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Preventing Argentium Sterling Tarnish


#1

How do I slow down the tarnishing of argentium?

I know there’s been posts about this. I’ve read that heat treating
will help. Time and temp are unclear. I’ve seen from 200-500f and
from twenty minutes to a few hours. I also talked to someone who
dipped his pieces in vinegar after final polish. How will vinegar
affect gold, brass or copper? I use argentium in my
mixed-metal/two-tone that are difficult to rhodium. Is there any
"conclusive" on preventing tarnish on argentium?

Thanks,
Ivan


#2

Ivan,

Is there any "conclusive" on preventing tarnish on
argentium? 

Argentium Sterling silver is tarnish resistant, not tarnish proof.
Tarnish on regular Sterling silver, fine silver and Argentium silver
is caused by a whole host of environmental contaminants.
Perspiration, lotions, soaps, perfumes, auto emissions, coal burning,
wood burning and an endless list of other things are involved.

I sent one pair of Argentium Sterling granulated earrings to Fort
Collins, CO, another to northern California and I wore a pair in
Wisconsin. Each person wore the earrings day and night (or left them
exposed to room air) for two months. The California earrings showed
no signs of tarnish, my WI earrings started to turn yellow (I live
about 5 miles up wind from a coal burning plant) and the Colorado
earrings were heavily tarnished. (Fort Collins energy is from coal
burning and they have a lot of oil wells. I should add that by
comparison, standard Sterling and copper tarnish with hours of
exposure in Fort Collins.)

Hope this adds to the discussion,

Nancy
www.psi-design.com


#3

Dear Ivan

I know there's been posts about this. I've read that heat treating
will help. Time and temp are unclear. I've seen from 200-500f and
from twenty minutes to a few hours. 

If I initially explain a little about how Argentium Silver works,
this should help you know what is happening in the alloy when
processes such as heat-treatment are applied.

Argentium Silver contains a small quantity of germanium, this
imparts improved properties to the alloy including firescale
elimination and tarnish resistance. The reason for these properties
is that when the Argentium is heated in air e.g. with a torch,
germanium oxide forms on the surface, this is a transparent oxide
which acts as a protective layer. Interestingly, tests have shown
that the germanium will also migrate to the surface naturally at room
temperature and will therefore replenish itself at any points of
wear. Heat treatments e.g. for precipitation hardening, will also
help to enhance the formation of germanium oxide on the surface.
Stern-Leach (the US manufacturer of Argentium Silver) now also take
steps to develop a protective surface oxide, as part of their
Argentium Silver manufacturing process. Please find below the
procedures for precipitation/heat-hardening:-

QUENCHING

The following precipitation hardening method will achieve a hardness
of approximately 120HV/DPH:-

  1. Heat the alloy to a pale red annealing temperature, wait until
    any visible red heat has disappeared and water quench. If using a
    furnace, the recommended temperature is 1050F/565C.

  2. Heat the alloy in a furnace/oven at 580F/300C for approximately
    45-60 minutes and then air-cool to room temperature.

AIR-COOLING

Argentium Silver will also harden after a slow air-cool. The
following method will achieve a hardness of approximately 110HV/DPH:-

  1. After annealing or soldering, allow the alloy to air-cool to room
    temperature.

  2. Heat the alloy in a furnace/oven at 580F/300C for approximately
    45-60 minutes and then air-cool to room temperature.

NB:

  • Lower temperatures can be used for Step 2 (minimum temperature of
    220C / 365F) with a corresponding increase in time, e.g. samples
    would need to be heat treated for approximately 2 hours at 220C /
    365F.

  • Ovens/furnaces and supports should be preheated to the required
    temperatures before commencing the heat treatment for the specified
    times. A slight discolouration may occur during the hardening cycle,
    this can be easily removed with a weak pickle.

  • Argentium Sterling shows a paler colour when annealed/soldered, it
    is therefore recommended to carry out heating processes in a shaded
    area, to prevent overheating.

As for degreasing after polishing, the dishwashing detergent Joy is
cheap, ph neutral and is used by several jewellers on their Argentium
Silver, just a few squirts into an ultrasonic degreasing tank with
tap water should do the trick at about 55C / 130F.

You should find that minimal cleaning is required, however if the
alloy does yellow slightly with time then washing with soap (e.g.
Joy) and water or a wipe with a Silver Cloth (the Goddard’s Longterm
and Tiffany Silver cloths can be recommended), will give both the
benefits of cloth and the tarnish resistant properties of Argentium
Silver. The cloth also helps to protect the surface against finger
marks and everyday dirt and grime.

You say that you use brass and copper in combination with Argentium
Silver. It could be that some “smearing” of the base metals on to
the Argentium occurs during polishing and this may cause the
decolouration you refer to.

For other people’s working experiences with Argentium Silver, you can
read Cynthia Eid’s technical paper, which can be found at
cynthiaeid.com and may I also recommend for you to take a look at
Trevor F’s blog at touchmetal.com - there is some very useful
on his site.

Regards
Peter

Peter Johns
Technical Director
Argentium Silver Co. Ltd


#4
Is there any "conclusive" on preventing tarnish on
argentium? 

Hi, I somehow missed the original post of this question. However,
the most conclusive proof that I have seen was the tarnish test done
by CATRA. (A link to the report is at the end of this post.)

Here’s an excerpt from the original article that I wrote for SNAG
News, which is posted on my web site:

  CATRA (Cutlery and Allied Trades Research Association) is an
  independent testing laboratory in the United Kingdom. They
  performed tests comparing the tarnish resistance of standard
  sterling silver and Argentium[tm] Sterling Silver. Here is a
  quote from their report: "Photographic records were used to
  visually document the tarnishing behaviour of the two alloys
  when exposed to the accelerated tarnish test procedures over
  set periods of time. In both the BS EN ISO 4538: 1995
  Thioacetamide test and the Ammonium Polysulphide test, Standard
  Sterling developed severe dark discolouration. In comparison,
  Argentium[tm] Sterling remained clean and bright." You can see
  the full report, with photos of the samples, at
  http://www.landellflutes.com/-Products/Assets/argreport.pdf. 

Cynthia Eid
http://www.cynthiaeid.com


#5

No Argentium is not tarnish proof

But I have a baby cup that was spun,soldered and finished when I
first met Peter almost 3 years ago now. It sits on my desk and is
almost like the day it was polished.


#6

Hi all. I looked at the CATRA link that Cynthia Eid posted
(Thanks!). While the tarnish resistance of Argentium was impressive
in the pictures, what really caught my attention was the interesting
coloration of the regular sterling, using two chemicals I never heard
of- thioacetamide and ammonium polysulphide. I haven’t checked on the
availability of either in the U.S., but I’d sure be interested in
trying them for a deliberate effect. I do wonder, however, how
durable those colors would be.

Allan Mason
www.silvermason.com


#7

Hi Allan,

Ammonium polysulphide is a mixture of 8% ammonia and 22-30% sulphur.
It is basically liver of sulphur with some added ammonia. Kathy
Palochak posted a silver pattination recipe using both of those and
some salt. It should give you the same colours as seen in the CATRA
photographs. The patina is reasonably stable.

Thioacetamide is a 2-carbon chain with a nitrogen and a sulphur atom
on one end. I’ve never used it but the Merck Index cites it as a
"pleasant substitute for H2S in laboratories". H2S, hydrogen
sulphide, is rotten egg gas.

Hope this helps
Eileen


#8

I remember thioacetamide well from my organic chemistry course. I
distinctly remember that it smelled just like an open sewer. To say
that it is a pleasant substitute for hydrogen sulfide is a pure
marketing stroke of genius!

steve