THE WET COLLODION PROCESS.
THE COLLODION.
Alcohol 30 ounces.
Ether 40 ounces.
Schering’s Celloidin* 1-1/2 cakes.
* Hance’s D. C. gun-cotton may be used instead of the
celloidin.
Cut the celloidin into thin strips, or, if it be hard, break it up in a
clean mortar, and dissolve in the above mixture of alcohol and ether.
When dissolved, this forms the collodion.
THE IODIZER
is composed of:
Bromide of Zinc 150 grains.
Iodide of Zinc 350 grains.
Alcohol 10 ounces.
When the salts are dissolved, filter and add to the collodion.
The filtering is best done by placing a pledget of cotton-wool in the
neck of a glass funnel and passing the iodizer through it. To prevent
evaporation, lay a glass plate over the funnel.
The iodizer being added to the collodion, shake them up thoroughly
and allow to stand for a week to settle, then decant into convenient
bottles; this collodion is ready for use in a week, but will improve
with age up to six months, after which time it should be mixed with new.
When coating plates with collodion, it is not a wise plan to pour the
surplus from the plate back into the bottle from which it was poured.
Pour it into another, kept handy for the purpose, the contents of
which, at the end of the day’s work, empty into the stock bottle after
such a quantity as is sufficient for next day’s consumption has been
decanted into the pourer.
The best bottle from which to pour the collodion upon the plate is the
tall capped bottle sold by the dealers as collodion pourers. |12|
THE NITRATE OF SILVER BATH (1).
The silver bath is a most important factor in the production of good
negatives. It must be compounded with care and used with skill.
To make it, dissolve 6 ounces of nitrate of silver in 10 ounces of
water, then add 10 drops of collodion, and shake up well; then add 70
ounces of water, and let it stand all night; then filter through a
pledget of cotton-wool packed loosely in the neck of a glass funnel,
into a clean bottle or jug; then add 1 drachm of nitric acid and let
stand all night before trying. Such bottle or jug, and also the glass
funnel, must be kept solely for use with the silver bath.
The bath holder may be an upright vessel of the ordinary pattern,
with a dipper with which to lower the plate into the solution; or it
may be a flat dish with a cover to keep out light and dust, using a
silver hook to lift the plate from the solution; if the former shape be
chosen, let the dipper be of glass, porcelain, silver wire, or of wood
soaked in melted paraffine, but on no account of ebonite, as such a
dipper will cause spots, and derange the bath sooner or later.
If a flat dish be used, the best form is of wood lined with asphaltum,
hanging on a cradle, the lower end being a well to hold the solution;
in this form of bath the plate, after sensitizing, is drained
thoroughly before taking it out. This is a great convenience, as not
only is silver solution saved, but the dark slide will last much longer.
The bath solution made up as above will be the right strength for
work, but as every plate sensitized therein, takes away its modicum
of silver, after a certain time it must be strengthened, as it is
essential for the production of good work that the solution be kept at
a proper strength. The best way of doing this is to add a drachm or two
of saturated solution of nitrate of silver, after each day’s work has
been done, and if the solution be worked in a flat bath, it will be as
well to pour it into a jug and filter it before using again; with an
upright holder, this filtering will only require to be done about once
or twice a week, as any particles of dust, etc., subside and have not
the same chance of falling upon the film as in a flat bath; but the
addition of the silver solution should be made, and the solution well
stirred up with the dipper.
In course of time a silver bath will become contaminated with organic
matter from various causes, and can also be supersaturated with ether
and alcohol—with iodo-bromo or nitrate of zinc, and will either refuse
to work, or only |13| yield imperfect films and thin images. In such
cases the best plan will be to take 20 ounces of the solution, dilute
it with clean water 60 ounces, filter, and add 6 ounces of nitrate of
silver, and again filter, when a new bath will be the result.
The silver in the rejected portion of the old bath should be
precipitated as a chloride, by the addition of a solution of common
salt, the precipitate dried and sent to a refiner, together with the
ashes of the filtering papers and blotting-paper used to drain the
plates upon, or to wipe the backs of the plates after leaving the bath
and before putting them into the dark slide.
