Casting processes divide into two broad categories, according to type of mold used: expendable-mold casting and permanent-mold casting. An expendable mold means that the mold in which the molten metal solidifies must be destroyed in order to remove the casting. These molds are made out of sand, plaster, or similar materials, whose form is maintained by using binders various kinds. Sand casting is the most prominent example of the expendable-mold processes. I sand casting, the liquid metal is poured into a mold made of sand. After the metal hardens, the mold be sacrificed in order to recover the casting.