Argentium sterling silver
Argentium™ Sterling Silver, described as a 'modern' Sterling Silver, is relatively new in terms of
precious metal alloys having been developed as recently as 1990 and it is not commonly known about as an
alternative to standard 925 Sterling Silver
Argentium Sterling Silver complies to the standard set for sterling silver of a minimum of 92.5% pure
silver however it utilizes a small amount of a metal called Germanium
in the balance of the 7.5% other metals
including copper. The use of germanium gives Argentium Sterling silver its remarkable properties of
unparalleled tarnish resistance as well as an increase in the lustre of the material.
Argentium Sterling Silver is slowly but surely gaining exposure with marketing in some of the better
jewellery stores and chains, not unlike the beginnings of the introduction of CZ (Cubic Zirconia) back in
the 60's which is now generally accepted and widely sold as a Diamond substitute. The market introduction
phase is where the similarity ends as Argentium Sterling Silver is not a substitute but moreover an
improvement on standard Sterling Silver.
Some Marketing statements about Argentium Silver
Argentium's 935 and 960 grades set new purity standards for silver. Argentium is always purer than
traditional sterling silver.
Argentium silver does not require plating and is the natural colour of pure silver.
Argentium silver is brighter and whiter than platinum, white gold and traditional sterling.
HYPOALLERGENIC & ANTIBACTERIAL
Argentium is a perfect choice for those who are unable to wear traditional sterling silver.
HIGHLY TARNISH RESISTANT
Argentium silver is low maintenance, easy to care for and simple to keep clean.
It is certified that Argentium is produced using only recycled silver.
Argentium® is a registered trademark of Argentium International Limited.
Further information is contained in this article from Wikipedia, the free encyclopedia, text is available
under the Creative Commons Attribution-ShareAlike License
Argentium silver is a modern sterling silver alloy which modifies the traditional alloy (92.5% silver + 7.5%
copper) by replacing some of the copper with the metalloid germanium. As
it contains at least 92.5% silver content of the traditional alloy, it is still referred to as sterling
Argentium silver 960 is a high purity jewellery alloy that meets the hallmarking requirements
for the U.K. Britannia standard. The 960 alloy modifies the conventional Britannia silver composition (95.84 silver,
balance copper) with the addition of germanium.
Argentium Silver is the result of research by Peter Johns at the Art and Design Research
Institute (ADRI), School of Art & Design, Middlesex University. 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:
- Firescale elimination
- High tarnish resistance
- Precipitation hardening and simple heat-hardening properties
- Increased ductility
- Increased thermal and electrical resistance (making alloys suitable for welding and laser
- Environmental advantages (associated with not having to remove or plate over firescale)
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 is patented and trademarked by Argentium Silver Company, UK.
Traditional sterling silver has a solidus melting temperature of 1475°F
(802°C) and a liquidus flow point of 1650°F (899°C). The solidus of
Argentium 935 Sterling silver is 1477°F (803°C) and a liquidus of 1657°F (903°C). The solidus of Argentium
960 silver is 1661°F (905°C) and a liquidus of 1697°F (925°C).
Tarnish testing Argentium silver
Argentium silver alloys are tested using three laboratory tests. These tests are designed to replicate the
effects of environmental pollutants and everyday conditions that cause tarnish.
Sulphur test The sulphur test reproduces the effects of sulphur and sulphurous gases found in
the atmosphere and everyday substances. This test is based on an ISO (International Organization for
Standardization) corrosion testing protocol used within the precious metals industry (ISO 4538:1978).
Perspiration test This test reproduces the effects of perspiration and skin contact with silver
alloys. The testing procedure is based on a standardised procedure used in the spectacles industry (ISO
12870:2004, now re-designated ISO 12870:2012).
Ultraviolet test The ultraviolet test determines whether alloys are photosensitive to
ultraviolet light. This is especially applicable to silver articles that are on display and exposed to
Measuring tarnish resistance
A double-cone 3D model of colour. The dark to light axis is the one used
to measure the tonal value of tarnish..
Tarnish resistance is measured through a scientific process using the CIELAB standard colour measurement
system. A colorimeter is used to measure the
change in surface colour on each test sample after exposure to the tarnish tests. The ‘dark to light’ scale
(the central vertical axis in the double-cone colour diagram) is the critical measure used to gauge the
degree of tarnish film that is formed on the silver alloy test samples.
