Photographic Reproduction Processes

A Practical Treatise of the Photo-Impressions Without Silver Salts
By P.C. Duchochois

New York
The Scovill & Adams Company
423 Broome Street.
1891





CONTENTS


INTRODUCTION.
THE DESIGNS.
THE CYANOTYPE OR BLUE PROCESS.
THE CYANOFER. (Pellet’s Process.)
THE BLACK OR INK PROCESS. (Ferro-tannate Process.)
THE CUPROTYPE. (Burnett’s Process.)
THE ANILINE PROCESS.
THE PRIMULINE OR DIAZOTYPE PROCESS.
TRACING PROCESS ON METAL.
GRAPHOTYPY.
THE URANOTYPE.
THE PLATINOTYPE.
   ARTIGUES’ PROCESS
   THE CARBON PROCESS.
   APPENDIX.





ILLUSTRATIONS


A Tournette
Chardon’s method of coating





PREPARER’S NOTE


Please remember that this book was published over a century ago, long
before today’s chemical safety standards.  Please get expert advice before
attempting to perform any of the procedures described in this book.





AUTHORS QUOTED


Artigues.
Bevan, E.J.
Bingham
Borlinetto
Brasseur, Chs.
Buckle.
Burnett, C. J.
Chardon
Cheysson
Colas.
Cooper, H.
Cross, C. F.
De la Blanchère, H.
De St. Florent
Draper, Dr. John
Ducos du Hauron
Dumoulin, E.
Endemann,H.
Fisch, A.
Godefroy.
Green, A. G.
Graubassi
Harman, Alfred.
Herschel, Sir John.
Houdoy
Hübl, Baron.
Hunt, Robert
Liesegang, Dr. L.
Loeffler, J.
Monckhoven, Dr Von.
Nièpce, de St. Victor
Obernetter, J. B.
Pellet.
Persoz.
Phipson, Dr.
Pizzighelli, Captain J.
Poitevin, A.
Roy, Paul
Sella, V. J.
Smee, Professor
Stephanowski, Karl.
Swan, J. W.
Willis, William
Wothly, J.
X.






INTRODUCTION.


The photographic processes with the salts of iron are all derived from the
researches of Sir John Herschel. The investigations of that great
philosopher are so valuable, so full of instructions that we are led to
reprint them, together with those of Mr. C. J. Burnett, on the salts of
uranium, etc., as an Introduction.  It will be seen that the process by
which blue prints are to-day obtained is exactly that Sir John Herschel
devised in 1840.

“It is no longer an insulated and anomalous affection of certain salts of
silver or gold, but one which, doubtless, in a greater or less degree,
pervades all nature, and connects itself intimately with the mechanism by
which chemical combination and decomposition is operated.  The general
instability of organic combinations might lead us to expect the occurrence
of numerous and remarkable cases of this affection among bodies of that
class, but among metallic and other elements inorganically arranged,
instances enough have already appeared, and more are daily presenting
themselves, to justify its extension to all cases in which chemical
elements may be supposed combined with a certain degree of laxity, and so
to speak in a _tottering equilibrium_.  There can be no doubt that the
process, in a great majority, if not in all cases, which have been noticed
among inorganic substances, is a deoxidizing one, so far as the more
refrangible rays are concerned.  It is obviously so in the cases of gold
and silver.  In the case of the bichromate of potash it is most probable
that an atom of oxygen is parted with, and so of many others.  A beautiful
example of such deoxidizing action on a non-argentine compound has lately
occurred to me in the examination of that interesting salt, the
ferrosesquicyanuret of potassium described by Mr. Smee in the
_Philosophical Magazine_, No. 109, September, 1840, and he has shown how
to manufacture in abundance and purity, by voltaic action on the common or
yellow ferrocyanuret.  In this process nascent oxygen is absorbed,
hydrogen given off, and the characters of the resulting compound in
respect of the oxides of iron, forming as it does Prussian blue with proto
salts, indicate an excess of electro-negative energy, a disposition to
part with oxygen, or which is the same thing, to absorb hydrogen (in the
presence of moisture), and thereby to return to its pristine state, under
circumstances of moderate solicitation, such as the affinity of protoxide
of iron (for instance) for an additional dose of oxygen, etc.”

“Paper simply washed with a solution of this salt is highly sensitive to
the action of the light.  Prussian blue is deposited (the base being
necessarily supplied by the destruction of one portion of the acid, and
the acid by the destruction of another).  After half an hour or an hour’s
exposure to sunshine, a very beautiful negative photograph is the result,
to fix which, all that is necessary is to soak it in water in which a
little sulphate of soda is dissolved.  While dry the impression is of a
dove color or lavender blue, which has a curious and striking effect on
the greenish yellow ground of the paper produced by the saline solution.
After washing the ground color disappears and the photograph becomes
bright blue on a white ground.  If too long exposed, it gets
‘over-sunned,’ and the tint has a brownish or yellowish tendency, which,
however, is removed in fixing; but no increase of intensity beyond a
certain point is obtained by the continuance of exposure.”

“If paper be washed with a solution of ammonio-citrate of iron and dried
and then a wash passed over it of the yellow ferro-cyanuret of potassium,
there is no immediate formation of true Prussian blue, but the paper
rapidly acquires a violet-purple color, which deepens after a few minutes,
as it dries, to almost absolute blackness.  In this state it is a positive
photographic paper of high sensibility, and gives pictures of great depth
and sharpness, but with this peculiarity, that they darken again
spontaneously on exposure to the air in darkness, and are soon
obliterated.  The paper, however, remains susceptible to light, and
capable of receiving other pictures, which in their turn fade, without any
possibility (so far as I can see) of arresting them, which is to be
regretted, as they are very beautiful, and the paper of such easy
preparation.  If washed with ammonia or its carbonate, they are for a few
moments entirely obliterated, _but presently reappear with reversed lights
and shades_.  In this state they are fixed, and the ammonia, with all that
it will dissolve, being removed by washing in water, their color becomes a
pure Prussian blue, which deepens much by keeping.  If the solution be
mixed there results a very dark violet-colored ink, which may be kept
uninjured in an opaque bottle, and will readily furnish by a single wash
at a moment’s notice the positive paper in question, which is most
sensitive when wet.”

“It seems at first sight natural to refer these curious and complex
changes to the instability of the cyanic compounds; and that this opinion
is to a certain extent correct is proved by the photographic impressions
obtained on papers to which no iron has been added beyond what exists in
the ferrocyanic salts themselves.  Nevertheless, the following experiments
abundantly prove that in several of the changes above described, the
_immediate action_ of the solar rays is not exerted on these salts, but on
the iron contained in the ferruginous solution added to them, which it
deoxidizes or otherwise alters, thereby presenting it to the ferrocyanic
salts in such a form as to precipitate the acids in combination with the
peroxide, or protoxide of iron, as the case may be.  To make this evident,
all that is necessary is _simply to leave out the ferrocyanate_ in the
preparation of the paper, which thus becomes reduced to a simple washing
over with the ammonio-citric solution.  Paper so washed is of a bright
yellow color, and is apparently little, but in reality highly sensitive to
photographic action. Exposed to strong sunshine, for some time indeed, its
bright yellow tint is dulled into an ochrey hue, or even to gray, but the
change altogether amounts to a moderate percentage of the total light
reflected, and in short exposures is such as would easily escape notice.
Nevertheless, if a slip of this paper be held for only four or five
seconds in the sun (the effect of which is quite imperceptible to the
eye), and when withdrawn into the shade be washed over with the
ferrosesquicyanate of potash, a considerable deposit of Prussian blue
takes place on the sunned part, and none whatever on the rest; so that on
washing the whole with water, a pretty strong blue impression is left,
demonstrating the reduction of iron in that portion of the paper to the
state of protoxide.  The effect in question is not, it should be observed,
peculiar to ammonio-nitrate of iron.”

“The ammonio and potasso-tartrate fully possess and the perchloride
_exactly neutralized_ partakes of the same property; but the experiment is
far more neatly made and succeeds better with the other salts.”

“The varieties of cyanotype processes seem to be innumerable, but that
which I shall now describe deserves particular notice not only for its
pre-eminent beauty while in progress, but as illustrating the peculiar
power of the ammoniacal and other parsalts of iron above-mentioned to
receive a latent picture susceptible of development by a great variety of
stimuli.  This process consists in simply passing over the
ammonio-citrated paper on which such a latent picture has been impressed,
_very sparingly and evenly_, a wash of the solution of the common yellow
ferrocyanate (prussiate) of potash.  The latent picture, if not so faint
as to be quite invisible (and for this purpose it should not be so), is
negative.  As soon as the liquid is applied, which cannot be in too thin a
film, the negative picture vanishes, and by very slow degrees is replaced
by a positive one of a violet blue color on a greenish yellow ground,
which at a certain moment possesses a high degree of sharpness and
singular beauty and delicacy of tint.  If at this instant it be thrown
into water, it passes immediately to a Prussian blue, losing, at the same
time, however, much of its sharpness, and sometimes indeed becoming quite
blotty and confused.”

“To prevent this confusion gum arabic may be added to the prussiated
solution, by which it is hindered from spreading unmanageably within the
pores of the paper, and the precipitated Prussian blue allowed time to
agglomerate and fix itself on the fibers. By the use of this ingredient
also, a much thinner and more equal film may be spread over the surface,
and _when perfectly dry_, if not sufficiently developed, the application
may be repeated. By operating thus I have occasionally (though rarely)
succeeded in producing pictures of great beauty and richness of effect,
which they retain (if not thrown in water) between the leaves of a
portfolio, and have a certain degree of fixity—fading in strong light and
recovering their tone in the dark. * * *”

“If paper be washed with a mixture of the solutions of ammonio-citrate of
iron and ferrosesquicyanate (red prussiate) of potash, so as to contain
the two salts in about equal proportions, and being then impressed with a
picture, be thrown into water and dried, a negative blue picture will be
produced.  This picture I have found to be susceptible of a very curious
transformation.  To effect this it must be washed with a solution of
protonitrate of mercury, which in a little time entirely discharges it.
The nitrate being thoroughly washed out and the picture dried, a smooth
iron is passed over it, somewhat hotter than is used for ironing linen,
but not sufficiently so to scorch or injure the paper.  The obliterated
picture immediately reappears, not blue, but brown. If kept for some weeks
in this state between the leaves of a portfolio, in complete darkness, it
fades, and at length almost disappears.  But what is very singular, a
fresh application of heat revives and restores it to its full intensity.”

“This curious transformation is instructive in another way. It is not
operated by light, at least not by light alone. _A certain temperature_
must be attained, and that temperature suffices in complete darkness.
Nevertheless, I find that on exposing to a very concentrated spectrum
(collected by a lens of short focus) a slip of paper prepared as above
(that is to say, by washing with the mixed solutions, exposure to
sunshine, washing and discharging the uniform blue color so induced, as in
the last article), its whiteness is changed to a brown over the whole
region of the red and orange rays, _but not beyond_ the luminous spectrum.
Three conclusions seem unavoidable: first—that it is the heat of these
rays, not their light, which operates the change; second—that this heat
possesses a peculiar chemical quality which is not possessed by the purely
calorific rays outside of the visible spectrum, though far more intense;
and third—that the heat radiated from obscurely hot iron abounds
especially in rays analogous to those of the region of the spectrum above
indicated.”

Sir John Herschel then proceeds to show that whatever be the state of the
iron in the double salts in question, its reduction by blue light to the
state of protoxide is indicated by many other agents.  “Thus, for
example,” says Robert Hunt, “if a slip of paper prepared with the
ammonio-citrate of iron be exposed partially to sunshine, and then washed
with the bichromate of potash, the bichromate is deoxidized and
precipitated upon the sunned portion, just as it would be if directly
exposed to the sun’s rays.”

“I have proved this fact with a great number of preparations of cobalt,
nickel, bismuth, platinum and other salts which have been thought hitherto
to be insensitive to the solar agency; but if they are partially sunned
and then washed with nitrate of silver and put aside in the dark, the
metallic silver is slowly reduced upon the sunned portion.  In many
instances days were required to produce the visible picture; and in one
case paper being washed in the dark with neutral chloride of platinum was
sunned and then washed in the dark with nitrate of silver; it was some
weeks before the image made its appearance, but it was eventually
perfectly developed, and, when quite so, remained permanently impressed
upon the paper.”

The following process, discovered at the same time as the cyanotype, and
termed chrysotype, is thus described by Sir John Herschel:

“In order to ascertain whether any portion of the iron in the double
ammoniacal salt employed has really undergone deoxidation, I had recourse
to a solution of gold, exactly neutralized by carbonate of soda.  The
proto-salts of iron, as is well known to chemists, precipitate gold in the
metallic state.  The effect proved exceedingly striking, and, as the
experiment will probably be repeated by others, I shall here describe it
ab initio.  Paper is to be washed with a moderately concentrated solution
of ammonio-citrate of iron and dried.  The strength of solution should be
such as to dry into a good yellow color, not at all brown.  In this state
it is ready to receive a photographic image, which may be impressed on it
either from nature in the camera obscura, or from an engraving on a frame
in sunshine.  The image so impressed is, however, very faint, and
sometimes hardly perceptible.  The moment it is removed from the frame or
camera, it must be washed over with a neutral solution of chloride of gold
of such strength as to have about the color of a sherry wine.  Instantly
the picture appears, not, indeed, at once of its full intensity, but
darkening with great rapidity up to a certain point, depending on the
strength of the solutions used, etc.  At this point nothing can surpass
the sharpness and perfection of detail of the resulting photograph.  To
arrest this process and to fix the picture (so far at least as the further
agency of light is concerned), it is to be thrown into water very slightly
acidulated with sulphuric acid, and well soaked, dried, washed with
hydrobromate of potash, rinsed and dried again. * * *”

“In point of _direct_ sensibility, the chrysotype paper is certainly
inferior to the calotype; but it is one of the most remarkable
peculiarities of gold as a photographic ingredient, that _extremely feeble
impressions once made by light go on afterwards, darkening spontaneously
and very slowly, apparently without limit so long as the least vestige of
unreduced chloride of gold remains in the paper_.  To illustrate this
curious and (so far as applications go) highly important property, I shall
mention incidentally the results of some experiments made during the late
fine weather on the habitudes of gold in presence of oxalic acid.  It is
well known to chemists that this acid, heated with solutions of gold,
precipitates the metal in its metallic state; it is upon this property
that Berzelius has founded his determination of the atomic weight of gold.
Light, as well as heat, also operates this precipitation; but to render it
effectual, several conditions are necessary:—First—the solution of gold
should be neutral, or at most _very_ slightly acid; secondly—the oxalic
acid must be added in the form of a neutral oxalate; and thirdly—it must
be present in a certain considerable quantity, which quantity must be
greater the greater the amount of free acid present in the chloride.
Under this condition, the gold is precipitated by light as a black powder
if the liquid be in any bulk; and if merely washed over paper, a stain is
produced, which, however feeble at first, under a certain dosage of the
chloride, oxalate and free acid, goes on increasing from day to day and
from week to week, when laid by in the dark and especially in a damp
atmosphere, till it acquires almost the black of ink; the unsunned portion
of the paper remaining unaffected, or so slightly as to render it almost
certain that what little action of the kind exists is due to the effect of
casual dispersed light incident in the preparation of the paper.  I have
before me a specimen of paper so treated in which the effect of thirty
seconds’ exposure to sunshine was quite invisible at first, and which is
now of so intense a purple as may be well called black, while the unsunned
portion has acquired comparatively but a slight brown.  And (what is not a
little remarkable, and indicates that in the time of exposure mentioned
the _maximum_ of effect was attained) other portions of the same paper
exposed in graduated progression for longer times, viz., one minute, two
minutes, and three minutes, are not in the least perceptible degree darker
than the portion on which the light has acted during thirty seconds only.”

“If paper prepared as above recommended for the chrysotype, either with
the ammonio-citrate or ammonio-tartrate of iron, and impressed, as in that
process, with a latent picture, be washed with nitrate of silver instead
of a solution of gold, a very sharp and beautiful picture is developed of
great intensity.  Its disclosure is not instantaneous; a few moments
elapse without apparent effect; the dark shades are then first touched in,
and by degrees the details appear, but much more slowly than in the case
of gold. In two or three minutes, however, the maximum of distinctness
will not fail to be obtained.  The picture may be fixed by the
hyposulphite of soda, which alone, I believe, can be fully depended on for
fixing argentic photographs.”

“The best process for fixing the photographs prepared with gold is as
follows: As soon as the picture is satisfactorily brought out by the
auriferous liquid, it is to be rinsed in spring water, which must be three
times renewed, letting it remain in the third water five or ten minutes.
It is then to be blotted off and dried, after which it is to be washed on
both sides with a somewhat weak solution of hydriodate of potash.  If
there be any free chloride of gold present in the pores of the paper it
will be discolored, the lights passing to a ruddy brown; but they speedily
whiten again spontaneously, or at all events on throwing it (after lying a
minute or two) into fresh water, in which, being again rinsed and dried,
it is now perfectly fixed.”

As the chrysotype will be no more referred to, we shall state, first, that
the image can be developed with a plain solution of silver nitrate or one
acidified with citric or any other organic acid, which generally gives a
brown impression that can be toned with an acid or alkaline gold bath, the
color varying with the solution employed; and secondly, that the process
may be employed to obtain outlines of any picture on paper or canvas to be
colored in oil-paints.  The impression developed with gold terchloride is
pale blue, _quite permanent_, and does not at all interfere with the work
of the artist.  The canvas should first be washed with a mixture of
alcohol and aqueous ammonia, then dried and rubbed with pumice stone
powder to give a _tooth_.  The modus operandi suggests itself.

The researches of Mr. C. J. Burnett on the application of uranium salts
and other compounds to photography are recorded in the _Photographic
Notes_ of Ths. Sutton for 1857.  We give in the following lines the most
interesting parts of the two papers of Mr. Burnett:

* * * “The next class of processes are dependent on the sensitiveness to
light of the salts of uranic oxide or sesquioxide of uranium, U2O3.”

“In the first process, the paper being charged with the uranic salt and
exposed to the solar influence under the negative to be copied, is washed
with a solution of the ferridcyanide or red prussiate of potash.  The
‘Harvest Scene’ in the exhibition, being from an albumen negative lent me
by Mr. Ross, the well-known Edinburgh photographer, is an example, the
salt of the sesquioxide of uranium being in this case the hydrofluate, and
the time of exposure from the strength of the albumen negative fully an
hour of good sunshine.  I have used for the solution of the uranic oxide
for this process a variety of acids with very similar results; the
sensitiveness of the prepared paper to light varying much, however.  For
instance, a collodion negative with the hydrofluate paper producing a very
good print in half an hour of unsteady sun, while with a paper prepared
with the tartaric acid solution of the oxide, it gave an equally good
impression in less than five minutes of the same intermitting sunshine,
indicating thus a difference of sensitiveness of six to one in favor of
the tartrate.”

“The rationale of this process is the reduction of the sesqui-oxide of
uranium, U2O3, on those parts of the paper exposed to the solar influence,
to a lower state of oxidation, the photo-oxide UO, the salts of which have
the property of forming with soluble alkaline ferridcyanides a rich
chocolate-brown precipitate, while the salts of the sesquioxide are
destitute of this reaction.  Hence the brown deposit on the parts of the
picture on which the sun has been allowed to act when the developing
solution is applied, and the absence of any such appearance on those parts
which have been protected from its influence.”

“As to the manipulatory details of this process, the paper is floated on
the solution in a dark room and hung up to dry, and then preserved from
light in a portfolio.  If carefully secluded from light it appears to keep
well.  After exposure for the proper time under this negative, there is in
some cases scarcely any visible impression; while in other cases,
particularly when using the tartaric solution, I have found the impression
very distinguishable, of a brownish or blackish shade, although still
quite faint.  The development is best conducted by floating it, anything
like rubbing the picture being very objectionable.”

“When the picture has fully come out, which is generally from three to ten
minutes at the very most, it is removed from the developing bath, placed
in cold water and washed very gently for a few minutes, the water being
frequently changed till it ceases to acquire a yellow tinge from the
dissolved red prussiate.  The picture is then drained from the water,
pressed between folds of blotting paper, dried (I dry in the dark), and
the process is complete. * * * I may state, as one recommendation of this
process to ladies and other lovers of clean hands, that any brown stains
left by it on the fingers or elsewhere are at once removable by a little
weak ammonia or soap and water. * * * I would particularly suggest, as
deserving of notice, the development of the salts of sesquioxide of
uranium, and still more iron, by the metals and metallic-cyanic alkaline
salts, as also by the mellonides and nitro-prussides, and the latter also
by itself and as developed by many metallic salts.”

“I have since had the opportunity of trying the nitro-prusside of sodium,
which, by itself, gives a blue and white picture, in color like that
obtained from the red prussiate of potash.”

