Improved Method of Producing an Even Silver Ground for Underlaying Enamel.
Year: 1896

page_text: Date of Application, 15th June, 1896-Accepted, 26th Sept., 1896
COMPLETE SPECIFICATION.
Improved Method of Producing an Even Silver Ground for
Underlaying Enamel.
We, CARL COWEN SCHIRM, Artist, of 51 Königin-Augustastrasse, and ALBERT
SILBERMANN, Manufacturer of 74 Blumenstrasse, both of Berlin, Germany, do
hereby declare the nature of our invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:
Hitherto it has only been possible to underlay transparent enamel with silver
leaf, in order to increase its illuminative powers, on a very small scale, owing to
the fact that with larger surfaces, the size employed to attach the silver leaf to the
backing, when fired rises up forming blisters and creases in the leaf. This produces
a pretty and lively effect in the case of small surfaces but prevents the manufacture
of uniform surfaces of larger area.
Then large surfaces cannot be coated with this class of enamel, because the thin
copper plate forming the back of the same warps, when fired, forming blisters, so
that it is not possible to attain even surfaces, which could be fitted together to
form a whole.
The employment of thick copper plates is impossible because the same expand
to such an extent when heated that they entirely ruin the enamel, cracking the
same even at ordinary temperatures.
The object of the present invention is to produce an even silver coating for
underlaying transparent enamels, formed on plates, which will not warp at the
temperature necessary for firing the enamel, and whose expansion and contraction
is so slight, that it is not sufficient to crack the enamel.
In carrying out our invention, we provide a cast iron plate with an enamel
backing, and then provide the same with a coating of binding material or size,
such as gum or the like, on which the silver leaf is placed, prepared in the manner
hereinafter described. The silver leaf sheet is laid on a piece of fine wire netting,
covered with cloth and then a thick sheet of caoutchouc is covered over the same
and the whole subjected to a high pressure in a suitable press. Thus the caoutchouc
will press the silver leaf into the interstices of the wire netting forming in the leaf
innumerable fine rents or cracks. If the silver leaf is now placed on to the plate
which is covered with the size, the products of combustion of the latter when the
whole is fired, will pass off through the cracks in the silver leaf, which melts
without forming blisters and forms a surface corresponding to the wire netting,
i.e. an uniform grained surface The curvature of the parts or "grains," so formed,
produces great brilliancy and is well adapted to receive the transparent enamel.
The cast iron does not warp even when fired several times, it expands so slightly
and so slowly when heated that the enamel will not crack and it cools so slowly
that the enamel is rendered stronger and less liable to crack as is the case with
well cooled glass.
"
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
A process for producing an uniform silver ground for underlaying enamel on a
backing which will not warp when subjected to high temperature, and which only
expands and contracts very slightly, which consists in pressing a sheet of silver

page_text: leaf on a wire netting or other uneven surface, so as to perforate said leaf, and
then applying the leaf thus perforated to the cast iron backing melting the same
and applying enamel substantially as described and for the purpose specified.
Dated this 15th day of June 1896.
BOULT & WADE,
Agents for the Applicants.