The silver solution named above, is suitable for negatives of subjects
in line, but for the production of negatives with delicate half
tones, such as portraits, landscapes, or of the many subjects which
are photographed direct, then it will be necessary to provide another
bath solution, made and managed in the same way, but only containing
sufficient nitric acid to just redden litmus paper, as a bath gives the
finest half-tones when nearly neutral, or only slightly acid. It should
be remembered that the deepest shadows are represented by clear glass
in the negative, to insure which would be impossible with the silver
solution inclining ever so slightly toward alkalinity.
The nitrate of silver bath may be made up with distilled water, if
pure—that is, if the water is bona fide distilled and not merely from
waste steam; if this cannot be guaranteed, the best plan will be to get
a gallon of tap water, dissolve in it one ounce of nitrate of silver,
then add saturated solution of bicarbonate of soda, until an alkaline
reaction to litmus paper takes place, then place the lot in white glass
bottles, and expose to the action of light for three or four days.
During that time the solution will, first of all, turn black, and
then will gradually become quite clear, the organic matter—which if
not removed, would have caused trouble—falling in a black mass to the
bottom.
Now filter the purified water and use it for compounding the nitrate of
silver bath, but do not use it for any other purpose.
The strength of a nitrate of silver bath, for line work, should be
thirty grains of nitrate of silver to each ounce of water, and should
not be allowed to fall below twenty-five; and for half-tone negatives,
nitrate of silver should be thirty-five, and not lower than thirty
grains to the ounce.
Be sure to keep all funnels, bottles, and dishes used for the silver
bath, separate and distinct from all others, and never use them for any
other purpose. |14|
THE NITRATE OF SILVER BATH (2).
In the ancient days of photography, when, to say it was possible to
prepare a dry plate nearly as sensitive as a wet collodion plate, was
to excite the risible faculties of the audience, the above heading
might almost always be seen in the journals, and the amount of matter
written under that heading would fill many good-sized volumes. Some
writers went into the subject in a very elaborate manner, whilst others
would counsel very simple methods of preparation and management.
The directions given above for making a bath solution for line
negatives, will, if carried out carefully and cleanly, at once yield a
solution giving good negatives. After the bath has been mixed, either
with distilled water, ordinary tap water (_in iron districts tap water
should not be used_), or water that has been sunned and filtered, as
soon as the bulk has been made up to the eighty ounces, the solution
should be put away all night before it is tried, then in the morning
filter it carefully through a pledget of cotton-wool stuffed loosely in
the neck of a perfectly clean funnel, into a perfectly clean bottle or
jug, which must be kept entirely for use of the silver solution. When
the bath solution has been filtered it should be _perfectly clear_; if
it is at all cloudy or turbid, the filtration must be repeated.
When the solution is perfectly clear and bright, pour sufficient into
a perfectly clean porcelain, glass, or papier-maché dish, then take
a clean plate (polished, or albumenized) and coat it with collodion;
close the door of the dark-room, and when the film of collodion
is perfectly set, raise one end of the dish containing the silver
solution, place one edge of the collodionized plate against the bottom
of the upper edge of the dish, then drop the plate upon the bottom
of the dish, and at the same time lower the dish; by this means the
silver solution will flow in an even wave over the surface of the
collodionized plate; now place the cover on the dish so as to exclude
light and dust, and allow the plate to remain in the solution for five
minutes, then with a silver hook lift the plate from the solution, and
allow it to drain (remember that no light must get into the dark-room
except what is filtered through either two thicknesses of golden
fabric, or one of canary medium); when the plate has drained so that no
solution drips from it, place it into the carrier of the dark slide;
then close the dark slide and let it remain there for five minutes,
at the end of which time remove the plate to the sink, and flood it
with sufficient developer (page 17) to just cover the film; keep this
solution flowing, to and fro, over the |15| plate for the space of
two minutes, then wash it under the tap until the surface is no longer
greasy; then apply the fixing or clearing solution (page 17) until the
whole of the yellow bromo-iodide is dissolved away; again wash, and
take the plate into the daylight.
