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Akoya Cultured Pearl Treatments
by: Yvonne

Morning Mary-Jo

your Mikimoto Cultured Pearls with light pink overtones sound just gorgeous! Mary Jo you might like to consider having them re-threaded.

You might be interested to know more about the identification of cultured pearls. Like many gem materials, Akoya cultured have a long history of "accepted" treatments to improve their appearance.

In the early years of the 20th century Japanese producers, such as Mikimoto developed a number of processes to improve the appearance of their pearls.

None of these treatments were disclosed and they remain undisclosed to this day. In recent years however, blurring of the boundary between "acceptable process" and a "treatment" as foreign substances are sometimes used to improve or change the color or add lustre.

The first step in traditional Akoya processing, called "maeshori" involves immersing the pearls in a solvent, usually methyl alcohol, for cleaning. Originally performed before bleaching to make that process more effective, it is now used alone on virtually all cultured pearls to improve their luster.

The next step in the traditional process is beaching which removes dark organic compounds and creates a purer white. This usually involved immersing the cultured pearls in dilute hydrogen peroxide under low heat in controlled lighting conditions.

After bleaching some pearls are are treated with an additive to create the slightly pinkish overtone seen in many Akoyas; like your Akoya pearls Mary Jo with the wonderful light pink overtone. Some dyes can even simulate attractive natural colors. In the early 1920s and 1930s the Japanese producers used "cosin" - a vegetable dye; today they use a variety of coloring agents. The final step is "tumbling" which improves the luster.

For an on-line valuation please see the expert appraisal page...

Warm Wishes,
Yvonne Hammpuda-Eyre

Reference:
Akamatsu, S. (2007) Sorting it all out. GIA's Pearl Report and industry opportunities. Panel discussion at GemFest Basel, Switzerland, April 14.

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