Pearl Treatments

When buying or selling pearls, the question of treatment often arises. Pearl treatments are defined as any process other than polishing that alters a pearl's appearance. These processes may include; irradiation, bleaching, heating, filling, waxing, drilling, cutting and working. After harvesting, pearls are always cleaned and polished and almost also treated in one way or another. Pearl farmers have several options for dealing with inferior quality cultured pearls. The pearls can be discarded, sold at a deep discount, or treated to improve its appearance. Treatment is the most cost effective approach for selling lesser quality cultured pearls.

The following important product knowledge is offered to help educate you about the common and acceptable types of pearl treatments encountered in the marketplace today.

• Pre-Treatment
  Most culture pearls, including saltwater, freshwater, and South Sea pearls are bleached to even out even dark area under the surface of the nacre. This is a permanent treatment that provides a more uniform appearance and prepares the surface of the pearls for other treatments.

• Dyeing
  Silver nitrate or other organic dyes are used to darken the nacre of freshwater pearls. The chemical reacts with light and hydrogen gas when pentrating the nacre and produces a rich black color. Because pearls are very porous organic and chemical dyes are easily used to produce colors in freshwater pearls. Pearl dyeing is a popular freshwater pearl treatment. Over time dyed pearls can fade, especially if exposed to sunlight or water for long periods of time.

• Irradiation
  Another common method of treatment is irradiation. This process involves exposing the pearls to gamma rays. This process darkens the nucleus of saltwater pearls and the nacre of freshwater pearls. Some irradiated freshwater pearls will develop an intense metallic sheen or iridescence after the process. Irraditation is a permenant and irreversible treatment.

• Luster Enhancement
  Some pearls are coated with a coating similar to clear nail polish. This is not an acceptable practice. The luster will appear to be as smooth as glass, but with time will chip and peel leaving a low luster pearl.

The value of a pearl is impacted by the type of treatments it is subjected to. Since most pearls on the market today are treated in some way, it is important to look for the tell-tale signs of treatment, especially if the cost seems out of line with the quality of the strand of pearls you are considering.

The string, dyed pearls are strung on will be the same color as the surface of the pearl and often the edges of the drilled holes in the dyed pearl will be a darker hue of the surface color. Irradiated pearls are hard to detect, but an intense metallic sheen is often an indication of irradiation.

Learn About Pearl Quality

Sources:
Pearlsby Fred Ward, Gem Book Publishers, Bethesda, Maryland
:http://gemologyonline.com/treatment.html
http://jewelry.about.com/od/gemstonetreatments/Gemstone_Treatments_Procedures_that_Enhance_Gemstone_Appearance.htm
http://www.gemsociety.org/info/igem7.htm