Learn About Bronze Casting
Gay Malin's Sculpture and Printmaking
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Lost Wax Bronze Casting: The Lost Wax or Cire-Perdue Process 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. A complicated and difficult process, it includes the following steps: A sculpture is created over an armature out of clay or plaster. A flexible rubber mold with a rigid jacket is made of the sculpture. The clay/plaster is removed from this mold and it is cleaned out thoroughly. The mold is tied together and wax is poured inside. The mold is removed and the seams and any casting imperfections are cleaned up by the artist. Wax sprues and vents are attached to the sculpture so that the bronze can eventually be poured into the piece and gases can escape. The piece is invested by making a mold of plaster mixed with grog around the wax. The investment mold is placed in a burn-out oven to melt the wax out and dry the mold. Bronze, which is an alloy consisting mostly of copper with small amounts of zinc, tin and lead, is melted in a crucible to a temperature of approximately 2000 degrees and poured into the warmed investment mold. After cooling, the investment mold is tapped off and the sprues and vents, which are now bronze, are removed and chased. The piece is sandblasted to clean the surface of the bronze from scaling and acids and oils. A patina is applied to the surface. This is a chemical process that is etched into the surface of the bronze. The finished bronze is now lightly waxed to preserve its patina.