reality, and so great is its educational power that I anticipate
that after the first dozen or so negatives we shall almost dispense
with the actinometer altogether, having by then trained the eye to
tell when a print is finished merely by the appearance of the
half-visible image. Do not let this prospect, however, tempt the
beginner to dispense with this valuable help at first, for to the
inexperienced eye the appearance of the platinotype image is very
deceptive, and having under-exposed the first print, it will not be
safe to judge the extra printing of the next print only by the eye;
the beginner is nearly certain to err, and the eye must not be
trusted until it has had considerable training.
After having had some considerable and varied experience in
platinotype printing, one feels no little regret that an operation
which has become so simple cannot be laid before a beginner in a
more precise and definite manner, and I can only assure my reader
that in a very little while what may now look like a very serious
business, only surmountable by long and serious practice, will
become a sort of intuitive faculty, and just as one feels after a
little practice the precise amount of pressure which one should use
when the fingers are placed on the notes of the piano, so just the
right _visible_ depth of print required to give a developed print of
such and such intensity comes to be a matter of instinct.
It may here be stated that paper which has been affected by damp
gives a slightly less visible image than dry paper. But moisture
alone without oxalate will effect partial development, and if the
time of exposure to light be so greatly prolonged, that despite all
precautions moisture obtains access to the print during exposure,
this may, as it were, start a kind of local development whilst the
paper is still in the frame and printing, so that on looking at the
print to watch its progress some of the deeper shadows may have
sprung quite suddenly into a deep blackish-grey colour. In many
cases this will quite spoil the finished result, whilst in others no
harm seems to be done when the print is ultimately developed.
Remembering that the high-lights and indeed some of the lighter
tints of the print are quite invisible until after development,
care should be taken to look at the paper only in decidedly subdued
light, or better still, artificial light, because the injury which
is being done by even a short exposure to actinic light is not made
manifest until after development, and as most of us know how soon a
piece of silver paper will discolour in even moderately faint
daylight, we should be additionally cautious with platinotype paper
which is from twice to three times as sensitive to light.
[Illustration: Fig. 4.]
SOME POINTS TO BE CONSIDERED WITH REGARD TO DEVELOPMENT.
To avoid confusion it will be well to repeat here that at present we
are only considering the practice of what is known as the cold-bath
paper. This term is applied only in a comparative sense. The older
hot-bath process requires the developing bath to be raised to a
temperature of about 170° F., whereas the best temperature for the
cold process is about 70° F. or even less; nevertheless, the
cold-bath paper _may_ be developed in an oxalate bath of 170° or
even hotter, so also it may be developed on a solution which is
quite cold. The result of altering the temperature is two-fold and
may be stated thus:--_The colder the bath_, the _colder_ the colour,
that is, the _bluer_ the greys and blacks, also development is
slower and takes longer, and the contrasts harder. _The hotter the
bath_ the warmer or browner the colour of the print; the more sudden
the development and the greater the amount of half-tone and
consequent softer contrasts.
With these maxims in mind some amount of control may be exercised
over the prints produced, especially as regards arresting
development at any point desired if a cold developer be used, but in
such case the print must be instantly removed to and plunged into
the acid bath, until which immersion development continues, even
after the print has been removed from the bath.
Development, as a general rule, should be conducted in feeble
daylight or artificial light.
Development need not take place immediately, but at some subsequent
time, provided the prints be meanwhile stored in a calcium tube and
in every way rigorously protected from damp.
The proportions which I have given for the oxalate of potash bath
represent the standard developer as given by the makers of the paper
for the hot-bath papers, and they recommend that this be diluted to
about half strength for cold-bath papers. Personally, I use it at
full strength for the cold process, and see no reason for diluting
it.
It may be said that such a course is calculated to give strong,
vigorous prints, for generally speaking, the stronger the bath, the
stronger the contrasts of the print. The difference, however,
produced by altering the strength of the bath is not very great.
