Dyed and irradiated pearls cost less than those of natural color. Irradiated pearls normally cost more than dyed pearls because the irradiation processs is more costly and because it's usually reserved for higher quality pearls. Other kinds of treatment and test for detecting dyed pearls.
The raw harvests are processed at the pearl factories. Firstly, The process starts with drilling holes. Drilling is followed by processing which means that the pearls are either bleached, chemically treated, artificially colored or polished. At last, the pearls are sorted according to the grading factors size, shape, color, nacre thickness, luster and surface.
Firstly, Pearls must be cleaned and washed to remove residue and odors. During this procedure, pearls are typically tumbled in rotating barrels with salt. The tumbling must be closely monitored; otherwise some of the nacre may wear off.
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.
Irradiation - This method works best on freshwater pearls, but off-color Akoya and South Sea pearls may also be darkened in this manner. It involves bombarding pearls with gamma rays. This blackens the shell bead nucleus of Akoya and South Sea pearls and can make their nacre appear dark if it is ' thin. Sometimes pearls are both dyed and irradiated. The irradiation will give them an iridescent bluish or greenish gray color and the dye will further darken their appearance.
Coloring or dying
Off-color pearls from the Akoya and silver- or gold-lip oysters are sometimes darkened with dye to improve their appearance. Then they are sold as "black pearls." Some of the dark dyes make the pearls look iridescent. If black pearls are smaller than 8 mm, just assume they are dyed Akoya pearls. Dyeing these small pearls is an accepted trade practice because it provides consumers with an option that is not available from natural-color Akoya pearls. Nevertheless, the treatment must be disclosed.
Light-colored pearls from the black-lip oyster are occasionally darkened when there is low demand for very light Tahitian colors. Many people associate the term "dyed" with the terms "cheap" and "fake. " However, dyed black pearls were sold in fashionable stores as far back as the 1930's-long before black pearls were being commercially cultivated. Dyed black pearls were considered elegant. They are still in demand. Plus, they have the added bonus of being much more affordable than their naturally-colored counterparts. A large percentage of the pink pearls sold in stores have also been dyed and this means there's a wider selection of pink pearls available for consumers.
If pearls are not properly dyed, the color won't be stable. Therefore it's important to buy dyed pearls from reputable jewelers. That way if there is a problem, you'll be able to return the pearls and get a refund. If you're buying expensive untreated pearls, have them checked by an independent gem laboratory. In recent years, there has been a problem of nacre peeling off of dyed Akoya pearls with thin nacre. On dark pearls, chipped nacre can be quite noticeable and unattractive. As a result, some dealers have stopped selling dyed Akoyas to avoid the hassle of returns and customer complaints.
Polishing - Coating a pearl to enhance its luster is not widely practiced and is greatly frowned upon.