Bronze statues aren’t made like marble statues. While marble statues can be carved from a single block, bronze statues are formed using a lost-wax process that was developed around 4500 BCE. When a sculptor is inspired by the human form to capture the essence in bronze, there are a series of steps that need to be completed before the final piece is produced. Each sculpture is unique and fabricated following careful consideration and planning.
The process involves forming a mold that is used to cast the bronze sculpture. The shape of the mold is determined by the final design.
Sculpting Clay
The creation process for bronze sculptures is a very detailed and labor-intensive process that begins with clay — your statue will be sculpted in clay first as it will allow for the most opportunity to capture fine details. Clay boasts very different properties than stone or any other material so it allows a lot more freedom to carve into the substance and sculpt more minute details.
Detailing can be an arduous process that requires the sculptor to become intimately familiar with the clay’s texture and characteristics. The sculptor then begins to sculpt their design into the clay using a traditional technique. In some cases, clay is cut into multiple sections that are individually molded and cast.
Rubber Molding
Once the clay has been sculpted, the statue will be cast in a mold. To create a negative mold of the clay piece, a liquid mixture of silicon rubber is applied to each section of the clay sculpture. When the rubber cures, it is encased it in a plaster mother mold to hold the form in place. Usually, molds are "walnut shell" concepts, comprised of two halves separated by a seam. Molds are used to duplicate sculptures in a limited edition and will be destroyed once the full edition has been cast.
Removing Wax
After removing the original clay sculpture from the rubber mold, wax is heated to approximately 200 degrees Fahrenheit and poured into the rubber mold, creating a thin coating. The wax pattern—with its delicate, refined details—work as a “guide” for further layers of wax buildup. Afterwords, the wax is hand finished, or “chased,” to reveal the originally sculpted details and textures.
Gating
Wax rods and funnels are attached to the wax sculpture to alleviate the trapping of air and gas. This action promotes a uniform temperature throughout the figure, avoids partial curing and warping, and gives it strength and integrity.
Investment & Burnout
The wax duplicate is coated with a liquid ceramic (Investment phase). This is done several times to create a stable mold. In this process, molten ceramic is poured around the wax piece. Once this bakes (Burnout phase), the shell and the wax melts out, leaving a hollow inside that is ready for the bronze.
Pouring & Removal of Ceramic Shell
Bronze is melted at 2,200 degrees Fahrenheit and poured into the cured ceramic shell. After the bronze cools, the ceramic shell is carefully removed. Our bronze sculpture is now ready for finishing.
Finishing Processes
Bronze sculptures are sandblasted and cleaned to remove any fragments of the mold. Artists will hand finish the bronze to look exactly like the original. A patina is used to give bronze sculptures an aged, stone appearance. This is done by rubbing the sculpture with ground sand mixed with acid. A coat of wax may be applied as a sealant to protect the sculpture's surface.
Conclusion
The lost-wax process can seem complicated, but when broken down into smaller segments, it is easier to see the overall picture. Artists must have a vision of what they are going to create and be willing to invest a lot of time and energy into their art.