Argentium alloys are required to pass predefined levels on the ‘dark to light’ scale, using the CIELAB
system. The results from all three tests are combined, using the following weighting coefficients, to give a
Tarnishing Index value:
- Sulphur - 0.6
- Perspiration - 0.2
- UV - 0.2
The overall test results are shown in Fig 1.
What is firestain? A copper oxide produced when sterling silver articles are heated during
production in the presence of air and where the copper in the alloy is oxidised. At red-hot temperatures silver
is permeable to oxygen, allowing the copper to be oxidised deep inside the alloy, making it difficult to
remove. This oxide is known as firestain (UK) or firescale (USA). Firestain is seen as a dark, purple-grey
Why is firestain a problem? Strong acids or abrasive processes are required to remove the
unsightly firestain. These procedures not only increase manufacturing costs but also raise environmental and
workplace concerns associated with hazardous chemicals. Manufacturers will often simply hide the firestain by
plating over it with pure silver. Plating is only a temporary solution as the thin surface layer may quickly
wear away and the firestain will be revealed again. The traditional sterling silver watch shown in Fig. 2 has
been used for just over a year and shows how quickly a silver plated surface can be worn away.
Fig 2. Firestain example-watch..
How does Argentium silver prevent firestain? The germanium alloyed in Argentium silver oxidises
preferentially to the copper. It produces a transparent, self-healing oxide that protects the copper from
oxidising and forming firestain. Unlike traditional sterling silver, Argentium silver does not require plating
or strong acids to hide or remove penetrating oxides.
Comparison test results The magnified cross-section photographs (Fig. 3) show samples of
Argentium silver and traditional sterling silver after being heated in air to a red-hot ‘annealing’
temperature. The penetrating layer of firestain is clearly visible on the traditional sterling sample. No
firestain is present on the Argentium silver. (Testing carried out by CATRA - Cutlery & Allied Trades
Research Association, UK).
Fig 3. Annealed Argentium Vs Sterling Silver..
Inside Argentium - How does it work?
Fig 4. Shows a cross sectional image of the surface region of Argentium
Investigations using a Transmission Electronic Microscope (TEM) have shown that a thin dense layer of
transparent germanium dioxide (GeO2) is formed on the surface of Argentium silver alloys when they are exposed
to oxygen. It is this layer that gives Argentium silver its protection against tarnish and firestain. The
germanium dioxide layer is self-regenerating. If the germanium dioxide is worn off due to abrasion, it will
reform. Stainless steel uses chromium oxide for protection in a similar way. When compared to the other coating
techniques used to protect silver alloys (e.g. rhodium plating and e-coating), the ability to re-form its
protective surface layer make the Argentium silver alloys unique.
The platinum layer deposited by Ion Beam-Induced Deposition (IBID) is required to shield the oxide film only
during the TEM process.
- Peter Johns (1997) Firestain Resistant Silver Alloys.
Santa Fe Symposium On Jewelery Manufacturing Technology. ISBN
- Johns, Peter and Davis, Sam (2007) The properties and
applications of Argentium (TM) Sterling Silver. In: 31st IPMI Conference (International Precious Metals
- Andrea Basso (2010) ‘The Tarnishing of Silver Alloys:
Causes and Possibilities’. Santa Fe Symposium on Jewellry Manufacturing Technology ISBN
- Eid, Cynthia (September 2006). "Road Testing Argentium Sterling". Art
- "Firestain—The Nemesis of the Silversmith". The Goldsmiths' Company
'Technical Bulletin', Issue 3: 10–11. April 2006.
- Haag, Terry (February 2006). "Shine On Silver". Jewelry Arts &
Lapidary Journal: 20–24.
- Martin, Eva (February 2006). "Step by Step — Argentium Silver Box
Clasp". Jewelry Arts & Lapidary Journal: 36–42.
- Edge, A. M.; V. E. Edge and J. J. Edge (2005). "Investigation on the
Quality of Enamel on Germanium Silver". The Goldsmiths' Company 'Technical Bulletin', Issue 2:
- Eid, Cynthia (July 2005). "Argentium Sterling Silver". SNAG (Society
of North American Goldsmiths) Technical Newsletter 13.