Wax jewelry models grouped in trees and attached to rubber bases. Red center wax is the sprue.
Lost Wax Casting is a process that began 6000 years ago and the overall method today is still about the same. It is a multi step process to form metal into a desired and precise shape. As the name implies, lost wax casting begins with wax. An exact copy of the final jewelry is formed in wax by carving and sculpting. Groups of waxes are attached to a center sprue which is attached to a rubber base. These groups are also called “trees”.
A metal sleeve is placed into the base to form a cup. A plaster substance called investment is mixed and poured as a liquid into the cup made by the base and sleeve. Lost was casting is also known as “Investment Casting”.
After the investment hardens, the rubber base is removed and the wax sprue is uncovered at the base of the sleeve. This center wax forms the drain for the wax when it is melted. Sleeves, also known as “flasks”, are placed in a kiln and slowly brought to the correct temperature to accept molten metal. A normal cycle for heating and cooling is between 8 and 12 hours. Shorter cycles are sometimes used for smaller flasks.
Once the wax has melted and drained and the flasks are cured, they are ready to be used as the mold for casting. Flasks are brought one at a time from the kiln and placed in a centrifical force casting machine. Silver metal is melted with a torch in one end of the machine and the flask is placed in the other end. When the metal reaches the desired temperature the spring is released and the machine spins. This forces the melted metal from one side to the other and into the waiting flask mold.
After casting, the flasks are cooled and the silver is removed from the investment. The pieces are still attached in groups to the trees as shown in the photo to the left. The pieces are cut apart and polished with a series of finer and finer grits until they are bright and shiny. Sterling silver is bright white when cast correctly. The shiny silver color of finished jewelry comes from polishing.
Each piece of jewelry was once a piece of wax and many steps make it into a finished treasure.