AN IMPROVED PROCESS FOR SENSITIZING PHOTOGRAPHIC PAPER AND DEVELOPING PICTURES THEREON
Year: 1883

page_text: LETTERS PATENT to William Robert Lake of the firm of Haseltine: Lake
& Co Patent Agents Southampton Buildings London for an Invention of
"AN IMPROVED PROCESS FOR SENSITIZING PHOTOGRAPHIC PAPER AND
DEVELOPING PICTURES THEREON Communicated to him from abroad by
Redfield Benjamin West and Benjamin Corey West both of Guilford
Connecticut United States of America.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at the
Office of the Commissioners of Patents on the 27th February 1883.
.
WILLIAM ROBERT LAKE, of the firm of Haseltine, Lake, and Co Patent Agents,
Southampton Buildings London, "AN IMPROVED PROCESS FOR SENSITIZING
PHOTOGRAPHIC PAPER AND DEVELOPING PICTURES THEREON," [A communication
to him from abroad by Redfield Benjamin West and Benjamin Corey West both of
Guilford Connecticut United States of America.]
L
This invention relates to photography, and has special reference to the sensitizing
of the paper before printing, and the development of the print, the object of the
Baid invention being principally to avoid the necessity for using the expensive
silver solution now generally employed in this class of work. The said invention con-
sists in subjecting the paper to a bath composed of potassium-bichromate, magnesium
sulphate, and mercuric chloride, to sensitize the paper, and then after the exposure
of the paper for printing in the usual manner, subjecting the print for development
to a bath composed of gallic acid, ferrous sulphate, aluminum and ammonium
sulphate, and sodium hyposulphite, as more fully hereinafter described.
In carrying the said invention into practice I provide a bath for rendering the
paper sensitive to light, as follows:-that is to say I take of potassium bichromate
three parts, magnesium sulphate one part, mercuric chloride one part, and I mix
and dissolve in the smallest quantity of boiling water for solution and crystallizing.
Of this compound I take seventy-five grains to each ounce of water employed in
the bath. The paper is floated in this bath for, say three minutes, and is then

page_text: dried in the dark; when required for printing it is placed under the negative a
sufficient time to make the lighter shades in the print visible, the time varying say
from three to ten minutes under direct sunlight
The exposed portions of the print will be light brown, upon a yellow ground.
So soon as this condition is attained, the paper is taken from beneath the negative,
and soaked in pure water, say for twenty minutes; if the negative be very intense,
such as to require ten or more minutes of direct exposure to the sunlight, the
soaking should be continued longer, say to about half an hour; this is desirable
because it facilitates the subsequent developing.
The excess of bichromate being removed leaves the whites of a faint yellow tint;
where pure whites are required it becomes necessary to destroy all traces of bichro-
mate where the light has not acted and which are not easily removed by soaking;
for this purpose the print is immersed in one per-cent solution of acid sulphite of
sodium for one or two minutes.
To prepare the developer I take of gallic acid two parts, ferrous sulphate three
parts, aluminum, and ammonium sulphate three parts, sodium hyposulphite twenty-
four parts; the ferrous sulphate, aluminum and ammonium sulphate and sodium
byposulphite are each dried separately until free from water of crystallization, and
are then pulverized and mixed with the gallic acid. This compound will keep and
retain all its properties if protected from dampness. Of this composition I take
fifteen grains to each ounce of water..
.
HAN
To develop the print I lay it in a suitable dish, and pour upon it theldeveloping
solution to cover it, say a quarter of an inch in depth, or if several prints are to be
developed at the same time, I take enough of the solution to cover, all, the prints.
While they are in the solution I move them frequently, so as to expose them equally
to the developing solution.
When the development of the print is completed, which will generally require
about ten minutes, the excess of the developer absorbed by the paper is removed
by soaking the print for half an hour in water, slightly acidulated with acetic acid,
after which, and when dry, the picture can be mounted. Its subsequent treatment
may be substantially that usually applied to photographic prints.
The sodium hypo-sulphite and alum in the developer exert a reducing action,
which prevents the ferrous salt from becoming oxidized readily when in solution
and exposed to the air, and enables the bath to be used repeatedly for several days,
if after use the precaution is taken of putting it in a tightly corked bottle, which
should be filled by the solution: .
"
Any color from black to brown can be obtained after soaking out the developer,
by immersing the print from one to five minutes in a bath composed of one part
taken from the sensitizing bath, to two parts of water, the time of contact with th
bichromate determining the shade, and after such treatment soak in water until
the yellow tint is entirely removed.
(F
I
ai
If desired to change the color of a print to reddish brown: I subject it after
development to a bath composed of a solution of carbonate of soda; (one ounce
carbonate to one quart water,) and dry immediately.
!
B 07 !
In case it is necessary to bleach the picture, it should be done after development,
and before any change of color is effected; and may be well done by subjecting
the print to a solution of one part citrate of ammonia in twenty parts of water. 1
The paper may be prepared for sensitizing by any of the known processes, but a
very good result is obtained from the following treatment that is to say take
paper of a good quality, coat it with a mixture composed of starch seven parts,
white sugar.two parts, glycerine two parts, boiling water two hundredi parts, and
_solution of pure caustic potash sufficient to cause the coating to dry, with an even
surface, which will require about one-fourth part potash; the first three ingredients
are mixed with a little cold water, and then stirred into the boiling water. The
coating is applied by floating the paper upon the mixture in the manner usually
employed in the application of albumen to paper. After drying, the paper is dipped

