How to Create Bronze Sculptures

The head and shoulders of a public religious bronze sculpture located outside Salisbury in Wiltshire, south of England.

Creating a bronze sculpture is an ancient process. Some of the modern tools sculptors use now are more advanced, but the steps themselves haven't changed much in thousands of years. Bronze sculptures exist in museums and public spaces around the world, and artists who create them are often renowned.

Things You'll Need

• Original wood, clay or metal sculpture Wax Polyurethane or silicone rubber Clay Metal dental tools Rubber gloves Vat of slurry Vat of sand Graphite crucible Furnace, Metal, Kiln, Welder, Water soluble chemicals, Clear wax

Instructions

Creating a bronze sculpture

1. Creating a bronze sculpture, an ancient process, is a series of negatives and positives. The first positive is the original work. This piece of art can be created from wood, metal, clay or stone. The final bronze sculpture will look just like this original piece of art, but will be cast in bronze.

2. Create the first negative based on the original sculpture. Make a rubber mold of the original piece by covering the original work in many thin layers of rubber. Consider making the mold in parts, creating the head in one mold and a detailed hand in another mold. Once dry, remove the original sculpture from the mold.

3. Pour wax into the rubber mold. Make sure the hot wax evenly coats the inside of the mold; this usually takes about three coats of wax. The result will be a hollow wax mold with a consistent thickness. This wax mold will result in one bronze statue. An artist would have to make one of these wax casts for each bronze he or she plans to create. Use the same rubber mold to create each wax cast. This wax cast is the second positive in the series.

4. The wax cast is "sprued" and "gated." This means the artist creates wax cups and rods to direct the molten metal into the piece and also releases trapped air from the mold. This is to ready the wax mold for the bronze pouring. Create a ceramic outer shell, or "investment," to the wax mold by dipping it in a "slurry," then coating it with heat-proof sand. About a dozen coats must dry before the ceramic is ready. Creating this second negative takes at least one week and sometimes longer.

5. Once the ceramic is dry, the piece is put into a kiln heated to more than 1,000 degrees. The heat strengthens the ceramic. The sculpture is put in the kiln upside down, and the heat melts the wax inside the hardened ceramic. This ancient process is known as the "lost wax" method. An artist is left with the empty ceramic shell, which is the second negative.

6. Put the ceramic shell into a sand pit with the pouring cup at the top. Pour the molten bronze, heated to 2,200 degrees, into the cup and down through the guiding rods into the shell. The bronze cools, hardens and creates the final positive.

7. Once the bronze is completely cool, break the ceramic shell. Now the sculpture is sandblasted, and parts that were created separately using smaller casts are welded together. Grind the bronze surface to erase irregularities. Use small metal tools to smooth delicate areas; dental tools work well. This process is known as "metal chasing" and can take a few days, depending on the individual artist.

8. Now the bronze needs to be oxidized to create a "patina." This process takes a few hours, and an artist sprays different chemicals on the surface to create the desired color. Different chemicals result in different colors. The final sculpture can be coated in clear wax.

References

• Modern Sculpture

Resources

• Sculpture making tools
• Sculptor.org