Lost Wax Method

The most common way is the lost wax method. This requires a three-dimensional model carved from a block of wax. The wax model is then carefully placed on a rubber base using a rod of wax, which is then surrounded by a metal cylinder container called a flask. A creamy liquid called investment is poured into the flask, fully covering the wax model. The investment dries hard around the wax model. The rubber base is removed and the loaded flask is then put into an oven for heating, which is called the burn out process, for a total of five to eight hours. As the flask heats at different temperature levels the wax model melts out and leaves an exact impression of the model. When the burn out process is complete, metal is melted, and cast into the hollow cavity to fill the impression.

There are two ways to cast metal into a flask. One involves using a centrifugal swing arm device that is spring-driven. The flask is put on a cradle with a crucible adjacent to it. With the swing arm wound and in position, the metal is heated in the crucible until fully liquid and then the swing arm is released causing the liquid metal to be thrown into the flask. Another method of casting metal involves pouring molten metal into the cavity of a flask while under vacuum. The air from the flask evacuates and draws the molten metal into the flask. The flask is allowed to cool and immersed into a trough of water, causing the hardened investment to break apart and release the newly formed metal model casting. After excess metal is removed, the piece is filed, sanded, and polished and stones are set if needed.

Images courtesy of the Revere Academy of Jewelry Arts.

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