IMPROVEMENTS IN THE PREPARATION OR PRODUCTION OF PHOTOGRAPHIC EMULSIONS
Year: 1880

page_text: LETTERS PATENT to Edwin Ambrose Brydges, of the Firm of Brydges & Co.,
Engineers & Patent Agents, No. 73, Koeniggraetzer Strasse, Berlin, in the
Empire of Germany, for an Invention of "IMPROVEMENTS IN THE PREPARATION
OR PRODUCTION OF PHOTOGRAPHIC EMULSIONS." A communication by
Professor Doctor Hermann Wilhelm Vocal of the City of Berlin aforesaid.
PROVISIONAL SPECIFICATION left by the said Edwin Ambrose Brydges at
the Office of the Commissioners of Patents on the 27th May 1880.
EDWIN AMBROSE BRYDGES, of the Firm of Brydges & Co., Engineers and Patent
Agents, No. 73, Koeniggractzer Strasse, Berlin, in the Empire of Germany.
"IMPROVEMENTS IN THE PREPARATION OR PRODUCTION OF PHOTOGRAPHIC
EMULSIONS." [A communication by Professor Doctor Hermann Wilhelm Vogel,
of the City of Berlin aforesaid.]
This Invention relates to the preparation, production, or manufacture of photo-
graphic emulsions.
The gelatine dry plates hitherto in use are extremely sensitive, and are
produced by pouring an emulsion consisting of an aqueous solution of gelatine
containing bromide of silver over the plates and allowing the same to dry.
This aqueous bromide of silver gelatine emulsion possesses the disadvantages
that it decomposes very rapidly, dries very slowly when distributed over the plates,
intensifies and washes with difficulty, and easily frills on the plate.
After many experiments I have succeeded in overcoming these disadvantages by
an entirely new process hitherto unknown in photography, for which purpose I use
gelatine containing bromide of silver (or chloride of silver and iodide of silver, or
a mixture of the same) in combination with pyroxiline.
No means of combining gelatine or gelatine emulsion with a solution of pyroxi-
line (ie., collodion) so as to form a homogeneous fluid has been known up to the
present time. If common collodion is added to ordinary gelatine emulsion the
dissolved matters will be precipitated in flakes.
I have now succeeded in obtaining a perfect homogeneous mixture by using a
solvent which will dissolve both substances, bromide of silver gelatine and
Dyroxiline.

page_text: Such solvents are the various organic acids, namely, the inferior members of the
fatty acids, such as formic acid, acetic acid, propionic acid, etc., and their derivatives
or mixtures of the same, alone or with methylated spirit, ethyl-alcohol, etc.
I found that gelatine bromide of silver dissolved in these solvents without
precipitating the salts of silver contained in the same, and that contrary to all
previous experience the photographic properties of these salts were not essentially
changed by the presence of the acids, that the properties of the gelatine emulsion
in the solution were improved, so that it no longer possessed the disadvantages of
the aqueous emulsion as mentioned above, and that its properties are still further
improved by the combination with pyroxiline.
To produce the combination aforenamed I use the following four various
methods:-
:-
I. I first produce a gelatine emulsion according to the customary process, which
is then dried by means of cold or warm air or other means for extracting the
water. This dry bromide of silver gelatine (which can also contain iodide of silver
and chloride of silver) I then dissolve warm in one of the above mentioned acids,
using three to ten times as much or even more acid.
The quantity of acid to be used depends on the solvency of the gelatine, and
must be tried for each kind.
This acidulous emulsion is now used alone after having been diluted with
alcohol to the required consistency, or can be mixed with pyroxiline.
The pyroxiline is dissolved in acetic acid, a like acid, or a mixture of such acid
with alcohol.
The most appropriate quantity of pyroxiline is about one per cent. of the
quantity of acidulous emulsion employed.
Instead of this process the following method can be used:-
II. Pyroxiline is dissolved in one of the fatty acids, for instance, formic acid or
acetic acid, or a mixture of such acid per se, or with alcohol or other solvent, which
will dissolve both gelatine and pyroxiline.
For easily soluble pyroxiline alcohol or methylated spirit, or a mixture of the
same, can be used as solvent.
The proportions can be varied in many different ways, so that the following
formula serves simply as an example, id est :-
2 grammes pyroxiline.
50 do. acetic acid.
50 do. alcohol.
The collodion produced by this process is mixed with about an equal quantity
of acidulous emulsion, as above described.
The gelatine emulsion collodion produced can be slightly warmed and applied
like ordinary collodion to glass plates, paper, etc., and exposed to the light either
in a moist or dry condition. A similar mixture can be prepared as follows:-
III. A collodion emulsion is prepared according to the customary formula, and
precipitated as usual by water; or the emulsion is allowed to dry up, then washed,
and the dry matter dissolved in one of the above mentioned acids or mixtures of
the same with alcohol.
Gelatine, either alone or after being dissolved in one of the solvents mentioned
above, is now added to the collodion preparation.
The proportions can be varied in the like degree as in the preparation of the
ordinary collodion emulsion.
The following is, for instance, one of the various proportions of the mixture:-
7 grammes of the precipitated pyroxiline containing bromide of silver are
dissolved in 150 grammes alcohol and 90 grammes acetic acid, then 2 grammes
gelatine are dissolved in 20 grammes acetic acid and added to the same. Another
process for producing a similar mixture is,-
IV. Dissolve gelatine and pyroxiline in one of the above mentioned solvents, or
dissolve them separately and then mix the solutions.
Finely powdered bromide of silver prepared in the customary manner, or any

