Cynthia  Eid SNAG News Technical Article by Cynthia Eid: Argentium Sterling Silver

I thought I’d arrived when first working in that sensuous, petulant metal, sterling silver, many years ago as a student. It quickly became apparent that the job was only half done because you still had to remove the firescale while maintaining the cool, unwavering mirror finish. In Cynthia Eid's astute article on Argentium, she makes a compelling case for a sterling renaissance. In it, she gives a broad range of theoretical and practical knowledge that will serve as solid base to go forth from. It’s the kind of article I love. Learning about other's experiences and delving into the important arcane minutiae that so distinguishes our field. I hope there is a renaissance for this metal by which the best metalsmiths are measured. —Sean Gilson, Tech Editor Argentium® Sterling Silver By Cynthia Eid ©2005 Cynthia Eid. Copies may be made for personal and instructional use, but not for profit . What is Argentium® Sterling Silver? Argentium® Sterling Silver is a patented and trademarked alloy that is at least 92.5% pure silver, just like regular sterling silver. What makes it different from regular sterling silver is that a small amount of germanium replaces some of the copper that is usually the other 7.5% of a sterling silver alloy. Peter Johns, a professor of silversmithing at Middlesex University in England, invented it in 1996. When I heard about firescale-free sterling silver sheet, I sought out sources, and hoarded whatever I could get my hands on, as I fell in love with the material’s working properties. What does Argentium® Sterling Silver look like? To me, it looks like any other sterling silver. Though some have said to me that it looks whiter than regular sterling, others say it looks grayer than regular sterling silver. I notice that the color seems to vary, depending on what the finish is on the metal, and what polishing compound may have been used. In my own studio, I have a difficult time keeping track of which is which, unless I have carefully labeled the metals. What makes Argentium® Sterling Silver special? This photo shows a microscopic cross-section of regular sterling silver that has been annealed in a kiln at 1076°F (580°C) for one hour. In this sample, fire scale (cuprous oxide) penetrated 20-26 microns. There is also a surface layer of black cupric oxide.   The Argentium® Sterling Silver sample was exposed to the same heat and temperature. The cross-section shows that there is no firescale, only a cupric oxide (black) layer on the surface, 1-2 microns in depth, which can therefore be removed by pickling. Firescale-free. When heated, regular sterling silver forms cuprous oxide (Cu2O, known as firescale or firestain), that annoying purplish layer that lurks under the surface of regular sterling silver after annealing or soldering. Firescale needs to be removed via abrasives or chemicals, covered with electroplating,

or covered by depleting the copper from the surface through repeated heating and pickling (often called “bringing up the fine silver”). Though Argentium® Sterling may oxidize when heated, the oxide is cupric oxide (CuO). This is a surface oxide that pickle removes completely; there is no underlying cuprous oxide (Cu2O) firescale. One of the unusual properties of the element silver (Ag) is that silver allows oxygen to penetrate through its surface, and into the interior of the metal. That is why the Cu2O/firescale is able to form under the surface of regular sterling silver. The addition of germanium to the sterling silver alloy stops the penetration of oxygen past the surface. Available in sheet, tubing, and wire, as well as casting grain. Most other “deox” alloys (a common term for firescale-free sterling alloys) include zinc, replacing some of the copper. The zinc/silver alloys have been working well as casting alloys for a number of years, but have not been easily available as workable sheet and wire. Highly tarnish-resistant. When I initially heard this claim, I was skeptical. I have noticed, however, that when I receive work back from an exhibition or gallery, the metalwork made with Argentium® Sterling Silver looks fine, though the work made with regular sterling silver is often tarnished, despite my habit of applying a coat of Renaissance Wax to work made with regular sterling when it is going to an exhibition. Recently, I borrowed a bowl I made of Argentium® Sterling for the Silver Triennial exhibition in Europe. The owner apologized that she had not had time to polish it before returning it, and that it had been sitting out on her dining room buffet for a year. I was therefore surprised to open the box and see that it looked nearly pristine. CATRA (Cutlery and Allied Trades Research Association) is an independent testing laboratory in the United Kingdom. They performed tests comparing the tarnish resistance of standard sterling silver and Argentium® Sterling Silver. Here is a quote from their report: “Photographic records were used to visually document the tarnishing behaviour of the two alloys when exposed to the accelerated tarnish test procedures over set periods of time. In both the BS EN ISO 4538: 1995 Thioacetamide test and the Ammonium Polysulphide test, Standard Sterling developed severe dark discolouration. In comparison, Argentium® Sterling remained clean and bright.” You can see the full report, with photos of the samples, at http://www.landellflutes.com/-Products/Assets/argreport.pdf. Greater ductility and malleability than regular sterling silver. (Ductility is the ability of a metal to be stretched or elongated. Malleability is the ability of the metal to be transformed—e.g, bent, formed, forged, etc.—without breaking. A metal can have one property without the other; lead, for instance, is malleable but not ductile.1  I realized this the first time I formed Argentium® in a hydraulic press with a matrix die. When I used the amount of force I expected to need for regular sterling silver, the entire flange was pulled into the negative space of the die! Since it was a large piece of Argentium® Sterling, which was hard to obtain at the time, I had to re-work the form for the teapot by hammering. I enjoy this greater ductility and malleability when I do fold forming, forging, die forming, anticlastic and synclastic forming, raising, and knitted chains.

This technical article was first published by the Society of North American Goldsmiths in its newsletter, under Tech News. All SNAG members automatically receive the newsletter five times a year. To sign up for membership, go to www.snagmetalsmith.org, or (630) 778-6385.

Cynthia  Eid

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