When I purchase Argentium, I always heat treat it to bring the
Germanium oxide layer to the surface (just to be safe). Does anyone
know what level of abrasion used in polishing will remove this layer
or skin making it necessary to heat treat a second time?
For example, I sometimes work with wire which only requires a final
polish (no metal removal or sanding). I am using 3M radial bristle
discs and typically do a two step final polish and then a rub with
Goddard’s polishing cloth. The first disc I use is 6 microns which
is described as “polishing” (peach color). The second disc I use is 1
microns and is described as “final polish” (light green) which
brings the silver to a brilliant shine. After this level of light
polishing, would the germanium oxide layer be thinned enough or
removed making it necessary to heat treat again to bring the layer
back to the surface?
We were interested in finding an answer to your question so we did a
little research and printed the answer in our newsletter:
Questions coming from some customers and a recent posting on the
Orchid Forum led us to seek an answer to the question: How to finish
Argentium silver so it does not develop a layer of tarnish (keeping
the germanium oxide layer)?
A quick bit of research brought us to a couple of interesting
websites. First of all, Cynthia Eid posted a very informative and
comprehensive writeup about working with Argentium on Ganoksin. This
article describes how to work with the metal but also has a section
on finishing. Cynthia also has more info relating to argentium on her
website. Road Testing Argentium Sterling and Argentium Sterling
Silver.
Second, A related article appears in the Touchmetal.com blog. Both
articles are informative and can greatly enhance your work with the
Argentium. Both sources helped us understand the science behind the
problem but we wanted to ask specifically (as our Orchid writer
asked), what if we use Scotch-Brite™ Radial Bristle Discs to bring
the metal to a high polish. Would that take away the necessary layer
of germanium needed to protect the silver from tarnish?
I decided to give Cynthia Eid a call and ask her what she thought.
Here is a bulletpoint summary of thoughts from our conversation.
Even though the abrasive in the Bristle Discs is very light, it
will probably remove some of the germanium layer.
However, the layer regenerates at room temperature so it will grow
back again–on it’s own.
If you want to add some insurance and accelerate the process, you
can heat up the piece at a low temperature (250 degrees F, 121 C) for
10 to 20 minutes.
Finish the process by using Goddard’s Long Shine Silver Cloth on
the metal. Note that other polishes that contain anti-tarnish
chemicals may work (Such as 3M™ Tarni-Shield) however, Goddards
has been extensively tested.
The simple process above should insure that your Argentium silver
will stay polished and tarnish-free. Thanks to Cynthia Eid for her
generous gift of time and insight.
Michael McKinnon
McKinnon Global, LLC
Fine Jewelry & Creative Supplies www.mckinnonglobal.com
I think that the metal will probably be pretty tarnish resistant,
but the only way to be sure is to try a test. Put a piece that you
have done everything to (including the Goddard’s) in the oven. If it
discolors, then that tells you that the abrasives took off too much.
If it stays silver, or simply turns white, then either the Goddard’s
is providing enough protection, or the abrasives did not remove much.
I certainly have enjoyed reading all of the on Argentium
from Cynthia, Trevor and also here on Orchid.
Cynthia, I took your suggestion and tested some round 20 gauge wire
this morning. I did a 2 step polish with my 3M radial bristle discs
(first peach, 6 microns, then light green, 1 micron) and finishing
with Goddard’s, I heat treated the wire in my over at 250 degrees for
about 1/2 an hour. It appears that there was no visible
discoloration.
I am planning to do more tests like this with a higher level of
abrasions (maybe more like a 4 step polish) to see if discoloration
occurs. This brings me to another question. If heating brings the
germanium to the surface, why does the metal turn black when heat
treating for hardening purposes at very high temperatures?
I sure appreciate your sharing the results of your experiment! Your
results fit with Trevor’s findings and theories—that once you have
heated the Argentium Sterling, the tarnish resistance is deeper than
the surface.
In my experience, Argentium Sterling does NOT always discolor when
it is heat treated for hardening. If the AS has been annealed or
soldered and pickled, but the surface has not been abraded (polished,
sanded, or filed…), then the AS usually stays white during the
hardening process. If the surface of the AS has been abraded before
hardening, then there is silver and copper exposed, and it tarnishes
before the germanium can grab the oxygen.
Ok, now let me suggest a really fun experiment. I do this at every
AS demo and class, yet I still have fun seeing the results of this:
Take a piece of AS that has turned black (through hardening, or
soldering, or whatever…) and heat the AS with a torch. Be sure
to move the flame on and off the metal, so that oxygen is available
to the metal. The germanium will grab the oxygen and the metal will
turn white! It is really fun to see this, since any other metal that
I have ever worked with stays black until it is pickled or abraded
clean.