“When mixed with a solution of ammonio-nitrate of copper, previous to its
application to the paper, the color obtained is pale purplish pink or
peach-blossom color. By mixing it in the same way with ammonio-oxalate of
sesquioxide of iron, we get a dull green picture, changeable through
intermediate stages into brown by alkaline carbonates, and that into a
_dirty_ black by gallic acid.  It may be well to know that the blue of the
picture given by the red prussiate in the process of Sir John Herschel may
be considerably modified or entirely changed to another color, in many
ways, without interfering with the purity of the white ground, by steeping
the picture, after the undecomposed red prussiate has been washed out, in
solution of salts of various metals, copper, uranium or cobalt, for
instance, and that the colors so produced may be modified as desired,
according to the stage at which the action is stopped.”

“There remains but one class of uranic photographs to be described,
namely, that obtained when we develop with a salt of silver or gold (or
platinum?).  This class may be made to print much more rapidly than our
ordinary silver printing process, approaching sometimes more nearly to the
calotype development in this respect.  We get the _minutest details_ with
great fidelity, and the picture is effectually fixed by a simple fresh
hyposulphite solution, with a good color in many cases, or by ammonia,
which will be considered an advantage by those who hold the hyposulphite
an enemy to durability.  Different shades of color are produced according
to different solvent acids and different details.  I have got a good black
perfectly like that of an engraving, by the nitrate of uranic oxide,
developed by ammonio-nitrate of silver (or plain nitrate) and fixed by
plain hyposulphite without any coloring bath. * * * I have tried the
hyposulphite of gold on some of the silver-developed prints prepared with
the hydrofluate of the uranic oxide and fixed with ammonia, which had an
exceedingly unpleasant raw-red color, a very agreeable gray was at once
obtained.  I have succeeded in getting very beautiful impressions by
development of the uranic paper by chloride of gold alone.”

In another communication to the _Photographic Notes_, more interesting
perhaps than the foregoing, Mr. Burnett says:

“The clearest and brightest of my results have been obtained by the action
of gallic acid, tannin, or especially a _mixture of tannin and carbonate
of ammonia_, potash or soda, on the blue pictures obtained by the
solarization of paper prepared with ferridcyanide of potassium,
ferrocyanide or ferridcyanide of ammonium. * * * I have also experimented
with the bichromate and iron, with gallic, tannin and other developer; but
I must confess to not having been, in this particular way, so successful
as Mr. Sella appears to have been in the preservation of the whites, owing
possibly to my not having taken the trouble to wash out sufficiently the
iron before toning.”(1)

“I have experimented most extensively in many ways with the chromates and
bichromates, and have succeeded in various ways in getting _very good_
results.  A very capital process for many purposes is to float or steep
your paper in a mixed solution of bichromate of potash and sulphate of
copper.  As for E. Hunt’s chromotype process,” (2) I have mixed gelatine,
or occasionally grape sugar, or both, with the solution, but instead of
developing it by a silver solution, as in the chromotype, wash out the
salts unacted on by light, and develop by floating on a solution of
ferrocyanide of potassium.  The color of the red copper salt which now
forms the picture may be modified or changed in many ways, viz., by
soaking the picture, after the ferrocyanide of potassium has been washed
out of the lights, in a solution of sulphate of iron (or the iron salt
may, but not so advantageously, have been applied to the picture before
the application of the ferrocyanide).  Solutions of chloride of tin,
gallic and tannic acids, alone or with alkalies or alkaline carbonates,
may also be employed to modify or change the color.  Instead of developing
by ferrocyanide you may develop by the cobalt or chromo-cyanogen salts, or
by an alkaline _mellonide_ arsenite, etc.  Sulphureted hydrogen, or a
sulphide, will give a _brown_, or _black_ tone, which may be protected
against oxygen and dampness by a resinous varnish.

“Of all the simple pictures obtainable with bichromated papers, without
complications or other tonings, those obtainable by the combination of a
salt (say the sulphate) of _manganese_, with the bichromate in the paper
preparation, are about the best; these pictures being, however, capable of
being toned and modified in many different ways if desired.  This may be
accomplished by the use of toning baths of ferridcyanide or ferrocyanide,
or other metal cyanogen salts, etc., or by either mixing the salts of
other metals, as copper or iron, with the cyanic toning baths, or using
them in the original solution, or by soaking the paper in them, as in
Sella’s process, previously to the application of the metal cyanic,
mellonic or other toning baths.  Alkalies and alkaline carbonates may also
be used to remove the chromic acid, and leave a subsalt, or the very
stable oxide or carbonate of manganese, which may be peroxidized by the
use of chloride of lime, peroxide of hydrogen, or ozone.”

“In all the processes with metallic salts, alone with bichromates, the use
of sized or unsized paper along with gelatine, etc., has some advantages.
I have got good results by such processes on albumen paper, the albumen
tending to prevent mealiness in the print; also on paper soaked in
gelatine before the application of the bichromic solution. * * * There is
great interest connected with the action of all such papers, along with
the tannin and vegetable coloring matters.  I have long been of opinion
that by the steeping of papers or textile fabrics, containing the salts
not only of iron, as recommended by Mr. Sella, but of tin, copper,
bismuth, lead, etc., in solutions of cochineal, red cabbage, beetroot,
grass or the most ordinary foliage, etc., that the most useful results
might be obtained; though for _certain_ permanence I am not sure but that
some of the other processes which I have briefly run over with the
cyanogen acid salts or metallic acid salts, as precipitators, may be more
to be depended upon.  The processes with _precipitated oxides_, such as
the one with manganese and similar ones, with other metals which I have
described, I also consider as deserving of more attention than almost any
processes which have been stated, on the score of probable permanence; but
perhaps the best process for black, or generally useful neutral tint,
without silver, that has yet been offered to the public, I believe to be
the process alluded to with the bichromate of potash and sulphate of
copper, toned by an iron salt.  *  *  *  This process, the cuprotype (as
also the uranotype and manganotype) is applicable perfectly to films of
_albumen_ or gelatine on glass or porcelain, textile fabrics, parchment,
paper, tiles and many other substances besides paper.”





THE DESIGNS.




                      HOW TO MAKE A NEGATIVE DRAWING


The drawing paper for designs to be reproduced by the cyantotype and the
other processes described in this book should be of a fine texture, free
from opacities and very white; and, as the design must serve as a cliché
it is a sine qua non that it be drawn with a very black ink and with
well-fed lines, especially those which are very fine.  To obtain a
complete opacity, and, at the same time, to keep the ink quite fluid,
which gives great facility to the designer, one adds some gamboge (or
burnt sienna) to the India ink.  The ink of Bourgeois, which is compounded
with yellow and can be diluted as easily as India ink, is excellent, so is
also the American ink of Higgins.(3)

As much as possible it is desirable to replace the colored lines
indicating the constructions, the axis, projections, etc., by differently
punctuated lines made with India ink.  However, if the use of colors be
obligatory on the original design, one should trace the red lines with
very thick vermilion or sienna, the yellow lines with gamboge, and the
blue and green lines with a thick mixture of Prussian blue and chrome
yellow in different proportions.

One must abstain from applying washes of any tints on the original. If
necessary they should be brushed over when the reproductions are made;
moreover they can be often replaced by cross-lines more or less open, and
the shadowing represented by thicker but not closer lines.

Tracing paper is recommended instead of linen, which latter, on account of
its thickness and granulation, gives less satisfactory results in regard
to the transparency of the ground and the continuity of the lines.

To reproduce a design on ordinary paper—not too thick—or an engraving,
etc., the paper is rendered transparent by rubbing over on the back of the
original a solution of 3 parts in volume of castor oil in 10 parts of
alcohol, by means of a small sponge.  When the paper is quite transparent,
the oil in excess is removed by pressure between sheets of blotting paper,
and the paper dried before the fire or spontaneously.  The design so
treated is not in the least injured, for it assumes its primitive
condition by dissolving the oil from the paper by immersion into strong
alcohol, which it is necessary to renew once or twice, then rinsing in
alcoholized water if the drawing be in India ink, or simply in water in
the case of an engraving, and finally drying between sheets of blotting
paper.

Instead of an alcoholic solution of castor oil, vaseline can be employed.
The paper is more transparent.

The method by which are made negative drawings, that is, those which can
be used as negative clichés to reproduce the design in black lines on a
white ground, is thus described by Mr. Cheysson, wlio originated it, in a
manual published by the Department of Public Works of France, from which
we have borrowed most of the above instructions for the drawing of designs
suitable for the photo-reproduction processes:(4)

“One can avoid the necessity of making a negative from the original
drawing by transforming the drawing itself into a negative.”

“To that effect it suffices to draw with lithographic ink, then to cover
the paper with aniline brown, and, after drying, to wash it with
turpentine oil which dissolves the lithographic ink without altering the
aniline.  The lines appear then white on a brown ground impervious to
light (that is, non-actinic).  The design is thus transformed into a
negative, and can yield positive impressions with paper sensitized with
silver salts, the ferriprussiate or the bichromate of potash.  The
lithographic ink should be very black and the lines well fed.”

“When the drawing is finished it is placed on a board lined with sheets of
blotting paper, then one spreads all over it the aniline brown with a
brush, and, lastly, after drying, the paper is carefully rubbed with a
bung of cotton or a rag imbued with turpentine until the lines of the
design are dissolved.”

In our practice we have often taken a negative cliché from drawings made
in the ordinary manner, without the aid of the camera obscura (which would
have been too expensive for drawings of a certain size), by simply
printing a proof by contact on plain or albumenized silvered paper, and
fixing, without toning, in a new solution of sodium thiosulphate, then
washing as usual.   The proofs thus obtained from designs drawn with an
opaque ink, which allows a long insulation and, therefore, yields an
intense reduction, are of a deep brick-red color, quite non-actinic, and
give very good positives by the Artigues process.

N.B.—Paper in drying never assumes its original shape; it is, therefore,
necessary to make the figures on the reproductions from plans when they
are not on the originals.




                         CHOICE OF PAPER. SIZING.


In all the photographic processes by precipitation of metallic oxides the
quality of the paper has a great influence on the results. When the paper
is not well sized and not well calendered, the sensitizing solution is
absorbed, instead of simply impregnating the surface of the paper, and not
only the image is sunk in and its sharpness impaired, but good whites can
never be obtained, especially if the image should be toned, owing to the
impossibility of eliminating the metallic salts not acted on, that is, not
reduced by the action of light which the fibers of the paper mechanically
retain.

The “endless” rolls of paper, 54: inches wide—or “blue print paper,” as it
is sometimes termed—of Blanchet fréres et Kléber, of Rives, better known
as “Rives’ paper”, that of Johannot, of Annonay (France), and the
Steinbach (Saxe) paper are recommended.

For small prints from negatives in half tone the positive paper, 18×22
inches, of Rives or Saxe, should be preferred to the heavy kind.  It is
advisable to size it, so that the impressions be entirely formed on the
surface of the paper.  Moreover, an additional sizing is always
advantageous, whatever be the photographic process employed, to prevent
the imbibition of the sensitizing compound and to obtain more brilliant
and vigorous images, for the iron, chromium, uranium and other metallic
soluble salts require the presence of an organic matter (alcohol, ether,
gum arabic, glucose, caseine, etc.) to be reduced by the agency of light;
and as a consequence, the greater, within certain limits, of course, the
amount of organic matters, and the more thoroughly they are mixed with the
salts, the more sensitive the preparation and the better the results.

Arrowroot is the best sizing for our purposes.  Gelatine may be employed,
albumen also, but the coating should be insolubized when applied on the
paper and dry.

_Sizing with Arrowroot._—In a porcelain dish diffuse 4 parts of powdered
arrowroot and one part of liquid glucose in 200 parts of distilled or rain
water and dissolve by heat over an alcohol lamp, stirring all the while.
Let the solution boil for an instant, and when the paste is homogeneous
let it cool down and then remove the skin formed on its surface and strain
it through a fine canvas.  Now provide with three small sponges free from
gritty matters and cleaned in water, and nail by the four corners, one
over the other, felt size uppermost, as many sheets of paper as you wish
to size on a board somewhat smaller than the paper.  This done, with one
of the sponges take a small quantity of the arrowroot and, brushing it
length-way and cross-way, spread the paste into an even layer, then, by
rubbing very lightly with the second sponge, efface the striae and smooth
the coating as well as possible.  The third sponge serves to remove the
excess of paste when too much is at first spread on.  From six to seven
sheets of paper, 18×22, can be sized with the quantity of arrowroot paste
above given.

Another, but not quite so effective a manner of sizing although sufficient
for the cyanotype, is the following, employed by Mr. Pizzighelli for the
paper used in the platinotypic process:

Ten parts of arrowroot are powdered in a mortar with a little water and
then mixed by small quantities to 800 parts of boiling water. After a few
minutes 200 parts of alcohol are added and the mixture filtered.  The
paper is immersed for two or three minutes in the warm solution and hung
up to dry.

_Sizing, with Gelatine._—Dissolve at a temperature of about 140 deg. Fahr.
(60 deg. C.) 10 parts of good gelatine in 800 parts of water, then add 200
parts of alcohol and 3 parts of alum dissolved in a little water.  Filter
and prepare the paper by immersion as above directed.  The gelatinized
paper when dry should be prepared a second time and dried by hanging it up
in the opposite direction in order to obtain an even coating.





THE CYANOTYPE OR BLUE PROCESS.


_This process gives white impressions on a blue ground with diapositives
or drawings on transparent or semi-transparent materials, and blue
impressions on a white ground from negatives._  It is commonly known under
the names of “blue print process,” “negative ferrotype process” and
“ferro-prussiate process.”

The process is indeed exceedingly simple.  A sheet of paper, impregnated
or sensitized, as it is termed, with a solution of ferric citrate and
ferricyanate is impressed under a cliché,(5) then immersed in pure water,
whereby the image is developed and at the same time fixed. It is on
account of the great advantages offered by its simplicity that this
process is generally preferred by civil engineers and architects for the
reproduction of their plans.

The sensitizing solution is prepared in mixing by equal volumes the two
solutions following:

A.   Iron, ammonio       20 parts
     citrate
     Water               100 parts
B.   Potassium           15 parts
     ferricyanate (red
     prussiate)
     Water               100 parts

Although the mixture keeps pretty well for a certain period in the dark,
it is best to prepare only the quantity wanted for actual use.(6)

The paper is preferably sensitized in operating as follows:

Take hold of the paper by the two opposite corners and fold it into a
loop, lay it on the iron solution, the center of the sheet first placed in
contact with the liquid, and then gradually spread it by lowering the
corners with a little pressure.  No solution should run over on the back
of the paper; it would be a cause of stain.  This done, and without
allowing the liquid to penetrate _in_ the paper, immediately take hold of
the two corners near the body and withdraw the paper by dragging it over
on a glass rod for this purpose fixed on the edge of the tray.  Now pin up
the paper to dry, which should be done rapidly, and sensitize a second
time in proceeding in the same manner.  If this second sensitizing be
found objectionable, let float the paper for no more than ten seconds; of
course this method of sensitizing is not applicable to prepare larger
sheets of paper.  In this case the paper is pinned by the four corners on
a drawing board or any other support, lined with blotting paper and
quickly brushed over with a sponge sparingly imbued with the sensitizing
mixture, so as to wet the paper with a very small excess of liquid.

The rationale of this manner of sensitizing is to impregnate only the very
surface of the paper with the ferric salts, and thereby to obtain an
intense blue with very good whites, which latter it would be impossible of
obtaining should the sensitizing solution be allowed to reach in the
fibers of the paper, for, in this condition, it is impossible, owing to
the exigencies of the process, to wash out thoroughly the iron salts to
prevent the chemical changes which cause the whites to be tinted blue.  It
is for this reason that better results are also obtained with well sized
papers.

The sensitizing should be done by a very diffused daylight, and the
drying, of course, in a dark room.  When sensitized the paper is yellowish
green.  It should be well dried for keeping, and rolled or wrapped in
orange or brown paper and preserved from the action of dampness and of the
air.  It does not keep well, however, no more than two or three months,
perhaps, in good condition; but the sooner it is employed the finer the
proofs, the better the whites and more rapidly is the paper impressed.

There is in the market a paper which keeps for a long time.  It is
prepared by adding a small quantity of gum arabic or of dextrine to the
sensitizing solution.  Good for the reproduction of line work, it does not
give very satisfactory results for pictures in half tones.

The following compound gives a paper much more sensitive, but not keeping
so long, than that prepared according to the formula previously given:

Tartaric acid               25 parts
Ferric chloride, solution   80 parts (in volume)
at 45 deg. Baumé
Water                       100 parts

When the acid is dissolved, add gradually concentrated aqueous ammonia,
just enough to neutralize the solution—170 volumes, about.  The chemical
change consists in the formation of ferric tartrate.  Let cool the
solution, then, after adding the following, keep it in the dark:

Potassium ferricyanate   21½ parts
Water                    100 parts

Another and very sensitive preparation is the following:

A.    Iron perchloride,   40 parts
      cryst
      Oxalic acid         10 parts
      Water               100 parts
B.    Potassium           20 parts
      ferricyanate
      Water               100 parts
Mix

_Printing._—The process we describe yields negative impressions, that is a
positive image from a negative cliché, and a negative image from a
positive cliché, exactly as the silver printing-out process ordinarily
employed in photography.  Consequently, for the production of non-reversed
proofs from plans, etc., the original drawing should be placed _face
downwards_ on the glass plate of the printing frame, and, upon the back,
the sensitive paper is laid and pressed into perfect contact by means of a
pad, felt or thick cloth.

The printing frame is that used by photographers. The lid is divided,
according to the side, in two, three and even four sections, held by
hinges and fastened for printing by as many cross-bars, in order that by
opening one section, from time to time, the operator can follow the
progressive changes resulting from the action of light on the iron salts.
To print, the frame should be placed in the light in such a manner as the
luminous rays fall perpendicularly upon the drawing or cliché.  The reason
of this is obvious, since the sensitive paper is not in direct contact
with the design, but separated by the material upon which it is drawn.

During the insolation—whose time depends necessarily from the more or less
transparency of the cliché, and, also, from the intensity of the
light(7)—the paper assumes first a violet tint, which gradually
intensifies to a dark shade; then this tint fades, becomes brownish, then
pale lilac, while the parts under the lines—that is, the design—upon which
the light has, therefore, no action, are visible by keeping the original
yellow-green tint of the prepared paper. It is when the lilac color is
produced that the exposure is sufficient.

To ascertain when the exposure is correct, a few black lines can be traced
on one of the edges of the margin of the design, and strips of the
sensitive paper placed upon them to serve as _tests_ in operating, as it
will be explained in the description of the Cyanofer process.  When one of
them is taken out and show, by being washed in water, a clear white line
on a deep blue ground, the exposure is at an end.  One understands that
the blue color of the ground is more or less intense according to time of
insolation, for the chemical actions between the reduced and the
non-reduced iron salts is so much more complete as the salts acted on are
more or less deoxidized, that is, reduced to ferrous salts; and that to
obtain the maximum of effect, which, therefore, depends on the allowable
time of exposure, the drawing ink should be opaque and non-actinic as far
as possible, because when, on testing, the lines are tinted the exposure
should be discontinued. However, a slight coloration of the lines is not
very objectionable, for it disappears by a longer washing after the
development.

The image is developed and fixed by washing in water two or three times
renewed.  The water must be free from calcareous salts; these salts
converting the iron into carbonates which impart an ochrey tinge to the
proof.   Rain water—any water in which no precipitate is thrown down by
the addition of a few drops of a weak solution of silver nitrate—may be
used with safety.

During the development the ground takes a blue color which rapidly
intensifies, while the iron compound, not acted on and imparting a yellow
green tint to the design, is washed out from the white paper.  If the
print has not been sufficiently exposed the ground remains pale blue, more
or less; the reason has been explained.  In this case the development
should be done quickly, as the blue is always discharged by washing.  On
the other hand, whenever the whites are tinted by excess of exposure, they
can be cleared partly or entirely by a prolonged immersion in water, but
the ground is also to some extent lightened.

When the proof is well developed and fixed, that is, when the soluble iron
salts are eliminated, the blue color can be brightened by adding to the
last but one washing water a small quantity of citric acid, or of
potassium bisulphate, or a little of a solution of hypochlorite of lime
(bleaching powder).