There are two alternatives to the oxalate of potash developer, both
possessing certain, if not very strongly marked characteristics. The
first of these is known as the "D" salts. These are sold in tins by
the Platinotype Company, and consist of a loose admixture of certain
salts, and hence it is essential that the entire contents of a
half-pound tin be dissolved at once and kept thus as a stock
solution.
The proportions to be used are as follows: Dissolve 1/2 lb. of D
salts in 50 ozs. water, and then take equal portions of this
solution and water, in other words, dilute it to half-strength.
The "D" salts are said to give colder colours and more half-tone,
but the colour derived from development on the first-named oxalate
bath may be made colder by adding to 20 parts of developer 1 part of
a saturated solution of oxalic acid, in like manner slightly warmer
colour may be obtained if the oxalate bath be made alkaline by the
addition of carbonate of potash, but only just enough should be
added to turn a red litmus test paper blue.
If prints developed on D salts should appear mealy or granulated,
the bath should be strengthened or used at the full strength of the
stock solution (salts 1/2 lb. to water 50 oz.).
Another developer, the effect of which is to minimize half-tone and
increase the vigour of the contrasts, and so give very brilliant and
even hard blacks and whites, is as follows:
Oxalate of potash 16 ozs.
Phosphate of potash 4 ozs.
Sulphate of potash 1/2 oz.
Water 120 ozs.
This should be made with hot water, and to get the full advantage of
its contrast-giving powers, used quite cold. Development will then
probably take one or two minutes, but can be arrested sooner when
the desired effect is attained.
It may now be as well to enumerate and describe the various kinds of
platinotype paper obtainable, and whilst the general treatment of
them all is the same as described in the foregoing, some special
recommendations may be made in each case.
The papers for the Cold-Bath process are two called respectively AA
and CC. AA is a smooth surface paper and is the kind usually
employed for portraiture and general small work. CC is a heavier,
stronger paper with a surface similar to stout cartridge or drawing
paper. For pictorial work and for landscapes, also for large
portraits or heads this paper is eminently suitable.
Next we have the papers for Hot-Bath process, to be presently
described. These are firstly A and C, both precisely the same in
character as the AA and CC just referred to, but intended to be
developed in a bath at high temperature. These four kinds of paper
all yield a picture of the normal platinotype black colour, the
black tending to cooler or warmer tints according to slight
modifications of treatment, but it is also possible to produce a
platinotype print of a rich sepia brown by using the papers S and
RS--these both in substance and character corresponding with AA or A
and CC or C respectively. Thus we have a thin smooth and a thick
rough paper for each Cold bath, Hot bath, and for Sepia printing.
DEVELOPMENT OF HOT-BATH AND SEPIA PAPERS.
With the Hot-Bath papers perhaps the precautions against damp should
be rather more stringent than for Cold-Bath papers, certainly they
may not be relaxed, and in the sepia papers, S and RS, there seems
to be even greater susceptibility still, but for this, printing and
development are performed precisely as already described, but the
temperature of the oxalate bath should not be less than 150° to
170°, whilst in some cases it may be convenient to raise it still
higher. The oxalate solution should, moreover, always be at full
strength, namely, 1/2 lb. in 25 ozs. of water or thereabouts, a much
more diluted bath will result in granular prints.
As a general rule the colour of A and C prints is a rather browner
black than their cold-bath equivalents--AA and CC--with also rather
softer contrasts.
Development takes place in shorter time than with cold-bath papers,
and is indeed so instantaneous that any control is next to
impossible. On this account, rather more dexterity will be required
in development, that is to say, between the time that one end of the
print touches the developer and the rest of the print is brought
into contact with it, the shortest possible time should elapse.
There must be no hesitation, the whole surface must be brought down
gradually but swiftly, and accompanied by a sliding movement in
order to squeeze out or wipe out any air bubbles which might cling
to the surface of the paper. If this be not done evenly and
continuously, it is more than likely that there will be marks of
unequal development on the surface.
[Illustration: Fig. 5.]
It is no uncommon thing for the tyro to let the print hover over the
bath before giving it its plunge in the hot solution, but in so
doing it should be remembered that he is submitting it to the direct
action of the steam which the bath is giving off, and so exposing it
to damp.
