[Illustration: CORK

ITS ORIGINS & USES]




  Copyright, 1909

  _by_

  ARMSTRONG CORK COMPANY

  PITTSBURGH

  U. S. A.




  Cork

  Being the Story o_f_
  the origin o_f_ Cork,
  the processes
  employed in its
  manufacture &
  its varied uses in
  the world to-day


  1909

  Armstrong Cork Company

  _of_

  Pittsburgh

  U.S.A.

[Illustration: A Monarch of the Cork Forest]




[Illustration: CORK]


Few things in general use in the great world to-day have the hall-mark
of approval of two thousand years set upon them. New materials, new
processes, new commodities have followed the train of advancing
civilization and the ensuing multiplication and alteration of man’s
economic needs. Even where the demand for a certain material to
fulfill a particular function has continued through the centuries,
widening knowledge of natural resources coupled with modern invention
has usually found some substitute cheaper, more efficient, and better
adapted for the purpose in question. Not so with cork. Recognized by
the ancients as peculiarly suited for certain uses, time has vindicated
their verdict; nothing has yet been discovered to supplant it in its
wide sphere of usefulness.

Theophrastus, Greek philosopher and writer on botany, who flourished
in the fourth century before Christ, was evidently familiar with the
material, for he mentions the cork tree as being a native of the
Pyrenees. For decades before the time of Horace cork was used for
stoppers for wine vessels. In fact, the poet tells one of his friends,
about 25 B. C., that on the occasion of a coming anniversary banquet
he expects to “remove the cork sealed with pitch” from a jar of the
rare vintage of forty-six years previous, the first but not the last
proceeding of this character of which history makes record.

[Illustration:

Gnarled Trunk of an Old Cork Oak]

It remained for the elder Pliny, however, in his wonderful work on
natural history, written in the first century of the Christian era,
to make the most remarkable reference to cork to be found in ancient
literature: “The cork oak is but a very small tree and its acorns of
the very worst quality * * *; the bark is its only useful product,
being remarkably thick, and if removed will grow again * * *. This
substance is employed more particularly attached as a buoy to the ropes
of ships’ anchors and the drag-nets of fishermen; it is used also for
the bungs of casks and as a material for the winter shoes of women.”
Cork jackets--life-preservers--are mentioned by Plutarch. Thus five
of the principal functions which cork fills in the world to-day were
recognized two thousand years ago. In the fifteenth century glass
bottles were introduced, which gave such great impetus to its general
use that the real beginning of the cork industry may properly be said
to date from that period. Some conception of its importance to-day may
be gathered from the fact that the importations of the United States of
crude and manufactured cork now aggregate almost $5,000,000 in value
annually.

[Illustration:

Cork Strippers’ Camp]

[Illustration: Stripping the Trees]

[Illustration:

Gathering the Bark]

[Illustration:

Cork Tree’s Foliage]

The word _cork_ is derived from the Latin _cortex_, meaning bark,
and the study of its origin and manufacture leads at once to those
romantic countries bordering the Mediterranean Sea. Spain and Portugal
divide honors among the nations of the world so far as yield of raw
material is concerned, with perhaps the advantage leaning slightly to
the latter. The cork-producing territory covers practically the whole
of Portugal, sweeps toward the east through the southern districts of
Spain known as Andalusia and Estremadura, thence northeast, embracing
thousands of acres of forests in Catalonia. Algeria, with Tunis,
ranks next in importance in yearly tribute of bark, southern France,
including Corsica, following closely after. Italy, too, with the help
of Sardinia and Sicily, continues to be quite a factor in meeting the
demand for the crude material, while across the Strait of Gibraltar
the sun-scorched forests of Morocco are as yet undeveloped. The
total area covered by cork forests is estimated at from four to five
million acres, while the annual production of bark is declared to be
not far from fifty thousand tons. Although no official statistics
are obtainable, these figures approximate the truth. In Portugal and
Spain, particularly in Catalonia, which is probably the greatest cork
manufacturing district in the world, a large portion of the corkwood
produced goes to supply domestic factories, where more and more
machinery is being introduced every year. With these exceptions,
however, the major part of the yield is exported to the United States,
England, France, Germany, Austria, Russia, Denmark, or Sweden, to be
turned into finished form.

