A New or Improved Process of Treating Metallic Plates Used for Lithographic Printing.
Year: 1896

page_text: Date of Application, 29th Feb., 1896-Accepted, 11th Apr., 1856
COMPLETE SPECIFICATION.
A New or Improved Process of Treating Metallic Plates Used for
Lithographic Printing.
I, EDWARD GRIFFITH BREWER of 33 Chancery Lanc, in the County of
London, and 30 East Parade, Leeds, in the County of York, Fellow of the
Chartered Institute of Patent Agents, do hereby declare the nature of this
invention (a communication to me from abroad by The "Societe Anonyme des
Plaques Lithographiques" of 7 Rue d'Egmont, Brussels, Belgium) and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
This invention relates to metallic plates, so prepared as to be used as a substitute
for the well known stones, employed in lithographic printing.
The stones commonly used in this special branch of printing, are costly, heavy,
and bulky. Many attempts have been made in the way of replacing them by light
metallic plates, but the results obtained heretofore, have never been satisfactory.
Such metallic plates could only be used for hand printing, but were useless for
mechanical printing, and it was impossible to rub out, or to retouch the drawing
on these plates, and it is well known that this operation is often necessary and
frequently practised on lithographic stones.
Now this invention has for its object, to remedy these inconveniences, and it
consists in so preparing the plates, that the draughts-man can work on these plates,
exactly in the same conditions as upon lithographic stones.
The process of treating the plates according to this invention is as follows-
The metallic plate is first cleaned by means of diluted hydrochloric acid (10 parts
acid to 1000 parts water, in weight) in order to eliminate any greasy substance
which may remain on its surface. The plate is then dried, and suitably grained by
any of the known means, the grain being very fine for pen drawings, and coarser
when intended to receive crayon work.
When the plates are to be used for photolithographic printing, they are
thoroughly smoothed instead of being grained.
The plate baving been treated as above, is then washed, dried and, during the
drying, the following composition is applied on its surface.
Zinc white
Hot water
Silicate of potash
5 parts in weight.
"
"
130 " "
"
1800
When the water is evaporated, the remaining substance is an excessively thin
coating, composed of zinc white and silicate, which strongly adheres to the
plate. This coating is suitably smoothed when its surface is not sufficiently
smooth; to this end the plate is moistened with water and brushed.
After this operation the plate is ready to receive the stone composition which
consists of
Water-
Pure powdered lithographic stone
Bicarbonate of soda
Silicate of potash.
-
100 litres.
1500 grammes.
450
"
130
100
ConsistS OF
Water-
Pure powdered lithographic stone
Bicarbonate of soda
Silicate of potash
Albumen
Perchloride of iron
100 litres.
1500 grammes.
4.50
"
130
"
100
وو
75
"

page_text: gentle heat, so that the water is evaporated, and a solid coating remains on the
surface of the plate. This conting has exactly the same colour, and the same
qualities as the ordinary lithographic stones.
When it is desired to obtain on the plate, a coating sufficiently thick to be used
for mechanical printing, (either on flat or rotating presses) the above operation is
repeated several times, the surface of each successive coating being thoroughly
smoothed before pouring the subsequent liquid layer.
The plates prepared according to this process, may be curved without any risk
of injuring the conting. The drawings made, or produced, on these plates may
furnish easily from 30,000 to 40,000 prints, with any of the ordinary inks, or
colours, used for lithographic printing.
The drawings may be easily retouched by using a mixture of 90% benzine
with 10% sulphuric ether which easily takes off the lithographic ink or crayon.
It is to be observed, that the proportions of the substances used in the
application of this process, may vary without departing from the invention. Any
of these substances may be replaced by others having similar properties, for instanco
either salts of soda, or potash, may be used, ie, silicate of sola, instead of silicate
uf potash, etc.
Having now particularly described, nud ascertained the nature of the said inven-
tion, and in what manner the sa:ne is to be performed, I declare that what I
claim is as follows-
1st. The process of preparing metallic plates for lithographic printing, which
consists in pouring on the cleansed, or grained, or smoothed plates, two successive
compositions, the first of which is a mixture of water with white zinc aml silicate of
potash, and the second, a stone composition containing lithographic stone,
bicarbonate of soda, silicate of potash, albumen, and perchloride of iron,
substantially as and for the purposes set forth.
2nd. As a new article of manufacture, the metallic plates covered with the
contings, obtained by means of the above specified mixtures, and by the process
described in the foregoing Specification, substantially as, and for the purposes set
forth.
Dated this 29th day of February 1896.
BREWER & SON,
London and Leeds, Agents for Applicant.