Things You'll Need
- Foundry with a crucible
- Plasticine clay
- Polyurethane rubber
- Artist's wax
- Bronze ingots
- An electric grinder
- Protective clothing
Bronze casting is an ancient art form that has been utilized in the artwork of many civilizations. Today, bronze casting continues to be practiced in modern foundries and is used to create some of the most durable forms of sculpture and other creations. Like many other metal casting methods, bronze casting utilizes the "lost wax' method. To learn more about the bronze casting process, visit your local foundry, which may even have classes open to the public.
Before the actual process of bronze casting begins, you must have the original piece of sculpture that you want to render into bronze. Any soft medium like plaster, wood, stone or clay can be used.
Make a rubber mold of the original piece by placing it on the plasticine clay and painting one side with polyurethane rubber. Let that side dry before turning it over and painting the other. Cover the rubber coating with plaster and let dry.
Open the rubber mold and remove the original sculpture. The plaster covered wax mold is then rejoined or separated into different sections if the sculpture is large, creating a negative copy of the original piece.
Heat the wax to over 200 degrees Fahrenheit and pour a thin coating into the mold or each section of the mold. Turn the mold over and around to make sure the wax coats all surfaces of the mold as it dries. After the first pour dries, add more wax, again turning the mold to ensure even distribution. Repeat until you have at about an 1/4 of an inch wax wall, evenly dried throughout the inside of the mold.
After the wax is completely dried, open the plaster and rubber mold to reveal the image of the piece rendered in wax.
Create a cylinder with the tarpaper that loosely fits around the wax piece. Fill the cylinder of tarpaper with wet plaster, making sure that every surface of the wax piece is covered, and let dry.
Remove the tarpaper and place the plaster covered wax mold in an autoclave. The high pressure steam will dissolve the wax, leaving you with a plaster mold of the original piece.
Fill the crucible with bronze ingots and heat to over 1700 degrees. Using protective gear, the molten bronze is then poured directly into the plaster mold. After two hours the plaster can be removed, revealing the bronze rendering of the original piece.
Finish the bronze piece by rounding all rough edges and smoothing it with an electric grinder and then finish it with a patina.
Bronze casting requires extremely high temperatures, and should not be attempted outside of a professional foundry under the supervision of experienced casters.
Based in San Francisco, Ocean Malandra is a travel writer, author and documentary filmmaker. He runs a major San Francisco travel website, is widely published in both online and print publications and has contributed to several travel guidebooks to South America.