page_text: in a two per-cent solution of acetic acid, and water, and when again dried it is ready
for use.
In cases where the intensity and appearance of the printing are of little
importance, paper may be used without this treatment Albumen paper does
not under this improved process produce so good results, chiefly on account of its
density.
From experiments it is believed the proportions for the sensitizing and developing
baths above given, produce the best results, but these proportions may be varied to
some extent without departing from the invention.
·
By this process photographic prints are produced fully equal to those produced
by the employment of silver, and it will be evident to those skilled in this art that
the cost of the production is very much less than by the usual process employing
nitrate of silver.
The printing is also more rapid than by the usual process, and colors may be
more readily applied to the print than when the print is prepared under the usual
process.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Robert Lake in the Great Seal Patent Office on the
22nd August 1883.
"
WILLIAM ROBERT LAKE, of the firm of Haseltine, Lake & Co, Patent Agents
Southampton Buildings, London, "AN IMPROVED PROCESS FOR SENSITIZING
PHOTOGRAPHIC PAPER AND DEVELOPING PICTURES THEREON A communication
to me from abroad by Redfield Benjamin West and Benjamin Corey West both of
Guilford, Connecticut, United States of America
..
:
This invention relates to photography, and has special reference to the sensitizing
of the paper before printing, and the development of the print, the object of the
said invention being principally to avoid the necessity for using the expensive
silver solution now generally employed in this class of work. The said invention
consists in subjecting the paper to be sensitized to a bath composed of potassium-
bichromate, magnesium sulphate, and mercuric chloride, and then, after the exposure
of the sensitized paper for printing in the usual manner, subjecting the print
for development to a bath composed of gallic acid, ferrous sulphate, aluminum
and ammonium sulphate, and sodium hypo-sulphite, as more fully hereinafter
described.
In carrying the said invention into practice I provide a bath, for rendering the
paper sensitive to light as follows; that is to say, I take of potassium bichromate
three parts, magnesium sulphate one part, mercuric chloride one part, and I mix
and dissolve in the smallest quantity of boiling water for solution and crystallizing.
Of this compound I take seventy five grains to each ounce of water employed in
the bath. The paper is floated in this bath for, say three minutes, and is then
dried in the dark; when required for printing it is placed under the negative a
sufficient time to make the lighter shades in the print visible, the time varying, say
from three to ten minutes under direct sun light.
The exposed portions of the print will be light brown, upon a yellow ground.
So soon as this condition is attained, the paper is taken from beneath the negative,
and soaked in pure water, say for twenty minutes; if the negative be very intense,
such as to require ten or more minutes of direct exposure to the sun light, the
soaking should be continued longer, say for about half an hour; this is desirable
because it facilitates the subsequent developing.
The excess of bichromate being removed leaves the whites of a faint yellow tint;
where pure whites are required it becomes necessary to destroy all traces of
bichromate where the light has not acted and which are not easily removed by
soaking; for this purpose the print is immersed in one per-cent solution of acid
sulphite of sodium for one or two minutes.
To prepare the developer, I take of gallic acid two parts, ferrous sulphate three
parts, aluminum and ammonium sulphate three parts, and sodium hypo-sulphite
twenty-four parts, the ferrous sulphate, aluminum and ammonium sulphate and
sodium hyposulphite are each dried separately until free from water of crystalli-
zation, and are then pulverized and mixed with the gallic acid. This compound will
keep and retain all its properties if protected from dampness. Of this composition
I take fifteen grains to each ounce of water.
To develop the print I lay it in a suitable dish, and pour upon it the developing
solution to cover it, say a quarter of an inch in depth, or if several prints are to be
developed at the same time I take enough of the solution to cover all the prints.
While they are in the solution I move them frequently, so as to expose them
equally to the developing solution.