The action of light in this, as well as in the other photographic
processes with metallic salts described in this work, is one of
deoxidation, as shown by Herschel.  The chemical changes which produce the
blue precipitate is quite complicated.  It is evident that both the ferric
citrate and the ferric cyanate are partly reduced to ferrous salts under
the luminous influence, and react in presence of water with the unreduced
part of each of these compounds, the ferric citrate with the ferrous
cyanate forming Prussian blue (ferric-ferrocyanate), and the ferric
cyanate with the ferrous citrate giving rise to Turnbull’s blue (ferrous
ferricyanate).  The blue of the print is consequently a mixture in a
certain proportion of the two compounds; and as the color of Prussian blue
is quite different from that of Turnbull’s, it follows that by varying in
a certain measure the percentage of the two ferric salts forming the
sensitizing solution, the color of the blue may be varied thereby. Hence
the difference in the formulas given by different authors.(8)

The blue color of the image can be changed into black or dark green. But
to that purpose the paper should be, although not exactly necessary, well
sized as before directed, and sensitized with extra care to prevent the
imbibition of the iron solution into the paper. After exposure the proof
should necessarily be thoroughly washed to eliminate the soluble iron
salts, then immersed for a moment in water acidified with nitric acid,
1:100, and this done and without washing treated by a solution of aqueous
ammonia at 2 per 100 of water.  In this the blue color disappears, being
changed into a red brownish tint, which indicates that the Turnbull’s and
Prussian blues are transformed, the former into ferroso-ferric hydrate,
with formation of ferrocyanate, and the latter into ferric hydrate.  It is
by the action of tannin (gallotannic acid) on the ferric oxides thus
formed that the black is produced, and by that of catechu-tannic acid
contained in the extract of catechu that one obtains a dark green, almost
black color.

To obtain the black tone it suffices to immerse the proof on its removal
from the ammoniacal in a solution of tannin at 5 per 100 of water, and
when toned, to wash it in a few changes of water.

The process to turn the blue color into a green was devised by Mr. Paul
Roy.  It is as follows: Dissolve 7 parts of borax in 100 parts of water,
and acidify the solution with sulphuric acid added drop by drop until the
litmus paper becomes red; then, in the same manner, neutralize with
aqueous ammonia not in excess, but just enough to show an alkaline
reaction; this done dissolve 1 part of powdered catechu and filter.  In
this the proof is immersed after development until the desired effect is
attained.  Wash, etc.

To clear the lines, or to make additions, or to write on the blue margin
of the proof a solution of potassium oxalate is employed. It dissolves the
blue without leaving scarcely any trace of it.  The solution can be
prepared by mixing the two solutions whose formula is given below:(9)

A.   Oxalic acid       10 parts
     Water             100 parts
B.   Caustic potassa   12½ parts
     Water             100 parts

The blue prints are permanent.  When drying they darken a little from
oxidation; exposed to sunshine for some hours, they bleach considerably;
but in the shade the faded pictures progressively absorb oxygen from the
air and assume their original intensity and color in a period so much the
longer as the insulation has been more prolonged; it may take weeks if the
picture were much bleached.





THE CYANOFER. (PELLET’S PROCESS.)


_This process gives blue impressions on a white ground from positive
clichés, and white impressions on a blue ground from negative clichés._
It is termed “positive ferrotype process.”

The cyanofer is an application of one of the numerous and useful
inventions for which photography is indebted to A. Poitevin.  In 1863 he
discovered that certain organic substances were rendered insoluble by
ferric chloride, and that they again became soluble; when under the
influence of light the ferric chloride has been reduced to a ferrous salt.
This curious phenomenon is the base of the process now to be described.
As usual the process has been modified by compounding the sensitive
solution in various ways and by minor details in the manner operating.
But although these modifications have rendered the process easier to work
with, there is not a great difference in the results obtained.  We give
two formulas.  Aside from the addition of gum arabic, which was suggested
by Mr. Pellet, and which constitutes the capital improvement of the
process, the formula is substantially that devised by Mr. Poitevin.

Prepare three solutions as follows:

A.   Gum arabic, best   50 parts
     quality
     Water              170 parts
B.   Tartaric acid      12 parts
     Water              80 parts
C.   Ferric chloride    35 parts in volume
     solution at 45
     deg. Baumé

Mix gradually B to C, then C, by small quantities, in agitating briskly.
It is important to prepare the solution as directed, for by adding the
ferric chloride before tartaric acid, the gum arabic would be at once
coagulated.  When the ferric chloride is mixed, the solution at first
thickens, but becomes sufficiently fluid for use in a certain period.  It
does not keep, and should be employed the day it is made if possible.

The paper, which should be well sized and calendered, and which, when not
giving good results by too much absorbing the sensitive solution, must be
starched as before directed, is coated either by brushing or by floating.
By the first method a roll of paper five yards long can be prepared
without great trouble, and give, perhaps, better results than if prepared
by floating; but the latter method is by far the the most convenient: one
does not generally prepare by brushing sheets of paper larger than about
30×40 inches.

For brushing, the paper is pinned on a board, then, with a large badger
brush dipped in the sensitive solution, the latter is applied as evenly as
possible; after which, by lightly passing the brush over, the striae are
removed, the coating well equalized, and the paper hung up to dry.  The
coating should not be very thin, and, above all, not too thick, for then
it would require an unusually long exposure to allow the light acting
through the whole thickness of the film, which is a sine qua non to obtain
a clear ground, i.e., not stained blue.

To prepare by floating, pour the solution in a shallow tray, which needs
not to be more than 20×34 inches, 30 inches being the width of the drawing
paper usually employed; then roll the paper and place it on the solution.
Now, taking hold of it by two corners, draw it out slowly: the paper will
unroll by itself.  This operation can be done by diffused daylight, but,
of course, the paper should be dried in a dark room.  It dries rapidly.
Endless rolls are prepared by machinery.  To expose, the drawing is placed
in the printing frame, face downwards, and the sensitive paper laid over
it. The whole is then pressed into contact by interposing a cushion
between the lid of the frame and the paper, and exposed so that the rays
of light fall _perpendicularly_ upon it.

The cyanofer preparation is quite sensitive.  From half a minute to two
minutes exposure, according to the intensity of the light and the
thickness of the coating, is sufficient in sunshine to reproduce a drawing
made on the ordinary tracing paper.  In the shade, by a clear sky, the
exposure is about five times longer, and varies from half an hour to an
hour and more in cloudy weather, but then the design is seldom perfectly
sharp.

The progresses of the impression is followed by opening one side of the
printing frame and examining the proof. The exposure is sufficient when
the paper is tinged brown on the parts corresponding to the ground of the
design.  The image appears then negative, that is, yellowish on a tinged
ground.

Another and more safe method of ascertaining the correct time of exposure,
which can be employed concurrently with the other, is to place a few
strips of the same sheet of sensitive paper between the margin of the
design, upon which a few lines have been traced, and the paper, and,
without opening the frame, to draw one of them, from time to time, and dip
it in the developing solution.  If the whole strip be tinted blue, the
proof is not sufficiently exposed; but if the lines soon appear with an
intense coloration on the yellowish ground of the paper, and the latter do
not turn blue in a minute, at the most, the exposure is right.  By excess,
the lines are with difficulty developed or broken.

For developing, we provide with three wooden trays lined with lead or
gutta-percha, or, more economically, coated with yellow wax.  The wax is
melted, then applied very hot, and, when it is solidified and quite cold,
the coating is equalized with a hot iron, whereby the cracks produced by
the contraction of the wax when cooling are filled up.

One of these trays should contain a layer, about three-quarters of an inch
thick, of an almost saturated solution of potassium ferrocyanate (the
developer); the next be filled with water, and the third with water
acidified by sulphuric acid in the proportion of three per cent. in
volumes.

All this being ready, the margin of the proof is turned upwards—so as to
form a disk of which the outside is the impressed surface—in order that
the ferrocyanate solution does not find its way on the back of the proof,
which would produce stains.  Now the proof is laid, the lower edge first,
on the developer, and gradually lowered upon it, when, taking immediately
hold of it by the two corners nearest to the body, it is lifted out and
held upright to allow one following the development of the image; and,
presently, if any air-bubbles are seen on the proof, they should at once
be touched up with a brush wetted with the ferrocyanate solution; the
reason explains itself.

The image appears at once.  As soon as the fine lines are well defined,
the blue intense, and, especially, when the ground has a tendency to be
tinged blue, the proof is placed in the tray filled with water and in this
turned over two or three times, when it is immersed in the diluted
sulphuric acid.  In this bath the print acquires a deep blue coloration,
consisting of Prussian blue, and the ground becomes tinted with a blue
precipitate without adherence, which is easily washed off by throwing the
liquid on the proof with a wooden spatula, or, better, by rubbing with a
rag tied to a stick.  When the ground is cleared, and after three or four
minutes immersion to dissolve the iron salts acted on, the proof is rinsed
in water several times renewed to free it from acid, and hung to dry.

There are two causes of failures in this process, viz., over and
under-exposure. In the former case the fine lines are broken or washed out
in clearing the proof (which may also arise from the drawing made with an
ink not opaque enough); in the latter the ground is more or less stained.

The blue stains, the lines for corrections, etc., are erased with the the
potassic oxalate (_blue salving,_ as it is termed) whose formula has been
given.

The additions, corrections and writing are made with a _Prussian blue ink_
prepared by mixing the two following solutions:

A.   Ferric chloride,   4 parts
     dry
     Water              350 parts
B.   Potassium          15 parts
     ferrocyanate
     Water              250 parts

The precipitate being collected on a filter and washed until the water
commences to be tinged blue, is dissolved to the proper consistency in
about 400 parts of water. This ink does not corrode steel pens.

It has been stated that the cyanofer process keeps for years if preserved
from the combined action of dampness and the air.  The writer found in his
practice that the ferric salts in presence of the organic matters (the
sizes) acts as does potassium bichromate and renders, in a certain period,
the cyanofer film insoluble even after a prolonged insulation.  Paper
freshly prepared is always more sensitive and gives better whites and
generally finer results.(10)

The prints can be toned black in operating as in the cyonotype, but the
results are seldom good.

Captain Pizzighelli’s formula is as follows: Prepare

A.   Gum arabic        15 parts
     Water             100 parts
B.   Ammonia ferric    45 parts
     citrate
     Water             100 parts
C.   Ferric chloride   45 parts
     Water             100 parts

For sensitizing mix _in order_:

Solution A   100 parts
Solution B   40 parts
Solution C   20 parts

The mixture very much thickens at first, but becomes sufficiently fluid
for use in a few hours.  It keeps well for two or three days. Leaving out
B and replacing it by rain water, this makes also a good solution for the
cyanotype.





THE BLACK OR INK PROCESS. (FERRO-TANNATE PROCESS.)


_This process gives black positive impressions on white ground from
positive clichés, and negative impressions from negative clichés._  It has
been attributed to Mr. Colas, but in reality it was invented by Mr.
Poitevin, who describes it as follows in his communication of May, 1860,
to the Société Francaise de Photographie:

“I make a solution containing—”

Iron perchloride, cryst   10 parts
Tartaric acid             3 parts
Water                     100 parts

“I apply the paper on this mixture and let it dry spontaneously in the
dark, and at the moment of using it I completely desiccate it at a gentle
heat. Thus prepared the paper is of a deep yellow color.  Light decolors
it rapidly, and ten or twelve minutes’ exposure through a positive cliché
suffices to well impress it, that is, to reduce in the whites the iron
perchloride to the state of protochloride.”

“To print, one is guided by the decoloration of the paper, and even for
more facility I add to the solution of iron perchloride and tartaric acid
a small quantity of a solution of potassium sulphocyanide for the purpose
of obtaining a red tint, which is more visible and disappears also under
the influence of light in proportion to the decomposition of the
perchloride.  One obtains then after exposure a red design on the white
ground of the paper.  This red color is not permanent.  It even disappears
by keeping the proof in the dark.”

“To develop and then to fix the design thus obtained I wash rapidly the
paper in ordinary water, or better, in water holding chalk in suspension.
The red coloration disappears, a part of the iron perchloride is washed
out, and in the parts which have not been acted on by light the
perchloride is transformed into sesquioxide.  I replace then the water by
solution of gallic acid or of tannin and the image progressively appears
in ink-black.  When I judge the image to be sufficiently intense I wash
the proof in rain water, in preference to ordinary water, which might
cause the gallic acid and tannin to turn brown. I sponge between sheets of
blotting paper and let the proof dry spontaneously.”

“If in place of gallic acid I use a diluted solution of potassium
ferricyanide (red prussiate of potash), Prussian blue is formed in the
parts acted on by light.  The preparation is even sensitive enough to
permit one to obtain an impression in the camera obscura in developing by
the ferricyanide.”

“As to the proofs in gallate (or tannate) of iron, they can be transformed
into Prussian blue in a solution of potassium ferrocyanide (yellow
prussiate of potash) slightly acidified by sulphuric acid.”

The paper most suitable for this process is that which has been previously
well sized with starch, as explained in a special paragraph of this
pamphlet. Paper prepared with a film of coagulated albumen gives also good
results.  It may be prepared by brushing as well as by floating, but in
either case the paper should be wetted on the surface only and dried
rapidly at a temperature of about 115 deg. Fahr. (46 deg. C.) and kept in
a dry place.  It does not keep for more than from ten to fifteen days,
owing to the hygroscopicity of the iron compound.  Mr. Colas, who prepares
the paper for the Parisian market, I think, states that he avoids its
deterioration by keeping it wrapped in blotting paper, between two sheets
of India rubber, to exclude air and dampness.  Silvered albumen and plain
paper, well desiccated, could be kept in that way for a certain period,
especially if the blotting paper is impregnated with sodium bicarbonate
and well dried.

Mr. A. Fisch advises to discard the preliminary washing and to develop
just on the removal of the proofs from the printing frame.  In operating
in this manner the development is best made by floating, taking care that
the solution does not run off the back of the proof.

The developer may consist of a dilute solution of nutgalls or of

Tannin or gallic acid   4 parts
Oxalic acid             0.15 parts
Water                   1,000 parts

After developing the proof should be washed rapidly—under a jet of water,
if possible—for were the iron salt and the reagent not soon removed, or
any remain in the paper, the ground would be tinted violet.  And whatever
be the care taken, it very seldom occurs that the whites are pure when the
proof is dry.  This for half-tone pictures has not a great importance, but
for the reproductions of plans it is sometimes objectionable.  In fact it
must be acknowledged that none of the processes now at our disposal—if we
except the so-called Artigues process described further on—gives an
entirely satisfactory result.  A simple and expeditious process, yielding
intense black impressions on a white ground, is yet to be found for the
reproduction of plans, maps, etc., without resorting to a negative cliché
or drawing.





THE CUPROTYPE. (BURNETT’S PROCESS.)


_This process gives positive impressions from negative clichés._

Uranic nitrate   10 parts
Cupric nitrate   2 parts
Water            100 parts

Float for a minute strong, well-sized paper on this solution and let it
dry spontaneously in the dark.  Expose until the image is visible, then
develop by floating on a solution of potassium ferricyanide at 5 per 100
of water—the image appears at once with a rich brown color.  When
developed, wash it in several changes of water until the unaltered salts
are eliminated.  The proof is then fixed, and, if too intense, can be
reduced in water slightly acidified with hydrochloric acid.  A fine black
image is obtained by toning in a solution of platinic chloride at 1 per
100 of water.

The chemical actions giving rise to the formation of the metallic
ferrocyanide, of which the image consists, are quite complicated.  Under
the luminous agency the uranic nitrate is first reduced, then the uranous
oxide acts on the cupric nitrate, forming cupric oxide, which is finally
reduced to the metallic state.  This metal now converts the ferricyanate
in the ferro compound, which, by another action, forms both cupric and
uranic ferrocyanate.

The following uranium process gives black impressions:

In a saturated solution of tartaric acid dissolve freshly precipitated
ferric oxide, and keep the solution—ferric tartrate—in the dark.  To
prepare the sensitizing solution, dissolve 20 parts of uranic nitrate and
from 1 to 3 parts of tartaric acid in 100 parts of water, and add a small
quantity of ferric tartrate, the proportion varying with the tint desired:
an excess gives a blue black. With this solution brush the paper over,
and, when dry, expose under the negative cliché, then develop with a
solution of potassium ferricyanate at 4 per 100 of water. To fix, it
suffices to wash in water, renewed three or four times.

As pointed out by Mr. B. J. Burnett (see Introduction), many photographic
processes can be devised by basing them upon the various chemical changes,
of which uranous oxide, reduced by light from the uranic nitrate or
sulphate, is susceptible by means of metallic or organic reagents.

In the Appendix some of the most important processes, with or without
silver salts as reagents, will be described.





THE ANILINE PROCESS.


The aniline process was published in 1865, by Mr. Willis, the inventor of
the platinotype.(11) It is based on the oxidation of aniline by chromic
acid, thus: A sheet of paper brushed with a solution of potassium
bichromate and sulphuric acid, dried, and after insolation under a cliché
exposed to the fumes of aniline which, in reacting with the chromic
compound not reduced by light, forms a blue-black image.  _The process
gives, consequently, a positive impression from a positive cliché._

There are various methods of operating; we will briefly describe them.

        SENSITISING SOLUTION.
1.      Potassium            6 parts
        bichromate
        Sulphuric acid       6 parts
        Magnesium chloride   10 parts
        Water                150 parts

Willis recommended 10 parts of solid phosphoric acid instead of sulphuric
acid; the latter forms a preparation about twice more rapidly reduced.

2.   Potassium            10 parts
     bichromate
     Manganous sulphate   4 parts
     Potassium            20 parts
     bisulphate
     Water                300 parts
3.   Ammonium             5 parts
     bichromate
     Ammonium chloride    5 parts
     Cupric sulphate      1 part
     Sulphuric acid       8 parts
     Water                150 parts

Good well-sized paper should be employed. Rives is too tender and absorbs
too much.  Steinbach is better.  For small sizes, whatever be the paper
selected, it is well to size it with starch and, if possible, to calender
it on a hot steel plate, or, in lieu, to iron it.  This is not, however, a
sine qua non. The paper is sensitized by brushing or by floating.  To
sensitize by floating, it should be left but for a few seconds on the
solution and removed by dragging it on a glass rod in order to remove the
superfluous liquid.  Only the surface of the paper should be impregnated,
otherwise the whites would be more or less tinted and the image imbedded
not as sharp.

Sensitized, the paper must be dried as rapidly as possible. It does not
keep, and should be employed the day it is prepared or the day after,
keeping it well wrapped in paper.

As said above, it is exposed under a positive cliché, plans, designs,
etc., drawn on tracing paper or linen.  The more transparent the material,
the more rapid the chemical changes.  During the insolation—and it is very
short—the chromic compound is reduced, the parts corresponding to the
ground, that is, the transparent parts of the cliché, are discolored,
while those under the design remain unaltered; the image being, therefore,
faintly visible, and being formed of the chromic mixture, it is developed
by the fumes of aniline in a blue black tone.  Therefore, if the paper be
not sufficiently exposed, the ground is colored like the image, although
not as deeply, since the dye formed is proportionate to the more or less
quantity of unreduced compound, and if exposed too long the image is
imperfectly developed or not at all by excess.

The discoloration of the ground, which turns to a greenish hue, easily
indicates when the exposure is sufficient.  But, to ascertain it, the
beginner should use _tests_ as in the cyanofer process.  Mr. Endemann
regulates the time of exposure by partly covering a strip of the sensitive
paper with a piece of the tracing material upon which the design is made,
and exposing the whole until the covered part of the paper assumes the
same shade as the part directly exposed to light.

To develop the print is placed in the bottom of a tray, which is then
covered with a lid upon which is pinned blotting paper well imbued with an
aniline and benzine mixture, or the reverse; that is, exposing the print
fastened to the lid and placing the aniline on the bottom of the tray.
The tray should be hermetically closed; that is a condition to obtain a
fine and equal coloration.  For this purpose the lid should be well lined
with sheets of blotting paper and a weight placed over it during the
operation.  Large prints are necessarily developed in a fumigating box
made ad hoc.  The aniline solution consists of

Aniline (commercial for   8 parts
red)
Benzine, rectified        100 parts

In place of benzine, ether U.S.P., sp. grav. 0.837, may be used.

When the proof is not over-exposed the development commences in a few
minutes.  The image first takes a dirty black olive color which turns blue
in water, then the tone darkens to a dark-brownish tint.  The time of
exposure to the aniline fumes depends on the time of insolation; if short,
the ground is soon tinted, and consequently the development should then be
stopped; if over-exposed, the development proceeds slowly.  The darkest
tone is obtained by a rather full exposure which admits a long fumigation.
Sometimes the image takes a green color; it suffices then to wash the
proof in water rendered alkaline by a few drops of aqueous ammonia to
obtain the normal color.

To somewhat improve the tone of the image and, if objectionable, to remove
the chromic oxide which tinges the ground greenish, the proof should be
immersed in a dilute solution of sulphuric acid 1:100, then washed twice,
and finally passed in ammoniacal water 1:100.

Mr. Hermann Endemann has published, in 1866, the following process in the
_Journal of the American Chemical Society_, pp. 189 et seq.:

The paper, which must be well sized with glue, 1:50, is sensitized with
the following solution and exposed when dry, but still slightly damp:

A.   Potassium         1 ounce or 480
     bicarbonate       parts
     Salt              1 ounce or 480
                       parts
     Sodium vanadate   2/3 grain or 0.66
                       part
     Water             20 ounces or 9,600
                       parts
B.   Sulphuric acid    2 ounces or 960
                       parts
     Water             10 ounces or 4,800
                       parts

When cold mix to A.

