Monday, March 24, 2014

Embedding Argentium® Silver Wire into Fine Silver Metal Clay

Most of the time we embed fine silver wire into metal clay because it doesn't tarnish, but it is so soft it doesn't hold its shape. Because sterling silver can be work hardened it's a better choice for embedding into metal clay, but it tends to tarnish.

Argentium® Silver is an alloy of fine silver + germanium + a smaller percentage of copper. It has a high tarnish resistance, doesn't develop firescale, and has the same strength as traditional sterling silver.

Argentium® Silver was invented in 1990 by Peter Johns at the Art and Design Research Institute (ADRI), School of Art & Design, Middlesex University. It is a new type of sterling silver. Traditional sterling silver is a combination of fine silver alloyed with copper (92.5% silver + 7.5% copper). It tends to tarnish over time and can develop firescale when heated with a torch. Firescale is a reaction of the copper and the oxygen in a torch flame that causes the metal to have a purple-grey appearance that doesn't polish to a shine. It can only be removed by abrasion or with chemicals.

When heated, the Argentium® silver may oxidize, turning gray, creating a fine layer of cupric oxide (CuO) that is easily removed by pickling. It also creates a germanium oxide (GeO2) layer on the metal's surface. This germanium oxide repels oxygen and keeps the silver and copper from tarnishing. Additionally, over time the layer of germanium oxide becomes thicker and creates an even more tarnish resistant surface. Heating Argentium® silver in a kitchen oven for 10 - 20 minutes at 250°F (121°C) and allowing it to air cool speeds up this process.

I recently tested embedding Argentium® silver in PMC3 and had great success. It did tarnish (cupric oxide), but this tarnish was easily removed just by tumbling with steel shot. Since I had a hollow form, I didn't want to get pickling solution inside the form. Brushing it with a soapy brass brush also removes this cupric oxide tarnish.

Heating the Argentium® annealed it, making it very bendable. I work hardened it by pressing the wire in several places with flat nosed pliers. Argentium® silver can also be work hardened or age hardened by heating it in a kiln at 580°F (304°C) for 45 - 60 minutes.

Argentium® Silver is still considered sterling silver and is marked as .925 G. It has a low melting temperature of 1610°F (877°C) so,  I fired it with the PMC3 using a fast ramp to 1250°F (677°C) and held it at that temperature for 30 minutes.

Argentium® Silver is a great alternative to using fine silver or sterling silver when embedding wire for a clasp, bail, as an earring wire, or any other use you may think of.

Until next time, have fun claying around!

by Janet Alexander 
Technical Adviser


Roxanne said...

That's good to know. I have used Argentium silver with my fused glass (fused at almost 1500F) and it comes out all black and the tumbler can't polish it up. However regular sterling works fine. I will have to try the Argentium with some PMC 3. I suspect if you used something that fired at a higher temperature it wouldn't come out as well. I will have to try seeing what happens when I put glass in the pickle!

Kris said...

I LOVE Argentium. Love it. So, this is very good to know. Thanks, Janet.

Anup Gupta said...

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GanpatiEngineering said...

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Janet Alexander said...

Thank you everyone!