page_text: one of the silver haloid salts, or a mixture of the same, is now added to the gelatine
collodion solution; or the silver haloid salts are produced in the gelatine collodion
solution through double decomposition.
These proportions can also be varied in different ways.
Having now described my said Invention, and the manner of carrying the same
into effect, what I claim and desire to secure by Letters Patent is,--
1. The manufacture, preparation, or production of a durable gelatine emulsion
by dissolving gelatine containing silver haloid salt in one of the solvents mentioned
in the foregoing Specification.
2. The mixing or the combination of gelatine emulsion and collodion, substantially
as described in the foregoing Specification under parts I. and II.
3. The combination or the mixing of a collodion emulsion with gelatine, sub-
stantially as described in the foregoing Specification under part III.
4. The preparation or production of a silver haloid salt emulsion by distributing
silver haloid salts in (or mixing such salts with) a gelatine collodion emulsion,
substantially as described in the foregoing Specification under part IV.
5. The application or employment of the combination of gelatine and collodion,
or gelatine and pyroxiline, for the preparation of emulsions, substantially as and for
the purposes set forth in the foregoing Specification.
6. The use, application, or employment of the aforementioned emulsions for
covering surfaces for photographic purposes, such as photographic plates, paper, etc.,
substantially as set forth in the foregoing Specification.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edwin Ambrose Brydges in the Great Seal Patent Office on the
27th November 1880.
EDWIN AMBROSE BRYDGES, of the Firm of Brydges & Co., Engineers and
Patent Agents, No. 73, Koeniggraetzer Strasse, Berlin, in the Empire of Germany.
IMPROVEMENTS IN THE PREPARATION OR PRODUCTION OF PHOTOGRAPHIC
EMULSIONS."
**
This Invention relates to the preparation, production, or manufacture of photo-
graphic emulsions.
The gelatine dry plates hitherto in use are extremely sensitive, and are produced
by pouring an emulsion consisting of an aqueous solution of gelatine containing
bromide of silver over the plates and allowing the same to dry.
This aqueous bromide of silver gelatine emulsion possesses the disadvantages
that it decomposes very rapidly, dries very slowly when distributed over the plates,
intensifies and washes with difficulty, and easily frills on the plate.
After many experiments I have succeeded in overcoming these disadvantages by
an entirely new process hitherto unknown in photography, for which purpose I use
gelatine containing bromide of silver (or chloride of silver and iodide of silver, or a
mixture of the same) in combination with pyroxiline.
No means of combining gelatine or gelatine emulsion with a solution of pyroxi-
line (ie., collodion) so as to form a homogeneous fluid has been known up to the
present time.
If common collodion is added to ordinary gelatine emulsion the
dissolved matter will be precipitated in flakes.
I have now succeeded in obtaining a perfect homogeneous mixture by using a
Bolvent which will dissolve both substances, bromide of silver gelatine and
pyroxiline.
Such solvents are the various organic acids, namely, the inferior members of the
fatty acids, such as formic acid, acetic acid, propionic acid, etcetera, and their
derivatives or mixtures of the same, alone or with methylated spirit, ethyl-alcohol,
etcetera.
I found that gelatine bromide of silver dissolved in these solvents without
precipitating the salts of silver contained in the same, and that contrary to all
previous experience the photographic properties of these salts were not essentially
changed by the presence of the acids, that the properties of the gelatine einulsion
in the solution were improved, so that it no longer possessed the disadvantages of
the aqueous emulsion, as mentioned above, and that its properties are still further
improved by the combination with pyroxiline.
To produce the combination aforenamed I use the following four various
methods:
I. I first produce a gelatine emulsion according to the customary process, which
is then dried by means of cold or warm air, or other means for extracting the
water. This dry bromide of silver gelatine (which can also contain iodide of silver
and chloride of silver) I then dissolve warm in one of the above mentioned acids,
using three to ten times as much or even more acid.
The quantity of acid to be used depends on the solvency of the gelatine, and
must be tried for each kind.
This acidulous emulsion is now used alone after having been diluted with alcohol
to the required consistency, or can be mixed with pyroxiline.
The pyroxiline is dissolved in acetic acid, a like acid, or a mixture of such acid
with alcohol.

