The Art Bronze Casting Process

The ancient art of lost wax casting is still used for quality art from items as small as jewelry and as large as life-sized figures riding on their horses. The process is demanding and expensive. Although labor intensive, the process lends individuality and character to each piece that evolves.

An original sculpture is created. It can be made from clay, wax, wood, or other materials. A silicone rubber mold is made around the original to shape the form and every nuance of the sculpture. The mold making process is critical, because it must capture every nuance of the original. The mold must be split into at least two pieces. This rubber is backed-up by either plaster, fiberglass, or another rigid material to support the rubber. The rubber mold is taken apart and the original sculpture is removed.

After putting the mold pieces together again and binding them together with heavy-duty rubber bands, hot wax is poured in the mold and is slushed around, to coat every part of the internal shape. After cooling, the wax is removed, and then refined. Any bubbles or imperfections are repaired. Additional fine details can be added, so that each wax becomes unique unto itself. The completed wax is then signed and the edition number is inscribed in the wax, so that this shows up on the subsequent bronze casting.

The wax is attached to a "pour-cup", which is funnel-shaped to channel the molten metal into the mold from the outside, using "gates"or "sprues" made from rods of wax. A venting system is made the same way to convey air and other gasses out of the mold when it gets filled with hot bronze. A ceramic shell mold is formed around the gated wax, and then put in a 1000-1300 degree Fahrenheit burnout furnace. This melts and burns out all the wax. The phrase ‘lost wax’ refers to this process of burning-out, or 'losing' the wax in this process. While the ceramic shell mold is still hot, 2100 degree molten bronze is poured into the ceramic shell mold, to fill the cavity where the wax was. This creates one bronze edition of the original sculpture.

Once the bronze has cooled sufficiently, the shell mold is broken off, to reveal the casting. The gaits are cut off and ground away, and any defects in the casting are repaired. It is then sandblasted, cleaned, sanded, and polished. Then heat and an acid patina are applied to give the sculpture a rich color, which sometimes simulates what centuries of oxidization and aging in the elements would normally do. While the sculpture is still warm, wax is applied, which seals, protects, and highlights the bronze and the patina. The bronze sculpture is then buffed and then mounted on an appropriate base, to accent the form.

Each bronze in a series must be a faithful reproduction of the original, in wax. It is retouched, signed, and numbered by the artist. This, plus the individual application of the patina, makes each bronze unique.