|
Image Transfer and the Hollow Cast
Indirect Lost Wax Casting Method
The hollow cast, “indirect” method of lost wax bronze reproduction
however solved these problems. The new method introduced two simple new “layers”
– one inside the wax core to form an armature and the other outside the
cast to form a “mother-cast” – that triggered the spectacular
Bronze Revolution in the arts of antiquity.
The first layer, inside the core, solves the problem of scale by making possible
the casting of large-sized hollow bronze sculptures that were theretofore inconceivable.
The bronze image is exactly the thickness of the wax it replaces. Therefore,
large hollow bronze objects could only be cast by replacing the solid wax core
of the direct method with an armature covered by a thin layer of wax.
The armature thus resembles less the candle-like solid wax core of the direct
method and more a thin dress draped over a light manikin. Now, with its double-layered
armature, the indirect method could produce life-size art objects in bronze,
the production of which had previously been restricted to wood or stone.
The other seminal innovation of the indirect method – covering the master
mould with a new layer, called the “mother mould” – made possible,
for the first time, the serial reproduction of the same image in several copies.
By wrapping the master cast in a mother cast, in effect creating a cast within
a cast, the indirect method preserves for later use the master cast that is
otherwise destroyed when casting bronze directly.
These technical innovations also had the consequence of doubling the number
of steps in the casting process so that, at first glance at least, the indirect
method appears unnecessarily complicated.
The entire casting sequence – from the first production of the positive
model to its final reproduction in bronze – increased the number of image
transfers from the three (as in the direct method) to the six separate transfers
that are required by the indirect method. The logic of casting remains unchanged:
it is essentially the three step image transposition – from the positive
of the master model, to the negative of the master cast and, finally, to the
positive of the bronze image – of the direct method described above.
However, the indirect method is designed to preserve for later use both the
master model (positive) and master mould (negative), which are destroyed when
casting bronze directly. As a result, extra steps are necessary to create duplicates
of the model and mould that can be destroyed in the final casting stage, preserving
the masters for later use.
The new steps of the indirect method extend the casting sequence thus: from
a positive (in clay) to a negative (in plaster) to a positive (in wax) to a
negative (in six layers of clay) and, finally, to a positive (in bronze). Let’s
follow the sequence step by step.
Next...
|
