What are Backup Molds, Mother Molds, Shells, and Keepers?
If you make a mold from a flexible material such as latex rubber, it may distort out of shape when you put a casting material into it. All of the above terms refer to a rigid mold made around the rubber mold, so the rubber mold will maintain the proper shape while you use it. The Latex Video demonstrates how to make backup molds from plaster, polyurethane, and fiberglass.
