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Argentium sterling molecular structure


#1

Just recently took a workshop working with Argentium silver. It was
excellent however the instructor did not know the actual molecular
structure of Argentium. I just wanted to know what the molecular
difference is verses sterling silver at high temps. Argentium becomes
so brittle and breaks apart and I want to understand why. Why is it
so willing to fuse? (Which is super cool - could not believe it.)
After it has been at it’s fusing temp is it more brittle? I fused a
bezel on it’s backplate and noticed after I set the stone "spiderweb"
looking cracking around the pushed down bezel edge. It was tiny,tiny,
tiny but it was still there. Also I was instructed to pickle
Argentium in cold pickle (separate from sterling pickle.) Why cold
pickle? Why are Argentium granulation granules $300.00 per ounce?
Made my own - but that seems really steep. Thanks so much to all that
answer.

Have a wonderful New Year.
Joy Kruse :slight_smile:


#2

Try this reference, with associated links:

John


#3

Hi Joy,

I don’t know about the molecular structure, either, but I’m trying
to find out. In terms of some of your other questions:

-My understanding of why Argentium Sterling is relatively easy to
fuse is that it is an alloy which has large temperature range between
when it begins to melt and when it totally melts. Fine Silver, which
most people feel is easier to fuse than traditional sterling silver,
melts at a single temperature, because it is a pure metal. Therefore,
it is tricky to reach fusing temperature without a complete
melt-down. I don’t know why AS is easier to fuse than SS----I simply
enjoy and appreciate it!

-I do not find that fused AS is brittle, if it has not been moved,
nor quenched too soon. When I demonstrate fusing AS links, I pull
them into ovals, without regard to where the joint is, to show that
the metal is not brittle.

-I do not know why your instructor said to use cold pickle. I find
that, as with most metals, cold pickle works, but hot pickle works
faster.

-I don’t really understand why AS granules are so expensive, either.
I was once told that it has to do with the labor of sorting into
size… I hope some of this is helpful to you.

Cynthia Eid
http://www.cynthiaeid.com


#4
Just recently took a workshop working with Argentium silver. It
was excellent however the instructor did not know the actual
molecular structure of Argentium. I just wanted to know what the
molecular difference is verses sterling silver at high temps.
Argentium becomes so brittle and breaks apart and I want to
understand why. Why is it so willing to fuse? (Which is super cool
- could not believe it.) 

All alloys have their quirks. Argentium is hot short. That means it
is brittle at elevated temperatures. The mechanism is that both
silver and germanium and copper and germanium form low melting point
eutectic alloys. Ag-Ge eutectic melts at 1203 F and Cu-Ge eutectic
melts at 1191 F. Tiny amounts of the matrix of the Argentium will
begin to melt at these temperatures. This greatly weakens the crystal
lattice so if you disturb it at elevated temperatures it will often
break. These temperatures are right smack dab in the middle of the
silver solder melting range so you must exercise care when working
with it at soldering temperatures. Standard sterling will do the same
thing because of the silver copper eutectic or the presence of excess
phosphorous from the deoxidizing process done when the sterling is
produced. But the temperature for standard sterling to begin
exhibiting this behavior is higher at 1435 F for the Ag-Cu eutectic
and 1371 for the copper phosphorus one.

Argentium fuses and welds better than standard sterling because it
has a reduced thermal conductivity. So the heat stays closer to where
the torch flame is than in standard sterling. So you can spot heat it
more efficiently. This combined with a lower solidus temperature this
makes for easier fusing.

Once you understand the quirks Argentium has many properties that
make it a very useful addition to the pallet of materials for jewelry
work.

Jim
James Binnion
James Binnion Metal Arts


#5

This is an interesting thread. I have been working silver for just
over a year now, basically I have only used Argentium. I love it and
find it frustrating at times. The frustration comes from what, I too,
would describe as a “brittleness.” I have many times had pieces
literally snap in a cross-lock tweezer using barely enough pressure
to hold the piece in place. Seems often to do with the heat
differential as the tweezer acts as a mini heat sink and it has to
do with the difference in expansion between the temperature
differentials. I know I am butchering the technical explanation,
sorry, but this is my “layman’s” approach. I feel the positive
qualities of Argentium far out weigh my negatives, as they challenge
me to grow, adapt, and try to comprehend what I “see.” If you have
not used it, give it a try. If you have used it, what is your
experience? I always keep my ears and mind open to ideas and
suggestions. peace, from a cold, “old-fashioned” Wisconsin winter…


#6

Cynthia -Thanks for your comments on Argentium. I don’t know why the
argentium bezel I used got a spiderweb crackle to it when I pushed
it around the stone? However I just fused a bunch of rings with all
kinds of detail and multiple fusion points, the seem for the rings
also fused-I hammered them as usual on a ring mandrel.I made some
round some square. I tried to put as much stress on them as I could
just to see what would happen. Can I get it to crack? Will the seem
break? Willthe ornamentation fall off? Well - nothing happen. I have
a dozen beautiful rings. Not one tiny puddle of solder to clean up on
anyone of them. I kinda of can’t believe it.

I did use warm pickle and it works faster as I expected but I was
wondering if there is some reason to not have it warm. I know you
need to bake your finished product in the oven for 20 minutes at 250
degrees to get the best tarnish resistant layer. I was wondering if
warm pickle effects this layering at the metals surface? Why would
that not be desirable? Someone knows and I hope they answer but in
the mean time I agree with you I am loving the easy fusion and will
keep on experimenting hopefully with the same nice results I have
gotten so far.

