Refining Silver -- Ancient Myth???

Is it true that in the ancient method for refining silver over an open
flame, that the stopping point was approximately when the refiner
could see their reflection in the silver?

Also is it critical to not get the silver too hot or it can be
damaged? Thus necessitating that the refiner pay clos eattention to
the process.

This is strictly for personal reference and I am not actually trying
to refine silver.

Please e-mail me the response in addition
toposting it here.


--
My Motto: The brave don't live forever, but the cautious don't live at
all. Here's to the brave!
Timothy Luce

TL wrote:
Is it true that in the ancient method for refining silver over an open
flame, that the stopping point was approximately when the refiner
could see their reflection in the silver?

It is true that ancient methods, inspite they did work sometimes are
full of physical faults. :-)

Have a nice day,
Heinrich

--
Heinrich Butschal
casting technologies
http://butschal.de/werkstatt

On Tue, 02 Mar 2004 19:56:02 -0800, in rec.crafts.jewelry
(TL) wrote:

Is it true that in the ancient method for refining silver over an open
flame, that the stopping point was approximately when the refiner
could see their reflection in the silver?


Out of curiosity, what method are you referring to? Just melting silver
doesn't refine it very well. it's most common natural alloys are with things
like gold and copper, which are not generally driven off by heating to silver's
melting point. Certain fluxes can be used to help remove impurities like iron,
or some of the lower melting metals like zinc, lead, etc, but at least in
naturally occuring silver deposits, these impurities aren't that common, or
that much of a problem, so far as I know...

also, though I'm unsure of the method you refer to, in general, melting silver
alloys is done in reducing atmosphere, and in those conditions, the molten
metal is bright and shiny without needing to be pure at all. Even in oxidzing
atmosphere, it will tend to be reasonably bright before it's all that pure,
especially if the impurity is gold, a common admixture with silver.

Now, perhaps you're referring to a traditional (and still used) method for
assaying gold in particular. In this process, called cupellation, the impure
gold is wrapped in a bit of lead foil, and melted in a porous bone ash crucible
called a cupel. The lead combines with oxygen and the baser metals in the mix,
and the combined slag of these impurities are absorbed by the crucible, leaving
just the gold and silver. In that process, it's complete when the molten
button of metal in the cupel is bright and shiney, indicating that the lead
oxide is fully absorbed by the cupel. I don't recall ever reading, though,
that this was ever used as an actual means of refining precious metals, since
the cost for the lead itself would end up being rather high.

Also is it critical to not get the silver too hot or it can be
damaged? Thus necessitating that the refiner pay clos eattention to
the process.

well, if you heat it hot enough, you'll start to vaporize some of it. And in
any melting environment, molten silver is capable of dissolveing considerable
amounts of oxygen, and some other gasses, which then come back out of solution
when the metal solidifies. This doesn't ruin it in chemical terms, but it sure
can make a mess of an ingot if you wanted solid metal without pinholes,
porosity, or the like. If you melt pure silver without protective flux or a
reducing atmosphere, there will be enough dissolved oxygen that when it
solidifies, that gas coming out of solutiona again can cause spitting and a
very very rough surface on the silver. Either pretty, or a mess, depending on
what you wanted to achieve. Again, fluxes can be used to protect the metal
during melting to minimize this, and it's less a problem melting alloys of
silver if the alloys are baser metals (like copper), since those then combine
with the oxygen forming oxides, which again, can have negative effects, though
as the oxides tend to slag off to an extent (baser metals especially), it does
have some refining effect. But gold isn't removed this way, for example


This is strictly for personal reference and I am not actually trying
to refine silver.

Please e-mail me the response in addition
toposting it here.


Peter Rowe

Peter, thanks for your response. This story told in the first person
is hwat inspired me to ask my question. do you think there is any
truth in this story?

BEGIN QUOTE FROM A STORY I FOUND_____________________
As I watched the silversmith, he held a piece of silver over the fire
and let it heat up. He explained that in refining silver, one needed
to hold the silver in the middle of the fire where the flames were
hottest, so as to burn away all the impurities.

I asked the silversmith if it was true that he had to sit there in
front of the fire the whole time the silver was being refined.

The man answered that yes, he not only had to sit there holding the
silver, but he had to keep his eyes on the silver the entire time it
was in the fire. If the silver was left a moment too long in the
flames, it would be destroyed.

I was silent for a moment. Then I asked the silversmith, "How do you
know when the silver is fully refined?" He smiled at me and answered,
"Oh, that's easy – when I see my reflection in it."
BEGIN QUOTE FROM A STORY I FOUND_____________________


Peter W. Rowe pwrowe@ixDOTnetcomDOTcom wrote in message
. ..
On Tue, 02 Mar 2004 19:56:02 -0800, in rec.crafts.jewelry
(TL) wrote:

Is it true that in the ancient method for refining silver over an open
flame, that the stopping point was approximately when the refiner
could see their reflection in the silver?


