Sherry Cagan

Creating a Bronze sculpture

The Loss Wax Process

#1 Casting a bronze sculpture is a skillful and lengthy process. Rubber molds are made from the approved master sculpture which is usually made from clay. Waxing involves repeated filling of the rubber mold with hot wax, slushing or otherwise making sure all areas of the mold are covered and pouring the wax out. After the wax is completed, the rubber mold is stripped away from the wax and a hollow pattern is cleaned. The piece is the ready to be gated. Additional wax pieces are attached to the pattern at specific points and then attached to a base to provide multiple entry points for the molten metal.  

#2 The tree is now ready for the shell to be applied. Each tree or assembly is dipped into slurry, (like cake batter), removed and allowed to drain. Then, a thin coat of sand is applied. Repeated dipping and sanding is required until sufficient strength is achieved to withstand the temperatures and the thermal shock of the hot metal. After the shelling is completed, the tree is placed in an autoclave, super heated steam penetrates the outer shell and melts the wax. The wax will leave the mold via the tree base and the gates leaving a shell without the wax pattern or tree.  

#3 The empty mold is placed into a oven, then baked at 1900 F for four hours to remove any possible trace of wax and to cure the mold. The mold is taken from the oven and the molten bronze is poured into it.

The shell is left until it is cool enough to handle. The shell material is removed from the bronze tree, by sandblasting or chipping away of the shell, though care is taken not to touch the sculpture.

#4 The tree is cut away from the sculpture and all areas where the gates were attached to the wax pattern are ground flush. Each piece is polished and any defects are removed. The bronze is prepared for patina.

#5 The patina is applied using chemicals and blow torches. The piece must be heated to 200 F before the chemicals are sprayed on. Repeated heating and applying of chemicals are required to achieve the deep multi-colored finish. Once the desired color is achieved it is waxed and allowed to cool. The piece is then mounted on its base and polished.