Year: 1899

page_text: I, GUSTAV SELLE, of Brandenburg on the Havel, in the Empire of Germany,
Physician, do hereby declare the nature of this invention to be as follows:-
A9
This invention refers to a method of forming the three primary colored films
described in the Specification of my Patent 7104 of 1895 which may be called a
mordant process.
The methods previously in use were the so called carbon pro-
cess where by partial or total washing away of pigmented gelatine a picture in
relief is formed, and the so called imbibition process where the sensitive gelatine
surface after exposure swells up in those parts where light has acted least where-
by such parts are rendered capable of absorbing color. Both these methods require
obviously thick layers of gelatine and proved unsatisfactory in practice.
explained under my Patent 7104 of 1895, I use extremely thin layers of gelatine
which on account of their fragility and also for the purpose of superposition are
supported on collodion films. The effect of using such extremely thin gelatine
is that the latter remains practically unaffected by the subsequent baths and
those parts on which the light passing through the negative has acted undergo
a chemical change whereby the bichromated gelatine is so to say converted into
a mordant capable of attracting the coloring matter held in solution by the baths;
moreover the combination imparts a satisfactory degree of permanency to other-
wise fugitive colors such as the aniline dyes. It is obvious also that on account
of their thinness the films when superimposed allow of an equable and luminous
blending of the 3 colors. My present object is to describe details giving the
best results. I have found that the strength of gelatine solution to be used should
be one between 5% and 7% preferably 6%, when poured on a rigid
surface such as glass or suitably mounted paper and the excess allowed
to drain off there will result a film of about 0.0015 millimeter in thickness. A
stronger solution would give not only a thicker and therefore less luminous film
but also a somewhat blurred and dirty picture. On the other hand a weaker
solution would not provide a sufficient hold for the coloring matter and would con-
sequently yield a pale and feeble image. The bichromate sensitiser used for
instance amm. bichrom., should be a solution from 2.5 to 3% strong if a
stronger solution is used say 4% the sensitiser will generally crystallize
giving an unserviceable surface; on the other hand a weaker solution say 2%
would yield a weak image since the coloring matter cannot bite
sufficiently. It is also desirable that the plate should drain off at a temperature
of about 40° Celsius and not exceeding 60° otherwise the gelatine by drying too
quickly would prevent an even draining off and a layer of unequal depth results.
Dated this 15th day of June 1899
HERBERT HADDAN & Co,
Agents to Applicant.

page_text: Improvements in the Formation of Films for use in Color Photography.
I, GUSTAV SELLE, of Brandenburg, in the Empire of Germany, Physician, 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: -
As
This invention refers to a method of forming the three primary colored films
described in the Specification of my Patent 7104 of 1895 which may be called a
mordant process. The methods previously in use were the so-called carbon pro-
cess where by partial or total washing away of pigmented gelatine a picture in
relief is formed, and the so-called imbibition process where the sensitive gelatine
surface after exposure swells up in those parts where light has acted least where-
by such parts are rendered capable of absorbing color. Both these methods require
obviously thick layers of gelatine and proved unsatisfactory in practice.
explained under my Patent 7104 of 1895, I use extremely thin layers of gelatine
which on account of their fragility and also for the purpose of superposition are
supported on collodion films. The effect of using such extremely thin gelatine
is that the latter remains practically unaffected by the subsequent baths and
those parts on which the light passing through the negative has acted undergo
a chemical change whereby the bichromated gelatine is so to say converted into
a mordant capable of attracting the coloring matter held in solution by the baths;
moreover the combination imparts a satisfactory degree of permanency to other-
wise fugitive colors such as the aniline dyes. It is obvious also that on account
of their thinness the films when superimposed allow of an equable and luminous
blending of the three colors. My present object is to describe details giving the
best results. I have found that the strength of gelatine solution to be used should
be one between 5 per cent, and 7 per cent. preferably 6 per cent. when poured on a
rigid surface such as glass or suitably mounted paper and the excess allowed
to drain off there will result a film of about 0.0015 millimeter in thickness.
stronger solution would give not only a thicker and therefore less luminous film
but also a somewhat blurred and dirty picture. On the other hand a weaker
solution would not provide a sufficient hold for the coloring matter and would con-
sequently yield a pale and feeble image. The bichromate sensitizer used for
instance amm. bichrom. should be a solution from 2.5 to 3 per cent. strong: if a
stronger solution is used say 4 per cent. the sensitizer will generally crystallize
giving an unserviceable surface on the other hand a weaker solution
say 2 per cent. would yield a weak image since the coloring matter cannot bite
sufficiently. It is also desirable that the plate should drain off at a temperature
of about 40° Celsius and not exceeding 60° otherwise the gelatine by drying too
quickly would prevent an even draining off and a layer of unequal depth results.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:-
In the formation of films for use in color photography
1. The method of forming a thin film substantially as described.
A
2. Drying the said films at the temperature mentioned for the purpose described.
Dated this 12th day of April 1900
HERBERT HADDAN & Co.,
Agents to Applicant,
18, Buckingham Street, Strand, W.C.