Green-sand molding involves the making of castings in molds that are composed entirely of damp sand, or that have their surfaces "skin dried," that is, dried by building a fire in the mold to harden its surface without baking its entire thickness.
In dry-sand molding, the sand is damp when the metal is poured, after which the mold is dried in an oven, or otherwise, so as to remove all moisture and leave the body of the mold dry and firm. In other words, the sand is drier than green sand.
In loam-sand molding, castings are made in molds constructed with skeletons of patterns. A mixture of loamy sand and other material is used to form the surface of the mold and to form its outer and inner supports. This class of work, like dry-sand molding, requires drying before it is ready to receive the melted metal.