How to Build a Bronze Sculpture

Bronze is often used for metal sculptures. There are several processes a sculptor can use to build a bronze sculpture, including the lost-wax method, sandcasting and centrifugal casting. Among these, the lost-wax method, discovered in China, is the oldest method of building bronze sculptures.

Things You'll Need

• Clay or plasticine
• Sculpture model
• Wax
• Liquid silica
• Stucco
• Kiln
• Bronze
• Corrosive chemicals

Instructions

1. Create a full-sized model of your sculpture with clay. Use oil-based plasticine for small sculptures and sculptures that will need less time to complete. Large models will require water-based clay.

2. Create a mold using the model. Plaster and flexible gel are the more popular materials used for this process. Once applied to the model, these materials copy the impressions and then harden to form a mold.

3. Use the mold to create a plaster master. The plaster master will be refined to further improve the quality of the sculpture. In earlier days, creating a plaster master was a way of preserving the as yet unproduced sculpture until there was enough money to pay for the bronze casting.

4. Cast a wax from the production mold. This involves pouring liquid wax into the mold and swishing it around until a thick coating of wax lines the walls of the mold.

5. Remove the hollow wax, then "chase" it by rubbing out the marks where the mold pieces came together. Add wax sprues to the mold. These sprues help direct the flow of the liquid metal and vents will be added to allow the escape of gases where needed.

6. Dip the wax mold into liquid silica and then into stucco. Let the mold dry. Repeat this process until there is about half an inch of this coating on the mold.

7. Place the wax mold in a kiln to harden the coatings and melt the wax. Cool the shell that remains. Reheat it and then place it in a tub of sand.

8. Fill the new mold with molten bronze to build your sculpture. Allow the bronze to cool and then hammer or sand blast the shell to remove it.

9. "Chase" the bronze to remove any telltale signs of casting.

10. Finish your sculpture. Once you have completed the steps required to build your sculpture, you will need to treat the surface by polishing it and then applying corrosive materials. These corrosive materials will form a patina on the surface that is usually black, green, white or brown.

Tips & Warnings

• If you want more control over the color of your bronze sculpture, apply the corrosive chemicals to it while it is still hot.