Year: 1888

page_text: We, FRANZ PONNINGER of IV Gusshausstrasse 5, Vienna, Austria, Director of the
Imperial Royal Foundry of Works of Art and GUSTAV KOLLER of 1 Hoher Markt
13, Vienna, Austria Chemistry Student, do hereby declare the nature of this invention
to be as follows :-
Whereas for casting works of art gypsum moulds were formerly employed
moulds of glue or gelatine are now generally used on account of their cheapness and
the sharp negatives they afford. But it has not been found practicable, hitherto,
to utilize these moulds for the production of gypsum or wax mouldings because the
gypsum becomes heated on hardening and thereby dissolves the surface or superficial
layer of the moulds, and as molten wax, poured into these moulds, attacks their
surface to such an extent as to prevent the production of so sharp a moulding
as required for artistic purposes.
According to this invention, this difficulty is obviated by treating the surfaces of
the glue or gelatine moulds with energetic oxidizing substances such as an aqueous
solution of anhydrous chromic acid, chromates or permanganates of alkalies, and
nitrate of silver, and by exposing the moulds afterwards to the action of solar or
artificial light. Finally the moulds so treated may be coated with oil varnish.
By the described treatment the surfaces or superficial layers of the glue or gelatine
moulds are oxydized and thereby rendered less sensible to the action of heat, while the
valuable properties of the moulds remain unimpaired.
M 1000

page_text: COMPLETE SPECIFICATION.
Improvements in Moulds for Casting Works of Art.
We, FRANZ PÖNNINGER, of IV Glusshaus-strasse 5, Vienna, Austria, Director of
the Imperial Royal Foundry of Works of Art, and GUSTAV KOLLER, of 1 Hoher
Markt, 13 Vienna, Austria, Chemistry Student, 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 relates to the preparation of glue and gelatine moulds as used for
casting works of art, and has for its purpose to so treat these moulds or the
material of which they are made, as to enable them to have serviceable plaster and
wax casts taken from them, and alloys of low melting point poured directly into
them.
Elastic glue and gelatine moulds have, on account of the cheapness of their manufac-
ture and of the sharp negatives they afford, superseded in many branches of reproduction
of plastic objects the plaster piece moulds formerly used. These giue and gelatine
moulds are however subject to a drawback which becomes sensibly detrimental alike
in taking plaster or stucco casts and wax casts.
As is known plaster of Paris and all compositions containing this substance, heat on
hardening in moulds, and the surface or superficial layer of the glue or gelatine mass
is melted thereby. The measures hitherto taken to prevent this action, viz. the
coating of the moulds with oil varnish and the addition of alum to the plaster mass
designed for the cast, are not satisfactory.
To obtain from glue or gelatine moulds, wax casts which fully meet artistic
requirements has hitherto proved impossible as the molten wax attacks the mould and
dissolves the surface or superficial portions of the same. In consequence of this and
notwithstanding the moulds being varnished, blunt and inaccurate casts can only be
obtained.
By treating or preparing a glue or gelatine mould according to this invention the
drawbacks herein before described are completely obviated. The surface or superficial
layer of the mould or the whole mass, is rendered resistant against a considerable
temperature without prejudice to the sharpness of the forms or to the elasticity of the
mould. A plaster cast may be allowed to cool within the mould and molten wax
heated to a temperature of nearly 212° Fahr., or molten alloys the melting point of
which is not considerably above this temperature may be poured into the same without
alteration of the surface. By this means there is afforded the possibility of using
elastic glue or gelatine moulds when making the wax casts or fillings which are
necessary in casting bronze upon a core.
This resistance to heat is imparted to a mould according to this invention by treating
its surface with energetic oxidizing ubstances. For this purpose there may be used
to advantage such substances as aqueous solutions of anhydrous chromic acid, chromates
or permanganates of alkalies, or nitrate of silver. After having coated the mould one
or more times with one or other of the said solutions, the mould is exposed to day light

page_text: or, if this is not practicable to artificial light, and so allowed to dry; afterwards it is
coated with a thin layer of varnish. The oxidized layer which is formed, imparts to
the mould a very considerable resisting power against heat, without impairing in the
least the sharpness of the forms produced.
By applying to the surface of a mould more or less concentrated solutions of the said
strong oxidizers, and by exposing the same during a longer or shorter space of time to
the action of light, a more or less thick layer of oxidized substance may be obtained,
according to special requirements. When it is not desired to use again the materiaĺ
of unserviceable moulds, the glue or gelatine may, instead of being dissolved in water
as usual, be dissolved in one of the aforesaid solutions. From the solution of glue or
galatine thus obtained, moulds are formed in the usual way, and afterwards they are
exposed to the action of light, whereby the whole mass is oxidized and so rendered
resistant against heat.
It has been found by experiment that an aqueous solution of anhydrous chromic
acid gives the best results. By applying this liquid from 2 to 6 times to the service
of the moulds and then exposing them to the action of light during about 6 hours,
moulds are obtained, which serve extremely well for plaster or stucco and wax casts
whether the casts are relievo plates or statuesque work. It is obvious that moulds of
the above described kind, can, owing to their resistance against heat, be directly used
for taking casts in alloys, the melting point of which is not considerably above
212° Fahr.
The glue or gelatine material of dried up or unserviceable moulds, in which the
superficial layer only has been treated with the said oxidizers can be utilized again for
the most part. To this end, the moulds are cut to pieces, which are boiled in water,
and finally the mass is caused to pass through a sieve. The oxidized portions which
are less soluble in water than ordinary glue or gelatine, will be retained by the
sieve.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. Treating the surface of a glue or gelatine mould with strong oxidizers and
afterwards exposing the same to the action of light for the purpose of adapting it for
the manufacture of casts in plaster, stucco, artificial stone, and like materials, wax and
alloys of low melting point substantially as described.
2. Dissolving glue or gelatine, designed for the manufacture of moulds, used in the
production of casts in plaster, stucco, artificial stone and like material, wax and alloys
of low meiting point, in aqueous solutions of energetic oxidizers, forming the moulds
in the usual way, and finally exposing the same to the action of light substantially as
and for the purpose described.