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2IO MECHANICAL DENTISTRY AND METALLURGY,

back of the mold. With this simple -instrument, a sound
ingot may be obtained at any time in a very few minutes.
Aside from the greater convenience and cleanliness, as
compared with the older method in which draft-furnace heat
is used, there is great economy of time in the use of the last-
named appliance combining crucible and mold, since an
ingot may be thus obtained, with the use of the bellows
blowpipe, in from two to three minutes. It is suitable for
melting from two to four ounces of gold or silver.
It not infrequently happens that, at the first pouring, the

Fig. 176.

metals arrange themselves in the ingot in accordance with
the density of the several components, those of greater
specific gravity passing to the bottom, and the lighter metals
remaining above. Whenever this occurs, the ingot must be
broken into pieces and remelted ; this should be repeated, if
necessary, until the alloy assumes a perfectly homogeneous
appearance. It should then be annealed in hot ashes, which
softens the gold and removes the adhering grease.
Forging.—Before laminating, the ingot should be reduced
somewhat in thickness by placing it on an even-faced anvil
or other equally smooth and resistant surface, and subjecting