Whilst with prints of 1/2-plate size and under it may be sufficient
to hold the print by one corner and wipe it across the surface of
the solution, pressing it down with the fingers of the other hand,
with larger sizes it will be well to cultivate a little trick in
manipulation, and the accompanying figure may perhaps be suggestive
(Fig. 5), in which it will be seen the left hand is bringing one
end of the print into contact with the bath, whilst the right hand
holds the opposite end above and well back, and the left hand will
next be moved in the direction of the arrow, drawing the print with
it along the surface of the bath, the right hand following but
simultaneously lowering the whole of the print--thus the solution
attacks the print smoothly and continuously, whilst the air is
pressed out in the opposite direction. Instantly the entire print is
floating on the bath it should be moved about a little, as a further
means of disengaging any air bubbles.
As far as possible, prevent the developer from flowing over the back
of the print, but this will be a far less evil than not bringing the
whole printed surface immediately and at one stroke on to the
developer. The print is next passed direct and without intermediate
washing into the hydrochloric acid bath, as already described.
The sepia papers, S and RS, are both hot-bath papers, and no special
instructions need to be given as regards development, except that to
get the full benefit of the sepia tint and secure a fine rich bright
colour, the Special Sepia Solution prepared and supplied by the
Platinotype Company should be employed in the developer.
Of this, one or two drams should be added to each ounce of oxalate
bath, either before heating it in the dish or afterwards and just
before floating the prints. In the latter case stir the whole so as
to get it equally mixed, and wipe the surface to remove any scum.
A good substitute for the bath as above prepared for sepia prints
may be made by adding one part of saturated solution of oxalic acid
to each ten parts of oxalate of potash solution.
The Sepia papers are rather more sensitive to light than the Black
papers, and hence all operations should be conducted in very subdued
daylight, a precaution even extending to the first acid bath.
The bath containing the special solution should be used for sepia
prints only, and when done with kept in a separate bottle for future
use, but the bottle must be kept from the light, and the sediment
which will fall should be left undisturbed at the bottom of the
bottle or filtered out, and the dish used for sepia development
should be well washed before using it for black prints.
Opinions seem to differ as to the wisdom of keeping old developing
baths, but as far as my own experience goes I use the oxalate
solution for black prints again and again, taking no heed of its
discoloured condition.
After developing, the bath is poured into the stock bottle, and so
long as undissolved crystals remain at the bottom of the bottle hot
water may be added from time to time to make up the loss occasioned
by spilling and waste, thus the stock solution is always a
combination of old and freshly-dissolved oxalate, and I have had one
large jar of solution thus in very frequent use for over twelve
months, a greenish-black encrustation gradually accumulating at the
bottom without detriment.
CONCERNING THE HYDROCHLORIC CLEARING OR FIXING BATH.
Little needs to be said as to the Hydrochloric Acid bath into which
the prints are passed immediately after development. The purpose of
the acid bath is to dissolve out the sensitive salts which have been
unaffected by light and which are still light-sensitive, the removal
of these making the paper white and clean. Thus the acid bath is
both fixing and clearing in its action.
Into the first acid bath the prints will carry a good deal of the
oxalate solution in which they have been developed, and it therefore
soon becomes very much discoloured, wherefore after a lapse of about
five minutes the print should be removed to a second acid bath of
the same strength as the first (pure hydrochloric acid 1 part, water
70 parts) and after five or ten minutes into a third.
After the prints (many may be done at the same time) have been in
the third acid for five minutes, the bath should be examined, and if
it is quite colourless, that is if the prints have not discoloured
it at all, we may rest satisfied that clearing and fixation are
complete, but if not, yet another acid bath should be given.
Whilst five or ten minutes in each acid bath is long enough,
probably no harm to the print itself, yet no good, will follow a
longer immersion. There may, however, be a danger of softening or
rotting the paper, a danger which is increased should the bath be
made stronger in acid.