Now comes the test; if the film is perfectly transparent, and clear as
the glass itself, the bath is all right; but if there is the slightest
deposit (which can be removed by lightly rubbing the finger along the
surface of the film), then the solution will require the addition of
a little nitric acid. After this stir it well, and after a rest of an
hour or two try again, repeat the addition of the nitric acid, and try
a plate; repeat until the film, after developing, washing, and fixing,
is perfectly clear, and free from deposit and fog.
The bath is now in proper working order, and if reinforced after
each day’s work with a sufficient quantity of saturated solution of
nitrate of silver (filtered), kept free from contamination with other
chemicals, and carefully filtered occasionally, it will remain in good
working order for at least six months, and then may be renewed by
treating as directed on page 12.
It will sometimes happen, notwithstanding that extreme care and
cleanliness is exercised in the management of the bath, that it will
not work properly, and the reason why cannot easily be discovered. In
such a case, steps must be taken to put the solution into working order.
In the case of rectifying a disordered bath, there are many methods of
procedure, but the simplest, and, as a rule, the most certain method,
is to render the solution alkaline by the addition of liquor ammonia,
adding the ammonia a little at a time; then, after well shaking, test
it with red litmus paper and continue the addition of ammonia until
the red litmus paper is turned blue. In this alkaline condition the
solution should be poured into a large flat dish, and exposed to the
action of the sun. That will speedily reduce and throw down in the form
of a black precipitate, any organic matter that may be in the bath,
and at the same time the heat of the sun will cause evaporation of the
ether and alcohol left in the solution by the collodion plates.
The bath solution should be exposed to the sun for two or three days,
or until such time as suffices to render the solution clear, and the
precipitate entirely separated out. But this cannot take place unless
the solution is decidedly alkaline, the presence of acid stopping the
action of light.
Do not be in a hurry about doctoring a bath solution (in fact, it
will be far best to have two solutions, one in use and one either
resting or being doctored), but give the light plenty of time to
reduce the organic matter, and also to |16| volatilize the ether and
alcohol; then filter the solution through filtering paper (don’t use
blotting-paper), as if it is attempted to filter through a pledget of
cotton-wool the fine precipitate of organic matter quickly clogs the
wool and stops the filtering.
The doctored solution being filtered, test it with a piece of perfectly
fresh, blue litmus paper, and add nitric acid, drop by drop—shaking
well between the additions of acid—until the blue litmus paper just
turns red. Do not add acid sufficient to make the litmus turn violently
red, unless the bath is for line negatives, as a bath for half-tone
negatives must be only just acid, whereas a bath for line work must
contain more acid.
If the color of the litmus paper shows that the alkali has been
neutralized, a plate is collodionized, then immersed in the bath for
five minutes, then drained, and placed in the dark slide, or in a dark
box for five minutes, then flooded with the iron developer (page 17);
if, upon the application of this the film should turn black, add more
nitric acid, stir up thoroughly, then try again, repeating the trials
until, upon fixing the plate with the solution of cyanide of potassium,
the film of collodion is left upon the glass plate as clear as it was
before it was immersed in the silver bath.
A little above here it is stated that less nitric acid is required in
the bath for half-tone negatives than for line work, and the question
may well be asked where may the line be drawn? The reply is that, for
half-tone work, a piece of blue litmus paper should, upon immersion
into the solution, turn red very slowly, but when the bath is required
for line negatives the blue litmus may at once indicate the presence of
acid.
After a bath solution has been renovated in the above manner, it
should be tested for strength, either by the volumetric method (by
preference), or by means of the ordinary argentometer sold by the
dealers, and, if, after testing, the strength is shown to be too
great, dilute with a sufficiency of sunned water (page 13); and if not
sufficiently strong, add crystals of nitrate of silver to make up the
strength to thirty or thirty-five grains per ounce.
A bath solution renovated as above, will generally be found to work
cleaner, and yield brighter negatives than a new solution, and it
will also, if carefully used, last longer; but it must be kept up to
a proper working strength by the occasional addition of a little of a
saturated solution of nitrate of silver.
The fact that the strength of the silver solution has got too low is
shown by the presence of semi-opaque, fantastic markings near the thick
edge of the collodion film, and also in conjunction with the presence
of organic matter in |17| the deposition under the surface of the film
of an extremely fine sand-like deposit, which, in the fixed negative,
develops into myriads of pinholes in the densest portions of the image.