“From the composition of the solution,” says Mr. Endemann, “it is evident
that it must be strongly acid; but when this solution is exposed to light,
in the presence of the organic substances of the paper, the acidity of the
solution disappears, we obtain potassium and sodium sulphates, basic
chromium sulphate, salt and vanadic acid.  While, therefore, the unchanged
parts of the paper remain acid, the changed parts acquire a neutral
reaction, and while the first will readily assimilate bases, the second
will not.  Exposed in an atmosphere laden with water and aniline, the
aniline will be absorbed in those parts where the solution remains acid
and in proportion to the remaining acidity.”

To develop the image the paper is spread over the opening of a frame
tightly placed on a pan, in the bottom of which is heated a solution of
aniline in water, 1:50, until the image appears brown, and for further
development in a box laden with steam water, which, according to Mr.
Endemann, requires two hours to obtain a deep black coloration.  To remove
the chromium compound the picture is immersed in a solution of aqueous
ammonia, 1:6, then washed and dried.

A few years ago the aniline process was improved by developing the image
with the aniline-benzine mixture vaporized by steam in a box made
specially for that purpose, whereby a reproduction can be obtained in less
than ten minutes.

In the photographic department of Messrs Poulson & Eger’s Hecia
Architectural and Ornamental Iron Works, which is directed by Charles
Bilordeaux, this process is worked in the following manner:

The developing is made of sheet iron with a door sliding up and down, it
being balanced by a counterpoise, and provided with a chimney.  In the box
is a gutter, extending the whole length of the bottom, covered with muslin
and connected to a steam pipe; there is also a coil similarly connected.
After the insolation, which requires about one minute in sunshine, the
print is suspended in the box, the muslin brushed over with the solution
of aniline, and live steam allowed to pass through the gutter for only two
minutes, whereby the aniline being vaporized acts on the chromic salt and
develops the image; then the steam is allowed in the coil, and, in from
three to four minutes, the paper is dry and the picture finished. The
image stands on a slightly greenish ground, which is not objectionable for
the purpose the reproductions are made.

The sensitizing solution is similar to that published by Mr. Endemann,
viz.:

Potassium bichromate   460 grams
Sodium chloride        460 grams
Ammonium vanadate      0.75 gram
Sulphuric acid         1 liter
Water                  13 liters





THE PRIMULINE OR DIAZOTYPE PROCESS.


Primuline, discovered in 1887 by Mr. A. G. Green, an English chemist, is a
dye of a primrose color, possessing a great affinity for cotton fibers, to
which it is readily fixed by simply immersing the material for a few
moments in a hot solution of the dye.  If the material so dyed be placed
in an acidified solution of nitrous oxide, the primuline is diazotized,
forming a derivative compound of a deeper color, which fades in the light,
and which in presence of amines and phenols gives rise to a variety of
dyes whose color depends on the reagent employed, while, when acted on by
light, the resulting compound is entirely deprived of this property.  In
other words, the diazotized primuline acts as a mordant only when not
altered by the luminous action.

The chemical change light effects in the diazotized primuline is not well
known.  It is pretty certain, however, that nitrogen is set free, for if
gelatine imbued with primuline be immersed in water after insulation,
nitrogen is set free and can be collected as usual in a tub filled with
water and inverted on the substance.

By itself diazotized primuline is slowly influenced by light, but quickly
acted on in presence of organic substances.  It is more sensitive when
applied on cotton or paper than on wool, silk, linen, and such organic
compounds as gelatine, albumen, caseine, starch, etc.  Its sensitiveness
is about one-tenth less with gelatine than with cotton.

The sensitiveness of diazotized primuline to light, when united to organic
substances and the different colors which can be obtained with the
unaltered compound, have given rise to an interesting printing method, the
invention of Messrs. A. G. Green, C. F. Cross, and E. J. Bevan, which
yields _positive impressions from positive clichés_.  The manipulations of
the process are simple:

In a certain quantity of rain water, kept at nearly the boiling
temperature by an alcohol lamp placed under the vessel, dissolve per cent.
2 parts of commercial primuline, and in this immerse, by means of a glass
rod, some pieces of calico—free from dressing—turning them over several
times during the immersion.  When the fibers are well imbued, which
requires from four to five minutes, remove the calico with the glass rod
and rinse it thoroughly in water.  This done, wring out the superfluous
liquid as much as possible, and, finally, immerse each piece separately in
a solution of

Sodium nitrite,      7 parts
commercial
Hydrochloric acid,   16  parts
commercial
Water                100 parts

After turning the pieces of calico two or three times over, they are
rinsed to eliminate the acid, then drained and placed between sheets of
blotting paper to dry.  All this, except the impregnation with primuline,
should be done in the dark room.

As said above, primuline is transformed by nitrous oxide into a diazotized
compound, and consequently the material is now susceptible of being acted
on by light.  It does not keep, and should be exposed, etc., soon after
its preparation.

Paper is impregnated with primuline either by floating or brushing.  The
best results are obtained with paper previously sized with arrowroot or
gelatine in order to keep the image entirely on the surface of the paper.

Linen, silk and wool are treated as calico.

The clichés should be positive to obtain positive expressions and somewhat
more opaque than those employed in the processes before described, else
vigor and intensity could not be obtained.  Here we must state that the
primuline process seems to be better adapted for the reproductions of
drawings, such as made for the black process, and of opaque photo-clichés
in lines, or white and black, than for printing in half tone.

When the material to print upon is thick and wholly impregnated with
diazotized primuline, it is advisable, since the insulation could not be
prolonged to effect the change through, to expose the back of the material
for a certain but short period in order to _clear_ it.  This is especially
advantageous when the cliché is not of good intensity.

During the exposure, which varies from 30 seconds to 10 minutes and more
by a dull light, the progresses of the luminous action is seen by the
bleaching of the material which assumes a dingy coloration.  But in order
to ascertain when the decomposition is complete on the ground of the
image, it is well to use _tests_ as in the cyanofer process, dipping one
of them in the developer from time to time.

The developers are compounded as follows:

         FOR RED.
Beta-naphthol     4 parts
Caustic potassa   6 parts
Water             500 parts

Rub the alkali and the naphthol with a little water in a mortar and add
the remainder of the water.

    FOR ORANGE.
Resorcin   3 parts
Water      500 parts

When dissolved add

Caustic potassa   5 parts

          FOR YELLOW.
Carbolic acid, cryst   5 parts
Water                  500 parts

          FOR PURPLE.
Naphthylamine           6 parts
Hydrochloric acid, in   6 parts
volume

Mix in a mortar, then add

Water   500 parts

             FOR BLACK.
Eikonogen, white crystals   6 parts
Water                       500 parts

Pulverize the eikonogen, add the water and, at the same time, the material
on its removal from the printing frame, and keep in motion until the
development is effected.

      FOR BROWN.
Pyrogallol   5 parts
Water        500 parts

After the development, which requires but a few moments, it suffices to
wash the material to fix the image by eliminating the soluble compounds.
However, for purple the material should be passed in a dilute solution of
tartaric acid and not washed afterwards; it should remain acid.

When it is desirable to obtain an impression in several colors, the
various developers are thickened with starch, then locally applied with a
brush on the image, which is always visible after exposure.

For printing on wood, glass and porcelain, see further on.





            PRINTING ON WOOD, CANVAS, OPAL, AND TRANSPARENCIES


_Printing on Wood._—To print on a wood block a design to be engraved on
the same presents certain difficulties.  In the first place, the
sensitizing solution must not be absorbed by the wood, but remain wholly
on its surface; then the photo film, although thick enough to produce an
image sufficiently intense to be distinctly visible in all its details,
should not scale or clip away under the graver, and not interfere in any
way with the work of the artist; the least touch of the graver must reach
the wood and make its impression.  Lastly, the design should be permanent.
These difficulties will be avoided by adhering to the instructions given
in the lines following.

The solution to render impervious the surface of the wood consists of

Common gelatine   5 parts
Gum arabic        3 parts
Castile soap      3 parts
Water             100 parts

Dissolve by heat on a water bath.

To apply it, the wood is rubbed with fine sandpaper, then heated over a
spirit lamp to about 86 deg. Fahr. (30 deg. C.) and upon it is poured in
excess the liquefied and quite warm solution, which must be allowed to
penetrate in the pores of the wood by letting it gelatinize, when it is
wiped off clean.  Nothing must remain on the surface of the wood. This
done, and while still damp, the preparation is rendered insoluble by
pouring over a solution of alum at 5 per 100 of water.  The object of this
preliminary operation is to render the wood impervious, and therefore to
prevent the sensitizing solution to penetrate its texture.  The wood is
then heated again and its surface whitened with a little silver white or
sulphate of barium, diffused in a small quantity of the following warm
solution:

Gelatine   1 parts
Alum       0.1 part
Water      100 parts

While wet, this is smoothed with a jeweler’s brush, taking care to leave
on the wood, a very thin layer of the mixture, only sufficient to obtain a
white surface which, by contrasting with color of the wood assists the
engraver in his work.  The wood should now be allowed to dry thoroughly,
when it is coated with a tepid solution of

Isinglass   3 parts
Water       100 parts

and dried.

Now the sensitizing process differs according as whether the cliché is
positive or negative.  In the former case the preparation is sensitized
with the solution employed in the black process, proceeding afterwards as
usual; in the latter, that is, when the cliché is negative, the best
process is the cuprotype.(12)

For printing, special frames are employed to permit one to examine the
progress of the impression from time to time without the possibility of
either the wood block or the cliché moving.  These frames open in two.
The upper frame is provided with screws on the four sides to hold firmly
the block when it is placed into contact with the cliché by means of the
screws fixed on the cross bars.  As to the cliché, if it is made on a
glass plate, it is secured on the thick glass plate of the lower frame by
two wooden bars against it pushed by screws.

When the block is ready for printing, the prepared side is usually
concave.   It is straightened by slightly wetting the back and resting it
on one end, prepared side against the wall.

_Printing on Canvas.—_The canvas should be first brushed with a solution
of aqueous ammonia in alcohol, 1:3, to remove greasiness until the thread
just commences to show, then, when rinsed and dry, rubbed with fine sand
to give a tooth, dusted, washed with a sponge and then coated with the
following solution, proceeding afterwards as in the cuprotype process:

Isinglass        8 parts
Uranic nitrate   5 parts
Copper nitrate   2 parts
Water            200 parts

_Printing on Opal, Celluloid, etc._, is quite simple; it suffices to coat
the material with the following gelatine solution, and, when the film is
dry, to proceed in operating by any one of the processes before described.

The sensitizing compound may be incorporated to the gelatine solution, but
we prefer not to do it and to sensitize the plates as they are wanted for
use.

A.   Gelatine   4 parts
     Water      70 parts in volume

Dissolve and mix little by little in order:

B.   Chrome alum   0.25 parts
     Water, hot    20 parts
C.   Alcohol       10 parts

When coated place the plates on a level stand until the gelatine is set,
and let them dry on a rack.

_Transparencies._—Prepare the plate as directed above with

A.   Gelatine      6 parts
     Water         70 parts
B.   Chrome alum   0.3 part
     Water, hot    20 parts
C.   Alcohol       10 parts

Sensitize with the uranic-copper solution employed in the cuprotype.  By
this process transparencies of a rich brown, not actinic, color are
obtained.  Consequently they can be used to reproduce negatives by the
same process.  For lantern slides they may be toned black by platinic
chloride.

To strip off the picture, apply, first, on the glass plate a substratum of
India rubber, 2 to 100 of benzole, coat with plain collodion, immerse the
plate in water as soon as the film is set, and when greasiness has
disappeared pour on the gelatine solution and proceed.

For tranferring on any material, a sheet of paper is immersed in a
solution of India rubber cement in 20 parts of benzole, dried, coated with
the gelatine solution, sensitized, etc., by operating in the ordinary
manner.  After development, the proof, being dry, is brushed over with
alumed gelatine moderately warm, dried, immersed in tepid water until the
gelatine is softened and tacky, when it is placed on the material and
squeezed into contact.  This done, the transfer should be allowed to dry
thoroughly.  Now, by imbuing the proof with benzole to dissolve the India
rubber, the paper is easily stripped off, leaving behind the picture
adhering to the material.





TRACING PROCESS ON METAL.


We call the attention of metal engravers to this process.  It is well
known that wood engravers have their original designs photographed on the
block in order to save considerable time by not making the drawing
themselves; moreover the cost is nominal, so to say, and the copy more
true and perfect than it can be done by hand.  Why should not the copper
engraver and the aquafortist avail themselves of the same advantages?  A
few do it secretly, no doubt, but the generality not knowing the process,
or, if so, not having tried it, think it is not possible or that it may
spoil their plates.  This is an error.  It can be done and very easily by
adhering to the following instructions:

Dissolve 2 parts of ammonium bichromate in 100 parts of water, and in this
let soak for an hour or so 10 parts of Coignet’s best gelatine, then
dissolve on a water bath, filter through flannel, and the solution is
ready for use.

Before being coated, the plate should necessarily be cleaned free from
oxidation and greasy matters.  This is done by immersing the plate for a
few moments in a warm solution of common potash, then rinsing and rubbing
it with chalk moistened with a little water, when after rinsing again and
draining the plate should be immediately prepared.

To spread the gelatine solution in an even and thin layer, a tournette is
employed.  The most simple consists of a round wooden stick of which the
upper part is carved in the form of a cup with an edge, or rim, about one
quarter of an inch broad.  On this rim is melted some gutta-percha, upon
which the plate is pressed into contact and adhers quite firmly when the
gutta-percha is solidified.  The stick is perforated at the lower end and
revolves on an iron pivot fixed at the bottom of the support, being held
in the opening on the platform of the same, as shown in the diagram on the
following page.

The plate being fastened to the tournette, the warm gelatine solution is
flowed over it and spread to the edges by means of a glass rod or a piece
of cardboard, avoiding air bubbles.  This done the tournette is set into
motion, and when the film is equalized, which is done in a moment, the
plate is detached, placed on a leveled stand and slowly dried with the
spirit lamp.

                              [A Tournette]

By a good light the exposure on the shade does not exceed twenty minutes
with a pretty intense transparency, and should be regulated with a
photometer.  When the insulation is sufficient, the image is slightly
visible, and should be so.  The plate is then bordered with banking wax
and bitten-in with a solution of ferric chloride at 45 deg. Baumé, or—

Ferric chloride, crystal   20 parts
Hydrochloric acid          1 part
Water                      100 parts

The parts of the gelatine film the most acted on are impermeable, so to
say, and consequently do not allow the etching fluid to penetrate to the
copper; while those the least impressed are permeated according as to
their degree of insolation, Therefore, when the ferric chloride solution
is poured upon the film and carefelly brushed over with a soft brush, in a
few moments the image progressively appears, the deep blacks first, then
the half tints, and lastly the most delicate details, the whole requiring
but a few minutes. It is now that the etching action should be stopped by
washing under the tap.  However, should by excess of exposure, or any
other cause, the details not appear within five or six minutes, the ferric
chloride should nevertheless be washed off, for then it may find its way
under the film and the plate would be spoiled.  After washing the gelatine
is dissolved in a solution of potash, etc., when the image would be found
slightly engraved.

Should the image be in half-tints, it would be advisable to apply a grain
of rosin on the gelatine film just before etching.  To engrave on steel
the operations are the same, but on its removal from the printing frame
the plate should be soaked with water renewed several times until the
bichromate is washed off.  The film is then dried spontaneously and
afterwards flowed for about two minutes with the Solution A, then, this
being thrown away, with the Solution B, which is allowed to act for a
similar period.

A.   Nitric acid, pure   120 parts
     Silver nitrate      6 parts
     Alcohol, 95 deg     50 parts
     Water               75 parts
B.   Nitric acid, pure   5 parts
     Alcohol, 95 deg     40 parts
     Water               60 parts





GRAPHOTYPY.


This process consists in converting a cliché in half tones into one in
lines, which can be directly printed on paper, or impressed, by means of
an ink transfer made as explained before, on a stone, or on a zinc or
copper plate for etching in relief, or in intaglio, according as the
cliché is negative or positive.

A cliché on gelatine, but preferably on a collodion film, is varnished
with a solution of yellow wax and bitumen in benzole and turpentine-oil:

Bitumen of Judaea   8 parts
Yellow wax          2 parts
Benzole             40 parts
Turpentine oil      60 parts (filter)

then etched as done to engrave in the aquafortis manner, the corrections
being made by applying with a brush some of the above varnish on the
defective parts, which are worked over when the varnish is dry.

The tools are simply needles of various thickness ground in sharp square
and round points of different sizes.

When the etching is finished, the parts which should form the ground, or
white parts of the design, being covered with the bitumen varnish is
non-actinic, or, in other words, does not admit the light acting on the
sensitive plate preparation employed to reproduce the design, except by an
exposure a good deal longer than that necessary to reduce the metallic
salts.

The engraver will see at once that, although it greatly simplifies the
copying work and, consequently, saves much time, this process does not,
however, bind him to any rules and leaves him perfectly free to follow its
inspirations and make such alterations as he thinks proper to produce
artistic effects; in a word, the reproduction will no more be a picture
taken by a mechanical process, so to say, but an original drawing
reflecting his talent and characteristic manner.

A similar process much employed by photo engravers, and presenting the
same advantages, is to convert an ordinary photograph on paper—or a blue
print, as devised by the writer—into a design in lines by drawing with
India ink, or the special ink of Higgins, and, this done, to wash off the
photographic image, the design being afterwards reproduced by the ordinary
processes as a negative or a positive cliché.

When the photograph is a silver print especially made for the purpose in
question and, consequently not _toned,_ but simply fixed in a new
thiosulphate (hyposulphite) bath, and well washed—it is bleached by
flowing over a solution of—

Bichloride of mercury   5 parts
Alcohol                 40 parts(13)
Water                   100 parts

If the photograph has been toned, i.e., colored by a deposit of gold, or
if it was fixed in a thiosulphate bath in which toned prints have been
fixed, then the image is dissolved by treatment in a solution of potassium
cyanide in alcoholized water.

When a blue photograph is reduced, it is advisable before drawing upon it
to first reduce its intensity by a prolonged immersion into water.  Pale
blue is a very actinic color which is not reproduced in photography,
except by the ortho-chromatic process, or if it does, the impression being
very weak, is not objectionable.  When the image has not been sufficiently
or not at all bleached, the blue is dissolved by an alcoholized solution
of the blue solving.





THE URANOTYPE.


This process, devised by J. Wothly, in 1864, did not receive from the
photographers the attention it merits, as it is always the case when a
process is patented, and can be replaced by another equally practical
which is not.  It gives pictures of a very good tone, which are quite
permanent; we have some made in 1866, which are suffered no change
whatever, they seem to have been printed from yesterday.

The first process given by Wothly does not appear to be complete.  It has
been well described by H. Cooper and a gentleman who signs by the initial
letter X.

The process published in 1865 by Wothly is as follows: A sheet of paper is
sized by brushing with a paste made of 24 parts of arrowroot in 500 parts
of water, to which are added a few drops of a solution of citric or
tartaric acid, then coated with a collodion consisting of 100 cubic
centimeters of plain collodion, a few drops of oil of turpentine and 30
cubic centimeters of the following sensitizing solution:

Nitrate of uranium     30 to 90 parts
Chloride of platinum   2 parts
Alcohol                180 parts

The time of exposure is about that required for paper prepared with silver
chloride.  The image is bluish-black but weak.  After washing the print is
immersed in a solution containing 0.5 parts of chloride of gold for 2,000
parts of distilled water, and then fixed in a bath of sulphocyanate of
potassium, which tones the image blue-black.

It may happen that the proof is slightly tinted red. This arises from a
small quantity of lime in the paper which forms uranate of calcium.

To prevent the proofs turning yellow, it should be washed in an
exceedingly weak solution of acetic acid.

If, after exposure, the print is immersed, without it being washed, in the
gold bath, the image becomes rose-red, but the whites remain pure. The
effect is peculiar.




                       H. COOPER’S PROCESS (1865).


     PREPARATION OF THE PAPER
St. Vincent arrowroot   200 grains
Boiling water           10 ounces

Crush the arrowroot to fine powder, then rub it to a paste with a little
water, and let an assistant pour a few drams of boiling water while you
keep stirring all the time; finally, let him add the rest of the boiling
water, the operator still continuing the stirring.  The paste is allowed
to cool, and will be thicker when cold than when hot.  Remove the upper
portion entirely when quite cold, otherwise, if any left, it will give
rise to streaks.  The author insists upon the necessity of all these
cares.  Two sheets of paper are now placed side by side on a flat board,
then the surface of the first is covered with the paste by means of a
sponge, proceeding, before you leave it, all over the sheet in a
horizontal direction; the second sheet is covered in a like manner.  By
the time the second sheet is pasted, the first one will be partially dry.
The sponge is now drawn over each sheet, in succession, in a perpendicular
direction in order to efface the streaks from the first sponging.  If the
paste drags in a slimy manner, it is too strong, and a fresh arrowroot
must be prepared, because dilution only ends in failure.  Why dry, the
paper is rolled under moderate pressure, and when it lies smoothly the
maximum pressure may be applied.

