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Compressed Castings

This process is for making fine and artistic castings in brass, bronze, German-silver, aluminum, etc., and consists of preparing hard moulds containing the impress of the articles to be cast, the outside edges of which are square, so that they may be packed one on the other, and, when so packed, the gate of each leads to a central spruce. These are closely packed in an air-tight box. An opening in the cover-plate of the box directly connected with the sprue leads into a cylindrical reservoir containing the molten metal. This cylinder is lined with asbestos felt, the hole into the sprue being also covered with it, preventing the exit of the metal from the reservoir until the proper time. A piston, covered also with asbestos, fits closely into the cylinder, and pressure may be applied to it by hand through the action of a lever, rack and pinion, a screw or by other means. The reservoir being filled with the proper quantity of molten metal and the piston entered into the cylinder, connection may be opened between the mould and the vacuum-tank, causing the air in the mould to be drawn out, and at the same time pressure of any required degree may be applied to the piston. This pressure bursts that portion of the asbestos lining that lies immediately over the hole in the cover-plate, and the metal is instantaneously shot into every portion of the matrix in the mould.