Improved Process for Covering Zino Plates with a Layer of Material in Imitation of Lithographic Stone.
Year: 1898

page_text: Date of Application, 23rd Dec., 1898-Accepted, 18th Dec., 1898
COMPLETE SPECIFICATION.
Improved Process for Covering Zino Plates with a Layer of Material
in Imitation of Lithographic Stone.
I, JULIUS WEZEL, of 17, Dresdnerstrasse, Leipzig, in the Empire of Germany,
Manufacturer, 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:-
-
This invention for an improved process for covering zinc plates with a layer of
material in imitation of lithographic stone relates to improvements in the process
described in a prior Patent No 3305/85, for the production of a layer of material
on metal plates as a substitute for lithographic stone In the practical use of
the plates to which the process described in the patent referred to was applied,
it was found that the prepared laver on becoming discolored or soiled, could only
be partially remedied by the employment of aluminium palmitat and asphalte
(British Patent 12890/91), as the discolouring could only be prevented in respect
of small pintings but not with very large ones. The cause of this discoloration
was to be attributed to the quantity of fatty and resinous matter contained in the
substance sprinkled on the zinc plates and which caused the ink to be taken up
by those parts of the plate on which there was no drawing On the other hand,
however, it was not found possible to dispense with these additional materials
which favour discoloration, as it was by means thereof that the laver of material
was formed on the zinc plate.
Experiments made with the object of dispensing with these materials led to the
discovery that it is possible to form a layer composed of mineral matter only,
provided that the zinc plate be covered with a coating of some oxule previously.
According to this invention the desued result 18 secuted if the zinc plate, after
being cleaned, is either laid during a period of fiom 6 to 8 hours at the ordinary
temperature in an aqueous solution (about 10 per cent) of bi-carbonate of potassium
or is subjected to the action of a galvanic curient in a 2 to 3 per cent solution
of the same salt In this way, the plate is covered with a firm white laver of
carbonate of zinc which deprives the edges of the sharpness produced by the grains
of sand or emery, and to which the layer of material, now sprinkled on, firmly
adheres.
The solution suitable for this latter operation 18 produced by decomposing
limestone with 2 to 3 per cent of aluminium by means of muriatic acid and
sulphuric acid The correct proportions are:-
Limestone
Muriatic acid-
24 kilos
3
"

page_text: of the same composition as lithographic stones Thereupon, the paste produced
is freed from any remaining stones by the pouring on of water, and poured
through a sieve The remaining mass is now purified of any residuary acid by
frequent washings with water, the residue being thereupon placed in a cloth.
This cloth is twisted round like a ball and squeezed under a press, so that the last
of the water escapes and a thick mass remains The resulting thick mass is
well mixed with a weak solution of soda before it is blown on to the zinc plate by
means of an injector In order to secure a yellow tone similar to the natural
lithographic stone, a small quantity of chloride of iron is added to the mass before
its dilution with the soda solution
It should be mentioned that the oxide layer alone is quite suitable for printing
small impressions as well as for the production of original lithographs and
preservation of the same.
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 18:
'
Process for covering zinc plates with a layer of material in imitation of litho
graphic stone, this being effected by the application in a finely divided form of a
mixture of sulphate of lime, calcium chloride, and aluminium oxide, mixed
with a weak solution of soda to the plates, which are previously covered with an
oxide layer.
Dated this 23rd day of December 1898
at
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W C., Agents.