,
the product obtained in this way always containing a slight amount of
aniline, which reduces the solubility, and also gives rise to poisonous
oxidation products during the dyeing process; second, by the reduction
of paranitraniline, the quality and solubility of the product in this
case depending on the purity of the starting material; and third, by the
treatment of para-dichloro-benzol with ammonia under pressure, the best
product being obtained by this method. The crude para-phenylene-diamine,
made by any of the above processes, is generally distilled in vacuo, the
refined base being obtained as lumps with a crystalline fracture.

The first step in the oxidation of the para-phenylene-diamine is the
formation of quinone di-imine, NH:C₆H₄:NH. This is a very unstable
compound in the free state, and even in aqueous solution it decomposes
within a comparatively short time, or combines with itself to form a more
stable substance. Quinone di-imine has a very sharp, penetrating odor, and
produces violent local irritations wherever it comes in contact with the
mucous membrane. If a small quantity of para-phenylene-diamine is absorbed
into the human body, by breathing the dust, or otherwise, the formation
of quinone di-imine takes place internally with consequent irritation of
the mucous lining throughout the body. The various pathological conditions
mentioned before may be ascribed to irritation caused by quinone
di-imine. In any dyeing process where there is a possibility of the
formation of quinone di-imine, as is the case with most dyes containing
para-phenylene-diamine, special precautions must be taken by the workers
in handling the dye or coming in contact with its solutions, and no one
who is particularly sensitive to irritation should be permitted to work
in a place where such dyes are used.

The next step in the oxidation of the para-phenylene-diamine is the
formation of what is called Bandrowski’s base. Three parts of the quinone
di-imine combine with themselves, forming a substance of a brown-black
color, which was formerly regarded as the final oxidation product. The
formula of Bandrowski’s base is represented by the following chemical
hieroglyphics:

  (NH₂)₂.C₆H₃.N:C₆H₄:N.C₆H₃(NH₂)₂.

Further investigation has shown that the oxidation proceeds beyond this
stage with the formation of a compound of what is known as the azine type,
which is depicted by the chemist as

             NH      NH
  (NH₂).C₆H₃<  >C₆H₂<  >C₆H₃.NH₂.
             NH      NH

It is by no means certain that this substance is the true coloring matter
obtained by the oxidation of para-phenylene-diamine, for the reactions
may continue still farther, producing even more complicated oxidation
products. Scientific research and study has not as yet gone beyond this
stage.

The reactions of the other dyes of the Oxidation type are quite similar to
those of para-phenylene-diamine, some being simpler, and others being even
more complex. The presence of certain chemical groups in the intermediate,
or the relative position of such groups are factors responsible for the
variations in shade.

With the various mordants, the Oxidation Colors give different shades, and
a great range of colors can be produced either by combining mordants, or
combining dyes, or both. The following tables illustrate the shades formed
with the customary mordants.

  =========================================================================
           |    CHROME     |     COPPER     |     IRON     |    DIRECT
  ---------+---------------+----------------+--------------+---------------
  Ursol D  | brown black   | coal black     | coal black   | dark brown to
           |               |                |              |   brown black
  Ursol P  | dull red brown| dull dark brown| grey brown   | light brown
  Ursol 2G | yellow brown  | dull yellow    | yellow brown | dull yellow
           |               |   brown        |              |
  Ursol A  |    ...        |     ...        | blue black   | blue to blue-
           |               |                |              |   black
  Ursol 4G | light brown   | medium brown   | yellow       | pure yellow
  Ursol 4R | orange brown  | light yellow   | red brown    | orange red
           |               |   brown        |              |
  Ursol    |               |                |              |
    Grey B | greenish grey | greenish grey  | mouse grey   |     ...
  Ursol    |               |                |              |
    Grey R | brownish grey | brownish grey  | reddish grey |     ...
  ---------+---------------+----------------+--------------+---------------

Fur dyes of American make being equal in every way to the German product,
show the same color reactions with the various mordants. The following
table shows the shades produced with the same mordants as above:

  =========================================================================
           |    CHROME     |    COPPER     |     IRON      |     DIRECT
  ---------+---------------+---------------+---------------+---------------
  Rodol D  | brown black   | coal black    | coal black    | brownish black
  Rodol P  | red brown     | dark brown    | grey brown    | light brown
  Rodol 2G | yellow brown  | yellow brown  | yellow brown  | dull yellow
  Rodol 4G | light brown   | light brown   | reddish brown | pure yellow
  Rodol A  |     ...       | blue black    |     ...       | blue black
  Rodol    |               |               |               |
    Grey B | greenish grey | greenish grey | mouse grey    |     ...
  Rodol    |               |               |               |
    Grey R | greenish grey | brownish grey | mouse grey    |     ...
  ---------+---------------+---------------+---------------+---------------

All these shades are produced by dyeing in a bath containing a _neutral_
solution of the dye. Sometimes the dye comes in the form of a salt of
a mineral acid, like hydrochloric or sulphuric acid, in which case a
sufficient amount of an alkali, usually ammonia, is added to liberate
the free base. According to the Cassella Co., German manufacturers of the
Furrol brand of fur dyes, the dyeing can also be carried on in slightly
alkaline or in slightly acid solution, a different series of shades being
obtained in each instance. Ammonia is used to render the bath alkaline,
and formic acid to make it acid. The most customary practise, however, is
to use neutral solutions of the dyes.

For preparing the mordant solutions much smaller quantities of the
metallic compounds are used than in the case of the vegetable dyes. With
chrome mordants cream of tartar is always employed as an assistant, and
occasionally also with copper and with iron mordants. With copper, and
also with iron mordants no addition is made at all, or sometimes a small
quantity of acetic acid is added. The temperature of the mordant solution
is kept about 30° C., and the duration of the mordanting varies from 2–24
hours according to the depth of shade desired. The concentration of the
solution may also be varied, it sometimes being just as well to use a
strong mordant solution and less duration of mordanting. Chrome may be
combined with copper, and iron may be combined with copper, but chrome
and iron do not go together as mordants. Some typical average mordanting
formulas are as follows:

         Chrome mordant.
  Bichromate of soda    2.5 gms.
  Cream of tartar       1.5 gms.
  Water                   1 liter

         Copper mordant.
  Copper sulphate         2 gms.
  (Acetic acid 50%        2 gms.)
  Water                   1 liter

          Iron mordant.
  Ferrous sulphate        2 gms.
  (Acetic acid 50%        2 gms.)
  Water                   1 liter

or,

  Iron pyrolignite 30%   10 gms.
  Water                   1 liter

      Chrome-copper mordant.
  Bichromate of soda      2 gms.
  Copper sulphate      0.25 gms.
  Cream of tartar       1.0 gms.
  Water                   1 liter

       Copper-iron mordant.
  Copper sulphate         2 gms.
  Ferrous sulphate        2 gms.
  (Acetic acid 50%        2 gms.)
  Water                   1 liter

The killed skins are immersed in the mordanting solution, and allowed
to remain the required length of time. They are then thoroughly rinsed
to remove any excess of the mordant, and are hydro-extracted. Under no
circumstances should mordanted skins be permitted to dry, for they would
be unfit for use again.