If a number of prints are being made, or if numerous dishes for acid
constitute a difficulty or inconvenience, we may modify procedure as
follows:--
Make up the first acid bath to about half the prescribed strength,
say hydrochloric acid one part to water 120 to 140 parts. Into this
each print may be flung as soon as developed, until the entire batch
is thus far finished. In this weak acid bath the prints will take no
harm if left for several hours, when an acid bath (one to seventy)
of full strength having been prepared, the first weak solution may
be poured off and the fresh poured on. In this the prints should be
separately turned over, so that each receives thorough treatment,
when the second bath may be thrown away and a third substituted. One
dish thus serves for the whole series of acid baths.
If adopting this course, it will be safer not to mix sepia and
ordinary black prints in the same _first_ acid bath, after which,
however, they may be treated altogether.
Sufficient washing to rid the paper of acid is all that is required
to complete operations; but acid does not cling to the print as does
hypo, moreover, we have not an absorbent gelatine surface to deal
with, so that if prints were dealt with individually and washed by
hand, probably a few minutes sluicing under a tap would suffice, but
in a properly constructed print-washer, or even a large dish, twenty
minutes to half-an-hour should be ample. If any doubt is felt, the
last washing water may be tested with blue litmus paper.
MODIFICATIONS IN DEVELOPMENT.
To impart a warmer and richer tone to prints on CC (cold-bath)
paper, the following slight modification may be resorted to, but it
must be regarded merely as an exception for definite purposes, being
in violation of the instructions and rules already laid down. It
consists of developing CC paper as though it were hot-bath paper,
using a bath of about 170° F and submitting it to the influence of
damp to a slight degree. This latter very heterodox course may be
effected by leaving the paper laid out all night in a room where
there has been no fire to dry the air, or by using paper which has
been kept for a week or so in its tube without calcium chloride and
without sealing the lid, or yet again, the print may be held over
the steam of the developer for a few minutes before developing it.
It must be remembered that in doing this we are taking liberties
with the process, and if poor, "muddy" prints result, we can only
blame ourselves, but as a rule this will not be the case, the effect
being rather to impart a slight creamy tone to the whites without
otherwise degrading their brilliance, whilst the use of a hot bath
gives the whole a distinctly brown-black image, which combined with
the cream tint of the high-lights has a very luminous and warm
effect.
Another method of development which must also be taken as an
exceptional one, only to be used in special cases to attain special
ends, is local development with a brush, using glycerine as a
medium.
As may have been seen from the foregoing descriptions, the
development of a platinotype print, even with a cold bath, is so
rapid that there is not a possibility of developing one portion more
than another, or if such could be done, still it would be done with
the certainty of leaving a mark where development had been stopped.
These difficulties, however, may be overcome by the use of
glycerine, the effect of which is to retard development to almost
any degree, and by its soft, viscid character to soften and blend
the line of demarcation where greater or less development ceased.
The method of applying it is as follows: On removing the print from
the frame it should be fastened to a board with pins, print side
upwards. Next pour on to the surface a small pool of _pure_
glycerine, and with the finger tip, a brush or soft pad, spread it
_evenly_ and thinly over the print. It must not be allowed to remain
on the surface in irregular patches of unequal depth, but after
spreading it had better be wiped with a fresh pad of cotton wool, so
as to remove any superfluous glycerine. Now have four small vessels
at hand, and into No. 1 place an ounce or two of the ordinary
oxalate developing solution, in No. 2 put equal parts of oxalate
solution and glycerine, in No. 3 one part oxalate solution and two
parts glycerine, and in No. 4 pure glycerine.
With a broad, soft hair brush apply the contents of No. 3 to the
less printed portions of the image and wait results. These portions
will presently begin to gain in depth and to slowly develop up, now
spread the No. 3 mixture to the rest of the print and apply the
contents of No. 2 to the portions first treated with No. 3. The most
obstinate parts may be touched with No. 1, plain oxalate solution,
whilst any spots which have come up too quickly may be promptly
arrested from further progress by the application of pure glycerine.
Here we have a method of developing up any one part, and restraining
or entirely stopping any other.
