Photographic Printing.
Year: 1886

page_text: Photographic Printing.
I HENRY HARRIS LAKE of the firm of Haseltine Lake & Co .Patent Agents
Southampton Buildings in the County of Middlesex do hereby declare the nature
of this invention and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement:―
This Invention relates to improvements in Photographic printing and consists
in the improvements hereinafter described.
According to the said invention I first, sensitize 'the paper. To produce the best
results the paper is first coated upon both sides with a starch solution.
The sensitizing solution is prepared from the following formula :-
Potassium-bichromate: two parts.
Mercuric chloride: one part.
For convenience this may be in the form of powder.
:-
For the bath, take pure water according to the size of the bath, and to each
ounce of water add fifty grains of the above mentioned compound, and thoroughly
dissolve the same. The paper is immersed in the bath so as to wet both sides of
it for a period not exceeding one minute.
Care should be taken to protect the paper, during and after the sensitization,
from chemically active light as it is more sensitive than paper prepared under the
usual process for photographic printing.
The paper is dried by artificial beat, but coal-gas or kindred vapours should be
avoided as injurious to the surface. The paper thus sensitized should be used the
same day to secure the best results, but it may be kept for several days in a dark
cool, damp place.
The potassium-bichromate and mercuric-chloride may be combined and prepared
in mass, and sold as a sensitizing compound.
After the paper has been properly dried, it is printed upon by exposure to light
under a negative, in the usual manner.
The photographic prints thus produced are of a yellow color.

page_text: After washing the prints in clear water, they are subjected to a developing bath,
composed of a solution of the following compound in water. The said developing
compound consists of pyrogallol two parts, Gallic acid eight parts, ferrous sulphate
(dried), or other ferrous salt soluble in water, ten parts, sodium hyposulphite
(dried) eighty parts.
This compound is prepared in mass, and sold for use when required.
The solution is made by dissolving the compound in water in the proportion of
two per cent of the compound to the water.
By employing the pyrogallol in the solution, the color which is produced may be
changed to a brown or any intermediate shade, by subjecting the prints to a toning
bath, containing lead nitrate. Without the Pyrogallol a violet black is produced
by an aqueous solution of the three other ingredients, but the colour is not subject
to change in the toning bath.
The ferrous salt referred to is preferably ferrous sulphate, but ferrous tartrate is
sometimes used, or other ferrous salt, or these salts are produced in the bath by
adding to the compound an alkaline tartrate &°.
The advantage in substituting other iron salts for the sulphate is that by so
doing the color developed may be varied within certain limits, according to the
ferrous salt used, and the proportion of pyrogallol, from the violet black produced
by the sulphate alone, to a warmer tone, using the toning bath only when it is,
necessary to obtain well marked browns.
The print should be left in the developing bath from five to ten minutes, and
then removed from the bath, then washed in clear water. It may then be
bleached by the action of a dilute solution of chlorine or bromine the bleaching
action of the halogens should be modified by the presence of an acid, as it is then
more even.
The chlorine bath is best prepared by dissolving one part of calcium-hypo-chlorite
in three hundred parts of water and adding about two parts of an acid, preferably
phosphoric acid.
After the prints have been bleached, they may be mounted in the usual manner,
or if a brown color is desirable, they are toned by subjecting them to a bath
consisting of a one or two per-cent solution of lead-nitrate or a mixture of
potassium or sodium nitrite and lead-nitrate, but should a cold grey be preferred
to the brown, from 2 to 5 per cent of mercuric-chloride is added to the toning
bath. The prints are then washed in clear water.
'
The proportions mentioned for the ingredients in the several compounds and
baths, are such as in practice have produced the best results, but they may be
varied somewhat without departing from the invention.
It should be stated that in order to obtain the best results the paper should
possess a considerable degree of porosity, and be thickly coated with starch on both
sides of the paper, and the paper should be free from alkaline particles.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondents I declare that what I claim is:-
E
-
First: The improved compound for sensitizing paper for photographic printing,
consisting in the combination of Potassium Bichromate and Mercuric Chloride, in
the proportions substantially as described.
Second-The improvement in the process of photographic printing, consisting
in subjecting the paper to be printed upon to a bath composed of Potassium
Bichromate and Mercuric Chloride in the proportions substantially as described.
Third: The improved composition for a bath for the development of photo-
graphic prints, which are obtained by the action of light upon paper sensitized
with Potasium Bichromate and Mercuric Chloride, said composition consisting of
Pyrogallol, Gallic-acid, a Ferrous salt soluble in water, and Sodium Hyposulphite,
in the proportions substantially as described.

page_text: Fourth: The process herein described for developing photographic prints, which
are obtained by the action of light upon paper sensitized with Potassium Bichromate
and Mercuric Chloride, consisting in subjecting the print to a bath composed of a
two per-cent solution of Pyrogallol, Gallic-acid a Ferrous salt soluble in water and
Sodium Hyposulphite in the proportions substantially as described.
Fifth The herein described improvement in bleaching photographic prints,
consisting in subjecting the prints to a solution of Calcium-Hypochlorite and
Phosphoric acid in the proportions, substantially as described.
Sixth-The herein described improvement in toning photographic prints, which
are produced by the action of light upon paper sensitized with Potassium-
Bichromate and Mercuric-Chloride, where a cold grey color is desired, consisting
in subjecting the prints to a toning bath composed of a solution of Lead Nitrate
and Mercuric Chloric, in the proportions substantially as described.
HASELTINE, LAKE & Co.,
Agents for the Applicant.