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GOLD. 213

the purpose indicated, no cstinialc can ])e given that will
apply to all cases. Usually, however, plate for entire upper
(Iriiliires should correspond in lliickiicss :^'ilh ininiber 26 of
the gage plate; for the lozcer jcra', luuiiber 24 may he used
while for partial upper pieces, an intermediate number may

Fig. 178.

be chosen, unless atmospheric pressure-plates are used, when
the number recommended for full upper sets may be em-
ployed.
Thickness of Plate for Clasps, Backings, etc.—Plate
for these purposes should usually correspond with number
22 of the gage; a less amount of substance may be used,
however, when the alloy has incorporated with it a small
proportion of platinum.
—
Reduction of Gold Solders into Proper Form for Use.
The method of converting gold solders into the form of plate
does not differ from that already described in the manu-
facture of plate as a base, except that when zinc or brass is
used, the latter should be added after the other constituents
are completely fused, and then instantly poured, to prevent
undue wasting of the base metals by a too protracted heat.