[Illustration:

Pile of Bark in the Forest]

[Illustration:

Weighing Bark in the Forest]

The cork oak, known botanically as _Quercus suber_, attains a height of
from twenty to sixty feet and measures sometimes as much as four feet
in diameter. Its wide-spreading branches are rather closely covered
with small evergreen leaves, thick, glossy, slightly serrated, and
downy underneath. In April or May flowers of a yellowish color appear,
succeeded by acorns which ripen and fall to the ground in the late
fall. Pliny evidently knew whereof he wrote, for the cork oak’s acorns
are bitter and not at all pleasant to the taste. They form, however,
one of the forests’ chief sources of revenue, since, fed to swine, they
give a peculiarly piquant flavor to the meat, Spanish mountain hams
being noted for their excellence. Unfortunately, the herds in foraging
for food destroy the young trees and thus do serious and permanent
injury by preventing new growth.

[Illustration:

Virgin Cork and Second Stripping Bark]

[Illustration:

Cork Bark, “Back” and “Belly”]

The “corkwood,” or cork of commerce, is the outer bark of the cork
oak. When it has attained a diameter of approximately five inches,
or, to be more exact, measures forty centimeters in circumference
according to the Spanish governmental regulations, which the tree
does usually by the time it is twenty years old, the virgin cork, as
the first stripping of bark is called, is removed. This virgin cork
is so rough, coarse, and dense in texture that it is of very little
commercial value. Fortunately its removal does not kill the tree,
but, on the other hand, seems to promote further development, for the
inner bark--the seat of the growing processes--undertakes at once the
formation of a new covering of finer texture. Each year this, the
real skin, with its life-giving sap, forms two layers of cells--one
within, increasing the diameter of the trunk; the other without, adding
thickness to the sheathing of bark. After eight or ten years this is
also removed, and, while more valuable than the virgin cork, it is not
as fine in quality as that of the third and subsequent strippings,
which follow at regular intervals of about nine years. At the age of
about forty years the oak begins to yield its best bark, continuing
productive as a rule for almost a century, although cork trees several
hundred years old are not unknown. Flourishing as it does in a hot,
semi-arid climate, there seems to be no reason why this valuable tree
should not be successfully introduced in the southern and southwestern
sections of the United States; in fact, in the year 1858 the United
States Government took certain steps in this direction, and even went
so far as to distribute seedlings to interested persons in several
states. The Civil War interfered, however, and the experiments were
never fully carried out.

[Illustration:

Preparing Bark for Carriage to the Boiling Station]

[Illustration:

Cork under the Microscope]

[Illustration:

Bark arriving at a Boiling Station]

[Illustration:

The Common Carrier]

[Illustration:

A Boiling Station]

[Illustration:

A Wagon Load of Bark]

The stripping generally takes place during July and August, and is a
process which demands skill and care if injury to the tree is to be
avoided. In Algeria, the French strippers sometimes use crescent-shaped
saws; but under the usual Spanish method a hatchet with a long handle,
wedge-shaped at the end, is the only implement employed. The bark is
cut clear through around the base of the tree and a similar incision
is made around the trunk just below the spring of the main branches;
the two incisions are then connected by one or two longitudinal cuts,
following so far as possible the deepest of the natural cracks in
the bark. Inserting the wedge-shaped handle, the tree’s covering is
then pried off, care being taken not to injure the inner skin at any
stage of the process, for the life of the tree depends on its proper
preservation; and if it is injured at any point, growth there ceases
and the spot remains forever afterward scarred and uncovered. The
larger branches are stripped in the same manner, yielding thinner
but generally a finer grade of cork than that from the trunk. The
thickness of the bark is anywhere from one-half to two and a half
inches, while the yield also varies greatly--from forty-five to five
hundred pounds--depending on the size and age of the tree. As the
bark is removed it is gathered up in piles and left for a few days to
dry. Having been weighed, it is next carried either in wagons or on
the backs of burros to the boiling stations, where it is stacked and
allowed to season for a few weeks. It is then ready for the boiling
process, which at times is postponed until the crude material reaches
Seville or some other shipping point. But if the forest is distant, the
water supply adequate, and the quantity of bark ample to justify such
procedure, the vats are erected at a convenient spot and this operation
carried out on the ground. The outside of the bark in its natural
state is, as may well be imagined, rough and woody, owing to exposure
to the weather. After boiling, this useless outer coating is readily
scraped off, thereby reducing the weight of the material almost twenty
per cent. The boiling process also serves to remove the tannic acid,
increases the volume and elasticity of the bark, renders it soft and
pliable, and flattens it out for convenient packing.

