Slush Casting
It was noted in Fig. 10.11 that a solidified skin develops in a casting and becomes
thicker with time. Hollow castings with thin walls can be made by permanent-mold
casting using this principle: a process called slush casting. This process is suitable for
small production runs and generally is used for making ornamental and decorative
objects (such as lamp bases and stems) and toys from low-melting-point metals such
as zinc, tin, and lead alloys.
The molten metal is poured into the metal mold. After the desired thickness of
solidified skin is obtained, the mold is inverted (or slung) and the remaining liquid
metal is poured out. The mold halves then are opened and the casting is removed.
Note that this operation is similar to making hollow chocolate shapes, eggs, and
other confectionaries