THE DEVELOPING SOLUTION.
First purchase seven pounds of commercial sulphate of iron (copperas)
and put this into a gallon jug, and fill it up with boiling water
(clean); stir with a clean rod at short intervals for three or four
hours, then allow to stand until the sediment settles, and the top
portion of the solution is clear and bright; then decant as much as
possible into a bottle or bottles, and label “Saturated Solution of
Iron.” Then again fill up the jar with boiling water, stir until as
much as possible is dissolved, so as to be ready by the time the stock
in the bottle is exhausted, and repeat the process until all the
crystals are dissolved; then wash out the jar, reject the residue, and
begin again.
But bear in mind that, unless there are crystals left in the solution
after each addition of hot water, it will not be saturated; therefore,
before taking the solution into use, be sure there are undissolved
crystals in the jar.
For use, take of
Saturated Solution of Iron 10 ounces.
Acetic Acid 4 ounces.
Water 70 ounces.
Alcohol 1 ounce to 5 as required.
In the above solution, the alcohol is added to enable the developer to
readily assimilate with the sensitive film, and the quantity requisite
varies with the age of the silver bath, or, to be more correct, with
the quantity of plates sensitized therein. At first, little or no
alcohol will be required, but after a number of plates have been
sensitized the developer refuses to flow evenly, and seems disposed to
run over the edges of the plate; this is a sign that more alcohol is
required, and when more has been added the developer will flow evenly
as before; but when 80 ounces of developer require over 4 ounces of
alcohol to make it flow, it is a pretty sure sign that the bath wants
remaking.
The developer is applied to the plate after exposure, from a
straight-lipped cup, or glass measure, which should be kept for the
exclusive use of this solution, as the mixture of any of the other
solutions with it will at once counteract its working power. |18|
THE FIXING OR CLEARING SOLUTION.
Cyanide of Potassium 3 ounces.
Water 20 ounces.
This solution is highly poisonous, both in solution and vapor, so it
ought to be kept in an upright holder, the plate being lowered into
the solution on a dipper; keep the solution well covered up, so as to
prevent evaporation as much as possible.
After being in use a short time this solution will become weak and
should be strengthened by the addition in the evening of a lump or two
of cyanide and then stirred up with the dipper in the morning; the
negative must not be left in this solution too long or the density of
the film will be impaired, but must be removed and well washed directly
all the yellow iodide has been dissolved.
THE INTENSIFIER.
No. 1.
Water 80 ounces.
Chloride of Ammonium 2 ounces.
dissolve, then add:
Bichloride of Mercury 2 ounces.
dissolve, and filter.
No. 2.
Liquor Ammonia 0.880 5 ounces.
Water 20 ounces.
Solution No. 1 is best kept in an upright holder, as if kept in a flat
dish there is always the danger of cutting the skin with the glass
plate and getting the mercurial poison into the system.
No. 2 is kept in a well-stoppered bottle and only sufficient for each
plate withdrawn as required.
Another method of intensifying, for those who object to the use of
mercury, is to bleach the negative in a solution of
Ferridcyanide of Potassium (_Red Prussiate of Potash_) 6 parts.
Nitrate of Lead 4 parts.
Water 80 parts.
dissolve and filter. |19|
When the plate is bleached, wash it thoroughly under the tap, taking
care that the edges and corners of the film as well as the centre are
washed, then flood it with a sufficient quantity of
Nitric Acid 1 ounce.
Water 80 ounces.
Allow this to remain on a few seconds, then wash, and flood with a
sufficient quantity of
Sulphide of Ammonium 1 part.
Water 5 parts.
which will at once turn the film an intense black; again wash, and
flood with the nitric acid solution, and again wash; then the negative
is allowed to dry.
This method of intensifying is cheaper than the other, and if the
washes of acid between and after the other two solutions are carefully
done, and the stench of the sulphide is not objected to, then there
is little or no difference in the results; but if the acid washes
are omitted or (and) the sulphide has not been kept corked, and is
consequently not fresh, then there is great danger of a brown stain
upon the lines, which is more or less fatal to getting a good print on
zinc.