[Illustration:

Factory at Seville, covering Twenty Acres]

[Illustration]

[Illustration:

Trimming the Sheets of Bark at Seville]

[Illustration]

[Illustration:

Corner of One of the Sorting Rooms at Seville]

After being roughly sorted as to quality and thickness the bark is then
ready for its first long journey, and, as the forests are generally
located in hilly or even mountainous country, the faithful burro must
again be called into service. Truly the Spaniard’s best friend, though
the worst treated of all, these patient little animals present a most
grotesque appearance when loaded from head to hind quarters with a
huge mass of the light bark. Down from the hills they go in trains of
thirty, forty, or even a hundred, threading the rocky bridle paths in
single file and wending their way through the narrow streets of quaint
villages, where traces of Moorish occupancy may still be seen, to the
nearest railway station, or even to Seville itself. Of course, if
conditions permit, wagons are used, but since Spain is not a country
famous for its good roads, it is probable that for many years to come
the burro will play his part in supplying the cork markets of the
world. [Illustration:

Baling Corkwood at Seville]

[Illustration]

[Illustration:

One of the Corkwood Warehouses, Seville Plant]

[Illustration:

The Giralda, Seville]

Although large supplies of raw material are drawn from Portugal, the
principal foreign warehouse and Spanish factory of the Armstrong Cork
Company are situated in Seville; hence it is to that historic city
on the banks of the Guadalquivir that the bark from many hills and
valleys finds its way during the summer months. There the bales as
they come from the country are opened, the bark boiled and scraped, if
this has not already been done, and then, after the edges have been
trimmed, is sorted into a dozen or more grades of different quality and
thickness. The importance of this last mentioned operation cannot be
overemphasized, as the whole problem of the successful and economical
manufacture of cork centers about it. The expert Spanish sorters having
finished their work, the bark is ready to be rebaled for shipment to
America. Broad sheets are placed in a baling box to form the bottom of
the bale, and above them are laid smaller pieces, which are covered in
turn with larger sections; then the whole mass is subjected to pressure
to render it compact, afterward being bound up securely with steel
hoops or wire. Each bale is carefully stenciled with marks indicating
grade or quality. Loaded directly into ocean-going steamers alongside
the Seville docks, not infrequently a whole ship’s cargo of cork at a
time is transported to Philadelphia, New York, or Baltimore, and thence
freighted to the Pittsburgh factory.

[Illustration:

The Wharf at Seville. Loading Bales of Corkwood for America]

[Illustration:

Bale of Corkwood]

[Illustration:

Spaniards cutting Bark into Strips and Squares]

[Illustration:

Cutting Corks by Hand]

[Illustration:

The Factory at Pittsburgh]

From the mountain of cork unloaded at its doors a host of different
articles are produced by means of wonderfully ingenious machinery
coupled with hundreds of keen brains, for the human element must always
play a large part in cork manufacture. Among them corks rank first in
importance; hence the greater part of the floor space of this factory,
the largest of its kind in the world, is given over to their production.

[Illustration:

Slicing into Strips]

[Illustration:

Bales of Cork being unloaded at Pittsburgh]

For whatever purpose it is to be used, all bark removed from the
immense storage rooms is taken first to the sorting department, where,
under skilled eyes, the twenty-five or more foreign grades are resorted
into approximately one hundred and fifty different classes, according
to quality and thickness. The speed and skill with which this work is
done is astounding. So slight is the difference between some of the
grades that to the inexperienced eye none can be seen whatever, and yet
success hinges on the care and skill exercised in this and the other
sortings that follow.