The dyebath is next prepared by dissolving the necessary quantity of the
dye, varying from 0.1 gm. to 10 gms. per liter. Then if the solution must
be neutralized, the ammonia is added and the temperature of the bath is
brought to 30–35° C. by the addition of cold water. This temperature is
maintained throughout the dyeing operation. To the solution is added the
oxidizing agent. Ordinary commercial peroxide of hydrogen containing 3%
by weight is the usual oxidizer, although perborates have been suggested.
15–20 parts of peroxide of hydrogen for every part of dye are added, and
the dye solution brought to the proper dilution. As soon as the dyebath is
ready, the skins are entered, and worked for a short time to effect even
penetration. They are then left in the dyebath for 2–12 hours or longer
according to the depth of shade. After being satisfactorily dyed, the furs
are rinsed thoroughly, hydro-extracted and dried and finished. Where the
dye is to be applied by the brush to the tips of the hair, stronger dye
solutions are used, the brushed skins being placed hair together and let
lie for about 6 hours in order to permit the color to develop, after which
the furs are dried and drum-cleaned.

Some shades, particularly black, have a tendency to rub off slightly. In
order to overcome this, the dyed furs, after rinsing, are treated with a
cold solution of 1/2 part of copper sulphate per 1000 parts of water, for
3–4 hours, then without rinsing, hydro-extracted and dried. Furs which
have been tipped are brushed with a 1–2% solution of copper sulphate and
dried. Care must be taken in this after-treatment, for the use of too
strong a solution of copper sulphate, or too prolonged action of such a
solution will materially alter the shade of the dyed fur.

A few typical formulas will serve to illustrate the general methods of
employing the Oxidation Colors:


_Brown Sable Imitation on Unsheared Rabbit_

The skins are killed with soda, soured, and washed, then mordanted with

  Bichromate of soda      2 grams
  Copper sulphate       .25 grams
  Cream of tartar         1 gram
  Water                   1 liter

for 24 hours. Then washed, and dyed for 24 hours with

  Fur Brown 2G[3]         3 grams
  Hydrogen peroxide      45 grams
  Water                   1 liter

Wash and dry the skins, then brush the tips with

  Fur Brown D[3]         20 grams
  Hydrogen peroxide     400 grams
  Water                   1 liter

  [3] Inasmuch as most manufacturers use the same letters to designate
      the various dyes, any equivalent brand of fur dye may be used in
      place of those here mentioned.


_Black on Sheared Muskrat_

The skins are killed with soda, soured, and washed, then chrome mordanted
for 6 hours. Then they are dyed for 6 hours with

  Rodol P               1.5 grams
  Pyrogallic acid        .7 grams
  Ammonia               2.0 grams
  Hydrogen peroxide      45 grams
  Water                   1 liter

The dyed skins are washed and dried, then tipped with

  Rodol D                20 grams
  Rodol DB                2 grams
  Hydrogen peroxide     450 grams
  Water                   1 liter


_Brown on Thibet Sheep Skin_

The killed skins are mordanted for 6 hours with a chrome mordant, then
dyed for 6 hours with

  Ursol P                 1 gram
  Pyrogallic acid         1 gram
  Ammonia                 2 grams
  Hydrogen peroxide      40 grams
  Water                   1 liter

It is also possible to combine dyeings with the Oxidation Colors with
Vegetable dyeings, or with Aniline Black. For example, if it be desired
to produce an imitation skunk on a raccoon, and an exceptionally fast and
intense and lustrous black on the tips of the hair, the skins are dyed
in the bath with the Oxidation dyes, and the tips of the hair are brushed
with a mixture such as described under Vegetable Colors for the production
of French seal, as follows:


_Imitation Skunk on Raccoon_

The skins are killed with caustic soda, soured and washed, then mordanted
with an iron-copper mordant as described, and then dyed with

  Fur Grey R              3 grams
  Ammonia                 2 grams
  Peroxide of hydrogen   45 grams
  Water                   1 liter

After washing and drying, the dyed skins are brushed over with a mixture
such as used for dyeing French seal with Vegetable Colors.

In a similar manner, the Oxidation Colors may be used to give a base color
to furs dyed by the Aniline Black process.

It is apparent from these few illustrations that a great variety of shades
can be produced, and the dyeing of imitations of the better class of furs
on cheaper skins is a comparatively simple matter, after an understanding
of the nature of the dyes has been obtained, and a certain amount of skill
acquired in working with these dyes.




CHAPTER XVI

FUR DYEING

COAL TAR DYES


In addition to the Aniline Blacks and the Oxidation Colors already
discussed there are certain of the synthetic coal tar dyes such as are
generally used in the dyeing of textiles, which can also be applied on
furs. There are several classes of these dyes, varying somewhat in their
nature, and consequently in their manner of application; in the main they
produce bright shades, such as are but seldom used on furs, yet which may
occasionally serve for the production of novel effects. Basic, acid and
chrome colors are the types which can be employed.

