Improvements relating to the Manufacture of Photographic Printing Paper.
Year: 1894

page_text: Date of Application, 24th Oct., 1894
Complete Specification Left, 24th May, 1895-Accepted, 29:h June, 1895
[Communicated from abroad by the Firm of ARNDT & TROOST, of 7 Wingert-
strasse, Frankfort-on-the-Main, in the Empire of Germany, Manufacturers.]
Improvements relating to the Manufacture of Photographic
Printing Paper.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, do hereby
declare the nature of this invention to be as follows:-
This invention relates to the manufacture of photographic printing paper.
At the present time there is no heliographic process with silver paper which
operates without a special developing or fixing bath; only ferro prints have
heretofore been developed in pure cold water by a single washing operation.
Besides the well-known compounds of silver salt the improved paper contains
also an iron compound which in this combination performs a double function: in
the first place the compound of an iron salt and silver salt appears to be much
more permanent than that of silver salts alone, and in the second place the iron
salt, owing to its being reduced in the light, serves to precipitate silver from the
silver salt and thus produces the picture.
The primary material employed for the production of this improved paper is not
paper which contains chlorine; use is preferably made of pure rag paper and also
fabric for this purpose; the absence of wood is very desirable. These materials
are soaked with a solution which consists of silver nitrate, iron ammonia, tartaric
acid, citric acid, and preferably also gelatine.
It has been found that the tartaric acid or the citric acid may be dispensed with
without giving rise to a very great difference. The same is the case with the
gelatine. The quantity of the iron salts used determines the darkness in tone of
the copies obtained.
The conditions under which these materials have heretofore been used and have
given favourable results are for thousand cubic centimetres of distilled water ()
to 100 grammes of iron ammonium citrate, 12 to 20 grammes of silver nitrate,
15 to 20 grammes of tartaric acid and 10 to 15 grammes of gelatine. The paper
soaked with this solution keeps unchanged for several months in the unexposed
state. Exposed to the light it is five times more sensitive than the customary
paper containing hydrocyanic acid; the parts exposed to the light receive a
slightly yellowish colour which by the washing in pure water changes to deep
brown.
By reason of its very great sensitiveness the improved paper may be employed
in cases where such has not hitherto been possible, especially for printing on
rather thick cardboard and for producing negative stencils which may be used
directly with the same paper or with paper containing hydrocyanic acid for the
production of positives. The copies thus obtained are quite unchangeable in the
light after the washing and do not require any further fixing.
According to what is known regarding the several components of the solution
two operations must take place for forming the copy: In the first place a small
part of the silver nitrate, in the presence of the organic substances, will be directly
decomposed in the light and become coloured; in the second place, and this is

page_text: evidently the more important operation for imparting colour, the iron oxide
present is reduced by the exposure to light, in consequence of which metallic silver
is then precipitated from the silver nitrate. The opinion that the two operations
take place in conjunction appears to be supported by the brown colour of the
product obtained.
Although the pictures produced with this improved paper keep very long under
ordinary circumstances it is advisable, in cases where the pictures are brought
together with acids or substances containing acids, to submit them to a fixing
operation.
1004
.,HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.
-Improvements relating to the Manufacture of Photographic
Printing Paper.
1, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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 :-
This invention relates to the manufacture of photographic printing paper.
At the present time there is no beliographic process with silver paper which
operates without a special developing or fixing bath; only ferro prints have
heretofore been developed in pure cold water by a single washing operation.
Besides the well-known compounds of silver salt the improved paper contains
also an iron compound which in this combination performs a double function; in
the first place the compound of an iron salt and silver salt appears to be much
more permanent than that of silver salts alone, and in the second place the iron
salt, owing to its being reduced in the light, serves to precipitate silver from the
silver salt and thus produces the picture.
The primary material employed for the production of this improved paper is
not paper which contains chlorine; use is preferably made of pure rag paper and
also fabric for this purpose; the absence of wood is very desirable. These
materials are soaked with a solution which consists of silver nitrate, iron ammonia,
tartaric acid, citric acid, and preferably also gelatine.
It has been found that the tartaric acid or the citric acid may be dispensed with
without giving rise to a very great difference. The same is the case with the
gelatine. The quantity of the iron salts used determines the darkness in tone
of the copies obtained.
The conditions under which these materials have heretofore been used and have
given favourable results are for thousand cubic centimetres of distilled waters
80 to 100 grammes of iron ammonium citrate, 12 to 20 grammes of silver nitrate,
15 to 20 grammes of tartaric acid and 10 to 15 grammes of gelatine. The paper
soaked with this solution keeps unchanged for several months in the unexposed
state. Exposed to the light it is five times more sensitive than the customary
paper containing hydrocyanic acid; the parts exposed to the light receive a
slightly yellowish colour which by the washing in pure water changes to deep
brown.
By reason of its very great sensitiveness the improved paper may be employed
in cases where such has not hitherto been possible, especially for printing on rather
thick cardboard and for producing negative stencils which may be used directly
with the same paper or with paper containing hydrocyanic acid for the production

page_text: of positives. The copies thus obtained are quite unchangeable in the light after
the washing and do not require any further fixing.
According to what is known regarding the several components of the solution
two operations must take place for forming the copy. In the first place a small
part of the silver nitrate, in the presence of the organic substances, will be directly
decomposed in the light and become coloured; in the second place, and this is
evidently the more important operation for imparting colour, the iron oxide
present is reduced by the exposure to light, in consequence of which metallic
silver is then precipitated from the silver nitrate. The opinion that the two
operations take place in conjunction appears to be supported by the brown colour
of the product obtained.
Although the pictures produced with this improved paper keep very long under
ordinary circumstances it is advisable, in cases where the pictures are brought
together with acids or substances containing acids, to submit them to a fixing
operation.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondents, I declare that what I claim is :-
1. Highly sensitive, (permanent) silver paper for photographic printing purposes
produced by soaking the paper with a solution of silver nitrate and citric or
tartaric ferric salt, whereby a light yellow tinted paper is obtained which turns
brown when exposed to the light and becomes yellow again when moistened and
which when treated in the fixing bath turns dark brown.
2. For producing photographic printing paper such as described in the first
claim, the application of a solution consisting of silver nitrate, citric ammonio
ferric sulphate, tartaric acid and preferably also gelatine.
3. For producing photographic printing paper such as described in the first
claim, by using the solution stated in the second claim a composition of said
solution containing 1000 cubic centimeters of distilled water, 80 to 100 grammes
of citric ammonio ferric sulphate, 12 to 20 grammes of silver nitrate, 15 to
20 grammes of tartaric acid and 10 to 15 grammes of gelatine.
Dadhin Dich den of M- 1905
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.