Making the “Mother” Mold

The mold-making phase starts the realization of the final sculpture. To make pouring the bronze more effective and easier, predetermined parts of the clay model are removed for separate molds to be made. The next step is to establish shim lines. The shims are pieces of wax-coated cardstock that are pushed into the clay in positions that determine where the mold sections are to separate. Then, specially designed rubber is applied in layers within each of the shimmed areas. Usually, about five layers are required to reach a thickness of about one-quarter inch. Next, plaster of Paris is applied over the rubber mold to create the “mother” mold. After the plaster dries, the mother mold is removed, and then the flexible rubber mold is carefully removed. The artist reassembles and ties all the sections together for shipping to the foundry.