Basic colors possess great fullness and tinctorial strength, but have a
tendency to rub off, and the tips of the hair take a darker shade with
these dyes than the rest of the hair. The addition of acetic acid and
Glauber’s salt to the dyebath will result in a more uniform dyeing. On
account of the comparatively poor fastness to rubbing and washing, basic
dyes are used only for dyeing furs which are intended for cheap carpet
rugs, such as sheep and goat. They may also find use in the production
of light fancy shades on other white furs. The procedure is usually as
follows: The furs are killed in the customary manner with soap and soda
or ammonia, or if this is insufficient, with milk of lime. A soap-bath is
then prepared containing 2.5–6 grams of olive-oil soap per liter of water.
The temperature of the bath is brought to 40° C. To this is added the
solution of the dyestuffs, prepared by mixing the required color or colors
with a little acetic acid to a paste, and then pouring boiling water on
the mixture until dissolved. Undissolved particles or foreign matter are
removed by passing this solution through a cotton cloth or sieve, and
the clear solution then mixed with the soap-bath. The well-washed skins
are then entered into the dyebath and immersed for about half an hour,
or until the desired depth of shade is obtained. They are then removed,
pressed or hydro-extracted and dried. For the production of light shades,
the following dyes may be used:

For cream, light sulphur-yellow, maize, salmon, etc.
  Combinations of
  Thioflavine
  Rhodamine B
  Irisamine G

For greenish-yellows
  Combinations of
  Thioflavine
  Victoria Blue B

For light pink
  Rhodamine B
  Irisamine
  Rose Bengal Extra N

For purple
  Methyl Violet 3B–6B
  Crystal Violet

For sky-blue
  Victoria Blue B

For white
  Victoria Blue B (Milk-white)
  Methyl Violet 3B–6B
  Crystal Violet (Ivory-white)

To produce very delicate shades, the moist dyed skins are subjected to a
sulphur bleach overnight, to lighten the color, then rinsed, and dried.
Full, brilliant shades may be obtained by dyeing in a bath of 40° C.,
acidulated with 2–3 grams of acetic acid per liter of solution, the
following dyestuffs being suitable:

For yellow to orange
  Thioflavine
  Paraphosphine
  Rhodamine
  Safranine
  New Magenta O

For pink
  Rhodamine B
  Rose Bengal Extra N

For light red
  Safranines

For bordeaux and red
  Magenta
  New Magenta
  Russian Red
  Cerise

For violet
  Methyl Violet 6B–4R
  Crystal Violet 5B

For blue
  Victoria Blue B
  Methylene Blue BB
  New Methylene Blue N

For green
  Malachite Green Crystals
  Brilliant Green Crystals, or combinations of
  Thioflavine
  Diamond Phosphine
  Victoria Blue B

For brown
  Chrysoidines
  Bismarck Browns

In dyeing skins with harder hair than that of sheep or goat, mere killing
is insufficient to render the hair capable of taking up the dye. The
skins are therefore immersed before dyeing, in a cold, weak solution
of chloride of lime, the affinity of the hair for the dye being thereby
greatly increased.

Acid dyes are employed when a greater fastness is required than can be
obtained with the basic colors. Sulphuric acid in a quantity equal to
half the weight of the dyestuffs used, together with four times that
quantity of Glauber’s salt is added to the dyebath. Formic acid may be
used in place of the sulphuric acid, very good results being obtained.
The skins are immersed in the dyebath, and worked until thoroughly soaked
with the dye liquor, and then allowed to remain until the proper depth
of shade is attained, or overnight. The temperature of the solution is
about 40° C., and only very light shades can be produced in this manner.
In 1900 and again in 1914, the Cassella Co., a large German manufacturer
of dyestuffs, obtained patents for processes enabling the dyeing of
furs in hot solution with the acid dyes. The method required that the
skins be chrome-tanned in order to render them resistant to the action
of hot solutions, the addition of a small amount of formaldehyde to the
chrome solution increasing this effect. The skins are then treated with a
solution of chloride of lime in order to increase the affinity of the hair
for the dyestuffs. The method as it is now practised is as follows: The
skins which have been cleaned and washed are chrome tanned by the method
as described in the chapter on Tanning Methods, 60 grams of formaldehyde
being added to every 10 liters of the chrome solution. After proper
tanning the skins are rinsed, and while still moist they are subjected to
a treatment with chloride of lime. They are first immersed for 15 minutes
in a cold bath containing 120 grams of hydrochloric acid 32–36° Twaddell
per 10 liters of water, then without rinsing, they are entered into a bath
made up by adding gradually in four portions the clear solution of 2–4
grams of the chloride of lime per 10 liters of water. After working for
an hour, the skins are removed and entered again into the acid solution,
in which they are worked for another 15 minutes. In order to neutralize
and remove the last traces of the chloride of lime from the furs, they are
rinsed in a luke-warm bath containing 1–2 grams of sodium thiosulphate,
or hyposulphite of soda, in 10 liters of water. The skins are then rinsed
again, and hydro-extracted, or pressed, and are ready for dyeing. The
dyebath is prepared with the required quantity of dye, to which is added
10–20% Glauber’s salt and 2–5% acetic acid (both calculated on the weight
of the skins). The skins are entered at 20° C., then after three-quarters
of an hour to 40° C., and then after another hour slowly to 50–55° C. For
blacks, the temperature is raised as high as 65° C. After dyeing the skins
are treated with a solution containing per 10 liters

  90–120 grams of olive-oil soap
   12–25 grams olive oil
      12 grams ammonia

for 15 minutes, then hydro-extracted and dried, without further rinsing.

For this method of dyeing, the following dyes may be used:

For yellow and orange
  Fast Yellow S
  Acid Yellows
  Naphthol Yellow S
  Tropaeoline
  Orange GG, R, II, IV

For reds
  Acid Reds
  Lanafuchsine
  Azo Orseille

For violet
  Azo Wool Violet
  Acid Violets

For blue
  Cyanole FF
  Azo Wool Blue
  Naphthol Blue R
  Formyl Blue B

For green
  Naphthol Green B
  Fast Acid Green
  Cyanole Green

For brown, combinations of
  Fast Yellow S
  Acid Yellows
  Tropaeoline DD
  Orange GG
  Lanafuchsine
  Indigo Blue N
  Cyanole B
  Fast Acid Green BN

For black
  Naphthylamine Blacks
  Naphthol Blacks
  Naphthol Blue-black

For grey
  Silver Grey N
  Dyed with the addition of 1/2–1% of alum

The chrome colors are dyed on furs when very fast shades are desired, all
the fancy colors being produced in this manner, but for black, only the
acid dyes are suitable. The preparation of the skin is exactly the same as
for the acid colors, except that the treatment with chloride of lime may
be omitted, although for very full shades it is desirable. The dyeing is
carried out as follows: The dyebath is prepared with the requisite amount
of the desired dyestuff, which is previously dissolved, and to this is
added a solution of sodium bichromate, the amount of this substance being
half the weight of the dye. The solution is heated and the skins entered
and dyed for 1–2 hours at 70–80° C. Then the dyebath is exhausted by the
addition of 1/3% acetic acid, the skins being worked for another half
hour, then rinsed, hydro-extracted and dried. Any of the one-bath chrome,
or after-chrome colors may be used for this method.

