LOST WAX SCULPTURE
(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.

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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. The systems above are made of pink styrofoam and red wax.  The metal pins (core pins) serve to keep the core (interior investment) from shifting out of place. The toothpicks serve as temporary fasteners,
 

 

 

 

 

 

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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 (as shown here). The material itself is called "investment" and the wax in its encasing material, "an investment".

 

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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   Note that the kiln is set for 1,100 degrees to ensure that the investment will eventually reach 900 degrees in its interior. When the burn-out is complete, the wax, styrofoam etc. forms have all burned away and left hollow spaces where they had been.

 

 

 

 

 

 

 

 

 

 

 

 

 

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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.  At the same time, bronze is being melted in the furnace. 
 

 

 

 

 

 

 

 

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6. The investment is then filled with molten metal (the actual casting). The metal fills all the spaces vacated by the wax and styrofoam. The mold is left to cool overnight and then removed from the pit. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

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7. The investment is chipped away, the core (if any) is broken out, and investment is cleaned from the surface

 

 

 

 

 

 

 

 

 

 

 

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8. The sprues (gates and vents) are cut away along with any flashings. Then the cast’s surface is finished (chased).

 

 

 

 

 

 

 

 

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9. Later,the cast is patinaed (given a color) through the application of chemicals.

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N.B. The steps listed above give only a VERY cursory explanation. The whole process is technically quite complicated.

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