Page 59 - My FlipBook
P. 59
FLASKING, VULCANIZING AND FINISHING. 47
section may he made to cover the wax rim within half a
Hne of the porcelain gnms. This will protect the cast, so
that it will not he fractured when parting the flask or when
packing" the rubher. This method is represented in Fig.
22. Or, the base of the cast may be so trimmed that the
undercut will approach as nearly as possible the perpendic-
ular, as seen in Fig". 23. When the latter plan is adopted
Fig. 23.
the flask, before opening, should be moderately heated in
water to about a temperature of 120° F. Allow it to re-
main in the water for a few minutes, so that the heat may
penetrate to and soften the wax. Then remove the flask
and separate the two sections carefully. If these directions
are followed, the wax will generally part readily from the
teeth and plaster. If any adheres to the pins, it should be
carefully washed out with boiling water."
The necessity for removing every particle of wax is due
to the fact that its presence destroys the integrity of the
rubber and interferes with its vulcanization. It is better,
therefore, in all cases, to direct upon the cast a stream of
