Improvements in Photographic Emulsions.
Year: 1896

page_text: Date of Application, 17th Mar., 1896
Complete Specification Left, 14th Dec., 1896-Accepted, 13th Mar., 1897
PROVISIONAL SPECIFICATION.
Improvements in Photographic Emulsions.
I, HERMANN WANDROWSKY Chemist at Cologne-Ehrenfeld Venloerstrasse
No. 274 II Floor do hereby declare the nature of this invention to be as
follows:-
Photographic emulsions which are prepared with gelatine, starch, gutta-percha
or similar substances suffer from the disadvantage that they become sticky after
being spread on paper or glass and subjected to photographic baths, and dissolve
in warm or cold water causing various difficulties in the further manipulations.
This disadvantage can be obviated by adding white of egg to the gelatine &c.
emulsions when they are ready for use, the white of egg being rendered indissoluble
by the effect of substances causing it to coagulate. The emulsions that are to
receive an addition of white of egg must not contain any trace of free nitrade of
silver, otherwise the white of egg would be precipitated.
For HERRMANN WANDROWSKY,
Bernh. Brockhues.

page_text: Improvements in Photographic Emulsions.
I, HERMANN WANDROWSKY Chemist of 274 Venloer Street, Cologne-
Ehrenfeld in the Province of Rhineland and Kingdom of Prussia 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:-
Photographic emulsions which are prepared with gelatine, starch, gutta-percha
or similar substances suffer from the disadvantage that they become sticky after
being spread on paper or glass and subjected to photographic baths, and dissolve
in warm or cold water causing various difficulties in the further manipulation.
This disadvantage can be obviated by adding white of egg to the gelatine etc.
emulsions when they are ready for use, the white of egg being rendered indissoluble
by the effect of substances causing it to coagulate. The emulsions that are to
receive an addition of white of egg must not contain any trace of free nitrate of
silver, otherwise the white of egg would be precipitated.
In 1000 grammes of water are dissolved
100 grammes of gelatine
5
"
3.75
4
"
"
chloride of sodium
citrate of potassium
citric acid.
After this, a solution of silver nitrate is added, drop by drop, the solution being
stirred meanwhile until a sample shows an excess of silver nitrate when treated
with potassium chromate. After this a few drops of a solution of chloride of
sodium is added, until the excess of silver nitrate has again disappeared.
Then the emulsion is mixed with 100 grammes of dried white of egg in
500 grammes of water.
After it has been spread on paper or glass and been dried, the layer is made
indissoluble by means of a bath of alcohol or alum. In most cases however,
the toning developing and fixing baths contain substances which make the white of
egg indissoluble.
For the preparation of emulsions which are to be used in developing, bromides
and iodides or similar substances may also be used in place of chlorates and
citrates.
Having now particularly described and ascertained the nature of my inven
tion and in what manner the same is to be performed, I declare, that what I
claim is :
Emulsions sensitive to light prepared with gelatine, starch, gutta-percha or
similar substances, to which white of egg is added after the emulsions have been
prepared, in order that the white of egg, after the emulsions have been spread on
glass or paper and been dried, may be made indissoluble by treatment with
substances which coagulate the white of egg.
Dated this 12th day of December 1896.