Chemistry:Argentium sterling silver
Argentium silver (patented in 1998)[1] is a brand of modern tarnish-resistant silver alloys, containing either 94% or 96% silver. Argentium alloys replace some of the copper in the traditional sterling silver (92.5% silver + 7.5% copper) with the metalloid germanium.[lower-alpha 1][1][2] Both argentium 940 and argentium 960 alloys exceed the standard required for hallmarking as sterling silver, and argentium 960 silver meets the standard for hallmarking as Britannia silver (95.84% silver).
Origins and description
Argentium silver is the result of research at the Art and Design Research Institute (ADRI), School of Art & Design, Middlesex University, by Peter Johns and colleagues. The project began in 1990 with research on the effects of germanium additions to silver alloys. Germanium was discovered to impart the following properties to sterling silver:[3]
- firescale elimination
- high tarnish resistance
- precipitation hardening and simple heat-hardening properties
- increased ductility
- increased thermal and electrical resistance[lower-alpha 2]
- environmental advantages[lower-alpha 3]
Many of these properties significantly affect the traditional methods of working silver. For instance the absence of firescale eliminates tedious and time-consuming steps required by the silver worker using traditional sterling silver. It also eliminates the need for plating the final product which is often done on manufactured items because of the problems introduced by firescale. Tarnish resistance is of significant importance to both silver workers and the wearer of silver jewellery.
Argentium silver was patented[1] and is trademarked by Argentium Silver Company, UK.
Physical properties
Refractory temperatures Silver
alloySolidus
melting
temperatureLiquidus
flow point
temperature°C °F °C °F traditional
sterling silver802°C 1475°F 899°C 1650°F argentium
935803°C 1477°F 903°C 1657°F argentium
960905°C 1661°F 925°C 1697°F
Footnotes
- ↑ Approximately 1% of the argentium alloy total weight is germanium; the patent[1] refers to possible trace amounts of boron, no more than 20 ppm.
- ↑ Increased resistance improves alloys' suitability for welding and laser forming.
- ↑ The "environmental" advantages result from eliminating the need for harsh chemicals involved in removing or plating over firescale.
References
- ↑ 1.0 1.1 1.2 1.3 Johns, Peter Gamon, "Method for joining materials together by a diffusion process using silver / germanium alloys and a silver / germanium alloy", patent,6168071 US patent, patent expired (lifetime) 6168071, issued 2 January 2001 class C22C5/06 "Alloys based on silver"; expiration 27 August 2016; link via Google Patents
- ↑ Johns, Peter (18–21 May 1997). "Fire-stain resistant silver alloys". in Schneller, Dave. 11th Santa Fe Symposium on Jewelry Manufacturing Technology, 18–21 May 1997, Albuquerque, New Mexico. Boulder, CO: Met-Chem Research. ISBN 978-0-931913-25-9. OCLC 47691741. ISBN 0-931913-25-X
- ↑ Johns, Peter; Davis, Sam (9–12 June 2007). "The properties and applications of argentium sterling silver". 31st IPMI Conference, 9–12 June 2007, Miami, Florida. Curran Associates (published October 2007). ISBN 978-1-60423-394-0.
Further reading
- Edge, A.M.; Edge, V.E.; Edge, J.J. (2005). "Investigation on the quality of enamel on germanium silver". The Goldsmiths' Company Technical Bulletin (2): 8–10.
- Eid, Cynthia (July 2005). "Argentium sterling silver". SNAG Technical Newsletter 13.
- Eid, Cynthia (September 2006). "Road testing argentium sterling". Art Jewelry: 25–33.
- Haag, Terry (February 2006). "Shine on silver". Jewelry Arts & Lapidary Journal: 20–24.
- Martin, Eva (February 2006). "Argentium silver box clasp". Jewelry Arts & Lapidary Journal: 36–42.
External links
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