Wax and Gating
The rubber mould created in the last step will now be used to create a wax replica of the original model. The rubber surface of the interior of the mould is first coated with a separator compound to allow the wax to be extracted easily. Next, molten hard wax is painted into the interior of the mould and allowed to cool, paying special attention to intracte or detailed areas. This ensures that the wax will have good detailed and textured surfaces and a minimum number of defects from air bubbles and seams.
Once the wax has been painted in, the various parts of the mould (most moulds can be made in only two parts, but more intricate forms often require more) are assembled and tightly secured to eachother to form a seal. Next, a different type of molten wax is poured into the mould at a lower temperature than the wax used to paint in the details. The different types and temperatures of the wax assure that the carefully painted in wax is not melted and washed away by the poured wax.
The poured wax is then allowed to cool for several minutes until it has built up a sufficiently thick wall all around the mould. Once this has happened, the balance of the wax is then poured back out of the mould.
The wax in the mould is then allowed to thoroughly cool before the mould is disassembled and a wax replica of the original model is extracted. This wax replica, like a casting in any material, is then touched up by hand to remove any surface imperfections and sharpen and restore any details that may have been diminished in the wax casting process.
Once a fully touched up wax replica is ready, it will be gated. Gating is a process by which wax sprues and rods are attached in a network around the wax. Once the piece is invested in ceramic and the wax burned out, this network of gates will allow for molten metal to flow into the piece and for air pockets to be vented out. Above, a gated wax is touched up to ensure a good quality casting.