IMPROVEMENTS IN THE PREPARATION OF PHOTOGRAPHIC EMULSIONS
Year: 1881

page_text: LETTERS PATENT to Joseph Plener, of Cockspur Street, Charing Cross, in
the County of Middlesex, for an Invention of "IMPROVEMENTS IN THE
PREPARATION OF PHOTOGRAPHIC EMULSIONS."
PROVISIONAL SPECIFICATION left by the said Joseph Plener at the Office
of the Commissioners of Patents on the 8th November 1881.
JOSEPH PLENER, of Cockspur Street, Charing Cross, in the County of
Middlesex. "IMPROVEMENTS IN THE PREPARATION OF PHOTOGRAPHIC
EMULSIONS."
My Invention consists mainly of the following particulars:-According to the
first part of my Invention, given an emulsion of chloride, iodide, or bromide of silver,
prepared in the usual way with any colloidal body, or any mixture of some of
these emulsions. I operato upon same just after it has been made sensitive by any
known means, and before any further operation has been proceeded with, I place
this emulsion in preferably a circular metallic vessel (although the shape may be
different), silver plated inside, which I make to rotate with the speed of, say,
between five and six thousand revolutions per minute, more or less. By the effect
of centrifugal force the heavy silver salts are driven to the extreme walls of the
vessel, and in about ten minutes separation, of powder and liquid is completed ;
the time varies with the quantity and the state of decomposition of gelatine in the
emulsion, also with sensitiveness of the emulsion. I then slowly stop the rotation,
throw out the solution by means of a syphon, pour into the vessel some water, and
with a brush remove the powder from the walls, mix it with water, make the
vessel rotate again, and so on. I repeat this operation till all traces of gelatine
and soluble salts are completely eliminated. The remaining powder of sensitive
silver salts to make emulsion of I mix with fresh gelatine, or any other colloidal
body destined to serve as vehicle for it in the dry plates. According to the second
part of my Invention, if the emulsion to be worked upon gives through overboiling
or digesting foggy plates, then I proceed thus :-I place it in the said vessel, and