I do not think any good will be done by a more detailed description
of its working, even if there be anything more to tell. It is
essentially a method of development in which the individual worker
will invent modifications and dodges for himself, and when all is
said for it, it must be admitted only as a means of improving a
subject when ordinary procedure fails.
THE CHARACTER OF THE NEGATIVE FOR PLATINOTYPE.
In the earlier days of platinotype printing it was generally
insisted upon that the most suitable negatives were such as we
should describe as somewhat vigorous or "plucky." Whether it is that
some alteration has been made in the manufacture of the paper or
that taste as regards what constitutes a good print has changed, I
cannot say. Certain it is that in the experience of a good many, a
"plucky" negative is by no means essential to the production of a
good platinotype print.
The soft, delicate negatives, of which the best professional
portrait negatives are a good sample, yield the best possible
results, whilst with the CC paper, negatives so thin and delicate as
to be suitable for hardly any other printing process, give all that
can be wished for.
Much, of course, will depend on the kind of print desired and the
paper used, and here it may be remarked that from a given negative
the different kinds of platinotype paper give different results.
From a given negative the hot-bath papers yield the greatest amount
of half-tone, the hot development tending to yield flatter results.
Next comes the smooth, cold-bath paper, and finally as yielding the
maximum amount of vigour is the CC paper. Hence if we make our
negatives specially for our chosen printing process, a stronger
negative will be needed for S, RS, A and C than for the AA and CC,
whilst for the latter a negative distinctly erring on the side of
extreme thinness will be best.
If a negative gives prints which are too weak and flat for our
purpose, a great improvement may be effected by printing through
blue glass. If on the other hand the prints are too hard and harsh
in contrast, it is advisable to print through "signal" green glass.
TONING PLATINOTYPE PRINTS.
Several formula and methods have been published from time to time,
the object of which is to change the colour of the platinotype print
by subsequent staining or toning, and whilst by such methods
pleasing colours may sometimes be obtained, they possess an element
of uncertainty, and must not be too much relied upon. An exception
in this respect must, however, be made in the case of what is known
as Packham's method, the effect of which is to change the black
platinotype to a sepia brown, or a brown slightly tinged with green.
The necessary "tinctorial powder" must be obtained from Mr. Packham
or through a dealer. To prepare the bath a packet of this powder is
dissolved by boiling for three or four minutes in five fluid ounces
of water, to which when cold add one ounce methylated spirit. This
forms the stock solution and will keep for a long time if well
corked. For use add thirty or forty minims of the stock solution to
one pint of water, and in this steep the prints, turning them over
frequently. Toning may occupy several hours. To expedite matters,
the dilute solution should be made with water of 150° F., and the
bath maintained at this temperature as in the case of hot-bath
development. As soon as the desired tint is secured, remove the
prints and wash well in three changes of cold water.
Prints may be so treated at any time after they have been made.
Glycerine developed prints are not suitable. Prints must have been
very thoroughly washed, so as to free them from every trace of acid,
also thoroughly fixed in acid if they are to be "toned" by Packham's
method. If after "toning" and washing the whites of the print appear
to have suffered, the prints should be placed for five or ten
minutes in the following bath, which should be kept at a temperature
of 180° F.
Castille soap 40 grains
Bicarbonate of soda 80 grains
Water, hot (180° F.) 1 pint
This will clear the whites and intensify the colour generally.
Platinotypes may be toned to a red-brown by uranium nitrate, or to a
bluer colour with chloride of gold. They may also be intensified by
pyrogallic acid or hydroquinone, but as the purpose of this article
was merely to give simple working instructions for platinotype
printing for the beginner, he may defer the consideration of such
side issues until he has become _au fait_ in the production of a
good platinotype print.
_A. Horsley Hinton._
_Contact Printing on Bromide Paper._
[Illustration]
It is well to bear in mind at the outset that bromide paper is
extremely sensitive to light, almost as much so as is a rapid dry
plate. For this reason, it is obvious that it must not be carelessly
exposed to actinic light. All manipulations except the actual
printing must be conducted by red or yellow light, such as is
allowed to pass through glass of these colours.