IMPROVEMENTS IN PHOTOGRAPHY
Year: 1857

page_text: LETTERS PATENT to Charles Cowper, of No. 20, Southampton Buildings,
Chancery Lane, in the County of Middlesex, Patent Agent, for the
Invention of "IMPROVEMENTS IN PHOTOGRAPHY."-A communication from
PROVISIONAL SPECIFICATION left by the said Charles Cowper at the
Office of the Commissioners of Patents, with his Petition, on the 12th
December 1857.
I, CHARLES COWPER, of No. 20, Southampton Buildings, Chancery Lane, in
the County of Middlesex, Patent Agent, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN PHOTOGRAPHY," to be as follows:-
In the ordinary photographic processes the image is produced by the action
of light upon a salt or compound of silver, but in the present Invention the
image is produced by finely divided carbon or other pigment, which is not or
need not be sensitive to the action of the light, but which is fixed upon tbe
paper or other surface or medium by a preparation which is acted upon by
light. A solution of bichromate of potash or ammonia is mixed with gelatine,
and the paper is immersed in or floated on the solution which is used warm or
hot. The paper is then dried, and its surface is covered with the pigment,
which may be applied in various ways. Thus the pigment may be rubbed
over the dry surface with a pad of leather or cloth or other suitable material.

page_text: This mole of application may be employed with plumbago, so as to imitate
pencil drawing or lithography; or lamp black or other pigment may be ground
up very fine with nut oil or other oil, and rubbed over the surface, which is
subsequently immersed in a bath of ether, to which a little collodion may be
added; or the paper may be immersed in a bath of indian ink or other pig-
ment ground up very fine with water and mixed with gelatine and a little gum
or dextrine, and used hot; or rollers or presses or other apparatus may be
employed to apply the pigment or assist the operation. The paper having
been prepared in the dark or by yellow light is exposed in the usual manner
in the camera or in a printing or copying frame, or otherwiso. It is then
washed in hot water which dissolves the gelatine which has not been acted
upon by the light, but does not dissolve that which has been rendered insoluble
by the action of the light, and which insoluble gelatine retains the pigment,
and thus produces the image. Various pigments may be employed, and
different coloured pigments may be applied on different parts of the paper,
so as to produce particular effects. The image may be produced on
glass or on collodionized glass or other surfaces as well as paper, and
both positives and negatives may be produced; finely divided gold or
silver or other metals may be employed as pigments in this manner. By
employing carbon or other pigments not acted upon by the atmosphere,
photographs or pictures of the greatest permanence and durability may be
obtained.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Cowper in the Great Seal Patent Office on the 4th
June 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
COWPER, of No 20, Southampton Buildings, Chancery Lane, in the County-of
Middlesex, Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twelfth day of December, in the year of our Lord
One thousand eight hundred and fifty-seven, in the Twenty-first year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Charles Cowper, Her special licence that I, tho said Charles Cowper, mỹ
executors, administrators, and assigns, or such others as I, the said Charles
Cowper, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during the
terin therein expressed, should and lawfully might make, use, exercise, and

page_text: vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN PHOTOGRAPHY,"
communicated to me from Testud de Beauregard, of Paris, in France, upon
the condition (amongst others) that I, the said Charles Cowper, my executors
or administrators, by an instrument in writing under my, or their, or one:
of their bands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the said.
Letters Patent.
NOW KNOW YE, that I, the said Charles Cowper, do hereby declare the.
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:-
The Invention relates to the production of photographic images, pictures,
or proofs, without salts of silver. For this purpose carbon or other pigment
is employed, and it is fixed on the paper or other surface by means of a pre-
paration which is acted upon by light. If gelatine or gum be added to a
saturated solution of bichromate of potash or ammonia, and the mixture after
being dried is exposed to solar light, the gelatine or gum is rendered insoluble
in water. If, before exposing the mixture to light, an insoluble colouring
material is added to it, such as carbon or black lead for a black colour,
vermillion or carmine for a red colour, indigo for a blue colour, or other
pigments or mixtures of pigments, the result is, that when the mixture is
exposed to light and thus rendered insoluble, the colouring matter or pigment
is imprisoned or retained by the mixture and rendered indelible. When such
a preparation is exposed to light under a photographic negative or other trans-
parent or partially transparent picture, and is afterwards washed with water,
the pigment becomes fixed at those parts where the light acts upon it, but is
removed by the water from the parts which are shielded from the light, so
that the picture is reproduced in a similar manner to that in which pictures
are reproduced by the ordinary photographic processes with chloride of silver.
This mode of proceeding is not new, but in applying this principle in practice
there are certain difficulties to be overcome: Thus, it is necessary to preserve
the whiteness of the paper in the whites of the picture, and to prevent the
adhesion or fixing of the pigment or colouring matter in the parts which have
not been exposed to light, and also to employ the pigment in an extremely
fine state of division, for in the ordinary photographic processes the molecules
of silver may be said to be in an infinitely fine state of division. It is also
:

