Pro Mold Making

Mold making. A mold is made from the original model. The rigid outer molds contain the softer inner mold, which is the exact negative of the original model. Inner molds are usually made of latex, polyurethane rubber or silicone, which is supported by the outer mold. The outer mold can be made from plaster, but can also be made of fiberglass or other materials. Most molds are at least two pieces, and a shim with keys is placed between the two halves during construction so that the mold can be put back together accurately. In case there are long, thin pieces sticking out of the model, these are often cut off of the original and molded separately. Sometimes many molds are needed to recreate the original model, especially large ones.

Once the mold is finished, molten material is poured into it and swished around until an even coating, usually about 1/8 inch or 3 mm thick, covers the inner surface of the mold. This is repeated until the desired thickness is reached. Another method is filling the entire mold with molten wax, and let it cool, until a desired thickness has set on the surface of the mold. After this the rest of the wax is poured out again, the mold is turned upside down and the wax layer is left to cool and harden. With this method it is more difficult to control the overall thickness of the wax layer.

Removal of wax. This hollow copy of the original is removed from the mold. The technician may reuse the mold to make multiple copies, limited only by the durability of the mold.