For half-tone negatives, instead of fixing or clearing with the cyanide
of potassium, the developer is washed off directly, and then they are
intensified at once by the application of a mixture of pyrogallic acid,
citric acid, and nitrate of silver, as follows:
No. 1 Solution of Pyrogallic Acid 40 grains.
Citric Acid 30 grains.
Water 20 ounces.
As much of this solution as will cover the washed plate is put into a
small cup, and flowed all over the film, then returned to the cup, and
a few drops of
Nitrate of Silver 30 grains.
Water 1 ounce.
is added. Then the mixture is poured over the film, and rocked to and
fro for a short time; the intensifier is then returned to the cup, the
negative held up to the light, and examined, and if not intense enough,
the intensifier is again applied. Great care is requisite at this
stage, as if the process be carried on too |20| far the negative will
be too intense, and will either be spoiled, or take an abnormal time
to print; practice and observation are the only guides to success. The
grand rules for half-tone negatives are, collodion free from dust, the
glass plate clean, the bath at its full strength and in good working
order, proper time allowed the plate in the sensitizing bath, well
drained, afterward a good exposure, develop until all details are out,
then wash thoroughly, intensify with judgment, wash well, fix, and
again well wash, and then, but never till then, open the dark-room door
and examine your new negative by daylight.
In making the collodion, soak the celloidin in the ether for about
twelve hours before adding the alcohol; be sure the ether is at least
0.725 specific gravity, and that the alcohol is very clean, and free
from gum. After mixing the collodion and iodizer, shake up well, but do
not do this before decanting. Always decant sufficient for next day’s
use, into the bottle used for pouring, over night, so that it gets a
chance to settle, and allows the air-bubbles to escape.
Keep the collodion in as cool a place as possible, and in decanting it
be very careful to do it away from fire, or lighted gas or paraffine,
especially where flame is below the bottle, as ether vapor does not
rise, but falls.
In hot weather and during long exposures, wet plates are very prone
to have a peculiar stain upon them, called oyster-shell markings, the
remedies for which are careful draining before putting them into the
slide, and covering the bottom of the carrier with clean filtering
paper, so that the silver solution, on draining down, is absorbed by
the bibulous paper instead of going back up the plate by capillary
attraction.
In hot weather the back of the plate, when put into the dark slide,
should be covered with a wet piece of red blotting paper, or orange
calico, _but not white_; a wet cloth laid in the camera will also tend
to keep the plate moist. These precautions, however, are not required
unless the exposure is likely to exceed a quarter of an hour.
PROTECTING THE COLLODION FILM.
A collodion film, when dry, is very delicate, and, except for line work
in the hands of an expert, will require protecting. This is usually
done by slightly warming it (when quite dry) in front of a fire, and
then pouring over a sufficient quantity of thin spirit varnish. After
the superfluous varnish is well drained off, dry by again holding it
in front of the fire. The spirit |21| varnish answers perfectly for
ordinary work, but for printing upon metal for relief blocks, or upon
glass for collotypes, it will be best to use a benzole varnish, such
as is sold by dealers for protecting the films of glass positives or
ferrotype pictures. Anthony’s “diamond” varnish is good.
But the best plan of all is to use a water varnish, made by dissolving
half an ounce of borax in a quart of boiling water, then adding a few
pieces at a time (stirring meanwhile), one pound of ordinary shellac;
if the quantity of borax named does not suffice to make all the shellac
dissolve, add more, a grain at a time, until the shellac is dissolved;
then add half an ounce of white sugar, cool and filter it.
When the negative is washed for the last time, allow it to drain, then
flood with the above solution, and let it dry. This will be found
a quicker, cleaner, and more satisfactory method of protecting the
delicate film than with the spirit varnish.
THE GLASS PLATE.
_The glass_ used as a support for the collodion film should be thin
flatted crown of the best quality, for the negatives, as a rule, are
not required again after once the zinc is etched, so that the film may
be washed off, and the glass used again, which cannot be done so often
if the glass be of bad quality; flatness is a _sine qua non_, as it has
to be subjected to heavy pressure between a zinc plate and the front
glass of a printing frame.
