The origins of the “lost wax” process are shrouded in antiquity. The method has been used for thousands of years to produce objects in metal which could not otherwise be produced. The “lost wax” process permits anything that can be modeled in wax to be faithfully converted into metal.
In current times, it is possible to cast wax into molds so that multiple copies can be made of an object. Modern synthetic rubbers have been developed which capture very fine detail. Waxes can be cast, either solid or hollow---the wax will coat the inside of a mold after it is filled and poured out. This process is repeated to build up the desired thickness of wax.
After the model is made and touched up, it is attached to a “pour-cup” which is funnel-shaped. The metal is then channeled into the mold from the outside using “gates” or “sprues” made from rods of wax. Once the model is set up with its gates and vents, it is surrounded with a material that will cover it smoothly when wet and withstand high temperatures when baked.
After the plaster mixture has set, the flasks are placed in a kiln, slowly heated to between 1000 and 1250 degrees F and held at that temperature until all wax residues have disappeared. The place where the wax was is now a void---hence, the “lost wax” designation for this process.
The metal is then melted and the molds are filled with liquid bronze or whatever other metal is being used. The flask is allowed to cool, and then the plaster mold is broken away, revealing the metal part which faithfully reproduces every detail of the original wax.
Silver, gold, aluminum, brass or bronze may be used interchangeable with this method. Special investment materials and melting equipment are necessary to deal with the higher temperatures of platinum, iron or stainless steel, but the process is pretty much the same. A variation of the lost wax method is also used for casting objects in glass.
