Process for Reproducing Original Plastic Works.
Year: 1897

page_text: Date of Application, 23rd Apr., 1897-Accepted, 12th June, 1897
Process for Reproducing Original Plastic Works.
We CARL COWEN SCHIRM, Landscape Painter and OTTO LESSING Professor,
both of No. 51 Königin Augusta Strasse 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 :-
Original models of clay and similar substances have hitherto been copied or
perpetuated by forming a plaster of Paris mould on the same and then making a
plaster of Paris casting from the said mould. This process for reproducing
originals particularly when applied to complicated models having intricate and
fine perforations, is extremely difficult and the reproductions often lose much
of the fineness of the original owing to the difficulties experienced in the
reproduction.
In the above process it is necessary to chisel off the mould after the casting has
been allowed to harden which operation requires a great deal of practice and care
notwithstanding which the casting is often broken.
Other known processes for instance that which consists in the employment of
elastic moulds (gelatine glue and the like) has the advantage of enabling several
castings to be obtained from one and the same mould, but at the same time
possesses the. disadvantage that the original has to be covered with an intermediate
coating (siccative or varnish) which tends to destroy the fineness of the surface of
the original. Then again the mould shrinks on hardening to a very considerable
extent, even changing or varying its shape at various points; another disadvantage
of this process is that in moulding isolated complicated figures in standing attitudes,
the mould has to be divided into a great number of parts, which easily readers the
subsequent building up of the same for a later casting, inaccurate.
The object of the present process is to obviate these disadvantages entirely.
According to the present process a closed plaster of Paris mould is moulded on.
to the original and allowed to harden, the original is then removed from the mould
in that the same is chiselled or washed out of the said mould. A mixture consisting
of one part of plaster of Paris, five parts of porcelain powder. and one part of flux
is then cast into the mould and this mass hardens therein in about a quarter of an
hour. The mould with the casting therein is now placed in a potters furnace and
fired at a temperature of about 1000° Celsius for a period of from five to six hours.
When the whole has been allowed to cool the plaster of Paris mould falls to pieces,
when dipped in water and the casting remains as a properly fired, weatherproof
porcelain-like mass, in which all the fineness of the original is very perfectly
reproduced.
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 reproducing models of clay or other similar substance, which
consists in casting into the plaster of Paris mould, made in the known manner, a
ceramic mass, drying the whole and firing the same in the manner of other ceramic
masses by which means the plaster of Paris mould will be destroyed after having
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page_text: cooled and the casting remains as a fired weatherproof mass having all the intricacies
of the original substantially as described.
BOULT & WADE,
Agents for the Applicants.