As a good and suitable negative is the foundation of success in
the subsequent processes, so is a properly cleaned glass plate the
foundation of a successful negative; unless the glass is chemically
clean, the collodion film will either be stained or marked, or it
will split off in drying, therefore care and attention are requisite;
even in preparing a piece of glass for the reception of the film of
collodion care is especially requisite, as the want of it cannot be
seen until after all the operations, therefore the labor and time are
not thrown away.
There are two methods of cleaning the glass plate: one quite
mechanical; the other is a mixture of the mechanical and the chemical.
Both are good. The second is perhaps the best, as it is simple and more
certain.
In the first method the glass, when new, merely requires polishing with
clean wash leather kept for this purpose.
The best way of doing this is on a flat board 24 by 18 inches, or
thereabouts, |22| covered with good American oil-cloth, glazed side
out. A plate laid upon this will not slip about when being polished.
Both sides and edges of the plate must be well cleaned, as one of the
most prolific causes of derangement of the silver bath is from organic
matter introduced by imperfectly cleaned glass plates.
One side of the plate, if gently rubbed with the thumb nail, will be
found smoother than the other, and is the suitable side for the support
of the collodion film; this side is polished with the leather until,
upon breathing gently upon it, the film of moisture is quite free from
marks or streaks, not only in the centre but at the sides and corners.
It is absolutely necessary that the plate be chemically clean all over,
else the film of collodion, upon drying, will split, and the negative
be spoilt.
When the plate is clean, an edging of India-rubber dissolved in
benzole, about an eighth of an inch wide, is run all round the edge,
by means of a small camel’s-hair brush tied to a stick, the end of the
stick being level with the point of the brush. The stick acts as a
guard against the brush going too far from the edge.
In the second method, the new glass plate is soaked an hour or two in a
mixture of 5 ounces of common spirits of salt (hydrochloric acid) in 80
ounces of water. After both sides of the plate are rubbed with a rag,
and well washed under the tap, it is put in a dish of clean water. When
all the plates have been so treated, they are taken out singly, again
well rubbed on both sides with another rag, and well washed; then the
smoothest side having been selected, it is twice flooded with a mixture
of albumen and water, draining the surplus into the sink each time of
flooding. The plate is then placed upon a rack to drain and dry; the
drying should be effected in a current of hot air freed from all dust.
The albumen mixture is composed of the white of one egg well beaten,
then diluted with 40 ounces of water and ten drops of liquor ammonia
added, and again beaten. It must then be very carefully filtered
through cotton-wool, and used as above.
In placing the albumenized plates upon the drying rack, care must
be taken to face the coated sides all one way, as when dry there is
nothing to indicate to the eye which is the back and which the front.
The albumenized plates, when dry, should have the backs cleaned with a
cloth or a leather before using, so as to clear away any albumen which
may have adhered during coating. |23|
Albumenized plates stored in a dry place will keep good for months,
_and do not require any edging with India-rubber_, as the most horny
collodion film will not split off an albumenized plate.
Glass plates that have been used, and not varnished, are freed from the
films by being immersed in a mixture of hydrochloric acid and water for
a few hours, then washed under the tap, well rubbed with a rag, and
put into clean water, from which they are taken singly and coated with
albumen; or they may be allowed to dry, and are then polished by means
of the wash leather.
Negatives that have been varnished are cleaned by first immersing in
a hot solution of common washing soda until the film comes off, then
wash them under the tap, rubbing well with a rag, then immerse them in
the acid solution so as to neutralize the alkali. Finally they may be
treated as above.
The films that are removed from the glass plates must not be thrown
away, but should be carefully collected, dried, and sent to a refiner
with the other silver waste; a good plan for saving these films, and
at the same time keeping the acid and soda solutions clear of them, is
to filter each solution occasionally through an old felt hat suspended
conveniently over the tanks, using one for each of the tanks.
The polishing of the glass plate must not be done in the dark-room,
or the crop of comets, spots, etc., upon the negatives will be
exasperating in the extreme; let this operation be conducted in a
clean, quiet corner of the studio, where no other operation will
disturb, and where the fluff from dusters and leathers will not
interfere with anything else.
|24|