Thanks Again
Take Care Joy Kruse


#7

Jim - Thanks that was the techinical info I was looking for. I
actually printed it out and will pin it up for awhile at my benchso I
can make a mental note of what tempurature my torch is burning at and
what is happening to the metal as I work with it.

Thanks Again - Joy


#8

Hi Joy,

I asked an engineer who works for Argentium International if he
could help answer your question about molecular structure, and why it
fuses well. Here is his response, which I find interesting and
edifying. I hope you do too!

"The simplest way of thinking about the difference in structure
between Argentium Sterling and regular sterling silver is to think of
the difference in composition between pure silver, regular sterling,
and 930 Argentium silver which contains 1% germanium.

Each element has a different atomic diameter; so if we have a piece
of pure silver, the atoms are the same size and join together nice
and evenly. That is why pure silver has a single melting point. All
the bonds that join the silver atoms together break at exactly the
same time as heat (energy) is applied to melt the silver. In pure
silver the silver atoms are all joined together in a crystal
structure which is known as face-centered-cubic by metallurgists and
this is the preferred crystal structure for all ductile metals.

If we now take the pure silver and add copper so that we have a
traditional sterling silver alloy we have a mixture of silver and
copper atoms present. These silver and copper atoms are of different
sizes and although they still form the same face-centered-cubic
structure, it means that some of the bonds in that crystal structure
are under more strain as they have to adjust to the different sizes
of the two elements present in the sterling silver. This means that
as you apply heat and start to melt the sterling silver, the bonds
which are under the most strain break first and the bonds under the
least strain break last. This is why the sterling silver alloy has a
melting range; it is the difference between the energy needed to
break the weakest and the strongest bonds. This is also why the
melting range for sterling silver is lower than the melting point of
silver, even though you have added a higher melting point metal to it
in copper.

So if all that makes sense, we can now think about 930 Argentium
Silver. This alloy contains three elements; silver, copper and
germanium. This means that we have three different atom sizes to
consider and this means that we have silver to copper bonds, silver
to germanium bonds, and copper to germanium bonds, as well as bonds
of each atom to others of the same type. Again, although the
underlying crystal structure is face-centered-cubic, some of the
bonds are under considerable strain and do not require much energy
(heat) to break.

This is why Argentium alloys are able to fuse. At lower temperatures
just enough bonds are broken to enable the alloy to join onto
another metal, without becoming completely molten. This is also the
reason why you need to let the alloy cool before quenching, to ensure
that it is completely solid to prevent cracking. There is no reason
for fused Argentium silver to be any more brittle than metal which
has not been fused, providing it has been allowed to cool slowly."

Cynthia
http://www.cynthiaeid.com


#9

Question. If baking the Argentium in the oven increases the tarnish
resistance and the strength of the material, then should I “cook” my
chain maille bracelets and earrings? If so, how long and at what
temperature? The jump rings are not thick like fabricated pieces.
Does this make a difference? Will be appreciative of any input in
this area.

Pat Klein


#10

This is an interesting thread. I have been working silver for just
over a year now, basically I have only used Argentium. I love it and
find it frustrating at times. The frustration comes from what, I too,
would describe as a “brittleness.” I have many times had pieces
literally snap in a cross-lock tweezer using barely enough pressure
to hold the piece in place.Argentium at fusing temp is very unstable

  • breaks up like potato chips.I support argentium on a charcoal block
    or support odd shapes on a piece of fiber blanket from my kiln. I
    have even stuffed hollow shapes andrings with fiber blanket to
    support the metal while fusing. I used a crosslocking tweezer once -
    amazing breakage!! Try some fiberglass kiln blanket - works super!
    Have fun - I have found argentium to be amazing. Fun experimenting
    and fun with great results! Make great stuff and have a great time!!

Joy Kruse


#11
If baking the Argentium in the oven increases the tarnish
resistance and the strength of the material, then should I "cook"
my chain maille bracelets and earrings? If so, how long and at what
temperature? The jump rings are not thick like fabricated pieces.
Does this make a difference? Will be appreciative of any input in
this area.

I was told in the workshop I took if I wanted increased tarnish
resistance to "bake"my finished pieces in the oven a 250 degrees for
20 minutes. I was told this helpsthe germanium come to the surface of
the metal and create a stronger even coat that is “more” tarnish
resistant. I have seen the yellowing of Argentium especially in
tropical areas where people are using sun screen. When I wear my own
Argentium rings they leave black rings on my fingers and the black
does not come off easily even with scrubbing. During this post
someone asked about Argentium rings turning black and scratching
easily- I agreed with the returning comment that the customer might
be soaking herhands in bleach and then maybe building a masonary rock
wall wearing her (or his) jewelry. I have not had any of my pieces
turn black or scratch any easier than any other soft metal. Hope
someone comments on the “baking” of Argentium and it’s effectiveness.

Take Care All - Joy Kruse


#12

Hi Pat,

If baking the Argentium in the oven increases the tarnish
resistance and the strength of the material, then should I "cook"
my chain maille bracelets and earrings? If so, how long and at what
temperature? The jump rings are not thick like fabricated pieces.
Does this make a difference? Will be appreciative of any input in
this area. 

It does not matter how thick the AS is----hardening is hardening. I
think it is all the more helpful for thin metal! Use the same
temperatures I gave in one of the previous emails. The only thing to
keep in mind about different size and thicknesses of metals is that
the timing starts when the metal reaches temperature—not when you
put it in the oven or kiln.

Any heat accelerates the formation of the protective germanium
oxide. This is why some people put their AS in an oven at 250 degrees
F for 20 minutes. 250 does not harden the AS, but it is unlikely to
discolor the metal, and some people don’t have pickle, etc.

I hope this helps!

Cynthia Eid
http://www.cynthiaeid.com