Lost Wax (Bronzing) Process

Often I am asked to describe the process for creating a bronze sculpture. The casting process takes several weeks from start to finish. The amount of time it takes to create a single work of bronze sculpture, gives the collector a greater appreciation of the works value.

The first step in the bronzing process is the creation of an original sculpture. The sculpture can be created in almost any media, usually clay or wax.

Once the sculpture is completed, a rubber mold is made from the original sculpture. This mold allows the detail of the sculpture to be captured, this being one of the most critical steps in the process.

The mold is used to yield a wax casting that produces a detailed copy of the original sculpture. The wax casting is hand finished and treated as an original work of art.

Wax rods, called gates or spruces, are strategically attached to the wax casting to allow for the even flow of the molten bronze while allowing any trapped air to escape.

The wax is coated with a liquid refractory ceramic called an “investment”. This investment has been formulated to withstand the high temperatures realized in burnout. Several layers are applied to the wax surface to create a hard mold which is allowed several days to cure.

The wax sculpture, coated in the hard ceramic shell is then placed in a kiln. Placing this in the kiln bakes the hard shell and melts the wax, leaving only a cavity in its place. The wax is “lost” and a cavity now exits in the ceramic shell.

The ceramic shell is immediately removed from the kiln and while still warm from burnout. The molten bronze is immediately poured into the mold, where it assumes the shape of the original model.

After cooling for several hours, the shell is carefully broken away and releases the casting.

Fine particles of sand under air pressure, blasts the remaining ceramic particles that still remain on the bronze.

The spruces and gates are then cut away. Grinding and chasing, polishing, sanding are then utilized to make the bronze look exactly like the original.

The bronze is then treated with chemicals and heat to give the artist the desired coloration. The patina is sealed under a wax coating and is a permanent part of the sculpture.