MOLDING or POUNDING.— The making of molds for metal castings. The molds are made in sand, loam and plaster of Paris. with or without the aid of patterns. There are three classes of molding — green-sand molding. in which damp sand is used, and the castings are made in damp molds, or in molds the surfaces of which have been " skin dried;" dry-sand molding in which the damp sand molds are thoroughly dried in an oven preparatory to casting; and loam molding. See Loam Work.
Moinnen SAND.— Sand is used for molding, in preference to all other materials, on account of its refractory nature, which enables it to resist the destructive action of molten metal at high temperatures; on account of its porosity, which allows the free escape of the gases generated in casting; and on account of its peculiarly compact and adhesive properties, which not only permit of its being molded to any desired shape, but also enable it to resist a great amount of pressure exerted by a liquid. The best
molding sand is obtained from the coal measures, and the later red sandstone formations. Sand from the green-sand and chalk formations is also very satisfactory. The most suitable sand is that which contains a large percentage of silica, with alumina and magnesia present in small quan tities. The various grades of molding sand are designated as green-sand, dry-sand, core-sand, facing-sand, and parting sand, according to the purposes for which they are used. MOLDING molder's small tools are a variety of spoonlike slicking tools, a lifter, an oval or " dog-tail." a heart and square, and square and half-round corners, for more perfectly shaping the sand molds.