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Tarnishing Argentium


#1

Hi All;

I’ve been having some problems with Argentium and I wondered if
anyone could shed some light on the situation. Seems the stuff is
turning fingers green. I’m casting it just like I can regular
sterling. The mold is regular Satin Cast investment, burnout cycle
by the book, flask temperature 750-850 Fahrenheit depending on
detail, melting with mapp gas and air, using granular borax flux, and
vacuum assist. I quench in water just after all visible red leaves
the sprue button. I got casting grain from Stuller, and a funny
thing… after I had the problem, I took out the Argentium and it was
turning black in the plastic bag, whereas the sterling grain I’ve had
for a couple years was still bright.

I called Stuller but they never got back to me about it. I bought
another batch which hasn’t turned dark in the bag yet, but I’m
having the problems with the cast article tarnishing again. Am I
missing something?

David L. Huffman


#2

David, awhile back I got an e-mail from somebody at the University
that developed Argentium (in Great Britain) about the possibility
that one of their suppliers had mixed up Argentium and standard
sterling or fine silver.

Being by no means competent to figure out what was going on or what
I had said that made the woman think I might have received something
other than the Argentium, I passed the whole thing off to Stuller
and never heard a thing back about it.

I do know that some of my “dead soft” argentium 18g wire (all of it,
actually) was pretty durn springy for dead soft wire of any kind. I
was at a wire weaving/knotting workshop this past Monday and tried
some of the Argentium in this work. It work hardened a lot faster
than I thought it ought, but then again, as I said before, it
started out pretty hard for “dead soft”, it seemed to me. I gave a
piece of it to the guy teaching the workshop (Loren Damewood of
golden-knots.com) and he was going to work it over with his torch
and see how soft “dead soft” OUGHT to be.

I got all my Argentium from Stuller. I can’t say I’ve noticed any of
it turning black, and I’ve not had anyone come back and tell me its
turning anything green (can’t imagine where that’s coming from).
However, my volume heretofore has not exactly been real high and I’m
doing no casting whatsoever.

I’m not sure if I still have the correspondence from this woman and
she never did get back to my last question to her (asking what I’d
said to make her think I didn’t have genuine Argentium), but I’ll
try to hunt it up. If I find it, shall I forward it to you?

I’ll try to work up a ring in the finer wire I have. It’ll work
harden more than the fine silver I used before, but I’m pretty sure
I can “anneal” it in a friend’s oven and keep working it until I
finish a ring. I’ll wear that daily as an experiment to see if I can
get anything to turn green.

It’s not casting, but now I’m curious about what’s going on, and
whether it’ll happen with stock metal.

Sojourner


#3
I've been having some problems with Argentium and I wondered if
anyone could shed some light on the situation. ... 

Hello David,

FWIW I’ve given some thought to the problems you’ve reported and I
think I might have some insights that could help.

Because of it’s length (900 words) I’ve posted the details on my blog
under the title “Discoloration issues?” (see
http://www.touchmetal.com/blog/argentium-blog.html) however the jist
of it is this:

  • under normal circumstances Argentium Sterling (AS) should not, and
    in my experience does not, do what you’ve seen it do. Yet at least
    one other person has seen something similar. So what’s up?

  • certain things about AS make it different from regular sterling
    –oxygen is good for AS for instance-- and that requires us to
    change our procedures a little. Not a lot, but a little.

  • in general we have no idea if our suppliers have heated the AS in
    an oxygen rich environment (like our atmosphere) or not. But it
    should be in order to get the germanium oxide on the surface since
    that’s what provides the firescale and tarnish protection. Given
    that, it’s up to us as makers to see that that step is done.
    Fortunately it’s simple to do so no worries, but it does need to be
    done.

  • the less copper AS sees the better. Clean firebricks and clean
    buffs are good for AS. “Clean” to me more or less means “never seen
    copper or copper alloys”, other than AS itself of course. This may
    be a bit dogmatic but it’s easy to remember. :slight_smile:

  • to get that germanium oxide layer we have several options including
    torch annealing, precipitation hardening and/or the “activation” step
    of baking it for 20 minutes at 120 C (250 F) in a clean oven.

I’ve heard from at least person that they had no idea of the need to
follow these procedures, particularly the need to “raise” the
germanium oxide, and that’s what’s got me thinking that a little TLC
may eliminate these troublesome issues. Compared to some of the
"special procedures" that other alloys require of us I’d say that
this is not a big deal, assuming of course that it helps.

As mentioned, and FWIW, I go into greater detail on these things in
the blog for those who might be interested.

