Page 275 - My FlipBook

GOLD. 273

times, making; a broad ribbon, which may be cut either lengthwise or
crosswise of the ribbon in pieces one-sixteenth or one-eighth of an inch
in width (see Fig. 225). This is a very convenient manner of working
cohesive gold. Or the heavier foil up to No. 20 or Xo. 30 in thickness
may be cut in strips of a single thickness and of the widths above indi-
cated, and after annealing may be packed into the cavity—the essential
idea being ever in mind, that but a small quantity of the gold shall be
under the instrument at a given time. Cohesive gold which has been
rolled instead of beaten to the desired thickness is much prized by some.
It has been asserted that greater softness is obtained when gold has been
thus ]ireparcd. Such gold should not be more than No. 20 or No. 30
in thickness to insure the best results. It should be cut in narrow
strips and after annealing be folded back and forth as rapidly only as
each previous fold has been well conden^^ed. Good results are only
attainable if each lamina be thoroughly welded.
The loosely rolled cylinders and blocks which are prepared by some
dealers and offered as cohesive gold are usually but slightly cohesive,
and if used in this form, without re-annealing, may be packed in the
interior of cavities without danger of clogging, but if freshly annealed
they are contraindicated, since there is more or less danger of imper-
fect union of all particles of the gold. It is questionable whether the
larger sizes are admissible when the filling extends beyond the cavity
walls and great solidity is an essential factor.
Crystal Gold.—This form of gold was introduced by Mr. A. J.
"Watts in 1853, and as prepared at the present time is one of the best
preparations of cohesive gold. When first brought out the method of
manufacture was faulty, since it was difficult or impossible to rid the
spongy mass of nitric acid which was used in its preparation, but since
Mr. AVatts adopted electrolysis instead of chemical precipitation the
objectionable features no longer exist. Gold thus prepared manifests
great cohesive properties, and when used with care as beautiful opera-
tions can be made with this gold as with any form of cohesive foil. The
operator should not lose sight of the fact that the gold is to be intro-
duced into the cavity in small quantities. Should failure attend its
use, it would doubtless be from the attempt to introduce it too rapidly.
Gold of this variety comes in bricks containing one-eighth of an ounce
each, and is either torn apart in irregnlar-shaped pieces or cut by means
of a razor into small cubes. This gold should be excluded as much as
possible from the atmosphere and when used should be well annealed,
although when recently made it is quite cohesive. There is no prepara-
tion of gold better adapted for starting fillings in shallow or irregular
cavities, or for surfacing fillings. Many operators make use of it
always for starting and for finishing fillings.
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