TREATMENT AND CARE OF PEARLS 377
to
skin off the outer layer, an operation which was performed with so much
success that the original brilliant black hue was fully restored,
proving that the action of the sunlight had only changed the color of
the surface. We may add that the pearl, although it was shown in the
sun, may never have had a good "skin" or layer exposed; or the layer
which was not perfect may have been affected by an exudation of the
wearer produced by illness or medicine.
When
pearls are of a poor yellow or dull brown tint, unscrupulous dealers
sometimes intrust them to an operator who drills them almost entirely
through, cracks the skin slightly and impregnates them with a solution
of nitrate of silver ; this affects the outer layers of the pearls,
and, after its decomposition, the metallic silver is deposited, and
they become absolutely black. The effect is sometimes hastened by
exposing them to the fumes of nitrate of silver. These pearls are then
rubbed up or slightly polished and may retain a good appearance for a
number of years. The upper layers, however, which have been injured by
the chemicals used in the coloring, often scale off, and the poor and
unattractive color beneath appears. This is sometimes not detected
until years after and when the dealer from whom they were purchased has
been forgotten. The breaks or cracks which have been made can readily
be detected by means of a pocket lens, if the observer is at all
experienced. In many cases the outer layer of the pearl has been
colored a good black, although scarcely any crack is visible.
Frequently,
when a small knob or protuberance appears in the pearl, or when it has
adhered to another pearl or to the shell itself, this protuberance is
polished off, and the pearl is drilled at this point. This portion of
the surface, however carefully polished, will never have the true
orient, but it is placed in the necklace in such a way that it is
completely hidden. Often pearls become scratched through rough usage,
or by the knife used in opening the shells. These are occasionally
polished by means of pearl-powder, or else the entire outer layer is
removed, the new skin beneath appearing absolutely bright and perfect.
It sometimes happens that a pearl will have a good luster, but a
slightly roughened skin. This is at times polished down; but an
experienced eye easily detects that it has been tampered with.
Yellowish pearls are sometimes bleached by means of strong bleaching
substances such as chlorine or other powerful reagents, which, although
they may whiten the pearl, cause it to become very friable, as the
animal substance becomes more brittle. Pearls treated in this way
frequently wear off, layer by layer, until fully one half of the pearl
is worn out of the setting. When pearls are stained yellowish from the
exudations of the skin, grease, or other impurities, they can be
cleaned by putting them in moist caustic mag-
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