page_text: cause the vessel to rotate for, say, about 15 minutes, at a speed of between two and
three thousand revolutions per minute, more or less. In this case only the largest
grains of silver salts, those which are more sensitive to developer than to light, and
which produce fog, are deposited on the walls of the vessel.
Having stopped the vessel, I throw out the emulsion, which I treat afterwards as
before described.
According to the third part of my Invention, in cases when the sensitiveness of
the washed emulsion is insufficient, be it through faulty preparation or through
action upon it of some oxidizing solutions, known in photography as fog-destroyers,
then I add about five grains of ammonium bromide to each ounce of emulsion, and
digest or boil it in usual way till the desired degree of sensitiveness is reached.
After this I treat it as described in the first part of this Specification.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Joseph Plener in the Great Seal Patent Office on the 6th May
1882.
"IMPROVE
JOSEPH PLENER, of Cockspur Street, Charing Cross, now of Cadby's Steam
Works, Leather Lane, Hatton Garden, in the County of Middlesex.
MENTS IN THE PREPARATION OF PHOTOGRAPHIC EMULSIONS."
My Invention consists substantially of the following particulars:-According to
the first part of my Invention, given an emulsion of chloride, iodide, or bromide of
silver, prepared in the usual way with gelatine, gum, or any collodial body, or any
mixture of some of these emulsions. I operate upon same preferably just after it
has been made sensitive by any known means, and before any further operation
has been proceeded with I melt this emulsion by heating if it is set, and place it
in a metallic vessel, preferably having the form of a truncated cone (although the
shape may be different), silver plated inside, which I make to rotate with the speed
of about four thousand revolutions per minute if the vessel is one foot in diameter.
But should the diameter be larger then the number of revolutions must be in
inverse ratio of the diameter. During the rotation of the vessel I heat it with a
flame of gas or a lamp to prevent setting of emulsion should it have a tendency
to it. By the effect of centrifugal force the heavy silver salts are driven to and
deposited on the circumference of the bottom of the vessel, and in about ten
minutes the separation of powder and liquid is effected.
The time varies with the quantity and the state of decomposition of gelatine in
the emulsion; also with the size of the grains of silver salts. I then slowly stop
the rotation, throw out the solution by means of a syphon, pour into the vessel
some warm water, and with a brush mix the powder with water, make the vessel
rotate again, and so on. I repeat this operation till all traces of gelatine and
soluble salts are eliminated. The remaining powder of sensitive silver salts to
make emulsion of I mix with fresh gelatine, collodion, or any substanco destined
to serve as vehicle for it in subsequent operations. To prepare the collodion
emulsion I mix well the powder isolated from gelatine with about half of its weight
of glycerine, and emulsify the mixture in a large quantity of alcohol, allow the
powder to settle, pour off the supernatant liquid, repeat the operation with fresh
quantity of alcohol, and the dry powder so obtained I mix with plain collodion.
According to the second part of my Invention, if the emulsion to be worked
upon gives through over boiling or over digesting foggy plates, then I proceed
thus I place it in the said vessel, and cause the latter to rotate for, say, about
fifteen minutes, at a speed of between two and three thousand revolutions per
minute, more or less; in this case only the largest grains of silver salts, those which
are more sensitive to developer than to the light, and which produce fog, are
deposited as before described. Having stopped the vessel I throw out the emulsion,
which I treat afterwards as described in the first part of this Specification.
According to the third part of my Invention, in cases when the sensitiveness of
the washed emulsion is insufficient, be it through faulty preparation or through
action upon it of some oxidizing solutions known in photography as fog destroyers,
then I add five grains of ammonium bromide to each ounce of emulsion, and digest
or boil it in the usual way till the desired degree of sensitiveness is reached. After
this I treat it as described in the first part of this Specification.
The accompanying Drawing shows form of vessel preferred for carrying out my
Invention. A is vessel mounted on spindle B, to which spindle is attached by
suitable means a pulley for driving the vessel, the vessel being secured to spindle
as shown.

page_text: Having now particularly described and ascertained the nature and object of
the said Invention, and in what manner the same is to be performed or put in
practice, I hereby declare that I claim the said Invention of "Improvements in
the Preparation of Photographic Emulsions," substantially as hereinbefore set forth
and described, in which the following are particular and important points or
features, viz. —
(1). The application of centrifugal force for the isolation of silver salts from an
emulsion, as described in the first part of this Specification.
(2). The application of the same force for the division of an emulsion into several
parts, according to the different size of the grains of silver salts, as described in
the second part of this Specification.
(3). The emulsion may be made to contain during the boiling or digesting
unlimited quantity of water and gelatine, and thus is obtained the fine granular
state of the silver salts in emulsion.
(4). By eliminating the decomposed gelatine and replacing it by fresh gelatine,
all the defects in dry plates caused by the decomposition of gelatine, viz., frilling,
faintness of images, etc., are got rid of.
(5). The silver salts eliminated from emulsion so as not to be liable to change
under long keeping, whereby the storing of same and mixing up in great quantity
become possible, and thus uniformity of dry plates may be secured.
(6). When the emulsion gives foggy plates, same may be restored to good
quality, as described in the second part of this Specification.
(7). To increase the sensitiveness by boiling or digesting, which may be repeated,
as described in the second part of this Specification.
(8). The silver salts once isolated from gelatine so as to serve for the preparation-
of collodion-emulsion, as described in the first part of this Specification.
In witness whereof, I, the said Joseph Plener, have hereunto set my hand
and seal, this Fifth day of May, in the year of our Lord One thousand eight
hundred and eighty two.
Witness,
T. MORGAN,
21, Cockspur Street,
Charing Cross, S. W.
JOSEPH PLENER. (L.S.)