Improvements in the Method of Moulding with Molten Wax for the Reproduction of Casts.
Year: 1894

page_text: Date of Application, 31st Jan., 1894-Accepted, 5th May, 1894
CUMI DDIM DIUIFICATION.
Improvements in the Method of Moulding with Molten Wax for the
Reproduction of Casts.
We, CHARLES AUGUSTE LE BOURG, Manufacturer, and VICTOR MARIE
CossÉ, Refiner, both of 21 Boulevard Poissonnière in Paris, 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 :-
Our invention relates to Improvements in the Method of Moulding with Molten
Wax for the Reproduction of Casts, and has for object to obtain a more satisfactory
result than is possible by existing methods, to simplify the operation and render it
more certain at every stage, and to effect considerable economy in the process of
producing bronze and other metal casts.
Casting with a wax core as at present practised although it yields good artistic
results is still wanting in accuracy of workmanship and mechanical perfection.
The methods commonly employed are somewhat antiquated, the operator works to
a great extent by groping blindly and the results are that the cores are not smooth
nor homogeneous, they do not effectually resist heat and casting, whilst the wax
proof requires frequent trimming and retouching during the execution of the work.
Hence the great expense of production of casts renders the operation practically
unprofitable.
One of the processes hitherto employed consists in forming the core in halves
by pressing it in a hollow plaster mould and fixing these halves together by means
of wormseed; then scraping the entire surface down to a thickness equal to that
of the metal to be cast. The core thus produced-though costly-is by no means
firm and renders it necessary to provide studs on the core-iron for the purpose of
strengthening the core against bursting from the effect of heat or casting, and
consequently adhering to the interior sides of the mould. Moreover the wax after
being pressed in the hollow mould has to be cut into sections which are numbered
Iso that they may be pieced together on the core. This antiquated method does
not tend to the accurate reproduction of the work, since its success depends mainly
on the skill of the operative in reconstructing a new model from the pieces. As
will readily be understood all sharpness and delicacy of form are destroyed by
cutting the wax into sections, and each reproduction also involves practically the
execution of a new work at great expenditure of time and labour, and with no
certainty of success.
Another method now in practice consists in casting molten wax in the mould,
withdrawing from it the hollow proof and pressing moist clay into this wax cast.
This process though advantageous for small objects and moulds with wide openings
produces generally unfinished and defective models, owing to the core becoming
distorted during the casting of the wax through the moisture of the clay.
Evaporation during the drying of the clay core within the mould also injures the
sharpness of this interior mould and detaches fragments therefrom, which
necessarily cause defects in the bronze reproduction.
A third process consists in casting or pressing into each half of the mould the
wax which is to form the proof, and joining together these sections of the mould
and the two halves of the proof contained therein, and then casting a metal core
with rod embedded in a plaster core. Defects are caused in this process by the
liberation of gas from the substance of the core by heat, and the consequent
interruption of the flow of metal around the core thus producing irregularities in
the cast.
According to our invention the objections and defects described in the above

page_text: The work or figure to be cast in metal is first reproduced in plaster by any
ordinary known process. Two proofs are taken from it.
As shewn in Figure 1 one of these proofs is retouched by the artist and serves
as a permanent artistic model.
The other proof shewn in Figure 2 is reduced by scraping its entire superficies
down to a depth equal to the thickness of the metal cast required, and constitutes
the model for the core. These two proofs are provided with similar dowels or
joining-pieces formed and arranged in exactly the same manner and position. The
first proof or "proof model" shewn in Figure 1 is used for the production of a
hollow mould in gelatine, or of a hollow plaster mould in sections with a suitable
shell or casing furnished with dowels. The second proof or "reduced proof
illustrated in Figure is used to form a mould in sections, upon the casing of
which are shewn the dowels. This second mould is the core mould.
"
In Figure 3 is shewn the core mould made in plaster having its lower part made
in a single piece or in sections, but tapered so as to correspond with the contour or
outline of the model, whilst its upper part is always made in pieces and each piece
is similarly tapered. The special feature of this upper part of the core mould is
that the sections a are all transverse and of narrow form; they are distinctly
numbered with one or two figures.
MOULDING THE CORE.
In the mould formed as above described, the clay is pressed in the following
manner: The upper part of the mould, shell and sections being removed, a suitable
metallic rod with cross-piece and core iron is placed upon the uncovered lower
part, the core iron serving to support and retain the clay of the core and to form
the necessary dowels; then the first section of the upper part is put in place.
Pressure with the fingers is then applied upon the clay within the cavity of the
mould.
The sections a are finally enclosed in their shell or casing, and the mould is
allowed time to dry and to set to the necessary consistency. The core thus formed
is afterwards taken out from its mould, being then a perfectly homogeneous single
piece without a seam and it contains a metallic rod or core embedded firmly in the
clay. The composition of this clay is optional, its essential feature being that it
contains no calcareous substance. With the same mould as many cores may be
produced as are required and these cores reproduce exactly the "reduced proof"
of the model.
In the mould formed as above described, the clay is pressed in the following
manner: The upper part of the mould, shell and sections being removed, a suitable
metallic rod with cross-piece and core iron is placed upon the uncovered lower
part, the core iron serving to support and retain the clay of the core and to form
the necessary dowels; then the first section of the upper part is put in place.
Pressure with the fingers is then applied upon the clay within the cavity of the
mould.
The sections a are finally enclosed in their shell or casing, and the mould is
allowed time to dry and to set to the necessary consistency. The core thus formed
is afterwards taken out from its mould, being then a perfectly homogeneous single
piece without a seam and it contains a metallic rod or core embedded firmly in the
clay. The composition of this clay is optional, its essential feature being that it
contains no calcareous substance. With the same mould as many cores may be
produced as are required and these cores reproduce exactly the "reduced proof'
of the model.

