After harvest pearls are always processed in one way or another. Akoya and freshwater pearls are routinely bleached, and all pearls are cleaned and polished before sale. But there are treatments that should be noted on cultured pearls that change the aesthetic qualities of the gem.

After cleaning a polishing a low-quality cultured pearl, and if the pearl does still not have a good luster or color, the farmer is left with few options. He can sell the pearl at a steep discount, dispose of the pearl, peel the nacre to be sold and reuse the nucleus, or impose a treatment to the pearl that will change its appearance. If the pearl is a good candidate for treatment, this is the most common and economically sensible approach for the farmer. There are three main treatments that low-quality pearls undergo:

• Dyeing - The use of silver nitrate to darken the nacre of the pearl.
• Irradiation - The use of gamma rays to darken the nucleus of the pearl in akoya pearls and the nacre layers in freshwater.
• Luster treatments - Typically a coating treatment placed on the surface of the pearl to artificially enhance the luster.

Silver nitrate has been used for many decades to darken the appearance of pearls. The chemical penetrates the layers of nacre and has a chemical reaction with light or hydrogen sulfide gas to create a rich black color. If the farmer wishes to create colors other than black he may also use organic or inorganic dyes to produce another color variation. This is a very popular treatment done to freshwater pearls as the lower values give farmers more opportunity to experiment. Akoya pearls are also routinely "pinked" to enhance a more desirable rose overtone.

Irradiation has differing effects from freshwater to saltwater cultured pearls. The gamma rays do not affect the nacre layers of a saltwater cultured pearl, but in fact darken the nucleus of the pearl. An irradiated saltwater pearl appears to be gray or blue. The nacre of freshwater irradiated pearls, on the other hand, if affected by the gamma rays and can become very dark. Some of these freshwater treated pearls will also have an intense metallic sheen and iridescent orient over their surface.