Bronze Casting Process The process documented below is the “lost wax” process, which has been used for casting bronze since c. 3000 BC. The pictures were taken at the foundry at the University of Miami. Freda now teaches bronze casting at Miami-Dade College, Kendall campus. For more information, contact her at the email address on the Home page. A model is first made in wax, then “invested” or encased in a refractory material. In this case the investment is plaster, silica sand, and perlite and is known as “traditional” investment. The investment is then placed in a kiln where the wax is melted and burned out. The hollow left in the investment is the exact negative of the original . Molten bronze is poured into that hollow and duplicates the shape of the wax. After the bronze cools, the investment is broken open, the sprues cut off, the surface restored, and a patina applied to color and protect the finish of the bronze.

Bronze Casting Process

The process documented below is the “lost wax” process, which has been used for casting bronze since c. 3000 BC. The pictures were taken at the foundry at the University of Miami. Freda now teaches bronze casting at Miami-Dade College, Kendall campus. For more information, contact her at the email address on the Home page.

A model is first made in wax, then “invested” or encased in a refractory material. In this case the investment is plaster, silica sand, and perlite and is known as “traditional” investment. The investment is then placed in a kiln where the wax is melted and burned out. The hollow left in the investment is the exact negative of the original . Molten bronze is poured into that hollow and duplicates the shape of the wax. After the bronze cools, the investment is broken open, the sprues cut off, the surface restored, and a patina applied to color and protect the finish of the bronze.

The original wax

The wax prepared for investing with sprues attached. The sprues are channels for the bronze to flow in and the air to escape.

Investment flask made of roofing felt lined with chicken wire. The wire reinforces the plaster/sand mixture.

Finished investment. Note the cup and riser sprues coming through the top of the investment. Bronze will be poured into the cup and air will come out of the risers.

The burn-out kiln with roof off and door open for loading or unloading investments.

Packing investment into the sand pit after the wax is burned out in preparation for pouring the bronze. Kiln is in the background.

Ingots of bronze weighed and ready to go into the crucible in the furnace.

Using tongs to load bronze into the hot crucible in the furnace.

Removing the crucible from the furnace at c. 2200º F

Pouring molten bronze into the investments.

Tools used for removing sprues (now bronze) and restoring the surface of the sculpture

Tools used for breaking open the investment. The investment material is discarded.

The result:

“Sybil,” (detail), 2001, cast bronze, 9.5’ x 6.5” x 8.5”