Sizing a Platinum Ring

April 1998

For Your Staff:Platinum Bench

Sizing a Platinum Ring

The ins and outs of ups and downs in changing sizes

by Jurgen J. Maerz, Manager of Technical Education
Platinum Guild International USA

Many factors determine the best method for sizing a platinum ring.

As a general rule, the lowest melting point of an alloy mix is the highest melting point of the solder used. If you have a bimetal ring, such as platinum/18k, use a gold solder. Otherwise, the high temperature used with platinum solder would damage the ring. In this case , the platinum portion can be sized with a 19k white hard solder. This solder looks like platinum and the seam can be hidden or made invisible with a tungsten burnisher and a gentle polish.

Meanwhile, keep in mind that one size equals 2.25mm or 1/10th of an inch. Sizes or other fractions of a size are a fraction of this measurement. For multiple sizes just multiply by 2.25.

The preferred method of sizing a platinum ring is welding. Wedge a small piece of thin platinum sheet into the seam and weld it all the way around using a very hot oxidizing flame. Then file the weld away for a seamless repair. You usually can use the piece you remove from a ring when sizing it down. This guarantees a color match and identical alloy.

A platinum/cobalt ring should be sized with 1700 platinum solder. You can use the same wedging method outlined above. Because the ring will oxidize slightly, wait until it has cooled or has been quenched, then dip it in fire coat (boric acid/denatured alcohol mix) and heat to a bright orange. Then pickle and the oxidation will be done.

It's a good idea to keep a solution of 10% nitric acid in a small pickle pot. Soak your platinum in it before applying any heat. This dissolves many particles of other metals that may have become attached during filing.

When soldering or welding, always wear at least No. 5 welding goggles. If working near stones, you may have to remove them or use gold technique.

Copyright © 1998 by Bond Communications.


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