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Pearl Treatments
Pearl Treatments
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All pearls must be cleaned and washed to remove residue and odors. They are typically tumbled in rotating barrels with salt during this procedure. The tumbling must be closely monitored; otherwise some of the nacre may wear off. There are other processes which are not considered routine and which should therefore be disclosed. Some of these are listed below.

Bleaching:
Chinese freshwater pearls and medium-to low-quality Akoya pearls are often bleached with chemicals after drilling. This whitens them and makes the color look more even. Improper bleaching can soften the nacre and make it more susceptible to wear, especially if the nacre is thin. High quality pearls do not need to be bleached, and it would be pointless to possibly reduce their luster and durability by treating them. American freshwater pearls, black pearls and light colored South Sea pearls are not normally bleached. However, this is changing with white South Sea pearls. Some are now undergoing chemical bleaching.

Buffing:
This is occasionally done to improve luster and remove superficial scratches. Beeswax or chemical polishes are sometimes used during buffing to add luster. The wax wears off fast and the chemicals may eat away the nacre. Buffing without chemical intervention is considered acceptable if it's done to clean off oil and dirt from the pearl and remove minor scratches.

Coating:
There have been reports of pearls being coated with lacquer, but it's difficult to find samples. If pearls were to be coated in this manner, the lacquer would temporarily improve luster. It would eventually wear off over time, leaving buyers feeling deceived if they were not advised of the coating. Good-quality pearls do not have to be coated to look lustrous.

In a few instances, pearls have been darkened with thin plastic coatings to make them look like Tahitian pearls. This coating can be easily detected by its strange feel and by bald spots on the pearl where the coating may have worn away. Coating pearls in this manner is not an accepted trade practice.

Filling:
Low-quality cultured baroque pearls are occasionally filled with an epoxy substance if they are partially hollow or have a loose nucleus. This helps the bead nucleus stay in position when the pearls are restrung; it makes the pearls more solid and improves their durability.

"Hollow natural pearls are often filled with foreign materials to bring them to somewhere near the weight one would expect for a pearl of that size," reports Stephen J. Kennedy of the Gem Testing Laboratory of Great Britain. He provided this information with supporting photographs at the AGA Symposium `98 Seminar in Tucson, Arizona and in the January-March 1998 issue of the Australian Gemmologist. Natural pearls are often sold by weight. Fillings can be detected with x-radiographs.

Dyeing:
White or cream-colored pearls are sometimes soaked in pink dye to give them a desirable pink tint. This dye can often be detected in the drill holes or in cracks. Yellow and golden pearls may also be dyed. These pearls are especially popular in Asia.

Shane Elen of the GIA Research Department has written some excellent articles on how to identify treated and untreated South Sea yellow pearls in Gems & Gemology: Summer 2001, Spring 2002 and Summer 2002. In some cases, it can be very difficult and even
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