Permanent Mold Casting. A mold which can be used repeatedly. It is in contrast to sand casting (in which the mold is broken apart to remove the cast object) and die casting (in which the metal is applied under pressure). Although preparing the mold can be expensive, permanent mold casting is ideal for edition casting of art medals, say a dozen or more upwards. After the mold is cleaned (by compressed air) molten metal is poured in the mold, allowed to cool, opened to eject the casting; the mold can then be used to repeat the process. Permanent molds are often called dies, but what they produce is "gravity-die casting" (in contrast to die casting's "pressure-die castings"). Permanent molds do not have the restrictions that die castings have (limited to light metal compositions) and can be cast in any ferrous or nonferrous metals.