Shell Mold

(also, investment mold), a special type of foundry mold made of a thin shell of molding mixture that is applied directly to the model. As a result, the consumption of molding material is reduced and the path of gases released from the mold is shortened. This reduces the danger of the formation of gas cavities in castings. Shell molds are used to produce castings by a method called shell molding. They are also used in the lost-wax process.