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FLASKFNC^,, VULCANIZING AND FINISHING. 49

objects in view l)y affording too free an escape of the soft-
ened rnl)l)er, tlnis preventing that condensation of the in-
closed material which is necessary for the production of
the best results.
Before packing the rul)ber the case should be thoroughly
dried and the cast coated with something to prevent the
rubber from penetrating the pores of the plaster and ad-
hering to its surface, thus giving a smoothness to the pala-
tine surface of the plate. For this purpose tin-foil or
li(|uid silex is generally used, but we have found excellent
results can be secured by sprinkling lycopodium or soap-
stone upon the surface of the cast. This should then be
thoroughly brushed off wdth a jeweler's brush or a soft
brush wheel, leaving the surface of the model with a high
polish.
The case should now be made cjuite warm, by placing it
in an oven or over a gentle flame, which will aid materially
in packing the rubber, as it more readily adheres to a warm
surface.
Packing Rubber.—Before packing it is important to see
that the mold, instruments used, and the rubber are perfectly
clean. Then cut the rubber into narrow strips about an
inch in length, and in small squares, to pack around the
teeth, also one or tw^o larger pieces to cover the body of the
cast. Place these pieces upon a metallic plate (tin or zinc)
over a pan of hot water. The small pieces of rubber should
now be carefully worked beneath and between the platinum
pins, with small curved and straight pointed instruments.
Then proceed to fill the mold by adding small pieces, one
at a time, after each successive piece has been thoroughly
impacted, and finish the packing process by adding one
larger piece, which should be of sufficient size to cover the
palate, with a smaller piece over its center. This will
make the center a little fuller than the remainder of the