[Illustration:

Corks punched from Strips]

[Illustration:

One of the Fourteen Storage Rooms, Pittsburgh Factory]

[Illustration:

Cork Punchings]

[Illustration:

One of the Corkwood Sorting Rooms at Pittsburgh]

[Illustration:

Cutting into Squares]

In manufacturing corks it must be understood in the first place
that the thickness of a given piece of bark determines the maximum
diameter of the stopper which can be made from it, as the cutting
is done across and not with the grain. Leaving the sorting room the
corkwood is softened by placing it in a warm vapor bath. This process
increases its flexibility greatly, its bulk slightly, and prepares it
to undergo the various mechanical operations which follow in rapid
succession. The keen edge of the slicer first confronts the sheets of
bark, and it is at this point that the first mechanical obstacle in
cork manufacture has to be overcome, for the soft, light, elastic
material is, withal, very difficult to cut, as may be determined by
simple personal experiment. But before the onslaught of a circular
steel knife, revolving hundreds of revolutions every minute and kept
at razor-like sharpness, even this difficulty disappears, and the
sheets are readily cut into strips whose width is determined by the
length of the cork desired. From the slicer the strips pass to the
blocking machines, where, by means of a rapidly rotating tubular punch,
cylindrical pieces are bored out and released with almost incredible
speed. The operative, of course, must use care to avoid defective spots
in the bark, and also to cut the corks out as closely together as
possible so as to reduce waste to a minimum. The stoppers which come
from these machines are round with parallel sides. If tapered corks are
desired, larger at the upper end than at the lower, the cylindrical
or “straight” pieces must be passed through another machine, which
handles them deftly, holding them against the edge of another circular
knife. Seemingly motionless, the only outward indication of the speed
with which the keen blade is revolving is the delicate shaving which
curls upward for an instant, only to be drawn away through pipes by
powerful air-suction to the mill building a hundred yards distant,
where all such waste is ground up, to be disposed of in the form of
various by-products. Both “straights” and “tapers” next journey to the
washing rooms. There dumped in great vats, thousands at a time, they
are carefully washed and then dried by being whirled about dizzily in
great revolving cylinders of wire net located in heated chambers.

[Illustration:

Blocking Department at Pittsburgh]

[Illustration:

Cork Insoles]

[Illustration:

Making Tapered Corks at Pittsburgh]

[Illustration:

Washers and Gaskets]

[Illustration:

A Glimpse of Another Department, Pittsburgh Factory]

[Illustration:

Cork Balls]

Not all of the bark, however, that is destined to be turned into corks
follows the course that has just been described; for certain varieties
a different process of manufacture, approximating in many respects the
original Spanish method, is found more practicable. The crude bark,
after being sorted, is cut into strips on the slicing machines, the
width as before depending on the length of the stopper to be made. To
remove the rest of the hard back, or outer crust, much of which still
remains despite the scraping before shipment to America, the pieces
are then passed beneath a revolving knife which shaves off the rough,
uneven portion. Free now from objectionable matter, the strips are cut
into small rectangular blocks of the dimensions of the cork desired. In
this process, just as in blocking, care must be taken to avoid defects
in the bark, and at the same time to prevent waste. Passing to another
department the rectangular pieces are rounded into proper shape.

[Illustration:

Sorting Tapered Corks at Pittsburgh Factory]

[Illustration:

Cork Polishing Wheels]

In Spain, before the days of large cork factories employing labor
saving machinery, and even to a great extent at the present time,
all of these operations are carried out by hand. Whole families
participate, slicing the bark into strips, then into squares,
and finally cutting the corks from the square blocks slowly and
laboriously. This hand method of manufacture is gradually disappearing
as more and more machinery comes into general use. What are known as
hand cut corks are stoppers which are not exactly round, but of a shape
which might be appropriately described as a “square circle.” In the
judgment of some, they are better suited for certain purposes than
straights or tapers.

[Illustration:

Packing Department at Pittsburgh]

[Illustration:

Cork Paper]

[Illustration:

Putting Final Touches on Life-Preservers]

[Illustration:

Seine and Gill Corks]

From the driers all corks are taken to the sorting rooms, where they
are subjected to the last of the actual manufacturing processes, and,
from many standpoints, the most interesting of all. Here, again, the
importance of proper grading is paramount, and when one considers that
almost five million corks pour into this department every working day,
the magnitude of the task can be partly grasped. When the further
fact is known that this enormous output is to be sorted into about
twenty regular besides numerous special grades, one can still further
appreciate what the problem involves. The work itself calls for such
a peculiar combination of faculties that only one out of every five
operatives who are given preliminary training in this department is
found satisfactory; but so highly skilled do the regular workers become
that the sorting of thirty-five thousand corks may be considered an
average day’s labor. Experts exercise careful supervision and actually
test each lot of corks as they come from the operatives in order that
uniform standards may be maintained from day to day and month to month.

