An overview of the lost-wax process that translates a clay sculpture into final bronze.
Hot, liquid wax is brushed and “sloshed” inside each mold. The wax cools and hardens, yielding a “positive” copy of the clay pieces — only now in hard wax, about 1⁄4 inch thick. Wax bars and funnels are strategically attached; these will become conduits for pouring molten bronze.
The clay sculpture is cut into carefully determined parts, anticipating a later stage, when molten bronze fills each shape. These pieces are then covered with a thick rubber layer and encased in plaster, leaving the “negative” imprint of the sculpture’s surface in the rubber molds.
Next, each wax piece is dipped into a sand ceramic solution. Once dry, it’s re-dipped multiple times to build up a thick shell, covering the wax pieces.
This sand “shell” and wax combination is furnace-fired; the wax melts out (the “lost-wax method”), while the sand “shell” hardens into ceramic, which will be strong enough to withstand molten metal. Bronze is poured into these ceramic molds via the funnels and tubes created during the wax stage. After cooling, the shell is sand-blasted away to reveal rough cast metal shapes.
The final bronze pieces are then welded together. Weld joints are ground down, smoothed and textured to make seams invisible. More importantly, each piece must be reattached at precise angles, so the body and composition of the sculpture remain true to the original clay.
The fully reassembled statue is then heated with torches and brushed with several chemicals to seal the metal and develop a desired “patina,” the final appearance and color of the bronze surface.
Finally, the statue is hand-polished with multiple coats of wax, to protect the patina from long-term exposure to the elements.