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Friday, January 14, 2011

Jewellery And Dentistry Goes Platinum

For many centuries-from the days of the Egyptians up to about 1900 A.D-the metals used in jewellery were gold and silver. Copper and zinc were added to cheapen and to strengthen it. The processes of melting and refining were simple, well known, and adequately described in the literature. A person wishing to learn the art or trade could do so either through the printed word, or by apprenticing themselves to some older artisan.

But at about the beginning of the 20th century, platinum entered the fields of jewelry-making and dentistry. By the time we entered the first World War, it had burst like a nova into first magnitude in the jewellery firmament. Its sister metals, palladium and iridium especially, came along with it. Immediately the problems of refining, separating, and remelting the scrap metal became a problem.

At first, say up to about 1915, comparatively few jewellery shops in the whole world were equipped to melt their platinum scrap, and the task of separating the platinum from the gold scrap was equally beyond their powers; a handful of professional refiners handled the entire output. Reasons for this were several; preoccupation with war was only one. The habit of secrecy among many workers was a potent reason; the institution of apprenticeship was dying out; the literature of platinum was scanty and so highly technical as to discourage the average reader. Platinum was so valuable that in many shops the proprietor did all the melting and refining himself such as it was and excluded all workmen from the room where he worked, thus increasing the superstitions and mis-information that collected around the whole subject.

A practical reason was the fact that the melting point of platinum is much higher than that of silver or gold; so high, in fact, that an oxygen flame is required for melting it. That is, a gold-melting furnace, using gas or coke with compressed air, is not hot enough to melt platinum. The fuel must be combined with oxygen which is now provided in steel cylinders in order to attain the necessary high temperature. The lack of compressed oxygen was a major factor in the non-use of platinum; its introduction at low prices was a major factor in its popularization.

Nor were these the only complications that beset the precious metal worker of the early Nineteen Hundreds. New gold alloys appeared white golds, blue golds and green golds which made refining more difficult. Electroplating became more common, adding its cyanide solutions to the duties of the refiners. Chromium and rhodium plating did their bit to complicate matters. Stamping laws that insisted upon definite percentages of metal and alloy added further to the legal, as well as his ethical responsibilities.

Indeed it has been said, with truth, that there have been more changes in precious metal recycling technology during the last thirty years, than during the previous thirty centuries.
Posted by Mike Gupton at 3:54 PM 0 Comments