[Illustration:

Circle A Corks]

When past the keen eye of the tester, the cork, after its long journey
through the factory, passes either direct to the packing department or
to the warehouses. This last point involves a problem which is often
very puzzling and difficult of solution. Thousands of dollars’ worth
of corks are placed in the warehouses every year to remain there
indefinitely. An order for a quantity of corks of a certain size and
quality also involves, of necessity, the manufacture of a great many
corks of other grades. The reason for this is, of course, found in
the fact that the raw material, no matter how carefully sorted at the
outset, will not produce a finished product of uniform quality. Thus
frequently it becomes necessary to work over a given lot of corks for
which there is no demand into a smaller size for which orders are
pouring in.

[Illustration:

Circle B Corks]

Into the packing department streams a bewildering array of corks of
every conceivable shape, grade, and size. The tapers appear in a dozen
qualities, at the head of which stand the peerless “Circle A” and
“Circle B,” prescription corks found in every first-class pharmacy in
the land. The straights have been separated into various classes,
running from the fine champagne corks down to the common soda water
corks. Besides, there are keg corks, hand cut corks, mustard and jar
corks of large diameter, shell corks, perforated through the center,
and glued corks made up of several layers, all of which must be put up
in packages of suitable size, ready to be delivered to the shipping
department for transportation to the consumer.

[Illustration:

Tapered Corks, X Grade]

[Illustration:

Bobbers for Fishing Lines]

[Illustration:

Large Tapered Corks]

[Illustration:

Instrument and Fishing Rod Handles]

A host of other useful articles also find their way from the many
manufacturing departments to the shipping rooms. Of insoles thousands
of pairs are produced annually. Discs and washers by the million
are punched out for use in metal caps for bottles and jars, and as
gaskets in lubricator cups. Life-preservers, ring buoys, yacht fenders,
mooring and anchoring buoys are the specialties of one department,
while another pays particular attention to the manufacture of seine
and gill corks, and bobbers for fishing lines. So varied, in fact,
are the forms which cork assumes that the complete cataloguing of
the functions which it fills in the world to-day would be well-nigh
impossible. For instance, cork shapes may be found in animal heads on
rugs and fur garments, and, covered with suitable material, are used
as buttons on fur coats. Cork balls play their part in exhibiting
cutlery and in various games; the automobilist finds cork carburetor
floats indispensable; churn lids are made tight with cork gaskets;
pen holders have cork tips; hats are lined with thin sheets of cork;
friction clutches of cork are steadily growing in favor; the optician
employs small cork strips in connection with eyeglasses; the plasterer
uses cork floats; while the glass manufacturer knows no better medium
for polishing his wares than cork wheels. The finest pieces of bark
are made into cork paper, so thin that five hundred sheets measure but
one inch in thickness. Sorted into several different grades, this
beautiful, velvety material is practically all used in making cigarette
tips. Fishing rod, whip, bicycle, trowel, and pyrographic instrument
handles of cork are, of course, familiar to every one.

[Illustration:

Straight Wine Corks]

[Illustration:

Straight Soda Corks, D Grade]

[Illustration:

Granulated Cork]

But the manufacture of corks and of all these other articles involves
waste, and waste to an extent little dreamed of. In producing corks,
for instance, fully sixty-five per cent of the raw material which
started out on its journey through the factory may be found later in
the form of scrap at the blocking and tapering machines; but even in
this mutilated state the bark is still valuable, and after proper
treatment in the Pittsburgh plant, or one of the other factories of
the Company, appears in the form of numerous by-products of great
value and importance. As a matter of fact, nothing is wasted; even the
smallest particles are utilized. Large quantities of scrap are ground
up, sifted, and made into composition cork with the aid of suitable
binders. From “Suberit,” as the finest variety of this material is
termed--light, close grained, and tough, without the large pores of the
natural cork--table mats to be placed under hot dishes, pin cushions,
fishing line floats, polishing wheels, and instrument handles are
manufactured; while from “Acme,” a somewhat coarser grade, are made
insoles, bath mats, washers, gaskets, and entomological cork--thin
sheets for mounting insects.