page_text: The most appropriate quantity of pyroxiline is about one per cent. of the
quantity of acidulous emulsion employed.
Instead of this process the following method can be used;
-
II. Pyroxiline is dissolved in one of the fatty acids, for instance, formic acid or
acetic acid, or a mixture of such acid per se, or with alcohol or other solvent
which will dissolve both gelatine and pyroxiline.
For easily soluble pyroxiline alcohol or methylated spirit, or a mixture of the
same, can be used as solvent.
The proportions can be varied in many different ways, so that the following
formula serves simply as an example id est ..
50 do. alcohol.
The collodion produced by this process is mixed with about an equal quantity of
acidulous emulsion, as above described.
The gelatine emulsion collodion produced can be slightly warmed and applied
like ordinary collodion to glass plates, paper, etcetera, and exposed to the light
either in a moist or dry condition. A similar mixture can be prepared as
follows:-
III. A collodion emulsion is prepared according to the customary formula and
precipitated as usual by water; or the emulsion is allowed to dry up, then washed,
and the dry matter dissolved in one of the above mentioned acids or mixtures of
the same with alcohol.
Gelatine, either alone or after being dissolved in one of the_solvents mentioned
above, is now added to the collodion preparation.
The proportions can be varied in the like degree as in the preparation of the
ordinary collodion emulsion.
The following is, for instance, one of the various proportions of the mixture:--
7 grammes of the precipitated pyroxiline containing bromide of silver are
dissolved in 150 grammes alcohol and 90 grammes acetic acid, then 2 grammes
gelatine are dissolved in 20 grammes acetic acid and added to the same. Another
process for producing a similar mixture is,-
IV. Dissolve gelatine and pyroxiline in one of the above mentioned solvents, or
dissolve them separately, and then mix the solutions.
Finely powdered bromide of silver prepared in the customary manner, or any
one of the silver haloid salts, or a mixture of the same, is now added to the gelatine
collodion solution; or the silver haloid salts are produced in the gelatine collodion
solution through double decomposition.
These proportions can also be varied in different ways.
Having now described my said Invention, and the manner of carrying the same
into effect, what I claim and desire to secure by Letters Patent is,―
First. The manufacture, preparation, or production of a durable gelatine emulsion
by dissolving gelatine containing silver haloid salt in one of the solvents mentioned
in the foregoing Specification.
Second. The mixing or the combination of gelatine emulsion and collodion,
substantially as described in the foregoing Specification under parts I. and II.
Third. The combination or the mixing of a collodion emulsion with gelatine,
substantially as described in the foregoing Specification under part III.
Fourth. The preparation or production of a silver haloid salt emulsion by
distributing silver haloid salts in (or mixing such salts with) a gelatine collodion
emulsion, substantially as described in the foregoing Specification under
part IV.
Fifth. The application or employment of the combination of gelatine and
collodion, or gelatine and pyroxyline, for the preparation of emulsions, substantially
as and for the purposes set forth in the foregoing Specification.

page_text: Sixth. The use, application, or employment of the aforementioned emulsions for
covering surfaces for photographic purposes, such as photographic plates, papers,
etcetera, substantially as set forth in the foregoing Specification.
In witness whereof, I, the said Edwin Ambrose Brydges, have hereunto set
my hand and seal, this Twenty second day of November, in the year of
our Lord One thousand eight hundred and eighty.
EDWIN A. BRIDGES. (L.S.)