Popatiates fographic rurposes.
Year: 1887

page_text: Popatiates fographic rurposes.
We, CARL SALCHER of Harland Province of Lower Austria in the Austrian
Empire, Director of a Cotton Mill and HEINRICH SCHWERTSCHLAG of Harland aforesaid,
Foreman in a printing office 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 following statement :-
--
In consequence of the costliness of natural lithographic stones, attempts have been
made to substitute for them artificial stones or metal plates coated with a layer of
carbonate of lime, which offer the advantage of being cheaper and of being made of
any desired form or size.
These artificial plates are objectionable on account of the design transferred to them
often being indistinct and in certain cases not adhering to them.
Very skilful operators are therefore required to treat such artificial plates with the
greatest care in order that the transferring of the design and the subsequent etching
may be successful.
Our invention has for its object to obviate these inconveniences.
According to our invention, the metal plates intended for use are, first etched, then
coated with slaked lime, allowed to dry, brushed off and finally treated with a solution
of alum and washed. They can then be treated like lithographic stones but after
every grinding, and before transferring another design upon them the treatment
above described must be repeated.
As zinc plates are generally used, we will describe the practical application of our
process to them.
The plate is first etched with an aqueous solution of about 3 per cent. of nitric acid
whereby its surface is slightly roughened; it is then coated with slaked lime and
allowed to dry in a well ventilated apartment. Owing to the action of the air upon
the coating of slaked lime, some carbonate of lime is formed, which firmly adheres to
the surface of the plate and remains fixed to it after the dried plate is brushed. A
single coating of carbonate of lime is sufficient to ensure a good transfer of the
design, but the coating of carbonate of lime may be thickened by repeating the
application of slaked lime, drying and brushing off.
гр

page_text: Before transferring the design to the plate, the latter is to be washed with a strong
solution of alum, whereby a small quantity of alumina is added to the coating of the
plate, so as to render the coating more capable of absorbing fatty substances. The
plate is then carefully rinsed with water and is ready for the transfer, the process
being the same as with lithographic stones.
For etching, a mixture of 100 parts of liquid gum, 150 parts of water and 20 parts
of nitric acid may be used with advantage, and after every etching the plate is to be
washed with a mixture of 100 parts of gum and 10 parts of phosphoric acid and then
allowed to dry.
When corrections are to be made on the etched plate it is "necessary, to apply to it
a solution of 20 parts of alum in 2000 parts of water, to which 5 parts of acetic acid
are added.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is
The herein described process for preparing metallic plates for lithograpic nurnoses.
ABEL & IMRAY,
Agents for the Applicants.