Cheers,
Trevor F.
in The City of Light
www.touchmetal.com


#4

Sojourner

   I do know that some of my "dead soft" argentium 18g wire (all
of it, actually) was pretty durn springy for dead soft wire of any
kind.  I was at a wire weaving/knotting workshop this past Monday
and tried some of the Argentium in this work. It work hardened a
lot faster than I thought it ought, but then again, as I said
before, it started out pretty hard for "dead soft", it seemed to
me. I gave a piece of it to the guy teaching the workshop (Loren
Damewood of golden-knots.com) and he was going to work it over with
his torch and see how soft "dead soft" OUGHT to be. 

The result: not nearly as soft as fine silver, but softer than what
you had with you last Monday. I’d say it’s about the same as
Sterling, thereabouts, and that the wire you had was half-hard, not
dead soft.

When I order wire, I tell them that I want it not just dead soft, but
darned near limp. “Once you’ve got it annealed to dead soft, go back
and anneal it again one more time, for luck”. I have the impression
that the guys out on the floor don’t want to send out dull-looking
wire, so they always like to pull the wire through one last hole
before spooling it, so the surface is nice and shiny.

I try to make my point as clear as possible, that the wire I get is
going to be plenty shiny, and plenty hard, when I’m done with it,
before it goes into the tumbler, even. Yours looked pretty good,
didn’t it? :slight_smile:

Loren
http://www.golden-knots.com/


#5

Hello Zen;

I’m in contact with some of the folks at Argentium, so I expect I’ll
get some answers. There are some perticular characteristics of this
material that I don’t understand entirely, and I’ve been going over
any literature I have. Cast material may be somewhat a different can
of worms than pre-fabbed stock. Thanks for your offer of help.

David L. Huffman


#6

Dear Trevor and All,

Your posts have been enlightening, to say the least. I am guilty of
not investigating Argentium silver fully before use. I have been
dipping it in borax/alcohol before soldering, which appears to be a
no-no. It never occurred to me not to! At first I thought your
suggestion to bake the metal was redundant, as soldering the
jumpring on would have heated the disc well past 250 degrees.
However, I’m guessing the borax/alcohol dip probably prevented the
germanium oxide from forming- is that correct? Anyway, this weekend
I’m going to bake my Argentium silver disks in my oven and see what
happens. I have high hopes this will cure my problems.

Thank you again, all of you, for your help and advice.

Take care.
Brenda
Nesheim Fuller Design


#7

OH Trevor, you genius.

What you describe explains what I’ve observed. I made a nifty cuff
bracelet in AS and textured it, thinking “Goody, the sparkly texture
will remain undimmed by tarnish!” No torch whatsoever, just
work-hardening. Recently, when preparing for a show, I noticed the
bracelet had darkened!! Bummer. I thought, guess texturing messes up
the tarnish-resistance.

But wait. I had also made a bangle with a tension clasp which had
been soldered on before shaping and texturing. This bracelet had not
darkened - sparkles unchanged. Hmmm. Same time frame for
construction. Now I understand why the difference.

Thanks for sharing this I’ll pop that textured cuff
into the oven and see what happens. I’m wondering if it should be
pickled or cleaned ionically BEFORE precip hardening. Guess I’ll
find out if that’s critical.

Thanks also to Hanuman and Charles. Without Orchid, we’d all be
experimenting solo in the dark. With Orchid we can share what we
learn! It’s my birthday month, so here comes my annual donation to
Orchid.

Judy in Kansas, where the county fair is underway, but without my
tomatoes. I did enter some flowers and will enter my knitted A.925
necklet. That ought to make those knitting judges sit up and take
notice! :slight_smile:


#8
... I have been dipping it in borax/alcohol before soldering, which
appears to be a no-no. 

Well, it’s not really a no-no it’s just not helping you much, as
you’ve surmised.

Contrary to what we’ve all learned about heating regular sterling
silver my understanding and hands-on experience is that Argentium
Sterling (AS) should be allowed to suck up all the oxygen it wants. In
other words forget the firecoat (your borax dip). For that matter
forget about reducing flames and charcoal blocks too. Our
oxygen-rich atmosphere is good for AS, especially if there is heat
involved.

From what I can tell you guys have been getting oxy-starved AS stock
and grain so my recommendation is heat that AS, let it breath!

If you have no other choice then yes, the oven trick may help your
situation. But if it were me and I could possibly swing it I’d torch
anneal just to be on the safe side. My guess is that your AS is in
bad need of some heat and oxygen and the torch annealing will
certainly give it that.

Don’t forget that you can precip harden the stuff to stiffen it up so
the torching shouldn’t be a problem if you’re concerned about
softness.