page_text: necessary that the particles of colouring matter should be spread as uniformly
as possible upon the surface of the paper, and to give to the last operation of
the washing a liberty of action, such that the molecule or particle of pigment
which is not fixed may not carry off with it by its proximity or adherence the
neighbouring molecules, which ought to be fixed by the action of the light. A
saturated solution of bichromate of potash is heated in a water bath, and a
quantity of gelatine is dissolved in it. For one quart of the saturated solution
of bichromate of potash, from one ounce and a half to three ounces and a
quarter of gelatine may be employed, or in lieu of gelatine from ten ounces to
sixteen ounces of gum arabic with a slight addition of albumen may be
employed. I do not however confine myself to the above-mentioned propor-
tions, as they admit of considerable variation according to the quality of the
gelatino and the degree of sensitiveness required, a strong solution requiring
less exposure to light than a weak one. The strength or density of the
solution or chromo-gelatine should be such that it is syrupy at a temperature
of one hundred and forty degrees of Fabrenheit's thermometer, and becomes
solid or gelatinous when cold, and does not crystallize in cooling, and affords a
film or thickness of the mixture on the surface of the paper immersed in it.
This mixture or bath is used hot or warm, and the paper is either entirely
immersed or floated on the surface. The immersion may vary from two to six
minutes, according to the intensity of the light and the season of the year;
the more powerful the light, the stronger may be the solution and the longer
the immersion. The paper after removal from the bath is suspended in a hot
and dry place until quite dry. All these operations must be performed in the
dark or by artificial or yellow light. The carbon or other colouring matter or
pigment is now to be applied to the prepared paper. The colouring matter
being insoluble, the perfection and delicacy of the proof will depend on the
application of the colouring matter in an extreme state of division. The pre-
paration of the paper therefore consists of two operations, first, the application
of the chromo-gelatine to the paper, and second, the application of the
colouring matter, not to the surface of the paper itself, but to the surface of
the layer or film of chromo-gelatine on the paper, by which means the proof
admits of being perfectly cleared or cleansed as herein-after described. The
colouring matter may be applied in various ways, by the dry process or the
greasy process, or by the wet process. By the dry process the dry coated
sheet of paper may be rubbed mechanically with the colouring matter spread
upon a pad or rubber of cloth or leather; this method is particularly adapted
for the application of pluinbago or black lead.
moistening the rubber or pad' with alcohol.
The operation is facilitated by
The colouring matter ought to

page_text: be spread as uniformly as possible. By the greasy process, carbon or ivory
black or lamp black or other suitable pigment is ground up very fine with nut
oil or other suitable oil, and applied to the coated paper by a pad or dabber.
As soon as this mixture has been uniformly applied to the paper, it is
immersed very quickly in a bath of sulphuric ether, either alone or with a
slight addition of collodion. This last mixture has the effect of drying the
paper or removing the oil, and of causing the colouring matter to adhere to
the surface. By the wet process a bath is employed composed of carbon or
indian ink very finely ground with water and gelatine, and a small quantity of
gum arabic or dextrine. The coated paper may be immersed from ten
minutes to three quarters of an hour in this bath, according to thickness
of the film or layer which is desired; this bath containing gelatine is employed
warm or hot. A bath of indian ink with alcohol added to it gives good
results when the paper is removed rather quickly from it. As in other
photographic processes, practice and skill in manipulation enable the operator
to obtain superior results. Mechanical means, such as presses or rollers, may
be employed to facilitate the operations. Thus, the mixture of carbon and oil
may be applied by inking rollers instead of employing a dabber. As the
object of the paper is to form a support for the chromo-gelatine, other
materials or surfaces may be employed for this purpose. Glass, or collodion-
ized glass, may thus be employed and conted with the chromo-gelatine and
afterwards with the colouring matter, and thus transparent pictures and
negatives may be produced. Ivory, wood, and other materials may also be
used in lieu of paper. The paper or other surface having been prepared in
the dark, as above described, is then exposed to sunlight or daylight, or other
light of sufficient chemical power, either in the camera obscura or in contact
with or in close proximity to a photographic negative or other article to be
reproduced, in the same manner that ordinary photographic paper is employed.
The duration of the exposure to light varies with so many circumstances that
no rule can be laid down, but it is easy to ascertain the necessary time by
exposing pieces of of the prepared paper to light for several different lengths of
time, and noting which gives the best result. After exposure to light, tho
proof is fixed and cleared by simply washing it in hot water, either with or
without friction by a brush or sponge. The water dissolves out the gelatine
or guin which has not been acted upon by the light, and washes away the
colouring matter from those parts which constitute the lights of the picture,
while the parts which have been acted upon by the light remain undissolved,
and retain the carbon or colouring matter. The proof may thus be con-
sidered as an engraving produced by light, and not liable to be acted upon or

page_text: faded by the agencies which injure ordinary photographs. A great variety of
colouring matters or mixtures of colouring matters may be employed in the
manner herein-before described. Gold and silver in the metallic state and in
impalpable powder may be employed in the same manner; various effects
may also be produced by applying different colours to different parts of the
paper or surface. It will be seen that the paper or other surface is always
covered with a layer or film on which the colouring matter is superposed and
fixed. When the colouring matter is mixed with the chromo-gelatine, and
applied at once to the paper, it is very difficult or impossible to wash it off, so
as to leave the lights of the picture clean and white. The application of the
carbon or colouring matter by superposition in the manner herein-before
described is intended to obviate this defect.
Having now described the nature of the said Invention communicated to
me, and in what manner the same is to be performed, I wish it to be under-
stood that what I claim is, the mode or modes herein-before described of
producing photographic proofs or pictures by means of carbon or other
colouring matter applied by superposition as herein-before described.
In witness whereof, I, the said Charles Cowper, have hereunto set my
hand and seal, this Fourth day of June, in the year of our Lord One
thousand eight hundred and fifty-eight.
CHARLES COWTER. (L.S.)