page_text: CASTING THE WAX.
When the clay core has attained the necessary degree of dryness it is placed in
the hollow mould in gelatine or in sections in plaster produced from the "proof
model" (see Figure 1). To effect this, the dowels or joining pieces of the core are
placed in the. lower shell of the hollow mould which is exactly similar to that
corresponding with the core-mould. The core having been properly fixed in its
dowels or joining pieces on the lower half mould (shewn in Fig. 4) containing half
of the gelatine model c, the gelatine is withdrawn from the upper shell, & by reason
of its elasticity on being placed upon the uncovered part of the core, it expands over
the other half of the gelatine. Then the core is completely surrounded by the
two half sections of the gelatine mould as shewn in Fig. 5, leaving a space d between
it and the gelatine equal to the thickness of the plaster removed in fashioning the
reduced proof (see Fig. 2). It remains to cast the wax into the space d. To
accomplish this cast the mould is raised vertically so that the casting hole-which
is suitably arranged to admit a funnel-is at the top. The casting is facilitated by
vent holes arranged as desired. By this simple & certain method of surrounding
or enclosing the moulded core with wax, handling is entirely dispensed with, the
process being absolutely mechanical and the thickness of wax on the mould is
uniform throughout. The result is thus assured, besides which it will be found on
taking the core covered with wax out of the mould that this wax-model cast hollow
and lined with a complete core reproduces exactly the model in its entirety and in
all sharpness of form, and is so perfect that it requires no retouching by the artist.
It is only necessary now to remove the single seam left by the mould and even this
is reduced to a minimum by using gelatine. This operation may be performed by
any person besides the artist who need not therefore have anything further to do
with it. The gelatine mould will serve several times: in every case it is possible
to readily obtain from it other perfect reproductions of the proof model.
FINISHING THE PERMANENT MOULD.
Having formed the wax proof on the core as above described, we proceed to
cover it with putty or properly prepared clay and with a shell of sufficient rigidity.
The mould thus prepared is removed to a stove to melt the wax: then it is placed
in a kiln to get rid of the organic matter, and finally we cast the bronze which
takes the exact place of the wax and forms a faithful copy or reproduction of the
proof model (Fig. 1).
The core constructed according to our invention will effectually resist the heating
of the mould and the running of the metal cast, inasmuch as it is non-calcareous,
that it is in a single homogeneous piece, and that it is securely fixed to the metallic
core-rod 6 embedded in its substance. Moreover this core gives out no vapour so
that the putty mould does not become distorted, and the metal cast obtained
therewith will be free from seams and other defects.
In conclusion we reserve the right of employing with our invention any kind of
dowels and core-iron, of producing the gelatine moulds and fixing them in their
shells by any suitable method, of arranging the casting holes and vents in any
manner appropriate for reproducing the particular work, and of forming the putty
mould by any practical process.
Having now particularly described and ascertained the nature of our inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. In the process of moulding with molten wax for the purpose of obtaining a
hollow mould and a perfectly corresponding core, the production directly from the
object to be reproduced of two proofs in plaster, one Figure 1, being retouched by
the artist and intended to be used as a model for the hollow mould, and the other,

page_text: Figure 2, being scraped or ground over its entire surface and intended for use in
the completion of the core; the said proofs being provided with similar dowels or
joining pieces, substantially as described and illustrated on the accompanying
drawings.
2. In the process of moulding with molten wax the arrangement of a mould
having its upper part formed of transverse sections a of narrow dimension, in
combination with a metallic rod 6 for the purpose of forming by means of tamping
or pressing a seamless homogeneous core supported in the manner substantially as
described and shewn upon the accompanying drawings.
3. In the process of moulding with molten wax, the formation of clay cores
united in one piece with a metallic core rod and joining pieces formed in the mould
described in the preceding claim, said cores being characterised by capacity of
resistance to heat and casting so as not to become distorted thereby, and also by
absence of any evaporation of a nature injurious to the putty mould, substantially
as described.
4. In the process of moulding with molten wax, the combination of a core
moulded in one piece with a metallic core rod and joining pieces, and provided with
vent holes, with a hollow gelatine mould c, or with a plaster mould formed in sections
having suitable dowels in such a manner as to leave a space d into which the wax
is cast for the purpose of obtaining readily and economically at a single cast
requiring no subsequent retouching a wax proof on the core intended to form
ultimately the putty mould into which the metal is to be cast, substantially as
described and shewn on Figures 4 and 5 of accompanying drawings.
5. In moulding with molten wax the combined improvements claimed above, that
is to say: The production of a proof model and of a reduced proof for the
formation of a hollow gelatine mould, or of a plaster mould in sections, and also of
a core mould; this latter mould having at its upper part transverse sections of
narrow dimension for the purpose of forming a core in one piece with an inner core
rod, studs, and joining pieces; said core constituting in itself a novelty;-and the
use of this core with the hollow gelatine mould, or with a sectional mould, for casting
the wax.
The said improvements being used in combination with ordinary methods
for the certain, accurate, expeditious & economical reproduction in an artistic
manner of works of art substantially as described with reference to accompanying
drawings.
n1LT fiunt dere of Tonuerv 1804