Recently methods have been patented for the dyeing of furs by means of
the vat colors. Vat dyes are among the fastest coloring matters ever
produced, and their application on furs would be a great advantage, if
suitable shades could be obtained. The general process for dyeing with vat
colors, consists in reducing the dye, which is usually very insoluble,
into a soluble “leuco” compound, by means of hydrosulphites in the
presence of alkalies. The leuco compound is not a dye itself, but when
the fibre absorbs it, and is then exposed to the air, the leuco compound
is reoxidized to its original insoluble form, which remains fast and
permanent. The use of strong alkalies in vat dyeing has hitherto been a
great obstacle in the use of these dyestuffs, but in 1917, the Farbwerke
Hoechst, a large German dye works, patented a process as follows: “A
process for dyeing furs with vat colors. The dyeing is done in solutions
of the vat dyes (after the addition of gelatine or some other protective
colloid), which are rendered neutral or only slightly alkaline with
ammonia, by neutralizing the caustic soda of the solution of the leuco
compound of the vat dyes by the addition of ammonium salts, or suitable
acids. The dyeings thus obtained are uniform and fast, the leather is dyed
to only a slight degree, and shows no deleterious effects of the dyebath
on the tannage.” As a practical application of this process, another
patent was taken out by the same company, also in 1917, as follows:
“A process for producing fast blacks on furs, consisting of dyeing a
ground color with appropriate vat dyes in a hydrosulphite vat, and after
oxidation in air, topping with an Aniline or Diphenyl black. The dyeings
obtained by the combination of vat dyes which are fast to oxidizing
agents, with an oxidation black, have an appearance matching that of
logwood black in beauty; and with a dark-blue to blue-black under-color,
and a full, deep black top color, cannot be distinguished from logwood.
These dyeings also have the advantage of being faster to light than
logwood or other blacks.”

While these processes undoubtedly have many meritorious qualities which
make them interesting, they do not seem as yet, to have attained any
great practical application. However, it is a field of fur dyeing which is
worth while developing, and with certain necessary improvements in these
processes, the vat dyes may yet supersede partially some of the other
methods of dyeing furs.




CHAPTER XVII

BLEACHING OF FURS


Bleaching is for the purpose of lightening the color of furs, and is
most generally applied to white-haired skins such as white fox, ermine,
and occasionally white lambs of all kinds, and white bears. Among such
furs, pelts of a naturally pure white tone are relatively scarce, while
in the majority of cases the color ranges from a pale creamy white to a
decidedly yellowish shade. Colors which vary from the pure white detract
considerably from the attractiveness and consequent value of the fur, and
indeed, some pelts are so far off shade that they can only be used when
dyed a darker color. Most white skins which are but slightly inferior in
color can be brought to a pure white by bleaching, and they can then be
used natural. Some pelts, on the other hand, are particularly resistant
to the action of bleaching agents and cannot be sufficiently decolorized
to render them suitable for use natural, so these are also dyed. For the
production of certain delicate or fancy dyed shades on white furs, it is
often necessary to bleach the skins in order to be able to obtain pure
tones. Such instances are not very common, however. Occasionally dark
furs, such as beaver, are bleached on the tips of the hair, a golden shade
being obtained thereby, which at one time was quite popular, but recently
such effects have not been in vogue.

In the bleaching of furs, two steps may be distinguished, first
degreasing, and second, bleaching proper. In the preliminary operations
of fur dressing, the furs are treated with soap or weak alkalies to
cleanse them and to remove excess oil from the hair. During the various
processes and manipulations, the hair, especially on white skins, may
become soiled or somewhat greasy again, so it is advisable to repeat
the cleaning process. This should in every case be as light as possible,
using a weak solution of soap for the softer and cleaner pelts, or dilute
solutions of ammonium carbonate or soda ash for the more greasy-haired
skins. The skins are then thoroughly rinsed to remove all traces of
the degreasing material. This step is very essential in order to obtain
uniform bleaching.

Broadly speaking, there are two general methods which can be used in
bleaching furs, one involving the use of what are known as reducing
agents, and the other employing oxidizing substances.

Among reducing agents which can be used for bleaching furs are sulphurous
acid, and its salts such as sodium bisulphite and sodium sulphite;
hydrosulphites, and derivatives.

1. ~Sulphurous acid.~--When sulphur is burned, sulphur dioxide gas
is formed. In the presence of moisture, or when dissolved in water,
this gas forms sulphurous acid, which is one of the most commonly used
bleaching chemicals for all sorts of materials, and is very effective
for decolorizing furs. The procedure usually followed is to hang up the
moistened skins on wooden rods in a more or less cubical chamber made of
stone or brick, and lined with wood or lead. No other metals may be used,
because they are quickly corroded by the sulphurous acid. The requisite
quantity of sulphur is placed in a pot in the bleaching chamber, and then
ignited, after which the doors are shut tight. The fumes of the burning
sulphur in contact with the moist hair readily exert their bleaching
action on the furs, and the operation is allowed to proceed for six or
eight hours, or overnight. Then by means of fans or other devices, the
air filled with sulphur dioxide gas is withdrawn from the chamber, and
replaced by fresh air. The door is opened, the skins removed, exposed to
the air for a time, then rinsed, and finally dried and finished. Sometimes
one operation is not enough to sufficiently bleach the hair, so the
process is repeated. Sulphur dioxide gas can now be obtained compressed
in cylinders, which are more convenient to handle than burning sulphur.
The flow of gas which is introduced into the bleaching chamber by means
of a nozzle attached to the cylinder, can be regulated, and the bleaching
thus retarded or accelerated.

2. ~Sodium bisulphite and sodium sulphite.~--These salts of sulphurous
acid are effective in their bleaching action only when in solution in the
presence of acids. The acids liberate sulphurous acid from the salts,
so this method is virtually the same as 1. Instead of using the salts
of sulphurous acid, sulphur dioxide may be dissolved in water, and the
solution used for bleaching by immersing the furs in it. This procedure,
while consuming somewhat less time than the chamber process, is more
likely to affect the leather, which would have to be retanned. The
principle is the same as that involved in method 1.

