All About Pearls: Traditional Treatments

 

 

Baroque Freshwater Cultured Pearl and Diamond Earrings, Yael DesignsBaroque Freshwater Cultured Pearl and Diamond Coordinating Earrings, Yael Designs

Cultured pearls are well known for their delicate natural beauty. With what seems like minimal effort a beautiful gem is birthed from a strange and slimy sea creature. But it isn’t quite that simple. There are several treatments cultured pearls undergo that are considered “traditional”. Sometimes these traditional treatments are instead referred to as “processes” for reasons of legality and ease.  And depending on the quality of the pearl, amongst other factors, there are several treatments that a cultured pearl may or may not undergo which are not considered “traditional”.

Traditional treatments are those that have been practiced on a gem type for an unspecified “long” time. And because they are traditional and assumed to have been performed on most if not all gems of their type, they are generally not disclosed. There are many gems that undergo treatments, both traditional and not traditional.

 

Linseed Oil for Traditional Treatment of Emeralds, photo by Cecile Raley DesignsLinseed Oil for Traditional Treatment of Emeralds, photo by Cecile Raley Designs

Pliny the Elder lists some of the common treatments of his time as: foils, oiling, dyeing, and composite stones; though of these only oiling is considered a traditional treatment that does not need disclosing. The Papyrus Graecus Holmiensis, a document dating from circa 300AD contains many treatments that are old enough to be considered traditional, but no-one ought use and expect much in the way of success. One purported treatment is this: “Take the pieces of mother of pearl and put them into bitch’s milk. Put the cover upon the vessel and leave it there 2 days and 2 nights. Draw them out, as they lie there strung on asses’ hair, and observe whether they have become white. If not, put them in again until they become excellent in this respect. If you afterwards besmear a man with this he becomes leprous.”

 There are more recent treatments to whiten pearls and restore luster such as those contained in the Papyrus Graecus Holmiensis, and of equally dubious merit. This one comes from an Australian newspaper dating from 1911: “Procure a small loaf of brown bread, in which, before the loaf is baked, the pearls are laid, strung upon a silk thread; or they may be closely wrapped in a piece of gauze. The bread is then allowed to bake thoroughly but not to become brown. When the loaf is taken from the oven, it is allowed to cool, after which it is broken and the pearls removed.”

 

Matched Cultured Pearls

"Pinked" cultured pearls with still visible slight visual variation since pinking is not a heavy dye.

There are three specific traditional treatments or processes that are used on many, though not necessarily all pearls, and to great effect. They are first cleaned in a concentrated water and salt mixture to clean off the pearl. They are then bleached. This fully cleans and removes any organic material that might still cling to the pearl. It also removes or greatly lessens dark spots to even the color and lightens the pearls to a more preferred, whiter shade. The second process most pearls undergo is “pinking”. This is a delicate pink dye that gives a pink overtone to the pearl, which is generally the preferred shade in Western countries. Sometimes a silvery dye is used for a silver overtone. Factories say that the bleaching and pinking, or other similar pale dyes, are done to improve the ability to match pearls and to create a larger number of cultured pearls that are of appealing enough shades to purchase, and that costs would be prohibitive otherwise.

 

Polishing Machine filled with Walnut Chippings, photo by PearlescencePolishing Machine filled with Walnut Chippings, photo by Pearlescence

The third process is to tumble the pearls with gentle abrasive material such as slivers of bamboo, walnut shell or vegetable grit, often in an oily medium such as bees wax or oils. The abrasive material smoothes bumps and minor scratches, while the wax or oils fill small pits and improves the look of the luster. However, the bees wax and/or oils are not permanent.

 

Natural Pearl of which some of the Nacre layers have peeled awayNatural Pearl of which some of the Nacre layers have peeled away

There is one more traditional treatment, but it is seldom used. In this treatment, any stained, dull or damaged layers of nacre are carefully peeled away. This treatment requires a highly skilled hand. It was much more commonly used on natural pearls as there was no worry of peeling the nacre off the bead nucleus entirely.

Generally, those treatments that go under the heading of "traditional" are those that add to the beauty of the pearls, but are not detrimental to the pearl itself. There is no such guarantee with the non-traditional treatments, some of which may be performed in conjunction with traditional treatments. These can affect how well the pearls age over time. We will discuss them in our next blog post

Baroque Freshwater Cultured Pearl and Diamond Pendant, Yael DesignsBaroque Freshwater Cultured Pearl and Diamond Pendant, Yael Designs

 

 

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