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Burnout and Pouring

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Once the shell or investment process is completed, the flasks are placed in a kiln, heated to between 1000 and 1250 degrees F, and held at that temperature until all wax residues have disappeared. The place where the wax was, is now a void- hence the "lost wax" designation for this process. The metal is then melted and the moulds are filled with liquid bronze or whatever metal is being used. The flask is then allowed to cool, then the plaster mould is broken away, revealing the metal part, which faithfully reproduces every detail of the original wax, plus the gates and vents, which must be cut off. Silver, gold, aluminium, brass, or bronze may be used interchangeably with this method. Special investment materials and melting equipment are necessary to deal with the higher temperatures of platinum, iron or stainless steel, but the process is much the same. Lower-melting metals such as tin, lead, and zinc may also be cast by this method, but there are other easier methods of casting them, so it is not often done. A variation on the lost-wax method is also used for casting objects in glass.


The lost wax or cire-perdue process is the traditional method of bronze casting. It has been around for at least 5000 years and was used by the early Egyptians, Greeks, Africans and masters of the Italian Renaissance.