3. ~Hydrosulphites and derivatives.~--The bleaching agent can be prepared
by adding zinc dust to commercial bisulphite of soda dissolved in about
four times its weight of water until no more reaction is evident. Milk
of lime is then added to precipitate the zinc, and the clear supernatant
liquid of 1.5°–5° Tw. is used for bleaching. The skins are immersed
for 12–24 hours, taken out, washed and finished. Instead of preparing
the hydrosulphite, the commercial products may be used with greater
convenience, a solution containing 1–4% of the hydrosulphite powder being
used, and the skins treated in this until satisfactorily bleached.

The bleaching action of sulphurous acid and hydrosulphite is supposed to
be due to the reduction of the coloring matter of the hair to a colorless
compound; or possibly to the formation of a colorless compound of the
bleaching material with the pigment. The former seems the more probable
explanation, because the change is not a permanent one, the original
natural color returning after a long exposure of the bleached fur to air
and light. However, the results are sufficiently enduring to satisfy the
requirements of the trade in the class of furs on which these methods of
bleaching are used.

Bleaching chemicals with an oxidizing action generally used for
decolorizing furs are hydrogen peroxide and peroxides; occasionally
hypochlorites and permanganates are also used.

1. ~Hydrogen peroxide.~--Hydrogen peroxide is usually employed for
bleaching in the form of its 3% solution, to which is added about 20
cubic centimeters of ammonia per liter. The ammonia serves partially to
neutralize the acid which commercial peroxide generally contains, and
also to facilitate the bleaching action. The thoroughly degreased skins
are immersed in the solution until the hair is completely wetted by it,
are then removed, and evenly pressed or hydro-extracted, after which
the pelts are hung up to dry in the air. As the hair becomes drier,
the concentration of the peroxide becomes greater, and consequently the
bleaching action is stronger. Where there is a likelihood of the leather
being affected by the bleaching solution, the ammoniacal peroxide may
be applied to the hair with a fine sponge or brush until sufficiently
wetted, and then hanging the skins up to dry. Repetition of the process
is sometimes necessary to obtain pure white, but the results are always
excellent.

2. ~Peroxides.~--The most important of these is sodium peroxide, which
comes on the market as a yellowish-white powder, which must be kept dry,
and away from any inflammable material, as fires have been caused by the
contact of the peroxide with such substances. When dissolved in water, it
is equivalent to a strongly alkaline solution of peroxide of hydrogen.

   Na₂O₂  +  2H₂O  =  H₂O₂  +  2NaOH
   sodium    water  peroxide   caustic
  peroxide             of       soda
                    hydrogen

When dissolved in acid, the alkali is neutralized, and a neutral solution
of peroxide of hydrogen and a salt is obtained, and this method is used
to obtain peroxide of hydrogen cheaply.

  Na₂O₂ + H₂SO₄ = H₂O₂ + Na₂SO₄
        sulfuric         sodium
          acid          sulphate

3 parts of sodium peroxide are slowly dissolved in a cold 1% solution of
4 parts of sulphuric acid, stirring during the addition, and making the
resulting solution neutral to litmus paper, acid or more sodium peroxide
being added as needed. There is then added 3–6 parts of a solution
of silicate of soda of 90° Tw. The skins are immersed until properly
bleached, taken out, passed through a weak acid solution, then washed
and finished. This method generally requires the leather to be retanned
after bleaching. Another process, which involves the use of peroxides,
but which is not commonly practised, consists in rubbing the hair with
a pasty mixture of equal parts of water, barium dioxide, and silicate of
soda, hanging up the skins to dry, and then beating and brushing the hair.

3. ~Permanganates.~--The only member of this group that finds practical
application for bleaching purposes is potassium permanganate. The skins
are immersed in a 0.1% solution of the crystals of potassium permanganate,
until the hair acquires a deep brown color. They are then removed, rinsed,
and entered into a second bath containing sulphurous acid in solution,
prepared by acidifying a solution of sodium bisulphite. The skins are then
worked in this until fully bleached. It is the permanganate which does
the bleaching, the sulphurous acid being for the purpose of dissolving
the brown compound of manganese formed on the hair.

4. ~Hypochlorites.~--Chloride of lime and sodium hypochlorite, which is
prepared from the former, are the chief chemicals of this type used for
bleaching. The skins are entered into a weak solution of the hypochlorite,
and left until the hair is decolorized; then after removing, they are
passed through a dilute acid, and subsequently through a weak solution of
sodium thiosulphate in order to remove all traces of the hypochlorite.
This method causes the hair to acquire a harsh feel, and the yellow
color is never entirely eliminated. The hair, however, possesses a
great affinity for certain types of dyestuffs, and it is only when
these particular classes of dyes are to be applied to the furs, that the
hypochlorite bleach is used. (See dyeing with Acid colors).

The various oxidation methods of bleaching are supposed to change the
coloring matter of the hair into an entirely different and colorless
compound which cannot return to its original form. The bleach is therefore
permanent.

In common practise, the sulphurous acid, and the peroxide of hydrogen
methods are the two chiefly employed in bleaching processes. Sulphurous
acid is used to bleach the cheaper kinds of furs, while peroxide of
hydrogen is applied to the finer furs.

Whichever process is used, it is customary to give the bleached skins a
subsequent “blueing,” by passing them through a very weak solution of a
blue or violet dye, such as indigo-carmine, crystal violet, alkali blue
or ultramarine. The furs are then dried and finished off as usual. In drum
cleaning white furs, gypsum or white sand, or sometimes even talc are used
with the sawdust, or occasionally alone without the sawdust.




