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Expert gem setters share their
tips — and warnings — for working with colored stones.
By Suzanne Wade
remove the colored stone before working on a piece unless you are
confident it can withstand the heat of soldering and you can afford to
replace it if it's accidentally damaged.
coat sapphire or ruby with boric acid to protect the stone during
soldering. Although this is common practice with diamonds, heated boric
acid will etch the surface of corundum.
polish prongs and bezels aggressively when setting colored stones,
especially softer stones such as tanzanite. Bench jeweler Bradney Simon
suggests coating softer stones with fingernail polish. "The fingernail
polish is not hard enough to completely protect the stone, but it will
give some protection from abrasion," he says. "More importantly,
it will serve as an indicator. If you scrape the fingernail polish off,
you are too close!" After setting and polishing, a soak in acetone
will remove the fingernail polish. (Simon notes, though, that this trick
shouldn't be used on emeralds, where the acetone could remove possible
oiling.)
test your pumice wheels and other abrasive wheels on a piece of glass.
"If they do not abrade the glass, they will not scratch most faceted
stones and would be safe to use cleaning up the prongs," says Simon.
put any colored stone in the jeweler's pickle unless you're certain
it can withstand acids. (Pickle is an acid bath used to clean jewelry
after soldering and other repair processes.) Many colored stones — including
turquoise, pearl, and lapis lazuli — can be destroyed by acids.
put any colored stone in an ultrasonic or steam cleaner unless
you're certain it will not be damaged by these cleaning methods. For example,
ultrasonic and steam can strip the oil from a fracture-filled emerald,
leaving the jeweler to explain to the customer why their stone looks considerably
less attractive than when she left it for repair.
let accent diamonds touch a colored center stone. "If one of the
diamonds comes loose and rubs against the center stone, it will cut a
groove into the stone," warns Simon.
examine every stone for evidence of treatment, even if it's of a variety
that isn't typically subjected to enhancements, and it comes from a trusted
source. Custom jeweler Frank Goss of Houston, Texas, notes that he recently
was asked by another jeweler to set a 10-carat peridot. Since the stone
came from another jeweler, he didn't check it for treatments — until
the magnification he used to set stones turned up several anomalies. "I
cranked up the magnification on the microscope and surprise, surprise
— Opticon! Filled inclusions through the stone, as well as scratches
that had been filled," he says. "I thank my lucky stars I saw
it before I put the mounting in the ultrasonic or steamer. A very fine
trap for the casual and unsuspecting jeweler."
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