Cynthia Eid SNAG News Technical Article by Cynthia Eid: Argentium Sterling Silver |
The Society of North American Goldsmiths
TECH NEWS
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I have not tried chasing with it yet, but I expect that it will be a delight to chasers. To me, Argentium® Sterling is softer after
annealing than regular sterling, and can be worked longer and further before it needs annealing than regular sterling. Can be precipitation hardened using a kitchen oven. Consequently, an Argentium® Sterling Silver piece is sturdier and more dent-resistant. Tests made by Stern-Leach indicate that Argentium® Sterling Silver is capable of achieving hardness levels approximately twice those of fully annealed regular sterling silver. Naturally, results vary according to the situation, yet these hardnesses have been attained repeatedly both by Stern-Leach (their thermocouples and hardness testing instruments are calibrated regularly, to assure accuracy) and Peter Johns at Middlesex University in the UK. In my studio, my hardness-testing tools are my fingers, ears, and hammer. These have been “calibrated” by my 35+ years of metalsmithing, and their “readings” are that the Argentium® Sterling silver becomes much harder. I appreciated this feature when I made the SNAG Lifetime Achievement Awards (SNAG gives one at each annual conference). The textured part of the bowl is made of thin Argentium (about 26 gauge) in order to achieve the depth of the texture. The structure of the corrugation and cross-corrugation makes it very strong. However, I value being able to further harden the metal in my oven so that I can really feel confident about the award surviving being shipped across the country to the SNAG director, then schlepped to a SNAG conference, handed to a worthy recipient, and finally taken to a home. Tiffany is utilizing Argentium® Sterling’s hardness to make money clips. Laser and plasma-weldable due to its lower heat and electrical conductivity. One of the properties of metalloids, such as germanium, is that they are less conductive than metals. I don’t have access to welding machines, but I have seen incredible work done by folks who do have welders. The high thermal and electrical conductivity of traditional sterling silver alloys has made them difficult to weld. I have used this property to fuse links for a chain made of Argentium® Sterling Silver. I was pleasantly surprised to find it easy to do. I used liquid flux on the joint and the small, hot flame of my Smith Little Torch on a heat-reflective soldering pad. Since Argentium® Sterling Silver does not conduct heat very well, I focused the heat on the joint, rather than the whole link. Larry Blackwell 2 is a jeweler who specializes in sterling silver chains. He uses Argentium® Sterling Silver wire for his chains, and fuses whenever possible, since he finds it faster than soldering. He does not usually use flux to fuse, and varies the size of the flame, depending on the gauge of the metal. What is germanium? If you are like me, you don’t remember Germanium from studying the periodic table in chemistry. Germanium (Ge) is an element, named after being discovered in Germany in 1886. It is number 32, its atomic weight is 72.64, and it is next to silicon. It is chemically similar to tin. Germanium is not found as a free element in nature. Germanium is found in zinc ores, coal, germanite, and argyrodite. In researching this article, I have been intrigued to see that germanium is not listed in charts comparing metals and their characteristics in any of the jewelry or silversmithing books in my studio. Germanium is a metalloid, as are silicon, manganese, boron, and sulfur. These elements are on the border between the metallic elements of the periodic table, and the non-metallic elements. |
Metalloids have both metallic and non-metallic properties. Metalloids tend to be semiconductors rather than conductors.
Germanium is a semiconductor, with electrical properties between those of a metal and an insulator. (Definition of conduction:
the result of collisions between molecules; when one end of an object is heated, the molecules vibrate faster and the energy is
transferred to their neighbors.3 I think I’ve learned more about chemistry and metallurgy this year, trying to understand how and
why germanium affects sterling silver the way it does, than I did in my whole year of high school Chemistry class!) Pure germanium is crystalline, gray, and lustrous. It is very brittle; it shatters easily with a hammer. Interestingly, it seems to have a bleaching characteristic when alloyed—the alloys made with it look whiter, and less yellow. What else is Germanium used for?
Metaleurop, whose primary product was zinc, found that they had a lot of germanium on hand as a by-product from refining zinc ore. In an effort to find or create a market for this germanium, Metaleurop sent samples and inquiries to people with many different expertises, asking for ideas and advice for its use, including Peter Johns at Middlesex University, UK. The germanium that Metaleurop gave Professor Johns to experiment with was mixed with copper. When he melted this alloy, he noticed how cleanly and easily it melted and cast—which is unlike pure copper. From this observation, Peter Johns realized that the germanium was protecting the copper from oxidation. Soon after noticing this phenomenon, Peter Johns was explaining firescale to a student, and he began to wonder if germanium could be used to prevent firescale. Months of experimentation produced Argentium® Sterling Silver. Why does Argentium® Sterling precipitation harden so well? Until now, I had always thought precipitation to simply be the phenomenon we see when a solid settles out to the bottom of a container of a liquid solution, as happens when we make Prip’s Flux, or put sugar in water. Here is a definition of precipitation, used in Chemistry, which helps me understand how germanium can precipitate in a solid: To cause (a solid substance) to be separated from a solution.4 Because Germanium is a metalloid, rather than a true metal, germanium atoms tend to “float” around within the silver/copper |
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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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