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      Adstringentien” 1917

  Koenig, F. Zeitschrift für angewandte Chemie, 1914, Vol. 1, p. 529

  Lamb, J. W. Jour. Soc. Dyers & Colourists Dec. 1905, p. 323

  Lamb, M. C. “Dressing of Leather” 1908

  ---- Jour. Soc. Dyers & Colourists 1913, 29, p. 160–165

  Larish & Schmid “Das Kuerschner Handwerk” 1–3

  Laut, A. C. “The Fur Trade of America” 1921

  Lightfoot, J. “The Chemical History & Progress of Aniline Black”
      1871

  Mairet, E. M. “A Book on Vegetable Dyes” 1916

  Martin, G. “Industrial Organic Chemistry”

  Matthews, J. M. “Application of Dyestuffs” 1920

  Mayer, A. “Die Färberei in der Werkstätte des Kürschners”

  Mierzinski, S. “Die Gerb und Farbstoffextrakte”

  Noelting & Lehne “Anilin-Schwarz” 1904

  Perkins & Everest “Natural Organic Coloring Matters” 1918

  Petersen, M. “The Fur Traders & Fur-Bearing Animals” 1920

  Poland, H. “Fur-Bearing Animals in Nature and Commerce”

  Proctor, H. “Leather Industries Laboratory Book”

  ---- “Tanning”

  ---- “Making of Leather”

  Schlottauer, E. Deutsche Farber-Zeitung 1911, Heft 20, p. 397

  ---- Deutscher Färber-Kalender 1911, p. 65

  ---- Leipziger Färber-Zeitung 1909, p. 441

  Schmidt, C. H. “Handbuch der Weissgerberei”

  Setlik, B. Deutsche Färber-Zeitung 1901, p. 213

  Smith, R. W. Color Trade Journal Vol. 3, Sept. 1918, p. 304–310

  ---- Textile Recorder, Vol. 36, p. 292–293, Dec. 1918

  ---- Revue Generale des Matieres Colorantes, Vol. 23, p. 32–36

  Stevenson, C. H. “U. S. Fish Commission Report 1902–1903”, Bulletin
      No. 537

  Stickelberger, E. “Geschichte der Gerberei” 1915

  Strasser “Chemische Färberei der Rauchwaren” 1879

  Ullmann “Enzyklopedie der technischen Chemie”