   PLAIN COLLODION.
Alcohol      12 ounces
Ether        4 ounces
Pyroxyline   80 grains

       SENSITIVE COLLODION.
Plain collodion            1 ounce
Nitrate of uranium, pure   30 grains
Nitrate or silver          5 grains

Add the uranium first, and as soon as it has dissolved all that it can,
add a grain or two of soda, and when settled pour off the supernatant
collodion and add the silver.(14) To coat the paper with collodion, use a
board with a handle beneath, such as is used by plasterers.  On this place
a sheet of paper, the edges being turned up about the sixteenth of an
inch; this enables the whole of the sheet to be covered without spilling
the collodion or allowing it to run on the back of the paper.

There is a marked difference in the appearance of the prints when they
leave the pressure frame. Some samples of collodion cause the picture to
print of a beautiful green, others of a rich brown, and some of a yellow
or orange tint.  The last take the longest of all to tone, and difficultly
assume the tint of well toned silver prints,(15) those printing to green
or brown tone very rapidly.

After printing the pictures are placed in diluted sulphuric acid, 1 to 30
of water, until the high lights are perfectly clear and white; this takes
from ten to fifteen minutes.  After washing well under a stream of water,
they are placed in the toning and fixing bath.

         TONING AND FIXING BATH.
Sulphocyanide of ammonium   1 ounce
Water                       12 ounces
Chloride of gold            1 to 3 grains

After removing from this bath, the prints are immersed for a few moments
in water, and then rapidly washed.

    FORMULA FOR PREPARING THE PYROXYLINE
Nitric acid, sp. gr. 1.30   12 fluid ounces
Sulphuric acid, sp. gr.     36 fluid ounces
1.845
Water                       8 fluid ounces
Temperature                 130 degrees Fahr.
Time of immersion           15 minutes.




              X’S PROCESS (1865). (Secrets of the Uranotype)


_Preparation of the Uranium Compound.—_Precipitate the nitrate of uranium
from its solution by concentrated liquid ammonia.  Let settle the
precipitate, decant, and wash in several changes of water.  Dissolve it by
heat in pure nitric acid, _taking care not to add an excess of acid._  The
ammonio-nitrate of uranium salt is then crystallized and dried.  Mix a
solution of 6 drams of this salt, dissolved in 3 drams of water, to a
solution of 15 grains of silver in 30 minims of water, and crystallize.
This salt is called _ammonio-nitrate of uranium and silver._

     SENSITIZING SOLUTION.
Ammonio nitrate salt   3 drams
Alcohol                8 drams
Distilled water        15 drops
Nitric acid, pure      1 drop

_Plain Collodion.—_Dissolve in a small quantity of ether 1 dram of Canada
balsam and 1 dram of castor oil, filter and let evaporate the solution to
the consistency of oil.

Of this, add 10 minims to a collodion made of

Alcohol      10 ounces
Ether        20 ounces
Pyroxyline   220 grains

         SENSITIVE COLLODION
Plain collodion        12 drams
Sensitizing solution   6 drams
Nitric acid            2 or more drops

Keep this collodion in the dark, as it is quite sensitive.

     PREPARATION OF THE PAPER
Arrowroot, pulverized    1 ounce
Water                    32 ounces
Solution of acetate of   10 drops
lead

Heat to 100 deg. Fahr. and then add four ounces of albumen.  The paper is
floated on this solution for five minutes and hung up to dry.  The sizing
may also be applied with a sponge in the manner often described.

The proofs should be slightly over-printed and, before toning and fixing,
placed for about ten minutes in the following solution:

Distilled water     40 ounces
Acetic acid         1 ounce
Hydrochloric acid   1 ounce

After washing in several changes of water, the proofs may be toned in any
toning bath, and then fixed with sulphocyanide of potassium, washing
afterwards in the usual manner.





THE PLATINOTYPE.




This process, discovered by William Willis,(16) yields very fine
impressions which wholly consists of platinum and are, therefore,
chemically permanent.  It has been described theoretically and practically
by Pizzighelli and Kübl in a paper for which the Vienna Photographic
Society has awarded the Voightlander prize.(17) The following is an
abridgment of this important process, as described by the authors:

The paper, calendered or not,(18) is sized with gelatine or arrowroot.
The color of the proof with the latter size is brownish black, and bluish
black with the former.

To prepare the gelatine solution 10 parts of gelatine are soaked in 800
parts of water and then dissolved at a temperature of 60 deg. C. (140 deg.
Fahr.), when 200 parts of alcohol and 3 parts of alum are added and the
solution filtered.

To prepare the arrowroot solution 10 parts of the substance are powdered
in a mortar with a little water and mixed to 800 parts of boiling water,
added gradually in stirring.  After boiling for a few minutes 200 parts of
alcohol are added and the mixture filtered.

These solutions are employed warm.  The paper is immersed for two or three
minutes and hung up to dry in a heated room, then immersed a second time
and dried by hanging it up in the opposite direction, in order to obtain
an even coating.

The potassic platinic chloride is an article of commerce.  It should be
soluble without residue in 6 parts of water and without acid reaction.  In
this proportion it constitutes the normal stock solution employed in the
various formulas.

The standard ferric oxalate solution is also found in commerce. Treated by
potassium ferricyanate it should not be colored blue, nor become turpid
when diluted with one-tenth part of water and boiled.  The former reaction
indicates that it contains no ferrous salt, and the latter no basic
oxalate.

The authors give the following instructions for preparing the ferric
oxalate solution, to which they attach much importance:

Five hundred parts of ferric chloride are dissolved in 5,000 parts of
water and heated to boiling, when a solution of soda is added until the
liquid becomes alkaline.(19) About 250 parts of caustic soda are generally
employed for this purpose.  The precipitate—ferric oxide—is now washed in
warm water until the last washing water is quite neutral to test paper,
then drained and mixed with 200 parts of pure crystallized oxalic acid.
The mixture is then allowed to stand in the dark for several days at a
temperature not exceeding 30 deg. C. (86 deg. Fahr.)  At first the
solution from green turns to a yellow green, and finally becomes almost
brown.  At this moment the excess of ferric oxide is filtered out and the
liquor submitted to a quantitative analysis, the result of which leads to
ascertain the quantity of ferric oxalate in 100 parts of the solution and
the excess of oxalic acid.  The solution should then be diluted with
distilled water, such as it contains 20 parts of ferric oxalate per 100
parts of water, and oxalic acid must be added in the proportion of from 6
to 8 per 100 of the ferric oxalate, taking into account the quantity of
acid the solution already contains.  The solution should be kept in the
dark.  It is altered by light.(20)

       IRON CHLORATE SOLUTION
Ferric oxalate solution   100  parts
Potassium chlorate        0.4 parts

This solution is employed to obtain more contrasts.

  PREPARATION OF THE SENSITIZING SOLUTION
Platinum solution         12 parts
Ferric oxalate solution   11 parts
Distilled water           2 parts

This solution gives very soft tones with intense black.  To obtain more
brilliancy we use the following proportions:

Platinum solution           12 parts
Ferric oxalate solution     9 parts
Chlorate of iron solution   3 parts
Distilled water             2 parts

To obtain results comparable to those which the silver printing out
process gives, the following mixture is employed:

Platinum solution           12 parts
Ferric oxalate solution     8 parts
Chlorate of iron solution   4 parts
Distilled water             8 parts

For very weak negatives, reproductions of drawings, etc., we use—

Platinum solution   12 parts
Chlorate of iron    11 parts
Distilled water     2 parts(21)

To obtain proofs not completely black, as, for example, reproductions of
lead drawings, the solution may be diluted with half or the whole volume
of distilled water.  But if the solution be applied on little absorbent
surfaces or on paper strongly sized it is not advisable to dilute it.

_Preparation, of the Paper.—_The paper should be kept slightly moist in
order that it does not too completely absorb the sensitizing solution.
Therefore, when the atmosphere is very dry, it is well to keep the paper
in a damp place, in the cellar for example.  Before sensitizing, which
should be done by a very diffused light, a quantity of the solution
proportionate to the surface to be sensitized (about 15 c.c., for a whole
sheet of Rives’ or Saxe paper) must be measured, and spread with a large
brush(22) on the paper fixed with drawing pins on a board covered with a
sheet of blotting paper.  When well impregnated, the paper is hung up to
dry in the dark room, and as soon as the apparent dampness of the surface
has disappeared, it should be dried immediately at a temperature of 30—40
deg. C. (86—101 deg. Fahr).  If the paper be dried too rapidly the
sensitive compound remains on its surface, and in developing the image
does not come out well.  If, on the other hand, the drying is too slow,
the solution penetrates too much in the paper and the image is wanting of
vigor and does not appear very sharp.  One cannot depart from this rule
that the desiccation from the moment the solution has been applied until
the paper is dry should last no more than from twelve to fifteen minutes.

The sensitized paper is hygroscopic and must be preserved in a calcium
box.  _It is a conditio sine qua non that the paper must be quite dry
before, during, and after printing, to obtain good results._  Dampness is
the greatest enemy in this process.

For printing a pad of India rubber should be placed over the platinum
paper to prevent it from attracting the atmospheric moisture, and in damp
weather it is even advisable to cover it with several sheets of blotting
paper previously heated before the fire.

The platinum paper is at least three times more sensitive than the silver
paper used in the printing-out process, under the reductive action of
light the yellow color of the prepared paper turns brown and then becomes
of a lighter color, nearly orange, so that the darker parts of the image
often appears more luminous than the dark half tints.  No rule can be
given to regulate the insolation, but after a few trials it is easy to
judge when it is right by observing the progress of the reduction and the
color of the image. The orange color indicates the complete reduction of
the ferric oxalate.  When the details in the lights are _faintly_ visible,
the exposure is generally right.

The developer consists of an almost saturated solution of potassium
oxalate _acidified by oxalic acid,_ and for use heated to 80—85 deg. 0.
(176—184 deg. Fahr.),(23) in an agate glazed iron tray placed upon a water
bath at the above temperature. By simply drawing the proof over it, the
image is at once developed.(24)

When the proof is thought to be over-exposed, the oxalate solution can be
employed at a lower temperature.  If, on the contrary, it is
under-exposed, the solution may be heated even to the boiling point.

The developer can be used over and over again.  _It should always have an
acid reaction._

According to Mr. Borlinetto a sepia tone is obtained by using the
following cold developer:

Saturated solution of   120   parts
potassium oxalate
Saturated solution of   13   parts
copper chloride
Oxalic acid             1.5 part

After developing the proofs are _immediately_ immersed for fixing in a
solution of hydrochloric acid, 1 to 80 of water, renewed so long as the
paper is tinged yellow (about three times), leaving the proofs ten minutes
in each solution.  Lastly, they are washed to remove the acid.

The platinotype has been still improved by Captain Pizzighelli, who
devised the following methods of operating by which the impressions are
obtained by the continuous action of light, that is, without development,
thus rendering the platinotype just as simple as the ordinary printing-out
silver process.

In these new processes to the sensitizing solution is added the alkaline
oxalate, which effects the reduction of the platinous salt during the
exposure to light.  Consequently the prepared paper is insolated until the
image appears as it should be, or—which is exceedingly useful in cloudy
weather—until it is entirely visible but still deficient in delicate half
tones, for in the dark the action proceeds and the image developing itself
will be found finished in a period which may extend to a few hours.  But
it can be, however, developed in a few seconds by immersion in a cold or
slightly warm solution of sodium carbonate, 1:25 of water. The image is
fixed as directed in the foregoing process.

The paper, prepared exactly as in the former process and kept in the
calcium box until wanted for use, should not be employed quite dry, but
allowed to absorb a little moisture by hanging it in the dark room.
Hence, the India rubber and other protecting pads can be dispensed with.
They are even objectionable, for dampness is absolutely necessary to
promote the chemical changes by which the image is developed.

    A. AMMONIO-FERRIC OXALATE SOLUTION
Ferric oxalate solution    100 parts
Neutral ammonium oxalate   18 to 20 parts

    B. SODIO-FERRIC OXALATE SOLUTION
Ferric oxalate solution   100 parts
Neutral sodium oxalate    15 to 18 parts

To prepare these two solutions the ammonium or sodium oxalate is dissolved
by small quantities at a time, and when the emerald color due to the
formation of the double oxalate commences to darken, the saturation being
then complete, no more of either salt should be added.  The solution is
now well shaken with 3 parts of glycerine, allowed to settle and filtered.

Any one of the double oxalates can be used.  The ammonium tends to produce
softer pictures and bluish tones.  To obtain more contrasts a little
potassium chlorate may be added.

   C. IRON CHLORATE SOLUTION
Solution B           100 parts
Potassium chlorate   0.4 part

       D. MERCURIC SOLUTION.
Mercuric chloride         20 parts
solution at 5:100
Sodium oxalate solution   40 parts
at 3:100
Glycerine                 2 parts

      SENSITIZING SOLUTIONS.
         FOR BLACK TONES.
Platinite solution, 1:6   5 parts
Solution B                6 parts
Solution C                2 parts

        FOR SEPIA TONES.
Platinite solution, 1:6   5 parts
Solution C                4 parts
Solution D                4 parts

Intermediate tones are obtained by diminishing the dose of C and replacing
it by an equal volume of B.  For this process the paper should be sized
with

Arrowroot                 2 parts
Sodium oxalate at 3:100   100 parts

To dispense with this preliminary sizing Captain Pizzighelli adds gum
arabic to the platinite solution, whereby the sizing and sensitizing are
done in one operation.

The gum arabic solutions are prepared as follows:

E.   Gum arabic in       40 parts
     powder
     Sodium ferric       40 parts
     oxalate solution,
     B
     Sodium oxalate      100 parts
     solution at 3:100
     Glycerine           3 parts

Place the glycerine and the gum arabic in a mortar, then, stirring with
the pestle, dissolve by adding, little by little, the mixture, heated to
40—45 deg. C. (104—113 deg. Fahr.), of the solution of sodium ferric
oxalate and sodium oxalate.  Let stand for about two hours and grind again
to dissolve entirely the gum arabic. Filter through muslin.

F. Mercuric chloride       20 parts
solution, 5:100
Sodium oxalate solution,   40 parts
3:100
Gum arabic in powder       24 parts
Glycerine                  2 parts

Dissolve as said above.

      SENSITIZING SOLUTIONS.
         FOR BLACK TONES.
Platinite solution, 1:6   5 parts
Solution E                6 parts
Solution C                2 parts

        FOR SEPIA TONES.
Platinite solution, 1:6   5 parts
Solution C                4 parts
Solution F                4 parts

Mix just before use.  The solutions do not keep.  The paper prepared by
either one of these two processes can be exposed as in the _old_ process,
and the image developed bythe hot oxalate solution.

The preparation of wood, canvas, etc., for the platinotype printing need
not to be described; it suggests itself.




                           CAUSES OF FAILURES.


_The images are veiled._

This defect may result from various causes, viz.:

 1st. The stock ferric oxalate solution is impaired by a partial reduction
      of the ferric salt into ferrous oxalate.  The solution should be
      preserved in an orange colored vial, and kept in the closet of the
      dark room.  It should be tested from time to time for the ferrous
      salt with a solution of potassium ferricyanate.  If it does not
      contain any ferrous oxalate it can be used by adding to it a little
      of the iron chlorate solution.
  2d. The paper has been exposed to light during the sensitizing or the
      subsequent operations.  One should bear in mind that the platinum
      paper is twice more sensitive than silvered paper.
  3d. The sensitized paper has been dried at a temperature above 40 deg.
      C. (104. deg. Fahr.)
 4th. Over-exposure.

_The proofs are not sharp._

 1st. The sensitive paper has absorbed moisture.
  2d. It is too old.  The paper cannot be kept good for over six weeks,
      unless special care be taken.

According to Mr. Bory, the sensitive paper altered by keeping is restored
to its original good quality by simply brushing it over with a solution of
0.05 parts of potassium chloride or the same quantity of potassium
chlorate in 100 parts of distilled water, or a mixture of these two
solutions, or one of iron chlorate.

By treating the insolated paper with these solutions, the image is
destroyed, and the paper can be used again.  One operates as for
sensitizing, taking care to desiccate the paper, as it has been directed.

_The proofs are brilliant during the development, but become dull in
drying._

The paper not well sized. It has been dried too slowly.

Remember that it should be quite desiccated within fifteen minutes.

_The paper is more or less yellow._

 1st. The paper tinted with ultramarine.
  2d. The sensitizing solution or the developer are not sufficiently acid.
  3d. The washing (fixing) in the solution of hydrochloric acid was not
      sufficient to eliminate the iron salts from the paper.

_The proofs harsh, devoid of half tones._

 1st. The sensitizing solution contains too much iron chlorate.
  2d. Exposure too short.

_The paper is stained._

The brush not kept clean while sensitizing.

_Black spots._

They are generally due to metallic dust in the paste of the paper, or from
particles of undissolved salt in the platinite solution.

NB: No good results can be expected unless the paper be kept absolutely
dry before, during and after exposure, when using the former (original)
process.

Impaired sensitiveness of the paper, want of vigor, tinged whites,
muddiness, indicate dampness.




ARTIGUES’ PROCESS


The Artigues process, so called, is, without any doubt, the best to be
employed for the reproduction of plans and drawings in lines.  It is
simple, expeditious, and yields black impressions on a very pure white
ground which are absolutely permanent.  And this is of the utmost
importance when the copies are to be used for military purpose, or kept in
archives, such as those of the Patent Office, for example.  Should it not
require the use of negative clichés, it would certainly supersede any of
the processes previously described; moreover, as it will be seen, it can
be employed for many other purposes than that of obtaining duplicates from
original drawings.  The objection is not even very great indeed, for the
design can be, without great trouble, transformed into a negative by the
aniline method described in the beginning of this work.

The Artigues process is an adaptation for the purposes in question of the
carbon process invented by Poitevin.  We shall describe it in extenso.

The paper can be prepared with any one of the following solutions:

 1st. Dissolve 2½ parts of ammonium bichromate and 5 parts of best gum
      arabic in 15 parts of water and neutralize with a few drops of
      concentrated aqueous ammonia; then add 100 parts in volume of whites
      of egg and a certain quantity of thick India ink, and, this done,
      beat the whole to a thick froth.  In ten or twelve hours the albumen
      will be deposited and ready for use.

      The quantity of India ink added to the albumen should be such as the
      paper be black when coated, but, however, sufficiently transparent
      for one to see the shadow of objects placed on the back of it, and
      the coating should not be thick.  This is important in order to
      allow the light acting through the whole thickness of the
      preparation when the paper is insolated under the cliché, for, if
      the film be too opaque or too thick (by addition of too much gum
      arabic), it would be only impressed on its surface, and the image
      dissolved during the development.  The cause of this failure must be
      explained.  Under the action of light the bichromate employed to
      sensitize the albumen is reduced into chromic oxide which render
      insoluble this organic substance—or any other, such as caseine,
      gelatine, gum arabic, etc.; therefore whenever the film is not acted
      on in its whole thickness, the subjacent part being still soluble,
      is necessary washed off and with it the superficial impressed part,
      that is, the image.

  2d. Take 10 parts of lamp black and work it up in a mortar to the
      consistency of a thin paste by gradually pouring a little of a
      solution of from 6 to 8 parts of gum arabic and 1 part of liquid
      glucose in 100 parts of water, adding afterwards the remainder, into
      which 2½ parts of ammonium bichromate have been dissolved, and
      filter through flannel.  With this, coat the paper by brushing so as
      to form a thin and uniform film, and pin it up to dry in the dark.

These solutions keep well for a certain period.  We have kept the albumen,
which we prefer to use, for two months in good condition; but the
sensitive paper does not for more than three or four days in taking the
usual care.  It is more practical—and this is recommended—to leave out the
bichromate from the preparations, and to coat the paper, in quantity,
beforehand, and for use to sensitize it with a solution of potassium
bichromate at 3½ per cent. of water applied on the verso with a Buckle
brush.(25)

The bichromate solution should be allowed to imbue the paper for about one
minute, and having brushed it once more, the paper is pinned up to dry in
the dark room.  It can also be sensitized from the back by floating, if
this manner is found more convenient.

When dry the paper is impressed under a negative cliché of good intensity
until the design, well defined in all its details, is visible on the back
of the paper, which requires an insolation of about two minutes in clear
sunshine, and from eight to ten times longer in the shade.  In cloudy
weather the exposure to light is necessarily very long.