Cheers,
Trevor F.
in The City of Light
www.touchmetal.com


#9
    Bummer. I thought, guess texturing messes up the
tarnish-resistance. 

Hi Judy, I couldn’t resist adding a few more words on this. FWIW I’ve
been making nothing but heavily textured stuff this last month --lots
of anticlastic raising which I’ve thoroughly enjoyed-- and I’m having
no trouble with the sparkly finish at all. From what I can tell
nothing short of a chisel, file or saw seems to effect the tarnish
resistance of a nicely oxidized piece of Argentium Sterling (AS).

When I was forging a spoon a while back I noticed that after a few
annealings the spoon would not darken at all on subsequent
annealings. I concluded from this that the germanium oxide layer on
the metal is a lot deeper and more durable than one might think: I’d
bash away on the metal, heat, quench and go back to bashing. Pickling
was totally unnecessary because there was nothing to pickle off. In
fact, nothing short of actually cutting into the metal seemed to
damage the no-firescale (and by extension I include the tarnish
resistance) properties of the piece. (the pictures in the “Oxide and
annealing footnotes” post on the blog
(http://www.touchmetal.com/blog/argentium-blog.html) illustrate this)

    I'll pop that textured cuff into the oven and see what
happens. 

If I may suggest something, try this to be absolutely certain that
you’re getting the full benefits: torch anneal the cuff at least
once, pickle, then precip harden it. My guess is that your
discoloration problems will be history. I only suggest this because
it may well be that you’re starting with oxygen starved AS and the
torch annealing should solve that problem good and proper.

    I'm wondering if it should be pickled or cleaned ionically
BEFORE precip hardening. Guess I'll find out if that's critical. 

My experience is that precip hardening will often bring a slight
discoloration to a piece. This is easily pickled off which is why I
pickle after precip hardening and not before. Needless to say your
mileage, and needs, may differ.

Cheers,
Trevor F.
in The City of Light
www.touchmetal.com


#10
 I do know that some of my "dead soft" argentium 18g wire (all of
it, actually) was pretty durn springy for dead soft wire of any
kind..... see how soft "dead soft" OUGHT to be.
    The result: not nearly as soft as fine silver, but softer than
what you had with you last Monday. I'd say it's about the same as
Sterling, thereabouts, and that the wire you had was half-hard,
not dead soft.

That’s what I suspected. Argentium is about the same as standard
sterling, afik, which would typically compare to fine silver with
dead soft sterling being about the same Moh’s hardness as half-hard
fine silver.

I wasn’t sure, trying to compare it to dead soft fine silver might
have been throwing off my perception, but it seemed about half-hard
to me (for sterling). Thanks for checking that out.

    When I order wire, I tell them that I want it not just dead
soft, but darned near limp. "Once you've got it annealed to dead
soft, go back and anneal it again one more time, for luck". I have
the impression that the guys out on the floor don't want to send
out dull-looking wire, so they always like to pull the wire through
one last hole before spooling it, so the surface is nice and shiny. 

I had no idea that they were working the wire over once I ordered
it, although when I actually think about it, I guess they would have
to anneal wire before shipping because dead soft wire coiled on a
huge spool is not going to stay dead soft as they pull of pieces to
ship out. I guess I’ll make sure of what I’m gettting next time I
order, which will be pretty soon.

In the meantime it looks like most of the wire I’ve got is half-hard
when it was supposed to be dead soft and I still have no way of
annealing it. Well, soon, I hope. I have the torch head, now I
just need regulators and tanks.

    I try to make my point as clear as possible, that the wire I
get is going to be plenty shiny, and plenty hard, when I'm done
with it, before it goes into the tumbler, even.  Yours looked
pretty good, didn't it?  :) 

Yup. I still haven’t tumbled mine and its still plenty shiny.

Sojourner


#11
    What you describe explains what I've observed. I made a nifty
cuff bracelet in AS and textured it, thinking "Goody, the sparkly
texture will remain undimmed by tarnish!" No torch whatsoever, just
work-hardening. Recently, when preparing for a show, I noticed the
bracelet had darkened!!  Bummer. 

Well I’ve been wearing a bracelet made of Argentium wire, as-is from
the supplier (no heating whatsoever) for about a week now, and sure
enough, it’s darkening.

Oh well, it needs to be annealed before I can finish it up anyway.
I’ll take care of that at the class, where I’ll have torch access.

Sojourner


#12

I had some problems with discolored Argentium, which after reading
Trevor’s post, I’m sure is because I heated it on the same firebrick
that I’ve been using to anneal copper for fold forming…I heated a
different piece of Argentium silver on a different brick and didn’t
have the same problem.

Leah
www.michondesign.com
@Leah2