MAKING PEARLS TO ORDER

Press, Volume CIII, Issue 30633, 26 December 1964, Page 5

MAKING PEARLS TO ORDER

(Specially written for “The Press” by DAVID GUNSTON] FkESPITE enormous progress in modern synthetics, it still requires a living oyster to make a pearl. And as women the world over still wisely require pearls, human ingenuity still has to be linked with the humble mollusc. The latest development from Japan, traditional home of pearl production, is the growing of pearl oysters in tanks, indoors on the laboratory bench. Cultured pearls, known now for over 60 years, are merely ordinary oysters artificially “seeded” to yield a pearl but living in natural sea water in tidal beds. As such they were as much at the mercy of typhoons, tidal waves and unfavourable currents as their wild cousins. Glass Tanks Now. it has been proved possible to rear pearl oysters much more artificially in glass tanks of sea water, thereby freeing the industry from its great natural hazards. This is the very recent achievement of researcher Y. Kuwatani and his assistants at the National Pearl Research Laboratory at Kashikojima. and it opens up possibilities of real advance in the much more inexpensive culture of fine pearls.

Formerly it was thought that although oysters would survive in indoor tanks, they would not grow, let alone produce valuable pearls. There had also been much deIbate as to what an oyster

actually lives on. Prominent in an oyster’s diet is plankton, but other experts have maintained that the bivalve also requires ammonia, calcium, and other essential chemicals that it absorbs from the water. Tiny Plants Kuwatani and his team filled their tanks with aerated sea water containing plentiful supplies of microscopic plants called diatoms. These were specially grown in large numbers in the laboratory. The water in the tanks was changed every day, and was continuously purified and aerated except at the once-daily feeding-time. The initial experiments extended for three months, during which time all the oysters in the tests grew normally and began to produce cultured pearls. Six small tanks were used with their water kept at a constant temperature and their dissolved oxygen regularly replenished. Stagnation of the water was most carefully avoided and the plankton was diluted with fresh sea water and siphoned into the tanks. In these six tanks lay the hopes for future development of the entire vast Japanese pearl industry, and although much still has to be achieved, particularly in comparing results with different forms of oyster food, the results attained offer new hope for the industry. Kuwatani and his collaborators themselves are highly pleased with the promising results of their work, and are now engaged on a more comprehensive project aimed at generally improving oyster culture under these controlled conditions. Since 1900 The Japanese, of course, have always been prepared to work patiently with the lowly oysters to wrest from them handsome natural pearls for

the inexpensive adornment of women everywhere. It was in 1900 that the clever genius who invented cultured pearls, Kochiki Mikimoto, brought his iong battle with the fierce natural weather conditions of Japan to a successful conclusion by producing the first spherical pearl grown artificially in a living oyster. He eventually overcame many setbacks, most of them connected with the ravages of the weather, to build up the enormous pearl industry of Japan. Since his early beginning, and omitting the war years, Japanese pearl production has increased steadily every year. Now, rising 40 million dollars’ worth, or over 90 per cent of the total output, are exported. All this time vari-

ous improvements have been made in the arranged cycle from hatching of egg to the final harvesting of the pearl. Mikimoto himself, after much effort, induced his oysters to live longer. Normally the life span of a pearl oyster is only eight years, but he extended it to 10 years, largely by painting the molluscs with a special coating that strengthens their Shells. The productivity of each oyster has also been increased from one to three or four pearls. Another valuable discovery was that the salt content of the water affected the final colour of the pearl, which enabled especially favoured colours like pure white and pale blush pink to be concentrated upon. Under natural conditions a pearl is produced only when an oyster finds itself irritated by a minute particle of mud or sand that it cannot expel. The creature then coats the troublesome speck with a satin-like substance known as nacre. Layer after layer of nacre is coated on to the irritant, and each is bonded together by an organic material called conchiolin, which closely resembles the enamel on our teeth.

To make a cultured pearl a fragment of hard membrane from another oyster of the same species is grafted into each bearing shellfish. This sets up the necessary irritation so that a pearl begins to form inside its enclosed sac. To promote normal pearl growth and to support this sac a tiny white, spherical core made from the shell of a freshwater mussel is also carefully introduced into the mother oyster’s tissue. This is an operation requiring infinite care since the slightest error could kill the oyster or cause it to disgorge this nucelus. The Japanese long ago discovered that the

patience and dexterity required for this work were ideally suited to their own womenfolk, many of whom “seed” mother oysters at the rate of hundreds per day. With outdoor oyster beds this operation had to be confined to a limited season each year. Now, thanks to Kuwatani and his discovery, cultivated oysters may be “seeded” and harvested at any time.

All in all, the pearl looks like becoming even more widespread and favoured as a feminine adornment than it has ever been over the last 2000 years. If every woman’s dream of wearing fine pearls does not come true it will not be for science’s want of trying.