  Villon, A. M. “Traité pratique de la fabrication des cuirs, etc.”
      1900

  Werner, H. “Die Kürschnerkunst” 1914

  ---- “Das Färben der Rauchwaren” 1914

  Whittaker, C. M. “Dyeing with Coal Tar Dyes” 1919

  Wiener, F. “Weissgerberei” 1877

  Witt-Lehman “Chemische Technologie der Gespinst-Fasern” 1910

  Zeidler, H. “Die moderne Lederfabrikation” 1914




INDEX


  Acetate, aluminum, 118

  ---- chromium, 120

  ---- copper, 120

  ---- ferrous, 119

  ---- lead, 126

  Acetic acid, 112

  Acid dyes, 174

  Acids, action of, on hair, 29

  ---- ---- on skin, 26

  After-treatment with copper, 168

  Alaska fox imitations, 143

  Alkaline aluminum mordants, 122

  ---- chromium mordants, 123

  ---- iron mordants, 123

  Alum, 32, 53, 118

  ---- chrome, 57

  ---- -chrome tans, 64

  ---- tans, 54, 56

  Aluminum acetate, 118

  ---- mordants, 118

  ---- sulphate, 53, 118

  Ammonia, 110

  Ammonium sulphide, 126

  Aniline black, 144

  ---- ---- by dip process, 154

  ---- ---- chemistry, 145

  ---- ---- Green’s process for, 152

  ---- ---- nature of, 144

  ---- ---- One-bath, 149

  ---- ---- Oxidation, 150

  ---- ---- processes, 149

  ---- ---- ungreenable, 148

  Aniline oil, 145

  Astrachan 5, 7, 12


  Bacteria, 51

  Badger, 7

  Ball-drum, 62

  Bandrowski’s base, 164

  Basic dyes, 171

  Beam, 38

  Beaming, 38

  Bear, black, 5, 7

  ---- brown, 5, 8

  ---- white, 8

  ---- ---- bleaching of, 179

  Beating furs, 79

  Beaver, 5, 8, 25, 83, 94

  Beechwood ashes, 108

  Bichromate of soda, 121, 147

  Black, aniline, 144

  ---- ---- by Green’s process, 152

  ---- ---- chemistry of, 145

  ---- ---- nature of, 144

  ---- ---- One-bath, 149

  ---- ---- Oxidation, 150

  ---- ---- ungreenable, 148

  Black, diphenyl, 152

  ---- logwood, 139

  ---- on Chinese goats, 141

  ---- on lambs, 141

  ---- on raccoon, 130

  ---- on skunk, 130

  ---- on wolf, 130

  Bleaching of furs, 179

  Blending, 91, 104

  Blue-grey on white furs, 142

  Blueing, 184

  Blue salt, 120

  ---- vitriol, 119

  Borax, 39, 58

  Brasilein, 135

  Brasilin, 135

  Brazilwood, 135

  Bright shades on furs, 171

  Broadtail, 8, 12

  ---- dyeing of, 139

  Brown on Thibet sheep, 169

  ---- with natural dyes, 142

  Brush process, 98

  Brushes used in dyeing, 100

  Butter, 60, 63


  Cage, 80

  Cageing, 80

  Campeachy wood, 133

  Caracul, 8, 12

  ---- dressing of, 53

  Caracul, dyeing of, 140

  Carnivorous animals, furs of, 37

  Cased skins, 36

  Castor oil, 60, 63

  Cat, civet, 5, 8

  ---- house, 8

  Caustic soda, 44, 110, 113

  Centrifugal machine, 40

  Chamber drying, 73

  Chamois dressing, 31

  ---- tan, 49, 58, 61

  Characteristics of tans, 65

  Chestnut extract, 133

  Chinchilla, 5, 6, 8, 94

  ---- blending of, 91, 104

  Chinchillone, 9

  China goat, black on, 141

  Chlorates, 147

  Chloride of lime, 174

  ---- ---- bleach, 184

  Chrome acetate, 120

  ---- alum, 57, 120

  ---- colors, 176

  ---- -copper mordant, 167

  ---- -formaldehyde tan, 64

  ---- tans, 57, 174

  Chromium mordants, 120, 166

  ---- ---- alkaline, 123

  ---- salts in tanning, 53

  Cleaning pelts, 40

  Coal tar colors, 171

  Cocoanut oil, 60

  Cod-liver oil, 60

  Collagen, 25

  Colloidal solutions, 48

  Combination tans, 49, 64

  Conveying dyed skins, 104

  Conveyor drying, 73

  Copper acetate, 119

  ---- mordants, 119, 166

  ---- salts, 109

  ---- ---- after-treatment with, 168

  ---- sulphate, 119

  Copperas, 119

  Copper-iron mordant, 167

  Coriin, 21

  Corium, 21

  Cortex, 23

  Cottonseed oil, 60, 63

  Cuba wood, 134

  Cutch, gambier, 65, 135

  Cuticle, 23


  Davy, Sir Humphrey, 47

  Degreasing furs, 179

  Diphenyl black, 152

  Dip process, 98

  Dressing of lambs, 52

  ---- ---- rabbits, 54

  ---- ---- moles, 54

  Drum, 80

  Drum-cleaning, 105

  Drumming, 76

  Drying-oils, 60

  Drying skins, 71

  Durability of furs, 5

  Dyeing furs at higher temperatures, 174

  Dyeing of imitations, 93

  ---- ---- novelty shades, 92

  ---- with aniline black, 144

  ---- ---- coal tar colors, 171

  ---- ---- mineral colors, 125

  ---- ---- oxidation colors, 155

  ---- ---- vegetable colors, 128


  Egg-yolk, 63

  Emeraldine, 145

  Enzymes, 51

  Epidermis, 21

  Erdmann, 155

  Ermine, 5, 9

  ---- bleaching of, 179


  Fahrion, 48

  Fat-glands, 21

  Fats, animal, 59

  Fermentation, 51

  Ferrous acetate, 119

  Ferrous sulphate, 119

  Finishing dyed furs, 104

  Fisher, 9

  Fitch, 9, 94

  Flat skins, 36

  Fleshing, 41

  ---- knife, 38, 42

  ---- machines, 42

  Flesh side, 22, 37

  Formaldehyde, 63

  ---- -chrome tan, 64

  ---- tans, 49, 63

  Formic acid, 44, 50

  ---- ---- as soaking agent, 39

  Fox, black on, 140

  ---- blue, 9

  ---- cross, 4, 10

  ---- grey, 10

  ---- kit, 10

  ---- red, 4, 5, 10

  ---- ---- dyed imitation silver fox, 137

  ---- silver, 4, 10

  ---- ---- imitations, 137, 143

  ---- white, 11, 94

  ---- ---- bleaching of, 179

  French seal dye, 138, 144

  Furamine dyes, 162

  Fur beating machine, 80

  Fur dressing, 30

  Fur dyeing, 91

  ---- ---- difficulties of, 95

  ---- ---- with aniline black, 144

  ---- ---- with coal tar colors, 171

  ---- ---- with mineral colors, 125

  ---- ---- with oxidation colors, 155

  ---- ---- with vegetable colors, 128

  Fur-hair, 24

  Furriers’ guilds, 34, 90

  Furrol dyes, 166

  Furs, colors of, 3

  ---- description of, 7

  ---- durability of, 5

  ---- of carnivorous animals, 37

  ---- of herbivorous animals, 37

  ---- quality of, 3, 4

  ---- uses of, 1

  ---- valuation of, 6

  ---- weight of, 5

  Fustic, 134

  ---- shades with, 135


  Gall-nuts, 128, 132

  Gambier cutch, 65, 135

  Gelatine, 1, 25, 47, 48

  Genet, 5

  Glycerine, 63

  Goat, 5, 11

  ---- logwood black on, 141

  Green’s process for aniline black, 152

  Grey-blue on white furs, 142

  Ground water, 87

  Guard-hair, 24

  Guilds, furriers’, 34, 90


  Hair, 22

  ---- action of acids on, 27

  ---- action of alkalies on, 28

  ---- action of salts on, 28

  Hamster, 3, 11

  Hardness of water, 87

  Hare, 5, 11, 94

  ---- black on, 140

  ---- blue-grey on, 142

  ---- lynx dye on, 126

  ---- stone marten imitation on, 126

  Hematein, 133

  Hematoxylin, 133

  Herbivorous animals, furs of, 37

  Hudson seal, 144

  Hydro-extraction, 40

  Hydrogen peroxide, 168

  ---- ---- bleaching with, 182

  Hydrosulphite bleach, 181

  Hypochlorites, 184


  Imitations, dyeing of, 93

  Iron mordants, 119, 167

  Iron pyrolignite, 119

  Iron salts in tanning, 53

  Iron tan, 58

  Iron vitriol, 119


  Kangaroo, 12

  Keratin, 25

  Kicker, 61

  Killing, 98, 106

  ---- formulas, 108

  ---- nature of, 107

  ---- purpose of, 106

  ---- by brush process, 111

  ---- by dip process, 111

  ---- with caustic soda, 113

  ---- with lime, 112

