The Manufacture of Zinc Plates for Use in Zincography and the like.
Year: 1899

page_text: Date of Application, 15th Dec., 1899 -Accepted, 24th Feb., 1900
COMPLETE SPECIFICATION.
The Manufacture of Zinc Plates for Use in Zincography and the like.
I, ROBERT BOLTON RANSFORD, of 41, Waldegrave Road, Upper Norwood, in
the County of Surrey, Gentleman, do hereby declare the nature of this invention
(which has been communicated to me from abroad by la Société d'Edition
Artistique, of 32, rue Louis le Grand, Paris,) and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement:―
This invention has for its object an electrolytic process for the manu-
facture of zinc plates for use in zincography, which are also applicable in
photo chemical and photo lithographic processes.
The main danger of the use of zinc in the various lithographic and photo
lithographic operations rests in the impurity of commercial zinc. This metal
nearly always contains lead, sometimes iron, carbon and arsenic.
Another great fault consists in its lack of porosity. It is for this reason that
lithographic stone which possesses the porosity necessary for the subsequent
operations is preferred; for wetting the surface plays a preponderating part in
these subsequent operations.
If a galvanic deposit be made upon an ordinary zinc plate, this zinc plate is
endowed with the qualities necessary for making a lithographic surface giving
excellent results.
Zinc previously rolled or pressed is grained either by sand or other suitable
material by pressure or mechanically by the sand blast. One may also grain
the plate by acid vapours.
The plate is then submitted to a thorough scouring
with acids or alkalies.
The acid scouring which appears preferable consists in rapidly passing the
plate into water acidulated with 2% of sulphuric or other acid.
Liming or potashing and in general all means known in the galvano-plastic
art may be employed.
The well scoured plate is washed copiously under a large rose and placed in
Pure zinc chloride in plates
in distilled water.
These materials are separately dissolved and mixed together, a small quantity
of ammonia being added in order to clarify the bath, which is filtered. Any of
the baths employed in the galvano-plastic art for zincing metals may also serve
for the preparation of zincographic plates.
The plate of zinc to be treated is placed in the tank as cathode and a similar
plate also scoured serves as the soluble anode.
The source of electricity employed may be a battery capable of generating a
current of sufficient quantity with a small fall in potential or a dynamo electro
machine

page_text: As an illustration, in order to obtain a sufficient deposit on a surface of
1 square metre a current of 18 or 20 ampères with a voltage of 4 or 5 volts
allows a good result to be obtained in 20 minutes when operating in a bath of
90 litres.
These figures vary largely with the resistance of the baths employed and above
all with their composition.
Where multiple baths are employed they are arranged in shunt with a
resistance which may be altered for each bath. A circuit breaker may be inter-
posed in the main circuit in order to prevent the counter electro motive force
of the baths becoming greater than the electro motive force of the source of
electricity in consequence of the polarisation of the electrodes.
In general any arrangement of apparatus in use in electro chemistry may be
used if they admit of a regular deposit being obtained.
Although the galvanic deposit of zinc may be effected very easily upon plates
of ordinary zinc, one may before coating cover the plate with a very thin layer
of red copper, either by dipping or by means of a battery in the usual way.
It is essential to obtain a very thin and uniform galvanic coating of zinc
in order to avoid altering the original grain of the plate, for this grain has
special uses according to its texture. The deposit therefore should be obtained
slowly.
The plate on coming out of the bath appears to be of a dull blueish white
grey. The plate washed with much water in order to eliminate all trace of the
bath, is quickly dried with absorbent paper and placed to dry.
The zinc obtained electrolytically is very pure. It is to sum up the refining
of zinc by an indirect method which gives to it the lithographic qualities and
above all the porosity not present in ordinary zinc. The ordinary pen and
crayon works can be executed on it very easily.
Zinc treated in the manner described above is wonderfully well adapted for
use in photolithographic processes and in particular in the special process of
Y. Gaultier.
It may also be used in lithographic engraving and principally for forming
the matrix plates for printing maps.
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: —
The above described process which consists in electrolytically depositing upon
an ordinary plate of zinc or other metal a layer of pure zinc with a view to the
preparation of zincographic plates.
Doted this 15th day of December 1899