Improvements in Photographic Printing Processes.
Year: 1891

page_text: Date of Application, 28th Apr., 1891
Complete Specification Left. 27th Jan. 1892-Accepted. 27th Feb.. 1892
PROVISIONAL SPECIFICATION.
Improvements in Photographic Printing Processes.
I, WILLIAM WALKER JAMES NICOL, Master of Arts, Doctor of Science, of
Mason College, Birmingham, Lecturer on Chemistry do hereby declare the nature
of this invention to be as follows:-
:-
Suitable paper or other material is coated with a solution of a ferric salt such as
oxalate, citrate, or tartrate or a mixture of these, and a solution of a soluble silver
salt. After drying, the now sensitive surface is exposed to light under a negative-
& the image is developed on a strong solution of a tartrate citrate of oxalate of
potash soda or ammonia to which may have been added acetate or borate or other
salt of potash or soda which may be found to produce the desired tone. By the
addition of potassium or sodium oxalate citrate or tartrate to the sensitising
solution the image may be made to print out and thus development may be
avoided-contrast is obtained by the addition of an oxidising agent to the
developer. The prints are finally washed in water to which ammonia and citrate
or tartrate of potash or soda have been added.
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COMPLETE SPECIFICATION.
Improvements in Photographic Printing Processes.
1, WILLIAM Walker James NICOL, Master of Arts, Doctor of Science,
of Mason College, Birmingham, Lecturer on Chemistry, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
My invention has for its object the production of photographic pictures or images
in silver by improved methods of carrying into effect the processes described in
the Specification of my former Letters Patent No. 5374 dated March 29th 1889.
Whereas the processes therein described and set forth, though yielding excellent
results so far as the quality and tone of the resulting pictures were concerned, were
apt, inasmuch as the solutions employed for development contained soluble salts
of silver, to stain the hands of the operator, it was found that this formed a serious
objection to their general employment.
-1
I therefore now proceed according to the following method that is to say :—
coat in any convenient way paper or other material with an aqueous or other
solution of a ferric salt. This may be one or other of the following-Ferric oxalate
citrate tartrate or other ferric salt which is sensitive to light. These may be
employed singly or mixed together in suitable proportions with or without the
addition of citric tartaric oxalic acids or their sodium potassium or ammonium
salts. To the above solution is also added a suitable quantity of a silver salt and
the whole is thoroughly mixed together. The above solutions may be applied to
the paper or other material if so desired separately and in any order and in such
relative quantities as may be found to give results most suitable for the purpose in
view.
After the material thus prepared and rendered sensitive to light has been dried;
it is exposed to light under a negative or other screen. I then proceed to develop
the ferrous image produced by the action of light with a solution containing a salt

page_text: of citric, tartaric, oxalic, boric, carbonic or acetic acid with sodium potassium or
ammonium; or mixtures of these with one another in such proportions as may be
found to give the requisite tone and brilliancy to the resulting images. When
certain of these mixtures are employed, the addition of a small quantity of
potassium chromate or other suitable oxidising agent is necessary to ensure contrast
and purity of the high lights of the picture.
The resulting prints are then washed in several changes of dilute ammonia
to which may have been added a citrate or tartrate of potassium sodium or
ammonium.
Or, I adopt the following method the paper or other material having been
prepared as above described is exposed to light as before and is developed at once
on the dilute ammonia mentioned above, with or without the addition of one or
other of the salts mentioned as entering into the composition of the developer as
described above.
Or, I adopt the following method, viz.:-I prepare the paper or other material
with one of the above ferric salts and a suitable amount of one of the above
mentioned developing salts and a solution of a silver salt. I thus obtain a sensitive
surface which attains its full depth of tone by the action of light alone. The
print then requires only to be washed in the dilute ammonia above mentioned.
I. In practising my invention according to the first method above described I
use by preference solutions of the following composition.
Water one hundred (100) cubic centimetres.
Ferric oxalate fifteen (15) grammes.
Silver nitrate three (3) grammes.
The above forms the sensitizing solution.
The developer is as follows.
Water one hundred (100) cubic centimetres.
Rochelle salt ten (10) grammes.
Borax seven (7) grammes.
To this is added one tenth (0-1) to four tenths (0-4) of a cubic centimetre of a
five (5) per cent. solution of potassium chromate.

page_text: W. W. J. NICOL.