The Lost Wax Process

The Original Sculpture

The original sculpture can be made of any material, but most sculptors prefer to work in oil based clay or wax.

Bite Sized Pieces

In order to prepare the sculpture for molding, it is usually cut into pieces. 

First Layer of the Mold

Those pieces are then painted with several layers of liquid rubber to capture the surface detail.

Reinforcing The Mold

The rubber mold is then covered with a plaster  or fiberglass shell material in order to preserve the form.

Creating The Wax Pattern

The original sculpture is then removed from the finished mold. By building several layers of hot wax inside the rubber mold, and pouring out the excess wax between layers, a hollow wax copy of the original is made.

The Wax Pattern

Thorough attention is given to refining the wax pattern so that it exactly matches the original. This process is referred to as "wax chasing".

Spruing

The wax pattern is then sprued and mounted on a wax cup. The red sprues (solid wax rods) serve as gates and vents later in the casting process.

The Ceramic Shell

The wax is then dipped into a slurry tub and coated with ceramic slurry. While still wet, it is then coated with sand to build up the layer of ceramic shell. This process is repeated, and between each of the coats, the shell must dry.

Burnout

The dry shell is then placed into a burnout kiln where the shell is cured and the wax pattern is melted out. This is where the term "lost wax" comes from. Each time a piece is cast, a new wax pattern must be pulled from the rubber mother mold.

The Bronze Pour

The shell is then ready to receive the molten bronze. It is poured at a temperature of about 2000 degrees Fahrenheit.

Removing The Shell

The bronzed gates and vents are removed and once  the bronze is cooled, the shell is manually removed from the metal, usually by sandblasting.

Reconstruction

The cast parts are welded back together.

Metal Chasing

The weld lines are tooled out and any imperfections in the metal are corrected. The piece may be sandblasted to create a very smooth surface and remove any remaining ceramic fragments.

Patina

The completed metal sculpture is then heated with a torch and the patina is chemically applied to the surface, sometimes in many layers. The color achieved through this subsurface oxidation is referred to as "patina".

The Finished Sculpture

The finished bronze is then waxed or lacquered to protect the surface from any further oxidation, keeping the patina stable for many years to come.