  ---- with soda, 112

  Knapp, 46, 57

  Knife, beaming, 38

  ---- shaving, 38

  ---- fleshing, 38

  Kolinsky, 5, 12

  Krimmer, 5, 12, 13


  Lactic acid, 44, 51

  Lactic acid fermentation, 50

  Lambs, 12

  ---- dressing of, 50, 53

  ---- dyeing of, 92, 140, 141, 142

  Lard, 60

  Lead, acetate, 126

  Lead sulphide dye, 126

  Leather, definition of, 48

  ---- dressing of, 30

  Leopard, 5, 13, 94

  ---- tanning of, 43

  Lima wood, 135

  Lime, 108, 110, 112

  Linseed oil, 60

  Litharge, 109

  Loft drying, 72

  Logwood, 133

  ---- blacks, 139

  ---- shades with, 134

  Lynx, 5, 13

  ---- imitation on rabbit and hare, 126

  Luster of hair, 23


  Machines used in brush dyeing, 102

  ---- ---- dip dyeing, 103

  Marmot, 14, 68, 94

  Marten, blending of, 91, 104

  Marten, baum, 5, 14

  ---- stone, 5, 14

  ---- ---- imitation, 126

  Medulla, 22

  Meunier, 46

  Mineral colors, 125

  ---- oils, 59, 63

  ---- tans, 49, 53

  Mink, 5, 14, 68, 94

  Mole, 5, 15

  ---- tanning of, 54

  Monkey, 15

  Mordanting, 98, 114

  Mordants, alkaline, 121

  ---- aluminum, 118

  ---- chrome-copper, 167

  ---- chromium, 120, 166

  ---- copper, 119, 166

  ---- copper-iron, 167

  ---- iron, 119, 167

  ---- tin, 121

  Mucines, 25

  Muskrat, 5, 15, 68, 94

  ---- imitation seal on, 144, 169


  Neats-foot oil, 60, 63

  Neradol D., 64

  Nigraniline, 147

  Non-drying oils, 60, 63

  Novelty shades, dyeing of, 92

  Nutgalls, 33, 132

  Nutria, 5, 15, 94


  Oiling, 62, 77

  Oils, drying, 60

  ---- non-drying, 50

  ---- partially-drying, 60, 63

  Olive oil, 60

  One-bath aniline black, 149

  Opossum, 5, 15, 68

  ---- black on, 140

  ---- skunk imitation on, 138

  ---- seal imitation on, 144

  Otter, River, 5, 16, 94

  ---- Sea, 5, 16

  Over-hair, 24

  Oxidation aniline black, 150

  ---- colors, 155

  ---- ---- shades with, 165


  Para-amido phenol, 153, 157

  Para-phenylene diamine, 153, 157, 162

  Partially-drying oils, 60, 63

  Pelage, 2

  Pelt, 2

  Pernambuco wood, 135

  Peroxide of hydrogen, 168, 182

  Peroxides, 182

  Persian lamb, 5, 12

  ---- ---- dressing of, 50, 53

  ---- ---- dyeing of, 139

  Physical theories of tanning, 47

  Pickle, 49

  Pigment granules, 23

  Pony, Russian, 5, 16

  Potassium permanganate as a dye, 127

  ---- ---- as a bleach, 183

  Protective-hair, 24

  Pyrolignite of iron, 119


  Quercitron, 135

  Quinone di-imine, 163


  Rabbit, 6, 17, 94

  ---- imitation seal on, 144

  ---- lynx imitation on, 126

  ---- sable imitation on, 168

  ---- stone marten imitation on, 126

  ---- tanning of, 54, 65

  Raccoon, 6, 17

  ---- black on, 140

  ---- skunk imitation on, 170

  Rain water, 86

  Red fox, dyed as silver fox, 137

  Redwood, 135

  Rodol colors, 165

  Russian tan, 51


  Sable, 6, 94

  ---- American, 17

  ---- blending of, 91, 104

  ---- imitation on rabbit, 168

  ---- Russian, 18

  Salammoniac, 109

  Salt, 32, 49

  ---- -acid tan, 49

  ---- -water soak, 39

  Salts, neutral, 54

  ---- basic, 54, 115

  Sawdust in drum-cleaning, 80

  “Schrot-beize,” 50

  Seal, 6, 18, 94

  ---- fur, 18

  ---- dyeing of, 92, 144

  ---- hair, 19

  ---- imitation on muskrat, 138, 169

  ---- -oil, 60

  Shearing, 82

  ---- machine, 84

  Shrinking-point of skins, 66

  ---- effect of chemicals on, 67

  Silver fox imitations, 137, 143

  Skin, 21

  ---- action of acids on, 26

  ---- action of alkalies on, 27

  Skunk, 6, 19, 94

  ---- imitation on opossum, 138

  ---- ---- on raccoon, 170

  Soaking skins, 39

  Soda ash, 110, 112

  Sodium bichromate, 121, 166

  ---- bisulphite, 127, 181

  ---- chloride, 49

  ---- peroxide, 182

  ---- sulphite, 181

  Soft water, 87

  Softening skins, 38

  Souring, 113

  Squirrel, 6, 19

  Staking, 78

  Stannous chloride, 121

  Stiasny, 64

  Stone marten imitation, 126

  Stretching, 78

  ---- machines, 78

  Sugar of lead, 126

  Sulphonated oils, 63

  Sulphuric acid, 49

  Sulphurous acid bleach, 180

  Sumach, 128, 133

  ---- tanning with, 33

  Surface water, 87

  Sweat-glands, 22


  Tallow, 60

  Tanned furs, qualities of, 48

  Tanning methods, comparison of, 65

  Tannins, 32, 132

  Tiger, 19

  Top-hair, 24

  Train oils, 63

  Tramping machine, 61

  Turmeric, 136


  Under-hair, 24

  Under-wool, 24

  Ungreenable aniline black, 148

  Unhairing, 82

  ---- machine, 83

  Ursol dyes, 157, 165


  Vanadium compounds, 147

  Vat dyes, 177

  Vegetable dyes, 128, 136

  ---- oils, 59

  ---- tans, 49, 65

  Verdigris, 120


  Water, hard, 87

  ---- soft, 87

  Whale oil, 60

  White fox, bleaching of, 179

  Wolf, 6, 19

  Wolverine, 6, 20

  Wombat, 20

  Wood dyes, 128


  Yellow wood, 134




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Transcriber’s Notes:

Punctuation has been standardised--in particular, missing periods
and quotation marks have been supplied where obviously required.
Three entries in the bibliography were located out of alphabetical
order, and have been moved accordingly (Fougerat, Lamb, Martin).
All other original errors and inconsistencies have been retained,
except as follows:

  Page 7:   changed Enclyclopedia to Encyclopedia
            (in Encyclopedia Britannica, 11th Ed.)
  Page 20:  changed Kaola to Koala
            (Koala or Australian Bear.)
  Page 62:  changed partiular to particular
            (on the particular fur treatment)
  Page 67:  changed degress to degrees
            (almost 10 degrees higher than)
  Page 73:  changed samewhat to somewhat
            (based on a somewhat different)
  Page 93:  changed imitatations to imitations
            (dyeing of imitations to a great)
  Page 101: changed diagramatically to diagrammatically
            (and B shows diagrammatically, machines)
  Page 128: changed conjuction to conjunction
            (which in conjunction with certain)
  Page 136: changed curcuma to Curcuma
            (stem of the Curcuma tinctoria,)
  Page 137: changed simutaneously to simultaneously
            (and dye simultaneously; and third)
  Page 140: changed atmopheric to atmospheric
            (aid of the atmospheric oxygen.)
  Page 142: changed followlowing to following
            (successively in the following baths:)
  Page 149: changed ozidizing to oxidizing
            (is also an oxidizing agent and)
  Page 154: changed dryig to drying
            (several times, drying each time at)
  Page 161: changed manufacurers to manufacturers
            (Other manufacturers of coal-tar)
  Page 170: changed Racoon to Raccoon
            (_Imitation Skunk on Raccoon_)
  Page 185: changed Werkstatte to Werkstätte
            (Halle “Werkstätte der heutigen)
  Page 185: changed Gerben to Gerbens
            (Geschichte des Gerbens und der)
  Page 185: changed Astringentien to Adstringentien
            (und der Adstringentien” 1917)