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160 OPERATIVE DENTISTRY

SO stiff that the material just loses its gloss when being crowded by a
rotating spatula, yet can be made to show a glossy surface when patted
three or four blows with the spatula. In ease the material looks very
wet and glossy the mix is not yet stiff enough. If the three or four
blows do not produce gloss, the mix is too heavy and must be entirely
discarded.
Time of the Mix. The lower the temperature at which the sili-
cate is mixed the longer may be the time of manipulation; also
the thinner the mix, the longer will it be before the chemical ac-
tion of the setting will be noticed. By using the cold process of
mixing, the time of manipulation is lengthened and the time of set-

I"ig. 99.—The entire mix on the spatula.

lZH

I'ig. 100.—Illustrating in three successive steps the method of removing the mix from the
spatula to the slab.
ting after leaving the slab is materially shortened, due to the thick
mixture obtainable.
Making the Filling. It is important that all moisture be ex-
cluded, as we cannot manipulate silicate under moist conditions.
Agate or ivory instruments are preferred for placing the material
in the cavity. Those of bone or shell Avill do. If the instruments
are absolutely clean and polished so that they will give off no sub-
stance in the material, it is possible to place the silicate in the cav-
ity with steel instruments and get no subsequent discoloration.
Fill the cavity slightly to excess with absolutely clean instruments
by taking a quantity, one-half of that required to fill the cavity,
and crowed or wipe the material against every portion of the cavity
walls from cavo-surface angle to cavo-surface angle. The second
time, take up a sufficient quantity to more than fill the cavity.