As explained before, the luminous action, by reducing the chromic salt in
presence of certain organic substances, causes the latter to become
insoluble; consequently if, on its removal from the printing frame, the
proof be soaked in cold water, for, say, ten minutes, and, placing it on a
glass plate or a smooth board, gently rubbed with a brush or a soft rag,
the parts of the albumen or gum arabic preparation not acted on will
dissolve, leaving behind the black image standing out on the white ground
of the paper.  This done, and when the unreduced bichromate is washed out
in two changes of water, the operation is at an end.

As to the theory of this and similar processes, the insolubilization of
the bichromate organic substance acted on by light was formerly attributed
to the oxidation of the substance by the oxygen evolved during the
reduction of the chromic salt into chromic oxide; but from the fact that
oxidation generally tends to destroy organic matters, or to increase their
solubility, it is more probable that it results from the formation of a
peculiar compound of the substance with chromic oxide (J. W. Swan);
moreover, gelatine imbued with an alkaline bichromate, then immersed first
in a solution of ferrous sulphate and afterwards in hot water, is
insolubilized with formation of chromium trioxide, Cr2O7K2+SO4Fe =
SO4K2+C2O4Fe+C2O3 (Monckhoven).  A similar but inverse action occurs, as
shown by Poitevin, when gelatine rendered insoluble by ferric chloride
becomes soluble by the transformation, under the influence of light, of
the ferric salt into one at the minimum.

The writer has improved the above process by simplifying the modus
operandi as follows:

Instead of compounding the preparation with gum arabic and the coloring
matter, the albumen is simply clarified by beating the whites of eggs to a
froth, etc., and the paper is coated by floating for one minute, then hung
up to dry in a place free from dust.

If the reader has any objection for albumenizing his own paper, he can use
the albumen paper found in the market for the printing-out silver process
generally employed by photographers.

The paper is sensitized from the back with the potassium bichromate bath
by floating or by brushing.  When dry, it is exposed as usual, but for a
shorter period than when the preparation contains the India ink or other
coloring matters which impede the action of light.

The progress of the impression is followed by viewing, from time to time,
the albumenized side of the paper.  When the design is visible, well
defined and brownish, the proof, being removed from the printing frame, is
rubbed with very finely powdered, or, better, levigated graphite, and,
this done, immersed in cold water for from fifteen to twenty minutes, when
by gently rubbing it under a jet of water with a soft rag, or with a
sponge imbued with water, the albumen is washed off from the parts not
acted on, leaving the design on a perfectly white ground.

If instead of graphite, or any dry color insoluble in water, lithographic
ink, much thinned with turpentine oil, be applied on the print in a light
coating which permits one to see the design under it, and if, then, the
print be soaked in water and afterwards developed as just directed, an
image in greasy ink is obtained.  And, furthermore, by replacing the
printing by transfer ink, one readily obtains a transfer ready for the
stone or a zinc plate to be etched in the ordinary manner.

As usual there are two causes of failures in these processes, viz., under
and over-exposures.  In the former case the image is partly washed off; in
the latter the ground cannot be cleared.  The reasons are obvious.

Mr. de Saint Florent gives the following processes:(26) A sheet of
albumenized or gelatinized paper is sensitized from the verso on a
solution of potassium bichromate, dried in the dark and exposed under a
positive cliché.  After insolation, the proof is washed in water, to which
are added few drops of ammonia, then inked all over with an ink consisting
of 100 parts of liquid India ink, 7 parts of sulphuric acid and 3 parts of
caustic potassa, and dried in a horizontal position.  When quite dry, the
proof is placed in water, and after an immersion of about ten minutes,
rubbed with a soft brush: the image little by little appears, and if the
time of exposure be right, it is soon entirely cleared, and, then, if not
enough vigorous, it may be inked again.  The gloss of the image is removed
by means of a solution of caustic potassa at 10 per 100, and the proof
finally washed with care.

If in lieu of albumen paper, one employs paper prepared with a  thin
coating of gelatine, and dissolves the not acted on gelatine in warm
water, a very fine positive image is obtained by means of acidified inks
which will fix themselves on the bare paper.

Positive impressions from positive clichés can also be obtained in
operating in the following manner: On its removal from the printing frame
the proof is washed, sponged between sheets of blotting paper, then
covered with not acidified India ink mixed with potassium bichromate, and,
when dry, exposed from the verso to the action of light.  This done the
image is cleared with a somewhat hard brush.




THE CARBON PROCESS.


The carbon tissue is seldom prepared by photographers. However, for the
sake of completeness, we shall give the formula of the mixtures most
generally employed, and describe the manner of coating the paper on a
small scale.

_Preparation of the Tissue.—_The gelatine generally recommended to
compound the mixture is the Nelson’s autotype gelatine.  Coignet’s gold
label gelatine, mixed with a more soluble product, such as Cox’s gelatine,
for example, gives also excellent results.

Gelatine    110 parts
Sugar       25 parts
Soap, dry   12 parts
Water       350 parts

The coloring substances consist of:

 FOR ENGRAVING BLACK.
Lamp-black     20 parts
Crimson lake   2 parts
Indigo         1 part

   FOR WARM BLACK.
Lamp-black     3 parts
Crimson lake   3 parts
Burnt amber    2 parts
Indigo         1 part

         FOR SEPIA
Lamp-black         2 parts
Sepia of Cologne   18 parts

 FOR PHOTOGRAPHIC RED BROWN.
India ink        3 parts
Crimson lake     4 parts
Van Dyck brown   4 parts

For blue, Turnbull’s blue is employed; for yellow, light chrome yellow;
for red, carmine dissolved in aqueous ammonia, evaporating, then adding
water, etc. (See further on.)

To prepare the mixture, dissolve the sugar and soap in the cold water, add
the gelatine, let it soak for an hour, then dissolve it in a water bath
and mix by small quantity the colors finely ground together and wetted to
the consistency of a paste.  After filtering through flannel the mixture
is ready for use.

For coating, the method devised by Mr. Alf. Harman has been found
excellent in the hands of the writer, not only for the purpose in
question, but also for coating paper with gelatinous or viscous (gum
arabic) preparations.

“Take two tin dishes, such as used for the development of the carbon
prints; arrange one on your bench tilted to an angle; the lower angle is
intended to receive the warm water for keeping the gelatine mixture to a
proper temperature.  Into this angle of the tray arrange another tray
somewhat smaller, and keep it from touching the bottom of the outer one by
the insertion of any small article that will suggest itself. Into the
inner tray the gelatine mixture is to be poured.”

“The actual making of the tissue can now be proceeded with, and is so
simple and certain as not to be believed until put to the test.  Purchase
a roll of paper-hanger’s lining paper of good quality, cut it into widths
of about one and a half inch less than the width of your inner tray, and
in length of, say, thirty inches.  For the success of the operation it is
necessary that the paper be rolled up the narrow way.  Now having just
sufficient water at a temperature of 100 deg. Fahr. (38 deg. C.) into the
outer tray, pour the gelatine mixture into the inner one, and take one of
the lengths of rolled paper, and, holding it by both ends, gently lower it
on the surface of the gelatine; then at once slowly raise the end of the
paper, which will unroll itself and become beautifully coated in far less
time than it takes to describe.  Twenty sheets may be coated in a quarter
of an hour, and be equal in all respects to that made by the most
expensive machine.”

In the description of this method of coating, Mr. Harman does not explain
how the gelatine should be allowed to set before hanging up the paper to
dry, which is, however, obviously important.  It is as follows: Place on
the tray a smooth board a little larger than the sheet of paper, leaving a
small space at the end furthest from the body, and slowly, without a stop,
draw off the paper, prepared side uppermost, on the board upon which it
should remain until the gelatine is set.  If the paper curls up, wet the
back a little with a sponge before coating.

The following coating method, due to Mr. Chardon, is excellent for sheets
of paper of the ordinary photographic size, 18×22 inches.

On a glass plate placed on a leveled stand, is laid a sheet of paper
previously wetted, which is then flattened into contact with an India
rubber squeegee, taking care to remove the air bubbles interposed. The
quantity of gelatine necessary to coat the paper is regulated by means of
a glass rod held by an iron lath, which serves to handle it; at each end
of the rod is inserted a piece of an India rubber tube whose thickness
regulates that of the gelatine layer. The mixture is poured from a small
teapot, at the opening of which has been adapted a bent glass tube about
three-sixteenths of an inch in diameter, between the rod and the lath, so
that by a simultaneous motion, one can equalize the gelatine as it is
poured on. When the gelatine is set the paper is hung up to dry.  In
drying, the gelatine contracts, and, necessarily, causes a deformation of
the tissue, which curls up at the edges and loses its planimetry.  To
prevent this, while the gelatine is almost dry, the tissue is placed under
pressure until quite desiccated.  Dumoulin advises to apply on the film,
while still soft and tacky, a wooden frame, which, by adhering to it.
keeps the tissue perfectly plane as it dries.

                      [Chardon’s method of coating]

_Sensitizing.—_The tissue is sensitized in a bath of potassium bichromate.
The degree of concentration of the bath, which varies from 2 to 5 per
cent. of water, is important.  The tissue sensitized in a weak bath is
less rapidly acted on by light and yields more contrasts than when imbued
in a concentrated one.  The former should consequently be employed for
printing weak negatives, and the latter for those which are intense.  A
bath compounded with 30 parts of potassium bichromate, 1,000 parts of
water and 2 parts of aqueous ammonia, is used for printing negatives of
the ordinary intensity, the tissue being, then practically of the same
sensitiveness, a silvered paper insolated to obtain a print not
over-exposed.  For intense negatives the ammonia should be discarded and
replaced by the same quantity of chromic acid.

The time of immersion has also a certain influence on the results.  The
less the tissue is allowed to absorb the solution the less sensitive it
is, but also the more the tendency of the half tints to be washed off
during the development.  Generally the tissue should remain immersed until
it lies flat and the edges just commence to curl up, unless white and
black impressions are desired, but even then it is preferable to operate
as said above, using a bath at 2 per cent.

For use the bichromate bath should be cooled down to 15 deg. C. (59 deg.
Fahr.), and much lower in summer, say 10 deg. C. (50 deg. Fahr.), and kept
at about this temperature by placing pieces of ice around the tray.  At 20
deg. C. (68 deg. Fahr.) the prints are more or less granulated; above this
the gelatine is softened and the reticulation greater; at 25 deg. C. (75
deg. Fahr.) it may dissolve.

The addition of alcohol to the bichromate bath—sometimes recommended to
harden the film and allow it to stand a higher temperature, and to hasten
the desiccation of the tissue—is objectionable, for the spirits tend to
reduce the bichromate, which is transformed into the green salt, and,
therefore, a partial or complete insolubilization of the gelatine is the
result.

Aqueous ammonia added to the sensitizing solution has for its object to
permit one to keep the sensitive tissue for a somewhat longer period, but
it renders it less sensitive.  If enough be added to turn the solution
yellow weak prints are obtained.

The bichromate bath should be renewed often. It does not keep owing to the
presence of gelatine and other organic matters which it dissolves and
which cause the reduction of the chromic salt even in the dark.  The
tissue prepared in such a bath is not very sensitive and the image
develops with difficulty, and even cannot be developed at all.

As said above, the tissue is well sensitized when its edges commence to
curl up.  It is then removed from the bath by drawing it on a glass rod
fixed at the end of the tray, and placed, prepared side down, on a
slightly waxed glass plate, rubbing it with an India rubber squeegee to
remove the superflous liquid, when it is hung up to dry.

While wet the bichromated tissue is insensitive; the sensitizing can
therefore be made by daylight, but the drying should of course be done in
the dark room, that is in a room lighted by a candle or the sunlight
filtered through a deep orange window glass.

_Caution.—_The soluble bichromates are very poisonous.  By absorption they
produce skin diseases not without danger and very difficult to cure. Hence
when handling the wet tissue the fingers should be protected by India
rubber tips, and any yellow, stains on the hands should be rubbed with a
dilute solution of aqueous ammonia, and the hands well rinsed in water.

_Drying.—_When the tissue dries rapidly it adheres well on the support
upon which it is applied for developing and yields brilliant images which
are easily cleared.  On the other hand, were it allowed to dry slowly the
adherence would not be so complete, the image dull and developing with
difficulty.  They may even refuse to develop at all from the
insolubilization of the gelatine.

In winter and in the cool days of spring and autumn, the gelatine dries
quick enough in the air, but when the weather is warm and damp, the
gelatine, drying very slowly, may be so softened as to run off, or to
produce an entirely objectionable reticulation, or the defects above
mentioned.  This may be avoided by drying it pinned up in a box, or a
closet, over quick-lime.

When dry, the tissue is generally wrinkled, brittle, breaks easily in
handling and cannot be laid flat on the cliché; but by holding it over a
basin of boiling water, the steam in a few moments rendering it
sufficiently pliable to lay it flat between glass plates, where it should
be kept under pressure until wanted for use.

The writer always dries the tissue in the following manner, which he
devised about sixteen years ago.(27) And not only the least trace of
reticulation is avoided, but the tissue, drying quite flat, lies in
perfect contact with the negative, which is quite important to obtain
proofs exactly sharp all over.

A clean glass plate is rubbed with talc, or, which the writer prefers,
flowed with a solution of(28)
Yellow wax, pure   1 part
Benzine, pure      100 parts

then strongly heated, allowed to cool and rubbed clean (apparently) with a
piece of flannel.  After once more repeating this operation the plate is
coated with the following plain collodion:(29)

Ether, conc.      250 parts, in volume
Alcohol, 95 deg   250 parts, in volume
Pyroxyline        3 parts

When the film is set, the plate is immersed in filtered water until
greasiness has disappeared, when on its removal from the bichromate bath
the tissue is laid, without draining, upon it and pressed into contact
with the squeegee to remove the excess of liquid and, with it, the air
bubbles interposited.  The tissue is then allowed to dry in the air on the
collodionized plate in the cold season, or, when the weather is warm and
damp, in a box in the bottom of which is placed a quantity of quicklime in
earthen dishes.  When dry, the plates are placed one upon another, wrapped
in paper and kept in a dry place.  When wanted for use the tissue is
stripped off and will be found quite flat with a beautiful surface to
print upon.

One should avoid to keep the sensitized tissue in a moist and warm
atmosphere, for in less than ten hours it becomes insoluble even in
complete darkness.  It should neither be kept in the air contaminated with
gaseous reductive matters, such as the products of the combustion of coal
gas and petroleum, sulphydric or sulphurous emanations from any source,
the fumes of turpentine oil, etc., which, by reducing the chromic salt,
cause the insolubilization of gelatine, prevent the print to adhere on the
support or the clearing of the image, which may even refuse to develop.

The sensitive tissue keeps well for three or four weeks in cool and dry
weather, and no more than eight or ten days in summer unless well
desiccated and kept in a preservative box.  If kept too long the image
cannot be developed.

_The Photometer.—_The time of exposure is regulated by means of a
photometer.  Of all the photometers which have been devised for that
purpose we do not know any one more practical than that suggested in 1876
by Mr. J. Loeffler, of Staten Island. It is made as follows: On a strip of
a thin glass plate, 6×2 inches, make four or five negatives, 1½×1¼ inch,
exposing each one exactly for the same period and developing in the usual
manner, but without any intensification whatever.  It is even advisable to
reduce the intensity if they were opaque.  Fix, etc., and apply a good
hard varnish.  Now cover the back of these negatives with strips of
vegetable paper or transparent celluloid, or, better, of thin sheets of
mica, in such a manner as there be one thickness on the second negative,
two on the third, three on the fourth, etc., leaving the first one
uncovered.   Then place on the whole a glass plate of the same size as the
first and border like a passe-partout.

_The Negatives.—_For the carbon process the negatives should be intenser
than those intended for printing out on silver paper.  However, good
proofs may be obtained from any negatives, so to say, by varying the
strength of the bichromate solution, as, also, by _using the tissue
freshly sensitized for weak negatives,_ in order to obtain vigor, and _for
strong negatives, the tissue two or three days after its preparation,_
when it yields better half tones.  Printing dodges are also resorted to.
That the most commonly employed consists to varnish the back of the
negatives with a matt varnish, or to stretch on the same a sheet of
mineral paper upon which the retouches are made by rubbing graphite,
chrome yellow, pink or blue colors to strengthen the shadows or the
whites, as the case requires.  As a rule, it is advantageous to cover the
printing frame with tissue paper, whatever be the quality of the
negatives.

The negatives should be bordered with deep yellow or orange-red paper to
form what is termed a “safe edge” upon which should rest the tissue in
order to prevent the margin from being insolubilized by the reductive
action of light.  If this precaution were neglected it would be impossible
to strip off the paper without tearing the proof when the tissue is
applied on the support upon which the image is to be developed.

Before exposing it is advisable to ascertain what the printing qualities
of the negative are by making on silvered paper a proof of it—_not
over-printed—_and another of the photometer, both being exposed at the
same time and for the same period.  This done, compare the proof from the
negative cliché with those of the photometer, and mark the negative with
the number of that of the photometer to which it corresponds, stating the
shade of the proof next to it; for example: _No. 2_; _No. 3 faint, or
commences to appear,_ etc.  This No. 2 and the observation will indicate
the intensity of the negative and serve as a guide for printing on the
tissue, since, as before explained, the silver paper is practically of the
same sensitiveness as the tissue prepared for negatives of the ordinary
intensity.

_Exposure.—_To print, the tissue is laid over the negative, taking care
that it covers the safe edge, and a strip of silvered paper placed in the
photometer, then both the printing frame and the photometer are exposed to
light side by side.

Unless the negative be weak, when more vigor is obtained by exposing in
sunshine, the printing should be done in the shade.  It is a well-known
fact that the part of the bichromated film corresponding to the half
tones in the lights are not sufficiently impressed in comparison to the
blacks while impressed in direct sun’s light in this as well as in the
collotype, photogravure and other processes with the chromic salts,
because the luminous action through the bare glass, or nearly so, which in
the negative represent the shadows and half blacks, is more energetic in
proportion than through the other parts, from which it results that these
parts being most acted on are made deeply insoluble through the thickness
of the film, and then require to be cleared by a treatment with water at a
higher temperature than the parts representing the half tints in the
lights of the picture, which are but superficially and slightly insoluble,
can stand.

From time to time during the exposure the print in the photometer is
examined, and when a certain picture is printed to a certain shade, or
when the one next by commences to appear or is faintly printed, etc., the
exposure of the tissue is sufficient.  This, as the reader has already
inferred, is a matter of experience, the guide being the knowledge of the
intensity negative tested as above explained.

_Development.—_The carbon prints are developed either on a sheet of paper
upon which it should remain (single or simple transfer), or on a provisory
support to be afterwards transferred on paper or any other material
(double transfer).

_Simple Transfer.—_This process is quite simple: The impressed tissue and
a sheet of paper coated with alumed (insoluble) gelatine are immersed face
to face in cold water, and when the tissue is softened both are removed,
one superposed on the other, and the whole, being placed on a glass plate
and covered with a thin oil cloth, is firmly pressed into contact with the
squeegee.  The rationale of applying under water the tissue on the
gelatinized paper is to avoid the interposition of air bubbles.

To operate by simple transfer the tissue should be impressed under a
reversed negative.  The reason is obvious.

_Double Transfer.—_By this method the carbon prints are generally
developed on porcelain or opal plates, which more easily than glass plates
permit one to follow the progress of the development and to retouch the
imperfections before transferring the picture on paper.

In order that the image does not adhere on the provisory support a little
of the following mixture is spread over the plate, which is then pretty
strongly heated, and, when it has cooled down, polished lightly with a
piece of white flannel to obtain a very thin and even layer free from
striæ.  If the plate has not been used before for the purpose in question,
it should be waxed a second time in the same manner:

Yellow wax              4 parts
Rosin                   1 part
Turpentine or benzine   250 parts

The plates can be developed on the plates so waxed, but for “full gloss,”
that is, for enameled pictures, a film of collodion is applied on the
plates, which then, instead of being waxed, should to be simply flowed
with a solution of India rubber 1 to 100 of benzole:

Ether        250 parts
Alcohol      250 parts
Castor oil   1 part
Pyroxyline   5 to 6 parts

When the plate is coated and the collodion film set, it is immersed in
water until greasiness has disappeared and wanted for use.  Then the
tissue, previously soaked in water, is applied upon it (taking care to
avoid air bubbles) and squeezed, lightly at first, with some force
afterwards, to insure a perfect contact.

Zinc plates are also employed as provisory supports instead of glass, opal
or porcelain plates.   The modus operandi is exactly the same.(30) The
plates should be well planed, free from scratches, etc., and well polished
to obtain glossy pictures without one having recourse to a film of
collodion.  For matt pictures, i.e., without gloss whatever, the plate
should be finely granulated, and when waxing a very light pressure should
be exerted to remove the excess of wax, else it might be quite impossible
to strip off the picture in transferring on paper.

