How cultured pearls are made
A pearl, unlike gemstones or precious metals, is grown by a living creature. A natural pearl forms when an irritant, such as a parasite or a piece of sand, accidentally enters the body of some species of oyster, mussel, or clam and the mollusc cannot get it back out. As a defence mechanism, the mollusc secretes a smooth, crystalline fluid called nacre to coat the intruder. This is the same secretion it uses to build and line its shell.
Saltwater pearls
Start with baby oysters which are either artificially bred in a hatchery or allowed to spawn naturally
Baby oysters are put in cages and suspended in water,which also provides a good food supply.
Sea oysters likeis to be in a bay supplied by a freshwater river which brings food along with it, but too much freshwater is harmful.
Temperature is also important. Oysters like warm water...about 75 degrees is ideal.Sudden changes in temperature can injure or kill the oyster or affect any pearls. Some pearl farmers move their oysters to warmer seas during the winter.
To make the nucleus bead shells are cut into large strips, then the rough outer shell is chipped from the inner shell and broken into small chunks which are ground down to round balls which vary in size from 2.5-8 mm. These are fine polished.
Now, the nuclei are sold to pearl farmers for implantation.
Early in the morning of the day an oyster will receive a nucleus, they are taken out of the water and placed in dry containers in a shady spot. After about 1/2 hour all the oysters should have opened their shells. They are pegged open with a wooden wedge but if they have not opened they will be returned to water for a day
Now they are ready to be nucleated..
Each operator has strips of prepared living mantle/epithelial tissue to be inserted with the nuclei. One oyster must die to provide this tissue which is cut from its mantle and its rough edges cut away, for 14-15 inserted nuclei. The strip of tissue is cut into tiny squares and stays alive for only two hours.
The oyster is secured in a clamping device in front of the operator and either the wooden wedge is left in place or a retractor which allows the shells to be forced further apart is inserted. If the oyster is opened too far it will die.
The technician makes a 1/2 inch incision into the body of the oyster at the gonad or at the connective tissue then places the mantle tissue and nucleus (dipped in water and held by a suction tool) into this slit. The two insertions must be touching, or a pearl sac will not form.
The wedge or retractor are removed and the oyster placed straight back into sea water. This whole process takes less than a minute but it is reckoned it will take the oyster more than a month to get over the shock. At the same time the implanted epithelium should begin to form the pearl sac around the nucleus and start to add layers of nacre. It will take between two and four years for the pearls to form.
Nacre is mostly carbonated calcium. As long as the irritant is present the mollusc continues to add layers of nacre until a smooth lustrous pearl is formed.
Salt water cultured pearls are seeded with a round bead, which is why they tend to be more often a good round shape.
In freshwater mussels, the insertion alone is sufficient to start nacre production. No mother-of-pearl beads are needed. Therefore cultured freshwater pearls are all nacre, so they are real pearls, just like their natural freshwater and natural salt water counterparts. Salt water pearls can only be produced one per oyster, but freshwater mussels are willing to produce many pearls each.
(Majorcan pearls are not real pearls, by the way, they are wholly man-made)
There are many natural colours of pearls; pink, peach, purple, yellow, white, grey, brown, champagne and black. Only freshwater pearls are ever pink, peach and purple.. Black pearls are created by black oysters. The darker the colour is, the more valuable the pearl and black pearls with a little bit of green are the most precious.
Other colours are created artificially by dyeing or irradiating the pearls, or treating chemically. It is quite hard to tell with some colours whether or not a pearl has been treated (although a deep blue or hot pink pearl is never natural). White Pearls have sometimes been bleached). Irradiated pearls are often silver/grey, blue, green, or gold to brown. Most dyed pearls are colourfast, and irradiated pearls won't lose their colour, and are not radioactive.
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