Does anyone out there in Orchidland have experience using silicon
sterling? I’d primarily be casting it, but I’d like to be able to
solder it, and it would be great to avoid firestain. Enamelling would
be nice too, if it’s possible. I’ve used silicon bronze, and
appreciate its ability to melt cleanly without flux; does silicon
sterling act the same way? Any drawbacks I should know about? How
does it withstand tarnishing? Can anybody compare and contrast it
with Argentium silver or other de-ox alloys?
Andrew Werby
www.unitedartworks.com
Dear Andrew,
Does anyone out there in Orchidland have experience using silicon
sterling? I'd primarily be casting it, but I'd like to be able to
solder it, and it would be great to avoid firestain. Enamelling
would be nice too, if it's possible. I've used silicon bronze, and
appreciate its ability to melt cleanly without flux; does silicon
sterling act the same way? Any drawbacks I should know about? How
does it withstand tarnishing? Can anybody compare and contrast it
with Argentium silver or other de-ox alloys?
It is hard to generalize about alloys because there are several
silicon bearing silver alloys on the market and I haven’t cast all
of them. What can be said is you should expect that the silicon will
help protect the metal from forming copper oxides because silicon is
a powerful oxygen getter according to the literature. Your
experience with silicon bronze is not likely to be what you will
find with a silver alloy. Large amounts of silicon can be alloyed
with copper but silver and silicon don’t mix. All the silicon-silver
alloys I have cast are a bit softer than traditional silver-copper
alloy and the tensile strength is not as high. Some of them have a
tendency to have thermal cracks or ring shanks crack if they are
stretched to round up and size. I have attached a picture of a tree
that was cast with a silicon silver alloy that was brittle as glass;
however, this degree of brittleness is unusual.
Argentium has germanium in the alloy. The element Germanium looks
and acts a lot like silicon. Germanium makes metal more fluid for
casting and is a powerful oxygen getter so preventing fire stain
(copper oxide) and it allows for age (precipitation) hardening by
heat treating at 300C.
For reference, quench annealed traditional silver-copper sterling is
about 70 HV (Vickers hardness scale) and when age hardened get up to
140 HV. The quench annealed hardness of Argentium is 55 HV and 70 HV
when air cooled. After age hardening it reaches 130 HV which is
comparable to Ag-Cu sterling.
Now I would like to bend your ear about fire stain. If you have fire
stain on sterling it is because it was exposed to air when it was in
a very hot state. Fire stain is deep seated copper oxide that is too
deep under the surface to be pickled off. If no oxygen is allowed to
come in contact with the metal when it is hot there will not be any
copper oxide. If you are torch melting, put some flux in the bottom
of the crucible and put the metal on top of it. Make sure your torch
has a carburizing flame. When you start the heat, never take the
torch away from the melt until it is cast and cover the sprue button
with flux or charcoal as soon as possible. Make sure the investment
is well burned out because any carbon in the investment cavity will
cause fire stain in silver castings. Never melt silver that has even
a trace of investment on it and make sure pickle solutions are well
rinsed away before recycling the metal. Use feed sprues designed to
allow the lowest possible casting temperatures to prevent investment
reaction with the silver.
Eddie Bell
Silicon Sterling?
I agree with most all said about “silicon sterling” that my friend
and compatriot Eddie Bell had to say about the subject. His breadth
of knowledge on casting and metallurgy sometimes takes my breath
away. (Wheeeeeez…gasp…!!!)
It really all depends on exactly which silicon sterling you are
using. Much of the silicon additives in silver “anti-tarnish” alloys
(known as deox alloys, of which there are many companies that
produce these) are in minute quantities, as it should be. Too much
silicon in these alloys can cause more problems than they solve, ie:
cracking, etc.
And as a footnote…comparing silicon bronze to silicon sterling is
like comparing dragonfruit to mangos. Silicon bronze contains up to
95% Cu, and as Eddie so aptly described…silicon loves to mix
with copper, but hates to mix with an overabundance of silver. So
always try to check the % of silicon in the silver alloys you select
and choose one with the smallest of amounts of it.
The point I do not agree with Eddie on is on Argentium. A year or so
before Argentium hit the market, I experimented in my lab at
ABI-California with adding Ge to our Sterilite deox alloys. I hated
the way it cast, did not like the variety of added fabricating and
casting problerms it brought (many of which have been seen on this
Forum), and now…in subsequent tests done in 2 metallurgical labs
in the States…it has been found that it’s hardness is only
equal to the best “deox” sterlings and it’s tarnish resistance is
not much better than that…while the castability of the other
deoxs’ remains better than Argentium.
It seems to be fine for the small user where the problems can be
fixed easily…but in the large production shops I go to every day
in China and in Thailand, its’ use is non-existant. In the year I
have been here, there is only 1 major shop I have seen using it in
the Far East for production. The problems associated with Argentium
are easily dealt with on a piece by piece basis by the
artisan…but on a large scale basis, these problems cannot be
dealt with in a financially viable manner.
Thanks as always, Eddie, for your contribution to the knowledge of
the masses. You have my utmost respect.
Marc “Doc” Robinson
ABI Asia, Ltd.
Bangkok/Bali, Indonesia
Marc “Doc” Robinson
Hydrometallurgist/Director
ABI Precious Metals Asia, Ltd.
Hello Marc,
The point I do not agree with Eddie on is on Argentium.... It seems
to be fine for the small user where the problems can be fixed
easily....but in the large production shops I go to every day in
China and in Thailand, its' use is non-existant.
I think you’ll find your is out of date. As I understand
it over 1/2 ton of Argentium Sterling has been shipped from the US to
China and is in their production cycle as I type this. Like any new
process some tweaking was necessary but the latest reports are that
they’re doing fine with it and are having no such problems as you
claim.
FWIW I can appreciate that you’ve got your own products to push and
doubtless they have their merits too but it hardly seems sporting to
slag off Argentium – especially with outdated and distorted
– in the process. I don’t think you’ll do yourself much
good, at least not here on Orchid, by taking that approach.
Cheers,
Trevor F.
in The City of Light
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