Professional Jeweler Archive: User-Friendly Alloy

July 2000

Precious Metals & Bench/News

User-Friendly Alloy

Silversmiths will appreciate a new silver alloy that helps eliminate firescale, while its tarnish resistance should be a strong selling point to consumers

Imagine being able to work with, weld and solder sterling silver jewelry without worrying about firescale. A new silver alloy, soon to be distributed in this country by Vaasa Ltd., will eliminate firescale and allow silversmiths to create pieces that resist tarnish, says Frank McAllister, cofounder of Vaasa and former chairman and CEO of Asarco, a major silver producer.

The patented alloy is the most important development in silver in 5,000 years, says Richard Fox, chairman of the Association of British Designer Silversmiths, and resulted from 10 years of work by Peter Johns, a silversmith and instructor at Middlesex University in England.

The alloy contains 1.2% germanium, a semiconductor used in early transistors and now used mainly in fiber optic equipment. For the past six years, Johns has worked with Kultakeskus OY, an 81-year-old privately owned silver manufacturer in Finland, to determine the right amount of germanium and other metals to produce a silver product with the best characteristics of sterling without the firescale, says Tony Jackson, Kultakeskus’ technical development manager. The alloy is considered sterling because it is 92.5% pure silver. The germanium adds 7%-10% to the cost of sterling silver.

No Firescale

The most important aspect of the new alloy to silversmiths, say Jackson and Johns, is not its resistance to tarnish, but its elimination of firescale, also called firestain. Jackson says production time is less because the alloy can be welded with traditional methods or laser welders. Jared Sorensen, marketing director for Vaasa, notes the alloy can be welded and soldered, but points out low-temperature solders are needed because it has a lower melting temperature than traditional alloys. Laser welders work effectively because germanium is less heat-conductive than copper.

Sorensen also notes that without firescale to contend with, there is no need to use acid or other environmentally hazardous substances.

  • Vaasa Ltd., Bridgewater, NJ; (908) 526-3464.

– by William H. Donahue Jr.

Understanding Firescale

Silver has been prized for thousands of years for its intrinsic value and inherent beauty. In pure form, silver is too soft to use for utensils or jewelry so it’s alloyed with other metals. Laws regulating the content of silver products date back to the 1300s in England, but they don’t say what the base metal component has to be. Historically, the most common base metal is copper. Some modern silver also contains zinc or cadmium to increase ductility.

This mix of metals can cause firescale. In a presentation at the 1997 Santa Fe Symposium on Jewelry Manufacturing, British silversmith Peter Johns explained what happens. Pure silver doesn’t oxidize when heated in air, but the copper in the silver alloy does, forming cuprous or cupric oxide on the surface. Pickling the oxidized surface in hot diluted sulfuric acid removes only the outer layer of copper oxide. This leaves a surface of unalloyed silver over a layer of silver-copper oxide mixture. Oxygen from further heating easily permeates the pure silver and causes the underlying copper to oxidize. Lightly polishing the surface shows the white luster of silver; heavier polishing reveals the dark stains of firescale.

When the depth of the firescale exceeds 0.025mm, cracking can occur because the oxide skin on the metal is less ductile than the underlying metal. Also, solder joints made on a firescaled surface may fail.

To prevent firescale, silversmiths can cover the item with flux before heating to prevent oxygen from penetrating the silver and oxidizing the underlying copper. Annealing and soldering in an oxygen-free environment will do the same thing, but these methods are time-consuming and expensive.

– W.H.D.

The sterling silver groom’s gifts shown above were manufactured before the new alloy was available but are examples of accessories that can benefit from it. The hand-crafted flask is by John Hardy, the monogrammed keepsake box by Febres, the silver bands and pearl and silver tuxedo set by Slane & Slane, the miniature tray engraved with a message by Jeanine Payer and the watch by Lagos.

Photo is courtesy of the Silver Information Center, (201) 891-5960.

Copyright © 2001 by Bond Communications