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yS MECHANICAL DENTISTRY AND METALLURGY.

closely and firmly around and over the cast until the ring
is evenly filled. Considerable care should be observed in
manipulating the molding material when packing. If it
is too compact, the vapor formed in pouring the hot metal
will not be able to pass out readily, and may cause imperfec-
tions in the face of the die ; and, again, where it is too loosely
packed the fluid metal will, to some extent, permeate the
pores and render the face of the die rough and imperfect.
Level off the surface of the sand with a wooden rule, lift
the flask or ring with its contents from the bench, turn it
over carefully, and lay it down with the bottom of the cast
up. Now run the point of a knife or spatula, held at an
angle of about 40°, all round the cast, so as to make a bevel
in the edge of the sand. Next press the sand around the
cast firmly with the fingers, then brush away any loose par-
ticles that may remain, that none may fall into the mold
when the cast is withdrawn. The point of an ordinary tack
or pin, or the small blade of a knife, should now be carefully
driven into the center of the cast by a few gentle taps from
the hammer. Grasp the head of this firmly between the
thumb and fingers, and with a small hammer distribute a
few gentle taps over the surface of the cast. If the cast
cannot then be withdrawn, continue the process, and at the
same time give a few light blows to the edge of the molding
ring, when it will usually be found that the cast can be
readily lifted out.
All these manipulations must be very gentle, or the cast
may be tilted or rocked in the sand, thus making a false
impression.
Another method of removing the cast from the sand,
practiced by many and as usually given in the text-books, is
to re-invert the ring and contents, hold it above the table,
and dislodge the cast by tapping it gently underneath. It is
self-evident, however, that the former is the better method.