Improvements in or relating to the Production of Photo-lithographic Printing Plates.
Year: 1899

page_text: Date of Application, 15th Dec., 1899-Accepted, 3rd Mar., 1900
COMPLETE SPECIFICATION.
Improvements in or relating to the Production of Photo-lithographic
Printing Plates.
I, HERMANN SCHMIEDER, Manufacturer, of 149, Grays Inn Road, London, W.C.,
do hereby declare the nature of this invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and by the follow-
ing statement:-
My invention relates to a new or improved method of transferring photographic
pictures from negatives directly to lithographic stones, zinc-copper--aluminium
and other metal plates, in such manner as to produce upon said surfaces in a
few hours and with comparatively little trouble, a perfect positive copy of the
negative, ready for reproduction by lithographic printing.
The picture transferred to the stone or plate by the new method will appear in
print in one single pull in various graduated depths of tone, and the printed copy
will reproduce all details and light effects of the photographic negative so as to
give a perfect reproduction of the original of far greater artistic merit and
naturalness than can be obtained by other known processes or can be drawn by a
lithographic artist with long and close application and labour.
In other processes for reproducing photographs by printing, dots, lines and
various forms of graining and the like are used for producing the picture and its
shadings and tone effects, while by the method forming the subject of the
present invention the picture with all its details and light effects is reproduced
by gradual blending of the various depths of tone whereby a better and more
artistic effect is obtained, fully equal to that of the photo-collotype or heliotype
process. The plates produced by the latter and various similar processes rarely
yield more than about five hundred good impressions, even under most favourable
conditions, on the other hand a stone or plate prepared in accordance with this
invention, will easily give as many thousand perfect copies, without the details
of the picture and its luminous effects being in any way impaired.
In preparing the lithographic stone or metal plate for carrying out the new
process of imprinting thereon a picture or the like from a photographic negative,
the surface is first roughened or grained, preferably by means of very fine sand
blast, in order to obtain a uniform fine grain; it is then carefully dusted and
washed with a weak solution of nitric acid. The stone or plate is now warmed
and its surface coated with a weak solution of isinglass or other suitable gelatinous
substance, which coating is allowed to dry in a temperature of about
100° Fahrenheit.
100° Fahrenheit.
A solution consisting of
2000 weight units of distilled water,
20 weight units of albumen, and
10 weight units of saccharic acid

page_text: 15 weight units of bichromate of ammonium and
7 weight units of bichromate of potassium
equal quantities are mixed, and some of the mixture is poured over the prepared
surface, the plate or stone is then placed in an upright position to allow the
superfluous liquid to drain off.
When the film is thoroughly dry, the photographic negative is placed upon it
and the exposure is made. With a good light of normal intensity from 10 to 15
minutes will be required for completing the exposure.
The surface is then rolled with a specially prepared ink applied to a stiff roller.
The said ink comprises the following ingredients: -suitable proportions of lamp
black, wax, Venetian turpentine, lithographic ink, and a few drops of oil of
lavender are melted together, well mixed, and ground up with small quantities of
finely powdered asphaltum, colophony, or resin and pure beef fat.
The picture is thereupon developed by lightly passing over it a sponge saturated
with water until the picture shows clearly, when the surface is carefully cleaned
and covered with a coating of dissolved gum arabic for the purpose of protecting
it from impurities and dust.
The gum arabic is subsequently washed off and the ink is removed by the aid
of turpentine, whereupon the surface is washed with dilute nitric acid in order
to decompose the sensitive film. The surface is then, while being kept wet with
a weak salt water solution, rolled up with strong ink until the picture shows well,
and any necessary retouching may now be performed in lithographic ink or the
like.
Finally the surface is subjected to the known acid treatment as usual with
lithographic chalk drawings, and the stone or plate is then ready for the ordinary
lithographic printing process.
It will be observed that the picture is now on the stone or metal surface itself,
the sensitive film or coating having been destroyed by the decomposing process
as described, after having served to receive the impression of the photographic
negative.
One stone or plate is sufficient for producing a perfect monotone in several depths
of tone, gradually blending with each other, from negatives taken from nature, or
from Indian ink, wash or other drawings, etchings and like originals, with all
and every detail and graduation of light effects, while three or at most four stones
or plates will be required for reproducing originals in colours.
It is to be understood that the proportions of the ingredients given above are
not to be considered as absolute, but they may be varied within reason, and in
some cases equivalents may be employed for one or more of the materials, and
also in the case of the ink, where coloured inks are required, suitable colouring
substances may be used instead of the black ingredients described.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1. The method of transferring photographic pictures from negatives directly to
lithographic stones or metal plates, ready for reproduction by lithographic print-
ing consisting in coating the surface of the stone or plate with a sensitive layer
or film, imprinting thereon the negative by exposure to light, treating the
impressed film or layer with special ink, and subsequently destroying the said

page_text: layer or film by chemical decomposition, substantially as and for the purpose set
forth and described.
2. In transferring photographic pictures from negatives directly to lithographic
stones or metal plates as claimed in Claim 1, the composition and preparation of
the sensitive film or layer, substantially as described.
3. In transferring photographic pictures from negatives directly to lithographic
stones or metal plates, as claimed in Claim 1, the application, composition and
preparation of an ink or colour for imprinting the picture on the surface of the
stone or plate substantially as described.
4. An improved production of photo-lithographic printing plates substantially
as described.
Dated this 15th day of December 1899.
BOULT, WADE & KILBURN,
Agents for the Applicant.