Now that the desired outline has been obtained, the stone is firmly
affixed to a slender wooden or hollow aluminum dop-stick (fig. 4). The
process whereby the stone is attached to the dop-stick with a specially
compounded jeweler’s wax is called dopping. The dop-wax is heated over
an alcohol lamp or candle flame until it is soft and pliable and is then
spread around on the end of the dop-stick and formed into a mass about
the right size and shape to fit the back of the gemstone. The stone is
likewise heated, and the wax is applied to the back of the stone while
both wax and stone are hot. Upon cooling, the wax firmly fixes the stone
to the dop-stick. The dop-stick allows the lapidary to have firm control
of the stone during all later stages of cutting and polishing.
[Illustration: Fig. 4. Cabochon properly attached to dop-stick.]
CABOCHON
DOP-WAX
DOP-STICK
The top of the dopped gemstone is worked against the coarse carborundum
grinding wheel until it is a rough approximation of the desired shape.
The stone is then worked against a much finer-grained (about 220 grit)
grinding wheel to remove the irregularities left by the coarse grinding
and to further smooth and shape the surface of the gemstone. At all
times while grinding, a small flow of water should be directed on the
grinding wheel to keep the stone cool. Grinding on the stone for even a
few minutes without cooling may result in the shattering of the gemstone
because of heat created by friction of the stone against the grinding
wheel. If the lapidary keeps the surface of the grinding wheel wet,
there is little chance of damaging most gem materials.
The next phase of cabochon cutting and polishing is sanding. The
gemstone is worked against two sanding drums of different grit size.
This sanding can be done with the sandpaper surface either wet or dry,
as needed or as preferred by the lapidary. However, great care should be
exercised during sanding so that the stone is not overheated.
Overheating can easily occur whether the sandpaper is used wet or dry.
As in grinding, sanding is first done on coarser grit paper (about 300
grit) and last on finer paper (about 600 grit). It is in the sanding
process that the first hint of polish is noted on the surface of the
stone. After sanding, the gemstone should have perfect form with no
surface irregularities, a very finely textured surface, and only very
minor scratches left from sanding. The gemstone is now ready to be
polished.
[Illustration: Fig. 5. Cabochons at various stages of cutting and
polishing. Left to right: trimmed from slab: ground to outline; after
rough grinding; after sanding; polished.]
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