For double transfer on biscuits, objects in alabaster, porcelain, wood,
any even or curved rigid materials, flexible supports are employed to
develop the pictures.  These supports are prepared by fastening albumen
paper on a board and evenly brushing over the following hot compound,
filtered through flannel, which, when dry, is polished with a cloth:
Stearine   15 parts
Rosin      3 parts
Alcohol    100 parts

The flexible supports should be waxed, then collodionized for full gloss,
as the glass, porcelain and metallic plates.

Another method which the writer recommends is the following, due to Mr.
Swan: Immerse a sheet of paper in a solution of India rubber, 4:100 of
benzole, and let dry, which requires a few minutes.  This is the flexible
support.  Then after exposure, brush over the India rubber solution on the
carbon tissue, apply upon it the support when the benzole is evaporated,
and pass the whole under a rolling press to secure adhesion, then develop.
To transfer, soak the proof in tepid water, apply it on the material
prepared, as it will be explained further on, and when dry, imbue the
support from the back with benzole, to soften the India rubber, and strip.

To dispense with a rolling press, the proof may be developed on lacquered
vegetable paper prepared by immersion in a solution of 10 parts of red
shellac in 100 parts of alcohol.  After developing the proof is coated
with alumed gelatine, and when dry transferred as usual. To strip off it
suffices to imbue the paper with alcohol in order to dissolve the shellac.

When the picture must be transferred on small spaces or on small objects
the most simple method—the most effective, perhaps—is the following,
devised some years ago by the writer and now employed for the ornaments of
“articles de Paris:” Prepare the provisory support as usual, but with a
thicker film of collodion; then, after developing and coloring, if
necessary, the picture is coated with gelatine, to which may be added some
zinc white or other colored substance to form a ground.  This dry, strip
off, immerse the pellicle in water to soften the gelatine and transfer on
the material collodion side up.

The proofs should be developed within three or four hours after
insolation, for the luminons action continues pretty actively in the dark,
and this for a long time; thus: a proof rightly exposed in the morning
behaves as one over-exposed if developed in the evening, and after a
certain period either can not be developed or refuses to adhere on the
support.  However, the proofs can be kept for three weeks, may be more,
before development, if the soluble bichromate be washed off, the tissue
sponged and dried rapidly in the warm season.  This capital improvement is
due to Mr. Charles Brasseur.

It has been said that before being applied on the support the proof should
be immersed in water to soften the tissue.  The time which it should be
allowed to absorb water has an importance which must not be neglected.  If
it do not remain long enough to be soaked through, small invisible air
bubbles are formed on its surface, and interposing themselves between the
image and the support, form minute, brilliant, silver-like spots on the
finished picture; and, if the temperature of the water is above 20 deg. C.
(68 deg. Fahr.), the image will be more or less reticulated.  The
temperature depends a good deal of the softness of the gelatine; 15 deg.
C. (59 deg. Fahr.) is safe, except, however, when the thermometer is in
the thirtieths (90th Fahr.), when the water should be cooled down a few
degrees lower, but not at the melting ice temperature, for then the proof
would not adhere well.  As a rule, the tissue should remain in the cold
water until it becomes flat and shows a tendency to curl up.  It is at
this very moment that it should be squeezed on the support.

The proofs should not be developed immediately after transferring.  The
adherence is greater and the pictures finer and devoid of defects when the
development is made half an hour, and even an hour, after.  If developed
too soon the picture will be partly, and even entirely, washed off.
Hence, a number of transfers can be prepared beforehand, placing them,
face to face one upon another, in order that the tissue does not dry,
which is quite essential.

To develop, the plate, with the tissue adhering to it, is placed in water
heated to 30 deg. C. (80 deg. Fahr.), where it is left rocking the tray
occasionally until the paper rises up by itself at the corners, when
taking hold of it by one corner, it is stripped off, leaving behind the
image buried in soluble gelatine.  Should the paper offer any resistance
whatever, the gelatine should be allowed to become more soluble by
increasing the temperature of the water, or by a longer immersion.  There
is, in fact, no objection to this.  The plate—and that is a good
method—can be placed in an upright position in a tin box, made ad hoc, and
left therein in warm water until the paper detaches itself and the image
is partly developed _and the bichromate washed off._  This done, the plate
is held in an inclined position on a tray filled with water at 35 deg. C.
(95 deg. Fahr.), which is dashed with a wooden spoon on the image to clear
it from the non-acted-on gelatine.  Presently one can judge whether the
exposure is right.  If it is too short, the half tints in the shadows are
washed off, unless the negative be too intense, when a similar effect also
occurs in the whites.  If it is too long, either the image is with
difficulty cleared or remains undeveloped.  In the latter case, it is
recommended by some operators to increase the temperature of the
developing water to near the boiling point, and, for local clearing, to
pour it on.  This we find objectionable, for the half tints are easily
washed off.  A better process, when the picture can not be cleared by
water at 50 deg. (122 deg. Fahr.), or thereabout, is to use a solution of
common salt at 5 or 6 per cent. of slightly warm water.(31) It is even
preferable to finish the development in a tepid solution of potassium
sulpho-cyanide, 12:100.  The dissolving action is long, but not only, as
said above, the half tints are best preserved, but blistering  and local
washing-off are avoided.

After development the plate is rinsed under the tap, then flowed two or
three times with a solution of chrome alum at 1 per cent. of water, then
washed, and finally allowed to dry spontaneously.

It is objectionable to use a strong solution of alum, and in it to immerse
the plate for any length of time; the gelatine is considerably
hardened—which is not necessary—and more liable to crack by time in being
thoroughly desiccated.  We discard the common alum which we found liable
to produce a slight reticulation.

Two defects are complained of by the beginners, viz., the want of
adherence of the deep blacks, and, especially, the isolated and fine lines
when the picture is a reproduction of an engraving, a drawing, etc., and
the liability in half tone pictures of the delicate details being washed
out.  The first defects are avoided by pouring a solution of boric acid on
the transitory support before applying the tissue and developing at a low
temperature with salted water.  The second from an imperfect knowledge of
the properties of gelatine acted on by light in presence of a salt of
chromic acid.  One should bear in mind that the degree of solubility of
gelatine so acted on, as also its degree of impermeability—which is
important in certain processes of photogravure—is proportionate to the
degree of insolation; thus, when not impressed, bichromated gelatine
dissolves in water heated to about from 25 to 30 deg. C. (77 to 80 deg.
Fahr.), and when acted on between 30 and 100 deg. C. (86 to 112 deg.
Fahr.), according as to the degree of insolation, that is, of reduction of
the chromic salt, the latter temperature being that of insolubility of the
parts the most acted on.  The very delicate half tints do not, generally,
stand a temperature higher than 35 deg. C. (95 deg. Fahr.), and,
therefore, as the degree of insolubility of the various parts cannot be
ascertained, a priori, it is advisable during the development to increase
gradually the temperature of the water from this degree, and not to exceed
45 deg. C. (113 deg. Fahr.), in order to obtain the most perfect result
from a negative of good intensity.  Indeed, by placing the supports on a
rack and immersing the whole in water heated to 30 to 35 deg. C. (86 to 95
deg. Fahr.), the image will clear up by itself to perfection in a certain
period.  This method is excellent for proofs in lines.  Those from the
grained negatives employed in photogravure are still more perfectly
developed in a tepid solution of potassium sulphocyanate, since the
impressions wholly consist of insoluble parts (the lines) and gelatine not
acted on.

_Retouching.—_The retouches are easily made. They should be done before
transferring when working by the double transfer process.

The transparent spots, and any parts which should be altered, are
retouched with the material of the tissue dissolved in warm water; the
whites are cleared with a scraper; and any parts which are not intense
enough, or which should be blended by the addition of half tints, are
worked on the proof—to which a tooth has been given by rubbing with
cuttle-fish powder—by means of a stump and an appropriate color, a mixture
of lamp-black and carmine, for example, in very fine powder.

The proofs can also be colored by chemical means (see further on), or with
water colors employed with a solution of chrome alum, 1 to 200 of water,
or gilt, silvered or bronzed with metallic powders applied with the
gilder’s size thinned with turpentine on the proof previously coated with
a thin layer of alumed gelatine.

_Second Transfer.—_To transfer, a sheet of enameled or simple transfer
paper is immersed in tepid water until the gelatine is softened and feels
slippery to the fingers.  The support is then placed under water at
ordinary temperatures—not under 16 deg. C. (60 deg. F.)—for two three
minutes, then rubbed with a camel brush to remove the air bubbles, which
might be formed on the surface of the image, when, without draining, the
gelatinized paper is laid upon it, covered with the thin oil cloth, and
pressed into contact with the squeegee, commencing in the center to the
sweep off the water, then repeating the operation for the other half, as
explained to apply the tissue on the provisory support.  When the whole is
quite dry, which requires three or four hours, the edges are cut with a
penknife and the whole stripped off.  It may happen that the proof is
covered with minute, silver-like brilliant spots, which are nothing else
than very small air bubbles interposited between the carbon proof and the
transfer paper. They are caused by the gelatine paper not having been
sufficiently softened or not laid on the proof with proper care. The
defect may also arise from the transfer paper coated with not sufficiently
thick gelatine.

To transfer on any rigid material, the proofs on flexible supports are
coated by floating on the following gelatine solution, then allowed to
dry, and, when wanted for use, immersed in tepid water to soften the
gelatine and secure adherence:

Gelatine                   50 parts
Water                      400 parts
Solution of chrome alum,   6 parts
4:100

_Development on Absorbing Materials.—_The development of carbon prints on
absorbent material—such as canvas and palettes to be painted in oil,
etc.—cannot be made in the ordinary manner on account of the impossibility
to eliminate entirely the chromic salt which tinges the material yellow.
To turn the difficulty, it suffices to wash off in several changes of cold
water all the unaltered bichromate from the prints on their removal from
the printing frame, and to proceed as usual, or the prints can be allowed
to dry and transferred at some future time.

Canvas should be prepared by brushing with a solution of aqueous ammonia
in alcohol, 5:20, to remove greasiness until the thread is apparent, and,
when dry, rubbed with sand to grain it—or to give a tooth, as it is
termed—then rubbed dry with a solution of soluble glass, 1 to 10 of
beer.(32)

Palettes should be rendered impervious, or nearly so, by flowing upon them
a solution of alumed gelatine, which is allowed to penetrate into the
pores of the wood and the excess scraped off when solidified, when the
surface may be whitened, if necessary, as for printing on wood box, q.v.

Opals, porcelain, or ivory should be prepared with the following
substratum:

Gelatine             50 parts
Water                400 parts
Chrome alum, 4:100   6 parts

Very fine carbon proofs having the appearance of pictures on opal plates
are made by transferring in the following manner, devised by the author:

Develop on the ground surface of a glass or porcelain plate, well waxed,
to obtain a matt picture, or in the ordinary manner for "full gloss," and
when the image is retouched or colored, apply a thin coating of gelatine,
let dry and coat with the following opaque collodion:

A.   Ether, conc.         100 parts
     Alcohol, 95 deg      90 parts
     Pyroxyline           7 parts
B.   White zinc in very   9 parts
     fine powder
     Castor oil           3 parts
     Alcohol              10 parts

Grind in a mortar, adding ultramarine blue and carmine, or a little of any
suitable coloring matters, and mix to A. When the collodion is dry, which
requires a few hours, strip the whole or back with strong white or colored
paper before stripping. A solution of gelatine with glycerine, white zinc,
etc., may be substituted for collodion when the pictures are employed as
ornaments on wood, etc. Carbon prints on celluloid are now made for
similar purposes.
OPAL GELATINE SOLUTION
Gelatine      150 parts
Glycerine     15 parts
Zinc, white   40 parts
Water         600 parts

To which some coloring matters may be added according to taste.  Grind the
white with the glycerine and a little water, mix to the gelatine dissolved
in the remainder of water, and filter through canvas.  Apply the mixture
moderately hot, 30 deg. C. (86 deg. Fahr.)

_Transparencies.—_The transparencies are printed on a special tissue sold
under the name of “diapositive.”  It differs from the ordinary tissue in
this, that the mixture contains a greater quantity of the color matter,
India ink, which is ground exceedingly fine.

The proofs for transparencies should be printed deeper than those to be
seen by reflection, and developed on thin glass plates, free from any
defects, and coated with either one of the following substrata:

Soluble glass   5 parts
White of eggs   15 parts
Water           20 parts

The whole is beaten up to a thick froth and allowed to subside, when the
clear liquid is decanted, filtered through flannel and the glass plates
coated.  The substratum should be allowed to dry for a few hours, and
rinsed under the tap before use.

The other substratum consists of

Gelatine             35 parts
Acetic acid, No. 8   250 parts
Alcohol, 95 deg      50 parts
Water                700 parts
Chrome alum, 4:100   60 parts

Dissolve the gelatine in the acid at a moderate heat, add afterwards the
alcohol and water, and lastly mix the chrome alum by small quantities at a
time.

These substrata are employed to avoid the peeling off of the image.  To
prevent the entire desiccation of the gelatine, which is the cause of the
defect above alluded to, it is advisable to add glycerine to the washing
water after the image is cleared.  Some operators recommend a coating of
flexible collodion, that is, prepared with castor oil, for the purpose in
question.  We do not think that necessary when the transparencies are not
exposed to sunshine.  If anything should be applied we would prefer the
encaustic.

Carbon transparencies are invaluable for reproducing negatives in the
original size by the same (carbon) process, or for enlarging by the
collodion or gelatine process.  For these purposes they should be made on
the special red tissue manufactured by the Autotype Company, of London,
Eng.  They can, however, be made on the ordinary tissues.

Whatever be the tissue employed, the transparencies for the reproduction
of negatives are seldom opaque enough, and should be intensified.  This is
done by treating them with a very dilute solution of sodium permanganate,
which colors them olive green.

Transparencies for lantern slides, etc., are best colored with the
couleurs à l’albumine of L. Encausse, sold by J. Reygondaud, Paris
(France).  They are transparent.(33)

_Toning and Intensifying.—_The carbon proofs can be toned and at the same
time intensified by reagents acting with chromic oxide.

The dyes or coloring matters precipitated are not opaque, and, as a
consequence, not objectionable for transparencies.  The following
processes are the most employed:

Prepare three solutions as follows:

A.   Ferric sulphate    5 parts
     Water              100 parts
B.   Sodium carbonate   2 parts
     Water              100 parts
C.   Gallic acid        5 parts
     Water              100 parts

Dissolve the gallic acid in warm water.  Filter each solution.  They keep
well.

To tone, the plate is immersed for, say, ten minutes in A, then, after
rinsing slightly, it is placed in B for the same period, rinsed again and
flowed with C until the desired color is obtained.  The tone is a splendid
purple black color.  If a solution of pyrogallol be substituted to that of
gallic acid, the tone is green, and to a green bordering to black when a
solution of catechu is used, the catechu exerting at the same time a
tanning action on the gelatine.  After toning, the plate should be
thoroughly washed.

A similar process consists to wet the plate under the tap, then to flow
over a mixture by about equal volumes of

A.   Ferrous sulphate     5 parts
     Acetic acid, No. 8   5 parts
     Water                100 parts, filter
B.   Gallic acid          5 parts
     Water                100 parts

When toned, the plate is well washed, then flowed once with the alum
solution and again washed.  The tone by this process easily turns to an
inky blue not very agreeable.  The action should be stopped a little
before the desired color is obtained.

It sometimes happens that the image in drying intensifies more then
necessary.  It can be cleared with a solution of oxalic or citric acid.

A brown sepia is obtained by toning first with potassium permanganate, 1
per cent. of water, then, after washing, with a solution of pyrogallol.
If gallic acid be used instead of pyrogallol, the tone is black.  By this
process a great intensity is obtained.  A dilute solution of ammonium
sulphide can be employed as a clearing agent.

Pyrogallol and silver nitrate give a warm black tone.

Potassium bichromate followed by silver nitrate form a brick-red
precipitate of some opacity.(34)

Chloride of nickel and potassium ferrocyanate produce a fine brown.

Lime water and alizarine dissolved in alcohol dye violet.

Alizarine and the caustic alkalies produce a variety of tints, from violet
to purple, according to the concentration of the solutions.

Lead acetate and alizarine in ammoniacal solution dye purple.

Potassium ferrocyanide and uranium nitrate produce a warm sepia tone. With
chloride of nickel the tone is brown.

Ammoniacal solution of coralline diluted with water gives carmine red.

Potassium bichromate and extract of indigo produce a fine greenish tone
suitable for landscapes.

Extract of indigo colors blue(35)

Some of these reactions can be applied to the printing processes with the
bichromates, etc.  The paper should be coated with galatine.  See the
Appendix.

Other colorations can be obtained with dyes in utilizing (as shown by
Persoz) chromous chromic oxide as a mordant: alizarine, Brazil and yellow
wood (morus tinctoria), Fustet (rhus cotinus), etc.  The extent of this
work does not admit of describing the numerous processes which can be
employed; they will suggest themselves to the chemist.

The alkalies employed with the dyes should be employed in diluted
solutions, as being liable to produce reticulation.  By applying the
coloring matters and the mordants thickened with a little starch, the
image can be colored with different colors.  Lantern slides can be thus
colored with great ease.



PREPARATION OF RED, YELLOW, OR BLUE TISSUES.


_Red Tissue.—_Dissolve 10 grams of carmine in 1 liter of aqueous ammonia
and evaporate.  When the smell of the alkali has almost disappeared, add 1
liter of rain water.  Of this take 65 cubic centimeters, add 35 c.c.m. of
rain water, and in the solution let soak for an hour 15 grams of very
soluble gelatine, add 1 gram of sugar, and dissolve in a water bath.
Filter, and take of the mixture a sufficient quantity (25 c.c.m. for a
surface 18×24 centimeters) to cover a sheet of paper which has been
previously applied upon a glass plate in the following manner: In a tray
full of hot water, immerse the plate and the paper; remove the whole in
such a manner as the paper remains in contact with the plate; rub out the
excess of water with a squeegee, and flow the gelatine over the paper
still damp.  Let cool on a leveled stand, and when the gelatine is
solidified to a consistent jelly, remove the paper from the plate and
place it to dry in an oven heated at not over 24 or 25 deg. C.

It is desirable that in drying the paper does not curl up.  To that end,
apply over it, before it being removed from the plate a wooden frame to
which the gelatine, still sticky, will sufficiently adhere to hold the
tissue when it stretches in drying.

_Yellow Tissue.—_Pulverize to an impalpable powder 25 grams of light
chrome yellow in tablets (water color), and gradually add in stirring 1
liter of rain water.  Take 100 c.c.m. of this and into it let soak for an
hour 15 grams of the same gelatine used for the red tissue, add 1 gram of
sugar, then proceed as above.

_Blue Tissue.—_In a liquid consisting of 85 c.c.m. of rain water and from
12 to 15 c.c.m. of blue ink, such as sold by stationers, let soak for an
hour 15 grams of the same gelatine and 1 gram of sugar, and proceed.

_Preparation of Transfer Paper.—_Two kinds of transfer paper are
employed—the enamel and plain transfer paper.

To enamel the paper: Dissolve 100 parts of barium nitrate in 500 parts of
water, and, on the other hand, 200 parts of sodium sulphate in the same
quantity of water.  Mix, wash well the precipitate—barium sulphate—by
decantation, and when well drained, mix to the following solution:

Gelatine, Coignet’s   300  parts
Glycerine             80  parts
Ultramarine blue      1  part
Crimson lake          0.1 part
Water                 2,500  parts

Let soak the gelatine for, say, one hour, dissolve by heat, then add by
small quantities, stirring violently, 4 parts of chrome alum dissolved in
250 parts of hot water.  Filter through flannel and coat the paper as
directed to prepare the tissue.  The mixture should be employed
immediately after adding the chrome alum.

The plain transfer paper is prepared in the same manner, leaving out the
barium sulphate and the coloring matters.

_Preparation of the Silver Paper.—_Immerse the paper for two minutes in a
solution of—

Sodium chloride (common   2 parts
salt, dry)
Lemon juice               1 part
Water                     100 parts (filter)

When dry and wanted for use, sensitize the salted paper by floating for
one minute on—

Silver nitrate   8  parts
Nitric acid      0.1 part
Water            100  parts

On its removal from the silver bath, sponge the paper between sheets of
blotting paper and hang it up to dry.

ENCAUSTIC FOR SINGLE TRANSFER PROOFS.
White wax           25 parts
Mastic              3 parts
Turpentine          100 parts

Dissolve by heat, first the mastic, then the wax, and keep for use in a
large mouthed vial.

      MATT VARNISH.
Sandarac        6 parts
Mastic          6 parts
Lavender oil.   0.5 parts
Ether           100 parts

When dissolved, add 30 parts of benzine.  The opacity of the film varies
with the quantity of benzine added; by excess the varnish dries
transparent.

