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214 MECHANICAL DENTISTRY AND METALLURGY.

The solder should be reduced to plate somewhat thinner
than that used for upper dentures, about 28 of the gage plate.
It is customary sometimes to roll the solder into very thin
ribbons, but this is objectionable for the reason that a greater
amount of the alloying metals, being exposed in a given
surface to the action of the heat in soldering, are burnt out
or oxidized, which interrupts the flow and weakens the
attachment between the solder and plate.
Fig. 179.

Method of Obtaining Gold Wire.—To convert gold or its
alloys into the form of wire, the operator should be provided
with a draw-plate, a vise, and a pair of flat-nosed pliers. A
draw-plate (Fig. 179) is an oblong piece of steel, pierced
with a regular gradation of holes, or a series of progressively
diminishing apertures, through wdiich the gold bar, reduced
to a rod, is forced and made to assume the form and dimen-
sions of the hole through which it is last drawn. The holes
are formed with a steel punch, and are enlarged on the side
where the wire enters and diminish with a gradual taper to
the other side. A drazv-hcncli is sometimes employed in
extending the wire, the power being applied by a toothed-
wheel, pinion, and rack-work, and is moved by the hands