(A Very Brief Description)
Wax is one of the oldest sculptural materials. Its use extends back at least five thousand years. Although many sculptures are made solely, or mostly, of wax (think Madame Tussaud’s), wax is usually a transitory material. That is, a work is modeled or cast in wax as a step in the production of a metal casting. The use of wax in metal casting, called “lost wax” or “cire perdue”, is what this paper is about.
The basic steps in lost wax are these:
1. A form is modeled or cast in wax.
2. The wax form is provided with a system of gates/feeds and vents.
The gates allow molten metal to flow to the form and the vents let gases
escape. This system is called the sprue system or spruing.
3. If the form is hollow, the interior is filled with refractory material
composed of plaster and sand. This is called the core. The wax form,
cored or not, with its attendant sprue system, is encased (invested)
in more of the refractory material. The material itself is called "investment"
and the wax in its encasing material, "an investment".
4. The investment is heated in a kiln to remove all wax (and any other
flammable material). The investment must reach a temperature of approximately
900 degrees f. to ensure complete burn-out.
5. After the investment has cooled enough to be handled, it is removed
from the kiln and packed in a sand pit to support it during the pour..
6. The investment is then filled with molten metal (the actual casting).
The metal fills all the spaces vacated by the wax.
7. The investment is chipped away, the core is broken out, and the sprues
are cut away. The cast’s surface is finished (chased), and, finally,
the cast is patinaed (given a color) through the application of chemicals.
N.B. The steps listed above give only a VERY cursory explanation. The whole process is technically very complicated.
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