         WATER COLORS WHICH RESIST THE ACTION OF LIGHT.
Red.      Indian red.    Light red.
Orange.   Mars yellow.
Blue.     Cobalt blue.   French blue.   Smalt.         New blue.
Brown.    Raw umber.     Burnt
                         sienna.
Green     Terre verte.
Yellow.   Cadmium        Yellow         Roman ochre.
          yellow.        ochre.




APPENDIX.


Although we intended to only describe the printing processes without the
use of silver salts, we thought it would be well to complete this work by
giving the most practical and interesting processes ever published to
obtain permanent photographs; as they may give rise in the hand of
experimenters to useful applications.

From time to time processes are published under “queer” names, which are
based on the well known actions of reagents on the ferric salts reduced by
light.  They are derived from those described in the following pages.

We call specially the attention of the reader to the process of Poitevin,
by which one can experiment with every ferric salts, citrate, lactate,
oxalate, tartrate, benzoate, etc., by simply exciting with the
corresponding acid.  Observe that to obtain good results the paper should
be strongly sized; it is a sine qua non, although not recommended by
Poitevin.



C.J. BURNETT’S PROCESS(1857).


“A capital process for many purposes,” says Mr. Burnett, “is to float or
_steep_ the paper in a mixed solution of bichromate of potash and sulphate
of copper, as for Hunt’s chromotype process.(36) I have mixed gelatine, or
occasionally grape sugar, or both with the solution;(37) but instead of
developing it with nitrate of silver, as in chromotype, wash out the salt
unaltered by light, and develop by floating on a solution of ferrocyanate
of potassium.  The purple red color of the copper salt which now forms the
picture may be modified or changed in many ways,(38) viz., by soaking the
picture, after the ferrocyanate of potassium has been washed out of the
lights, in a solution of sulphate of iron.  Solutions of gallic acid,
tannic acid with alkalies of carbonate, may also be employed to modify or
change the color.  This process has the advantage that one may regulate
the exact tone (black or useful neutral tint) to the greatest nicety by
the time we allow the print to remain in the iron toning bath.”



GODEFROY’S PROCESS (1858).


Float the paper upon the following solution for three minutes and hang it
up to dry:

Uranium nitrate   30 to 60 parts
Silver nitrate    8 parts
Water             100 parts

(39)

The sensitiveness increases in proportion to the quantity of uranium
nitrate.  With the above formula the paper can be exposed in the camera,
or, for printing, under a negative cliché.

In printing an exposure of five seconds in diffused light gives an image
perfectly visible, and a grayish black tone; ten seconds gives a vigorous
image almost of a black color; in from fifteen to twenty seconds the image
is very strong, with the color of an engraving. In sunshine the action is
necessarily much more rapid.

The impression is developed by immersion in

Ferrous sulphate   8 parts
Tartaric acid      4 parts
Sulphuric acid     1 part
Water              100 parts

The image is rapidly developed. It is fixed by washing in water.



DE LA BLANCHERE’S PROCESS (1858).


Uranium nitrate   25 parts
Distilled water   100 parts

Filter the solution and keep it in the dark.

The paper should be sized with a gelatine solution at 5 per 100 of water,
and, when dry, kept in the dark.(40) It is sensitized by floating five
minutes.

The exposure under a negative varies from fifteen to twenty minutes in the
shade, and from one to three minutes, at the most, in sunshine.  As a
rule, it is advisable to somewhat underexpose in order that the
development be regular, progressive, under control.

The image is developed by floating, or immersion in

Silver nitrate       2 parts
Distilled water      100 parts
Nitrate acid, C.P.   a trace

When the image is intense enough it is washed in several changes of water,
then toned in a solution of gold at 1 per 1,000 of water acidified with
traces of hydrochloride acid.(41)

The following bath develops slowly, and gives very rich purple tones
without toning:

Nitrate of silver    3 parts
Nitrate of uranium   1 part
Nitrate of cadmium   1 part
Alcohol              10 parts
Water                100 parts
Nitric acid          traces

_The developing solutions should be as little acid as possible, but not
neutral, for then the proofs would be veiled and grayish._

The image can also be developed in a solution of gold, or in a very weak
solution of mercuric chloride at 1 per 10,000.  The proof must be
extremely well printed and left for from two to five minutes in the
mercuric solution.  If the time of exposure is right, the image will
change but little in the solution, and will take, when treated with silver
nitrate, the most splendid tones.

The proofs should be carefully washed when finished.  If they were
developed with silver, they must be immersed in diluted aqueous ammonia,
which will perfectly clear the whites.  If developed with chloride of
gold, the water should be heated to 60 to 80 deg. C. (140 to 176 deg.
Fahr.)



HOUDOY’S PROCESS (1858.)


The paper is floated upon a lukewarm solution of gelatine at 5:100, and
when dry, on a bath of uranium at 10 or 15 per 100 of water.  After
exposure to the sun the image is developed with a solution of silver
nitrate acidified with acetic acid.  The exposure varies, according to the
nature of the negative, from one to ten minutes; it must be long enough
for the image being developed in from thirty to forty seconds.  It is then
removed from the silver bath and placed in the following:

Ferrous sulphate   3 to 8 parts
Acetic acid        2 parts
Water              100 parts

In this bath the image takes a great vigor and appears entirely on the
surface of the paper.  When the proof has been too long exposed it should
be washed slightly before placing it in the iron bath.  Developed, the
image is, generally, of a sepia tone, which can be turned to black by a
solution of chloride of gold, 1:1,000, washing afterwards as usual.



NIÈPCE DE ST. VICTOR’S PROCESS (1859).


Red Prints.


Float the paper for fifteen or twenty seconds on a 20 per cent. solution
of nitrate of uranium and dry before the fire in the dark room.  This
paper can be prepared many days before use.  Expose in sunshine from eight
to ten minutes, according to the intensity of the light and the quality of
the negative, then wash in moderately warm water (50 to 60 deg. C.) for a
few seconds.  This done, immerse in a solution of red prussiate of potash
at 2 per cent. of water; in a few moments the proof will become of a fine
blood-red color, like “sanguine.”  Wash, etc.


Green Prints.


Make a red print as above described, immerse it for a few minutes in a
solution of nitrate of cobalt and dry it without washing.  Fix then in a
solution of sulphate of iron at 20 per cent. of water and 4 of sulphuric
acid.  Wash and dry before the fire.


Violet Prints.


Prepare the paper in the uranium bath, expose, wash and develop in a
solution of chloride of gold, 1:200, until the proof has assumed a fine
violet color.  Wash in several changes of water.


Blue Prints.


Sensitize the paper with a red prussiate of potash solution at 20 per 100.
Let dry, expose until the proof is slightly blue; immerse it for five or
ten seconds in a saturated solution of bichloride of mercury, wash only
once and immerse in a solution of oxalic acid—saturated when cold—heated
to about 55 deg. C.  Wash in three or four waters and let dry
spontaneously.


Black Prints.


Float the paper on a mixture by equal volumes of a solution of iron
perchloride and another of uranium nitrate, each at 10 per 100 of water.
Expose and develop on a saturated solution of gallic acid.



                    DR. T.L. PHIPSON’S PROCESS (1861).


Take a solution of perchloride of iron and, having precipitated the
peroxide with ammonia, collect the precipitate on a filter and wash it
with boiling water.  Add the precipitate in excess to a warm solution of
oxalic acid.  A beautiful emerald green solution is obtained, which must
be a little concentrated by evaporation and then set aside in a dark room
for use.  The paper is floated for ten (?) minutes upon the green solution
of ferric oxalate, to which has been added a little oxalate of ammonia and
hung up to dry in the dark.

Expose under a negative for from ten to twenty minutes, according to the
weather, and wash well the paper with rain water.  Spring water will not
do on account of the lime it may contain, which will form oxalate of lime
in the paper (insoluble).  When all the non-decomposed oxalate is washed
from the proof, a feeble image of oxalate of protoxide of iron, scarcely
visible, is left on the paper.  To develop it and to obtain the vigor, the
tone and color of silver prints proceed as follows:

Plunge the proof for a little while in a (weak) solution of permanganate
of potassium to which a few drops of ammonia have been added; in the bath
the image becomes brown and distinctly visible.  It is then withdrawn and
immersed in a solution of pyrogallic acid for half an hour, after which it
is washed and dried.

The image thus obtained can hardly be distinguished from silver prints;
the tone is soft, brilliant and permanent.

This process is quite original and interesting.  The theory is as follows:
Under the action of light the ferric oxalate is reduced in the ferrous
salt, insoluble, which, after the print has been cleared from the ferric
oxalate, is oxidized and reduced into ferric oxide by the alkalized
permanganate, the latter then forming colored compounds with reagents.

It has been lately published in England under the name of “kallitype,” a
new process—or old, ad libitum—which consists in developing the image in
ferrous oxalate by a peculiar silver compound whose formula is given
below.  The paper is prepared by brushing with a strong solution of
neutral ferric oxalate dried rapidly—which is a sine qua non when using
deliquescent salts; and after exposure the image is developed, etc.

Silver nitrate         50 grains
Sodium citrate         800 grains
Potassium bichromate   1 to 2 grains
Water                  10 ounces

“Dissolve the silver nitrate in 1 ounce of water, the citrate and
bichromate in the remainder and mix.  The precipitate—silver citrate and
chromate—is then dissolved by adding 1 dram of ammonia .880, and after 35
drops of strong nitric acid has been added the solution is ready for use.”

This process reminds us that of Robert Hunt (1842), and that of more
recent date (1863), of Borlinetto, who developed the image in black with a
silver nitrate alcoholic solution, 1:500, and after washing the picture in
a solution of citric acid, 1:10, fixed it by aqueous ammonia.  But,
although that is not absolutely necessary, we would advise one working
this, or similar processes in which a silver salt is employed for
developing, to fix the image, after treatment with citric acid to clear
the proofs from iron salts, in a solution of ammonium sulphocyanate—which
has not the injurious effect of sodium thiosulphate (hyposulphite)—in
order to prevent the paper to be tinged by the reduction of the silver
nitrate which is mechanically retained in its fiber.

The solution of ammonium sulphocyanate should be compounded with auric
chloride to tone the picture at the same time it is fixed; thus:

Ammonium sulphocyanate   35   parts
Gold terchloride         0.15 part
Water                    350   parts

The solution can be used over again.

In the processes devised by Dr. Phipson, Monckhoven and other authorities,
the double ammonio-ferric oxalate is rightly recommended instead of the
simple oxalate.  Not only is the preparation more sensitive to the
luminous action, but better half tones are obtained. As usual, it is
advantageous to size the paper with starch.

The ammonio-ferric oxalate is prepared by precipitating ferric chloride or
sulphate by aqueous ammonia, then washing the precipitate collected on a
filter until the washing water be neutral or does not evolve the smell of
ammonia.  The precipitate is then placed in an evaporating dish, and by
small quantity is added a hot solution of ammonium oxalate until it is
nearly (not entirely) dissolved, when the solution is set aside for a few
hours, then filtered and evaporated to crystallization.  For use, the
crystals of ammonio-ferric oxalate are dissolved in the proportion of 1
for 5 of distilled water.  The solution as well as the crystals should be
kept in the dark.

If one object to the trouble of crystallizing, the solution can be
prepared by dissolving the ferric oxide in a hot solution of 30 parts of
ammonium oxalate and 25 parts of oxalic acid in 180 parts of water
observing that the oxide must be in excess.(42)

The following sensitizing solution gives also excellent results:

Ammonio-ferric oxalate   10 parts
Ammonio-ferric lactate   4 parts
Water                    100 parts

After exposure, which varies from five to ten minutes, according to the
intensity of the light and the printing quality of the negatives, the
picture appears negative from formation of ferrous oxalate.  It may be
developed in a great many ways: by a solution of silver nitrate at 2 or 3
per cent. of water acidified slightly by an organic acid—citric acid, for
example—or a diluted solution of ammonio-nitrate of silver, which most
likely constitutes the best developer; the image is black and consists of
metallic silver and ferric oxide, with formation of silver oxalate, which
dissolve in the ammonia.  If the print be treated by a weak solution of
aqueous ammonia, the image turns green, then brown, and if, before the
latter coloration is obtained, gallic acid or pyrogallol be added, the
image becomes bluish-black or brown-black. In the same circumstances
tannin (gallo-tannin) produces a blue-black image; catechu-tannin(43) and
quino-tannin give green, etc. Employed as a developer, potassium
ferricyanate develops an image in prussian blue, and auric chloride one in
the characteristic violet metallic gold.  To fix the images obtained by
the latter reactions, it suffices to wash them in a few changes of water,
and, if developed with silver, they can be toned by any of the alkaline
solutions of auric chloride used in the printing out silver process, etc.

The photographs obtained by all these processes are permanent.



DR. J.B. OBERNETTER’S PROCESS (1863).


Copper chloride             100 parts
Ferric chloride, sol. sp.   13 parts
gr. 1.5
Hydrochloric acid, conc.    12 parts
C. P.
Water                       1,000 parts

Float the paper on this solution for about two minutes and hang it up to
dry.  The keeping quality of the prepared paper is remarkable; it has been
kept for two years without apparent change; its sensitiveness is at least
one-third greater than that of silver albumen paper.  Unless developed
within an hour or two, the vigor of the proof is much impaired; after
twenty-four hours a print can be taken over on the same.

When exposed, only a faint image is visible.  It should be fixed in the
following solution:

Potassium sulphocyanate   12 parts
Sulphuric acid, conc.     1 part
Sensitizing solution      10 to 12 parts
Water                     1,000 parts

A print is floated on this solution, face downward, for three or four
minutes, taking care to agitate the liquid as little as possible; the
print is afterwards immersed and another one floated in its place, thus
proceeding until all the prints are immersed or the solution can hold no
more.  A fresh solution is then added to strengthen it: the older the
solution the more rapidly and better it works.  In this developer copper
cyanide is precipitated on the parts acted on by light, and this exactly
in the proportion to the luminous action.  The time of immersion depends
on the method selected to finish the proofs; it its from five minutes to
half an hour.  If the proof is immersed for, say, twenty-four hours, the
image comes out in a relief which may bring the shadows to two lines in
depth.  When well developed and thoroughly washed, the proof can be dried
and the subsequent operations made at any convenient time.

Various processes may be employed to give to these proofs the tone
required; thus: the prints well washed are placed in a solution of
ferricyanate of potassium at 6 to 12 per 100 of water, where they take a
red color increasing in intensity.  If left over night the color becomes a
splendid velvet deep red with perfect clear whites.  To obtain the color
of silver photographs one hour’s immersion is sufficient.  After this
operation the proofs are washed until the water is no more tinged yellow.

By immersion in
Ferrous sulphate      100 parts
Iron sesquichloride   40 parts
Hydrochloric acid     80 parts
Water                 200 to 300 parts

the proofs undergo the following gradation of colors: red, reddish violet,
blue-violet, black and greenish black.  As soon as the desired color is
obtained, the proofs are washed in acidified water and dried.

The most beautiful purple violet is obtained by leaving the proofs in the
iron solution until green-black, and then washing for a moment in a dilute
solution of sub-acetate of lead.

A brown-black may be produced by treatment, after washing, with an
ammoniacal solution of hypermanganate of potash.

A weak solution of nitrate of silver also yields very fine pictures, but
the exposure should be very short, and the proofs must be fixed in water
containing a small quantity of oxalate of ammonia.

In order to impart to the proofs the gloss of silver photographs, they
should be albumenized in the ordinary manner, and the albumen
insolubilized by well known means.

The chemical actions in this process I explain in the following manner: On
the paper there are Fe2Cl3 and CuCl, the latter in excess.  By the action
of light, and according to the transparency of the negative, Fe2Cl3 is
reduced to FeCl, while CuCl suffers no alteration.

If the paper be immediately placed in an _absolutely_ dry room after
exposure, the picture remains unchanged.  In a moist atmosphere FeCl
attracts moisture and, with a part of CuCl, is so decomposed that Fe2Cl3
is formed together with Cu2Cl.

After this action has commenced, if the proof be not immediately immersed
in a solution of sulphocyanate of potassium, Cu2Cl passes over to a higher
combination of chlorine, and the paper is again fit to be impressed anew
by the action of light.

As long as FeCl or even Cu2Cl is present, if the print is immersed in the
sulphocyanate solution, sulphocyanate of copper is immediately formed on
the reduced parts, while on the others the sulphocyanide of copper, formed
and dissolved by the sulphocyanide of potassium in excess, becomes decom‐
posed with water in soluble sulphocyanide of copper and deposited as such
on the parts already covered with the salt.

Frequently the prints appear yellow from formation of the double
sulphocyanide of copper, but the color disappears by washing in water.
Red coloration is due to decomposition into ferrocyanide of copper.



L. LIESEGANG’S PROCESS (1865).


Pour ammonia into a nitrate of uranium solution, wash the precipitate of
uranate of ammonia in distilled water, then dissolve in citric acid.

Mix this solution of citrate of uranium and a little of a solution of
chloride of gold with a paste prepared by dissolving tapioca in hot water.
The quantity of chloride of gold must be small and the heat not too great,
otherwise the gold would be reduced.

Spread the mixture with a sponge on the paper, which takes a brilliant
yellow color, and expose when quite dry; the proofs have the delicacy and
vigor of albumen prints.

The proofs come from the frame with a bluish-black color; they should not
be toned, but merely fixed by washing until the yellow color of the paper
has disappeared.

The color of the picture can be changed to a purple by a solution of
chloride of tin.



GUARBASSI’S PROCESS (1867).


The paper is floated in the dark for four or five minutes on a saturated
solution of bichromate of potash.  When dry, it is printed a little longer
than for silver prints and afterwards floated, face upwards, on a water
bath until all the unaltered bichromate is dissolved.  It is then immersed
in the following solution, which improve by use and tones the pictures to
a reddish color:

Saturated solution       4 parts
nitrate of mercury, as
free from acid as
possible
Saturated solution       1 part
bichromate of potash
Distilled water          28 parts

This solution should be prepared, filtered and allowed to stand for some
time before use.  The print is left in the bath until it has assumed an
intense red color, the whites remaining perfectly pure.  It is then washed
and put in another bath to obtain a brownish tint.  This bath is thus
composed:

Conc. aqueous ammonia   2 parts
Distilled water         100 parts

The print must be immersed at once, and when, in a short time, it has
assumed the proper color, it should be washed immediately.

The picture is toned in a very diluted solution of chloride of gold,
1:7,000, in which the color passes from a light brown to a deep black or a
violet black tone, when it is washed in two changes of water.



A. POITEVIN’S PROCESS (1870).


“I use a paper prepared with iron sesquioxide rendered sensitive to light
by tartaric or, better, citric acid in concentrated solution.  This paper,
after desiccation and exposure to light, possesses the property of
reducing the solution of silver nitrate and that of chloride of gold, and
of turning blue with a solution of potassium ferncyanate in the parts
where light has reduced the iron sesquichloride into the oxide at the
minimum.”

“To coat the paper with an equal layer of iron sesqnioxide, I brush it
with a tuft of fine linen dipped in a solution of iron perchloride at 10
or 12 per cent. of water, and dry the sheets in the dark.  I immerse
afterwards these sheets, one after the other, in a tray containing aqueous
ammonia, in such a manner as to well wet each sheet successively.  A
sufficient number of sheets being immersed, I pour off the ammonia in a
vial, and, in the tray, I wash them several times, and remove them one by
one to hang them up to dry, even in full light, the iron sesquioxide not
being sensitive to light.”

“The paper can be prepared in quantities beforehand.  To use it I apply
upon each sheet a solution of citric acid at 30 or 35 per cent. of
water(44)—which may be done by daylight—and let them dry in the dark.”

“Exposed under a negative of the ordinary intensity, the paper is
impressed in sunshine in a few minutes; in the shade it requires about the
same time as chloride of silver paper.”

“After exposure the image is not visible, and without being obliged to
shelter it from light, I immerse the print in a solution containing about
1 per cent. of silver nitrate.  This solution can be used over and over
again, by adding to it a little of the silver salt.  It does not become
turpid by use; it simply turns slightly green from formation of iron
nitrate.  The image appears soon and rapidly becomes vigorous; in half an
hour it will be completely developed.  When the exposure is sufficient the
color is deep sepia, but not so intense if the quantity of citric acid is
feeble.  No fixing is necessary; it suffices to wash in several changes of
waters.”

“The image can be toned with great facility by a weak solution of gold or
of platinum chloride, or, better, by a mixture of these two salts.  If the
impressed paper be treated by a very diluted solution of potassium
ferrocyanate, one obtains very pretty blue proofs.”

“A weak solution of gold chloride develops a violet image. A solution of
platinum chloride has no effect.”

“All the various phases of this printing method can be followed in full
(diffused) light; there is only the desiccation of the paper when
sensitized with citric acid, which requires to be done in the dark.”