Thin layers of pearl removed by peeling (faking)
Examples of properly and poorly drilled pearls
Side view of same pearls
PEARL DRILLING
Streeter mentions a very interesting incident in regard to a genuine black pearl. This pearl, set with diamonds, was shown in a jeweler’s window; but after exposure in this way for some time to the sun’s rays, the brilliant black luster disappeared and gave place to a dull, grayish hue. When the pearl was removed from its setting, it was seen that the part which had not been exposed to the light was of as good color as when first removed from the shell. It was finally determined 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 magnesia and allowing it to dry on them. When this is removed, the pearls will often be found much purer in color than before.