Argentium - Quick question

[Nick martin]

Hello all,

Quick question for you all on Argentium if you dont mind. Been toying with the idea of using it for a while and only just about to get around to ordering some.

My question is about work hardening Argentium. If for example I made forged chain links out of Argentium, would the process of forging the links with a hammer work harden it sufficiently like it would do with regular silver alloys, and therefore give it strength? Or would I need to faff about afterwards conditioning it for hours in a kiln?

I'm aware of the brittle / sagging properties of it, just a bit baffled over the work hardening side.

Cheers,

Nick

[ajda]

Argentium work hardens exactly like sterling - some say it hardens a little more readily, though I can't detect any real difference. Fully annealed it is slightly softer than sterling, which may give you a little more wriggle room (literally) between anneals. Fully hardened it is a bit harder than sterling.

So for most ordinary purposes faffing about with a kiln is unnecessary. However, the option is there if you want to - even an hour or two in a domestic oven on its max temp (normally around 220-240C) will significantly increase finished hardness (though if you have a suitable kiln the recommended dose is 300C for up to 2 hours).

The other great advantage of heat treating is that it encourages the formation of germanium oxide on the surface which is what gives it tarnish resistance.

The two grades of Argentium (935 and 960) differ slightly in the way they behave - I assume you are using 935?

Alan

[Nick martin]

Hi Alan. About to buy from Cooksons. Do they offer the two different grades?

Presumably it's about the silver content like other alloys right?

I plan on buying a kiln in the near future but it's reassuring to know that I can make a start without one.

Nick

[ajda]

Yes, the grade just denotes silver content, parts per 1000, the rest being copper plus a little germanium which is what gives it its special properties - notably resistance to firestain and tarnish, and easy precipitation hardening by heat treatment. If assayed here, 935 will be hallmarked 925 (meeting/exceeding sterling standard) and 960 will be marked 958 (meeting/exceeding britannia standard).

I think Cooksons only offer 935. I get 960 from Allied Gold Ltd who are now one with Argentium International the patent holders - you need to phone or email as there's not much detail on their website, but they'll do it in pretty much any form/size/quantity you want. 935 is certainly the mainstream grade - in the US pretty much the only one available, except rarely 960 casting grain. In the long term, whether Argentium International continue to produce/license 960 or decide to focus entirely on 935 remains to be seen. Generally, if someone is talking about Argentium without specifying the grade you can assume they mean 935. I have got used to working with 960 and I like it, but there may be advantages to choosing 935 apart from easier availability and slightly lower cost - some people reckon it fuses more easily than 935, for example - and perhaps most important if you are just starting with it, there's a lot more info about it on the internet.

A few starting points for information gathering:
http://www.argentiumsilver.com/#!__about-argentium - this website is more promotional than informative, but you can download a useful fact file from the page linked here;
http://www.rondacoryell.com/ - this US silversmith seems to be the recognised authority on working with Argentium - she's produced a series of instructional DVDs (quite expensive - I haven't seen them) some extracts of which can be seen on her site and on YouTube;
http://riograndeblog.com/?s=argentium - Rio Grande sell Argentium in the US and have some interesting articles.

I have lots of other leads and links if you are interested.

Alan

[ajda]

Just spotted a typo in the above - 2nd para: some people reckon it fuses more easily than 935 should read some people reckon it fuses more easily than 960.

I can't speak from my own experience as I have so far done very little with 935 - too disorganised to keep more than one silver alloy in my workshop without muddling them. In any case, both grades can be fused - you need to ensure the pieces you're joining fit well and are clean; brushing a little Auflux (or the yellow liquid flux that Cooksons sell for Argentium) on the joint area seems to help the metal to flow. It takes a bit of experience to recognise the state of the metal close to fusing so not to over-do or under-do it. Problems can arise with with very small or very large joints, so there are occasions when soldering may be a better option.

Alan

[Nick martin]

Some great info there Alan, very useful indeed. Thank you, and thanks for taking the time to reply so comprehensively. Will order some in the next couple of weeks in order to have a bit of an experiment with it.

P.S. Do you find that it polishes up nicer than Sterling / Reflections silver due to being tarnish free?

Nick

[Lucie]

Argentium castings definitely have a nicer surface appearance, especially if you have a large, flat surface.
A lot of places call it "stain free silver" rather than using the brand name because you don't get the weird patchy surface colour that you sometimes get with sterling.

[ajda]

The harder the metal the higher the polish you can achieve and the better it resists scratching and wear. So that's one reason why I like to finish pieces to maximum hardness and why I reckon being able to harden Argentium so easily in a kiln or oven is such an advantage. Tarnish resistance (and firestain resistance) is different, though another reason why I prefer Argentium to traditional sterling.

It works in a similar way to stainless steel - when the surface is exposed to oxygen, the chromium in the steel and the germanium in the Argentium oxidise preferentially to the other elements and form an invisible "passive" layer which shields the rest of the material from contact with the surrounding atmosphere. If scratched or abraded to expose fresh material, it will reform naturally. The germanium oxide layer forms most rapidly when the alloy is heated. This is why you don't get firestain/firescale - you can blast it with a high-oxygen flame and it just gets whiter and whiter. It forms more slowly at room temperature. If you don't encourage the process at the outset, Argentium will dull and discolour a bit until the passive layer has fully formed, but it can be cleaned very easily with soapy water or a mild cleaning agent (Goddards and Tiffany's silver cloths are recommended).

A further advantage of the passive germanium oxide layer, especially in the case of jewellery, is that it also shields the wearer's skin from contact with the copper and copper compounds in the alloy so Argentium can often be worn by people whose skin is too sensitive for traditional sterling.

Encouraging the process at the outset is simple - the final stage for all my pieces is very careful cleaning (even a little grease from your fingers will prevent the germanium from oxidising) followed by several hours in kiln/oven at 100-120°C. Detailed advice on this can be found in the technical sheets produced by Argentium International which Allied Gold will email you on request, as well as in other places online.

Just to show how effective it is, here's a photo of a pile of bangles all heat treated first for hardening, then cleaned and heat treated again for tarnish resistance. Some of these were made months ago, some more recently, but you can't tell which is which from the look of them. They've been sitting around in my workshop and have been carried around on my travels, being rattled around in bags and boxes, handled, worn, stuffed into pockets, etc. I haven't cleaned or polished them at all since they were made yet they all look like new.