IMPROVEMENTS IN PREPARING AND OBTAINING PHOTOGRAPHIC IMPRESSIONS AND IN THE APPLICATION OF SUCH IMPRESSIONS
Year: 1863

page_text: PROVISIONAL SPECIFICATION left by William Clark at the Office of
the Commissioners of Patents, with his Petition, on the 2nd March
1863. A communication from abroad by Alphonse Louis Poitevin, of
29, Boulevart St. Martin, Paris, Civil Engineer.
I, WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex,
Engineer and Patent Agent, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN PREPARING AND OBTAINING PHOTOGRAPHIC IMPRESSIONS
AND IN THE APPLICATION OF SUCH IMPRESSIONS," to be as follows:-
Permanent or unchangeable photographic impressions have already been
produced by what are termed carbon processes, one of which is based on the
employment of matters of a gummy nature, with the addition of a soluble
bichromate, and the other of a mixture of perchloride of iron and tartaric acid
applied only on glass. These processes, which require the employment of
negatives, are very expensive and incomplete when acting on paper. The
improved processes of this Invention are based on the application of chemical
actions as applied hitherto, or otherwise in taking photographic impressions, by.
means of which I obtain impressions directly on paper, that is to say,
I reproduce a positive image from a positive; I have thus been led to observe
new properties in the surfaces prepared with the mixture above described,
which have entirely solved the problem I had proposed to myself.
Firstly, the paper, when prepared with a mixture of perchloride and tartaric
acid, or their equivalents, after it has been acted on by the light either through
a positive or a negative, coagulates at certain parts only of the mucilaginous
solution containing the carbon or other color. For example, the paper

page_text: prepared and receiving an impression through a positive when plunged in a
solution of caseine (milk for example) with the addition of color, the caseine
coagulates and adheres to the parts of the surface of the paper not acted on
by the light, and retains the mixed color. Thus I obtain a positive image, but
inversely to the positive. If I use a solution of gelatine also containing an
inert color, the gelatine will act on the parts influenced by the light, and thus
form the image. This reaction, however, necessitates the employment of a
negative. It will thus be easy to obtain permanent images on paper or other
surfaces by simply preparing them with the following mixture, viz., about 12
parts by weight of perchloride of iron, and about six parts of tartaric acid, and
allow them to dry in the dark afterwards, producing the impression either
through a positive, if I employ a developing bath of (caseine or albumine), or
through a negative (when employing gelatine); I then plunge them into the
bath containing the coagulating mixture of carbon or other inert color; the
image will then immediately appear; I then wash the sheet in water, and
allow it to dry, and next treat it with water acidulated by means of hydro-
chloric acid, for example, in order to dissolve all the colored salt which has
served for its preparation, and after being again washed in plenty of water,
and allowed to dry, the proof is completed, and will remain permanent if the
color contained by the coagulated substance be a permanent one.
I also
produce designs by superposing layers of different colors; it will thus be easy
to produce facsimiles of cameos, and also imitate the natural colors of objects.
Further, after its treatment in water or other suitable solvent the layer when
partially dissolved in the isolated parts presents a surface the delineation of
which is represented in a very regular manner; I then by the ordinary means
obtain plates either for relief or copper-plate printing, according to the type or
copy adopted. I thus reserve the right of producing this second improvement,
consisting in the application of a primary insoluble layer, and which becomes
insoluble by the action of light either through a positive or negative.
Secondly, the organic soluble matters, which are coagulated, and con-
sequently rendered insoluble in cold or hot water or other liquid when treated
by the mixture of perchloride and tartaric acid, or their equivalents, again
become soluble, either by heat or cold when exposed to the light. I utilize
this property, which has been hitherto neither observed nor employed for
producing on paper or other surfaces images in inert colors, such as carbon or
otherwise. By this action I always obtain a direct impression, that is to say,
the colored parts contained in the organic matter remaining insoluble after the
impression corresponds to the blank or opaque parts of the impressing surface,
the light forming the white on the prepared surface on which it acts. In this

page_text: improved process I employ a positive in order to obtain a positive image every
time that I apply an additional layer of white color on a previously blank
surface. The following is the method of operation:-I cover the sheets of
paper with a uniform layer of gelatine, for example, in solution containing the
color which is afterwards to form the design; from 2 to 3 grains of gelative in
3 ounces water is sufficient, while the quantity of color is regulated in pro-
portion to the intensity of tone to be obtained. When the layer is dry, [
render it sensitive in the dark by treating both sides of the paper with a
solution of perchloride of iron and tartaric acid in the proportion of 3 to 1,
the concentration of said solution varying with the quantity of paper employed,
ordinarily speaking 5 grains of perchloride to 3½ ounces of water is sufficient.
When the sensitive surfaces are dried, the organic matter is insoluble in cold
or hot water, and in order to take proofs, I impress the colored coating by a
positive image (reversed) of the design to be reproduced; or it may be
through the design itself if made on a transparent surface; and when it is
immaterial which position the proof obtained is in. This impression requires
more or less time, according to the opacity or distinctness of the design to be
copied; a few minutes only is sufficient for a positive on glass, and with
sunlight direct. After the impression, the image appears in the rough on the
black shining layer which covers the paper, and in order to develope it
I plunge the sheet into warm water, when all the parts which have received
the action of light will dissolve, and as the impression is produced from the
surface downwards, the half tints formed by the insoluble layers of greater or
less thickness will come in contact and adhere to the surface of the paper, and
cannot be removed by water, as is the case with the gelatine and bichromate
processes. The whites are very pure at those parts where the light has acted
freely on the sensitive coating, that is to say, in the parts which are perfectly
clear, as the organic matter completely dissolves and removes the black when
the surface of the paper appears perfectly clean. The image having been thus
obtained, I allow the sheet to dry; I then wash it in acidulated water, in
order to remove the tint of the sensitive preparation; I then rince it in plenty
of water, and dry it, when the proof will be completely fixed, the color being
contained in the layer of organic matter remains insoluble, and in contact with
the paper.
I also fix and solidify the organic matter after washing it in
acidulated water, either with alum, perchloride of mercury, tannin, or other
body in solution; I also apply these proofs when formed with metallic oxides
or vitrifiable matters on enamels or glass, porcelain or otherwise, to be there
fixed by fusion. After the impression is obtained, I may apply those parts of
the layer corresponding to the lights of the copy, which are soluble on stone

page_text: or metal, in order to serve for inking fatty matters for printing and other
purposes. I also employ the final image obtained on paper, the parts corre-
sponding to the black of the copy of which are covered with organic matters
of gummy nature, and place them on stone, metal, or glass, to serve for inking
fatty matters used for the impressions or for delineating on said surfaces; I also
cause inert matters in the form of a coarse powder to adhere to the organic
matter in order to form a design in relief on the paper, which may be moulded
or applied on any suitable surface to be there fixed. I reserve the right of
making these several applications of the preparations herein described, as also
the special preparation of the paper covered with colored layers suitable either
for sensitive or non-sensitive impressions of this kind.