[Illustration:

Keg Corks]

[Illustration:

Plasterer’s Float]

[Illustration:

Hand Cut Corks, A Grade]

[Illustration:

Cork Carburetor Floats]

Part of the waste is reduced to the form of cork shavings and used
to stuff mattresses and boat cushions, for packing eggs and other
fragile articles, and in making cork floor tiling. This material is
manufactured in three shades of brown, and its warmth of tone and
delicately mottled and veined appearance give it a distinctive charm
peculiarly its own. Smooth and soft as velvet to the touch, cork
tiling is nevertheless firm and resilient and able to stand years of
hard service. Thousands of square feet have been installed in hotels,
libraries, museums, clubs, and private residences.

[Illustration:

Hand Cut Corks, C Grade]

Cork flour is another by-product, and is manufactured from the waste
bark by much the same method as that employed in grinding wheat. This
beautiful light brown dust is one of the chief constituents of high
grade linoleum. In the Company’s plant at Lancaster, Pennsylvania,
thousands of yards of this material are produced every day.

[Illustration:

Mooring and Anchoring Buoys]

[Illustration:

Jar, Mustard, and Shell Corks]

[Illustration:

Ring Buoy]

[Illustration:

Life-Preserver]

The many different grades of granulated cork, made by grinding up
cork waste, find a wide sphere of usefulness for packing and heat
insulating purposes. In this last mentioned field, in fact, cork now
ranks preeminent. Its peculiar structure, which may be seen under
the microscope--myriads of sealed air cells, impervious to air and
water--renders it not only a splendid nonconductor of heat, but also
nonabsorbent of moisture. For loose filling between the walls of ice
boxes, water coolers, and cold storage rooms, and about the sides of
freezing tanks in ice factories, hundreds of tons of granulated cork
are employed every year. Comparatively recently, however, an insulating
material possessing permanency of form has been found desirable for
many reasons. To meet this demand granulated cork is transformed into
corkboard at the Company’s plants at Beaver Falls, Pennsylvania, and
Camden, New Jersey. Using the pure cork, either with or without an
asphaltic binder, three grades of this material are made, known as
Nonpareil, Impregnated, and Acme Corkboard, respectively. The sheets
measure twelve by thirty-six inches, of various thicknesses, and, as
they possess ample structural strength, may be nailed into place in
buildings or rooms of frame construction, or put up with Portland
cement against brick, stone, or concrete walls and ceilings. A plaster
finish is readily applied. Owing to its freedom from progressive
deterioration, its constant efficiency, its slow burning and fire
retarding properties, and its sanitary qualities, corkboard insulation
is now recognized as the standard throughout the land, and may be
found installed almost everywhere refrigeration is employed. Hundreds
of cold storage warehouses, abattoirs, fur storage vaults, breweries,
ice plants, dairies, creameries, candy factories, and bakeries are
insulated with it, not to mention refrigerated rooms in hotels, clubs,
private residences, and aboard the ships of the United States, British,
and Italian navies.

[Illustration:

Cork Floor Tiling]

Another by-product, and the last one of importance, is cork pipe
covering for insulating cold pipe lines. Made of pure granulated cork,
slightly compressed and molded in sectional form to fit the many
different sizes of pipe and kinds of fittings, it is a thoroughly
durable covering for brine and ammonia piping in refrigerating plants,
and for ice water lines in office buildings, hotels, and industrial
establishments. In this rôle the cork bark, after its devious career
in American factories, performs a service similar to that of its early
days in Spain, when, sheathing trunk and branches, it prevented the
sun’s rays and the parching winds from heating and drying up the cool,
life-giving sap of its parent tree.

[Illustration:

Nonpareil Corkboard]

[Illustration:

Cork Pipe Covering]

[Illustration]

  Rogers & Company
  Chicago and New York

       *       *       *       *       *




Transcriber’s note

  Minor punctuation errors have been changed without notice. All other
  inconsistencies are as in the original.

  In this version, some Illustration tags have been moved beside the
  relevant section of the text.