page_text: When the development of the print is completed, which will generally require
about ten minutes, the excess of the developer absorbed by the paper is removed
by soaking the print for half an hour in water slightly acidulated with acetic acid,
after which, and when dry, the picture can be mounted. Its subsequent treatment
may be substantially that usually applied to photographic prints.
The sodium hypo-sulphite and alum in the developer, exert a reducing action,
which prevents the ferrous salt from becoming oxidized readily when in solution
and exposed to the air, and enables the bath to be used repeatedly for several days,
if, after use, the precaution is taken of putting it in a tightly corked bottle, which
should be filled by the solution.
Any color from black to brown can be obtained after soaking out the developer,
by immersing the print from one to five minutes in a bath composed of one part
taken from the sensitizing bath and two parts of water, the time of contact with
the bichromate determining the shade, and after such treatment soaking in water
until the yellow tint is entirely removed:a.
If desired to change the color of a print to reddish brown, I subject it, after
development, to a bath composed of a solution of carbonate of soda, (one ounce of
carbonate to one quart of water,) and dry immediately.
In case it is necessary to bleach the picture, it should be done after development,
and before any change of color is effected, and may be well done by subjecting the
print to a solution of one part of citrate of ammonia in twenty parts of water.
The paper may be prepared for sensitizing by any of the known processes, but I
obtain a very good result from the following treatment that is to say, I take paper
of a good quality, coat it with a mixture composed of starch seven parts, white
sugar two parts, glycerine two parts, boiling water two hundred parts, and solution
of pure caustic potash sufficient to cause the coating to dry with an even surface,
which will require about one-fourth part potash; the first three ingredients are
mixed with a little cold water, and then stirred into the boiling water. The
coating is applied by floating the paper upon the mixture in the manner usually
employed in the application of albumen to paper. After drying, the paper is
dipped in a two per-cent solution of acetic acid, and water, and when again dried
it is ready for use. In cases where the intensity and appearance of the print is of
little importance, paper may be used without this treatment. Albumen paper does
not under this improved process produce so good results, chiefly on account of its
density.
From experiments it is believed the proportions for the sensitizing and develop-
ing baths above given, produce the best results, but these proportions may be
varied to some extent without departing from the nature of this invention.
By this process photographic prints are produced fully equal to those produced
by the employment of silver, and it will be evident that the cost of the production
is very much less than by the usual process employing nitrate of silver.
The printing is also more rapid than by the usual process, and colors may be
more readily applied to the print than when the print is prepared under the usual
process.
Having thus fully described the said invention, as communicated to me by my
foreign Correspondents, and the manner of performing the same I wish it understood
that I claim.
First The improved process of sensitizing paper for photographic printing,
consisting in subjecting the paper to a bath composed of potassium bichromate,
magnesium sulphate, and mercuric chloride, in the proportions substantially as
described.
Second-The improved process of developing pictures printed upon sensitized
paper, consisting in subjecting the print to a bath composed of gallic acid, ferrous
sulphate aluminum and ammonium sulphate, and sodium hyposulphite, in the
proportions substantially as described.
Third-The improved process of sensitizing paper for photographic purposes, and
developing pictures thereon, consisting in subjecting the paper upon which the

page_text: print is to be made to a bath composed of potassium bichromate magnesium
sulphate, and mercuric chloride, and then, after printing, to a bath composed of
gallic acid, ferrous sulphate, aluminum and ammonium sulphate and sodium'
hyposulphite, in the manner, and the said baths in the proportions, substantially
as described."
t
In witness whereof I the said William Robert Lake have hereunto set my
hand and seal this seventeenth day of August in the year of our Lord One
thousand eight hundred and eighty three.
W ROB LAKE (L.S.)