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76 MECHANICAL DENTISTRY AND METALLURGY.
is desirable in upper dentures, and which is not possible
to obtain with the ordinary soldered work.* The case is
now ready to be flasked, and should be treated as an ordi-
nary celluloid denture to the finishing process. Figs. 42
and 43 suggest the appearance of the denture before and
after the celluloid attachment is finished.

ARTIFICIAL DENTURES CONSTRUCTED BY
THE SWAGING PROCESS.

Forming the Dies and Counter-Dies.—From the various
methods which have been adopted, we will here consider only
the one which has proven the most satisfactory and is most
generally used. It consists in pouring melted metal into a
mold, made in sand or marble dust, from a plaster cast.
After the die is thus secured, the counter-die is obtained
by pouring upon it metal which melts at a lower temperature
than that of which the die is made.
Materials for Molding.—As we have stated, either sand
or marble dust is usually employed for making molds. Mar-
ble dust absorbs sufficient moisture from the atmosphere to
render it cohesive, which gives it the advantage of being
always ready for use ; it is also more cleanly to handle than
sand, and gives a very smooth and uniform surface to the
die. When sand is used it should be very fine, such as is
used by brass founders.
It should be mixed with just sufficient water to render its
particles thoroughly adherent. An excess of water should
be avoided, as the vapor formed by the molten metal, when
it is poured into the mold, will displace portions of the sand
and form cavities or blisters upon the face of the die; nor

* For a full description of this method see Richardson's " Mechanical
Dentistry," Seventh Edition.