Creating a Bronze Sculpture by the “Lost Wax” Casting Method
The following is a description of how a bronze sculpture is created using a technique called the “Lost Wax” Casting Method.
Model - An artist creates an original sculpture from clay or wax. An exact replica will eventually be made into a bronze sculpture.
Moldmaking - A rubber mold is made of the outside of the original model sculpture by applying multiple layers of liquid silicone rubber over the clay, which creates a flexible mold.
The Rubber Mold will show every exact detail from the original. It is coated in liquid fiberglass, which hardens into a supportive shell.
Wax Casting - The hardened mold is removed from clay sculpture. Molten wax is poured into the mold.
Removal Of Wax – The wax cools and the mold is gently removed from the wax, leaving an exact wax replica of the original sculpture.
Gating - Wax rods and funnels are attached to the wax sculpture to alleviate the trapping of air and gas.
Investment - The wax duplicate is coated with a liquid ceramic. This is done several times to create a stable mold.
Burnout - The ceramic shell coated wax sculpture is fired up in a kiln. The “burnout” process bakes the shell and the wax melts out. This is where the term “Lost Wax” comes from. The inside is hollow and ready for the bronze.
Pouring - Bronze is melted at 2,200 degrees Fahrenheit. The molten bronze is poured into the cured ceramic shell.
Removal Of Shell - After the bronze cools, the ceramic shell is carefully removed. We now have a bronze sculpture.
Sandblasting - The sculpture is sandblasted and cleaned to remove any fragments. Artists will hand finish the bronze to look exactly like the original.
Patina - A patina is applied with heat to color the bronze. A coat of wax is then applied to protect and seal the finished sculpture.