March 1998


by Jurgen J. Maerz, Platinum Guild International-USA

As you know, extremely high temperatures are used to work on platinum. This releases ultraviolet radiation, which along with the bright light created by the welding or brazing process, is harmful to the eyes. So No. 5- or No. 6-rated safety goggles are a must.

When sizing a platinum ring, welding is the method of choice. With platinum/cobalt alloy, however, the 1700 soldering method is preferred. There's no problem welding like platinum alloys together, but alloys of different composition can't be welded together as they have different melting points. For example, Pt/Ir can't be welded to Pt/Ru. However, Pt/Ru to Pt/Ru poses no problem.

Many fine pieces of jewelry are being manufactured using platinum and 18k gold. A piece of that metal combination requires gold technique for repairs. Platinum techniques would ruin the piece because the higher temperatures required are too high above the melting point of the gold.

Finishing platinum requires a special technique. Usually after the sandpaper finish of 600 grit, the polishing phase begins. A gray compound of 800 grit is followed by a white compound of 1,500 grit, which is then advanced to a prepolish with a 4,000 grit, to be finalized with a luster that a carrot or green rouge will create at about an 8,000 grit.

Slight surface irregularities and porosity can be removed with a tungsten burnisher before the final stage. It's important that a polishing wheel is dedicated to an individual compound and there's no cross-contamination among wheels. The jewelry and the hands must be cleaned between steps. When polishing bimetal pieces, the platinum portion should be finished first, as it takes more steps to polish. Polishing gold next to platinum in one operation will lead to the over-polishing of the gold portion.

Jurgen J. Maerz is manager of technical education for Platinum Guild International-USA. He can answer your technical questions 24 hours a day at PGI's platinum Hotline, (714) 760-8882. He was the fourth in the U.S. to earn the Jewelers of America certification as JA Certified Master Bench Jeweler.

Copyright © 1998 by Bond Communications.


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