How Cultured Pearls are Grown
Early pearl cultivation involved planting a nucleus in wild oysters. While some seek to jump-start the natural process by implanting a tiny piece of pearl mantle inside the oyster, others use beads designed to create a larger pearl in the shortest period of time and help to control its shape. Along the way, Japanese scientists identified strains of oysters with the best pearl-bearing qualities and focused on using them to produce pearls of high lustre and clear, uniform colour.
The Culturing Process
Technicians open the live pearl oysters then gently surgically implant a small shell bead along with a tiny piece of mantle tissue. This bead is the nucleus around which the oyster secretes layer after layer of nacre, the substance that forms the pearl. This step of the culturing process requires tremendous skill and precision. The oysters will only allow their shells to be pried open 2 to 3 centimetres or they will reject the nucleus. Experienced technicians use exacting tools to make the tiny incisions.
The nucleated oysters are quickly returned to the sea, housed in individual mesh pockets that are suspended from floating rafts. The oysters feed and grow in sheltered bays rich in natural nutrients. As time passes, the oysters secrete lustrous layers of nacre around the implanted bead. In winter, the oysters are moved to warmer waters. Pearl technicians monitor water temperatures and feeding conditions daily at various water depths and move the oysters to take advantage of the best growing conditions.
Periodically, the pearl-bearing oysters are lifted from the sea for cleaning and health care. Seaweed, barnacles and other growths are removed from their shells and they are treated with compounds to prevent parasites from injuring the tender flesh of the oysters. These precious oysters are meticulously protected from every conceivable threat to ensure the finest resulting pearls. However, typhoons, red tides of plankton and predators all take their toll before the pearls are ready to be harvested. Once the oysters are brought back to shore, the pearl farmers take inventory of the long-anticipated harvest. Of the millions of oysters nucleated every year, only a tiny fraction of them produce high grade pearls. On average, about half of the nucleated oysters do not even survive to bear pearls. Less than five percent of the survivors yield pearls of the ideal shape, lustre, and colour to be considered fine quality. The few pearls that make the cut are then cleaned, soaked and sorted.
The newest crop of pearls go through a series of gentle treatments to prepare them for jewellery. The pearls are first soaked for several days in a mild cleaning solution, under intense fluorescent light, to remove any deposits and odours they may have accumulated during their days in the ocean. The pearls are then bathed in a wooden vat of finely crushed walnut shells. The natural oils from the shells provide a soft, gentle polish without harming the integrity of the pearl's surface. After they receive their luscious spa treatments, these pearls are painstakingly matched.
Finding the Perfect Pearl
To assemble a single strand, workers must comb through thousands of pearls to find ones that match for size, shape, colour, lustre and surface quality. First, the pearls are poured into special sieves that separate them into size groups. They are then sorted into increasingly smaller batches according to shape, body-colour, overtone and, finally, quality. This time-intensive, detailed work can take months to complete.
Upon completion of this process, the pearls are finally ready to be drilled and mounted. However, before a pearl is set into a piece of fine jewellery, it undergoes more rigorous screening processes. The matched lots are further separated into perfect pairs to create, for example, a pair of earrings or a well-matched group will be carefully arranged to make a subtly graduated strand. One by one, each pearl is individually drilled and strung onto temporary strands called loose hanks. These hanks are sold at auction.