Out of curiosity, what method are you referring to? Just melting silver
doesn't refine it very well. it's most common natural alloys are with things
like gold and copper, which are not generally driven off by heating to silver's
melting point. Certain fluxes can be used to help remove impurities like iron,
or some of the lower melting metals like zinc, lead, etc, but at least in
naturally occuring silver deposits, these impurities aren't that common, or
that much of a problem, so far as I know...

also, though I'm unsure of the method you refer to, in general, melting silver
alloys is done in reducing atmosphere, and in those conditions, the molten
metal is bright and shiny without needing to be pure at all. Even in oxidzing
atmosphere, it will tend to be reasonably bright before it's all that pure,
especially if the impurity is gold, a common admixture with silver.

Now, perhaps you're referring to a traditional (and still used) method for
assaying gold in particular. In this process, called cupellation, the impure
gold is wrapped in a bit of lead foil, and melted in a porous bone ash crucible
called a cupel. The lead combines with oxygen and the baser metals in the mix,
and the combined slag of these impurities are absorbed by the crucible, leaving
just the gold and silver. In that process, it's complete when the molten
button of metal in the cupel is bright and shiney, indicating that the lead
oxide is fully absorbed by the cupel. I don't recall ever reading, though,
that this was ever used as an actual means of refining precious metals, since
the cost for the lead itself would end up being rather high.

Also is it critical to not get the silver too hot or it can be
damaged? Thus necessitating that the refiner pay clos eattention to
the process.

well, if you heat it hot enough, you'll start to vaporize some of it. And in
any melting environment, molten silver is capable of dissolveing considerable
amounts of oxygen, and some other gasses, which then come back out of solution
when the metal solidifies. This doesn't ruin it in chemical terms, but it sure
can make a mess of an ingot if you wanted solid metal without pinholes,
porosity, or the like. If you melt pure silver without protective flux or a
reducing atmosphere, there will be enough dissolved oxygen that when it
solidifies, that gas coming out of solutiona again can cause spitting and a
very very rough surface on the silver. Either pretty, or a mess, depending on
what you wanted to achieve. Again, fluxes can be used to protect the metal
during melting to minimize this, and it's less a problem melting alloys of
silver if the alloys are baser metals (like copper), since those then combine
with the oxygen forming oxides, which again, can have negative effects, though
as the oxides tend to slag off to an extent (baser metals especially), it does
have some refining effect. But gold isn't removed this way, for example


This is strictly for personal reference and I am not actually trying
to refine silver.

Please e-mail me the response in addition
toposting it here.


Peter Rowe

On Wed, 03 Mar 2004 23:51:01 -0800, in rec.crafts.jewelry
(TL) wrote:

Peter, thanks for your response. This story told in the first person
is hwat inspired me to ask my question. do you think there is any
truth in this story?


As I watched the silversmith, he held a piece of silver over the fire
and let it heat up. He explained that in refining silver, one needed
to hold the silver in the middle of the fire where the flames were
hottest, so as to burn away all the impurities.

I asked the silversmith if it was true that he had to sit there in
front of the fire the whole time the silver was being refined.

The man answered that yes, he not only had to sit there holding the
silver, but he had to keep his eyes on the silver the entire time it
was in the fire. If the silver was left a moment too long in the
flames, it would be destroyed.

I was silent for a moment. Then I asked the silversmith, "How do you
know when the silver is fully refined?" He smiled at me and answered,
"Oh, that's easy – when I see my reflection in it."

Veeery interesting. but kinda "full of it". And as told above, it's not true.

The story may have been "told in the first person", but that applies just as
well to fiction, as it does to fact, and I suspect that your story was from
something fictional, written by an author who knew little about what he was
writing about. Authors will often try to include lots of detailed info to
give their novels interest and reality, but sometimes, their research into what
details to put in isn't so good. I've more than once been asked by some author
or other to give them some background on some jewelry related topic (often gem
lore), and it's quite common that some of these folks don't have enough
scientific background (like third grade, elementary school science class,
sometimes...) to understand even the basics. What results in the books are
sometimes fully 180 degrees away from the truth, or just plain total fanciful
imagination.

This is not that unusual, nor out of average for the population, when you
consider that the so called science of astrology, defined and started in
egyptian times when the understanding of the nature of the universe postulated
things like the planets being supported on the backs of celestial giant
turtles, or crystal spheres, or what have you, and of course everything
revolved aroung the flat earth. Even with all the wonderful obvious evidence
people can avail themselves of these days, including pictures of our nice round
planet taken from the moon and more, statistics still show there are more
people who believe in astrolgy, and think the postitions of stars and planets
in the sky can affect their fate, than there are folks who actually understand
much about what current astronomy tells us about the large structure of our
universe, or what physics says about the nature of matter and energy, etc. So
folks who've got no clue about refining, writing about it with seeming
authority should come as no surprise at all.

Silver cannot be refined by just holding a solid piece in the fire. Normally,
refining by "fire' methods needs the silver to be molten, not solid, and most
modern methods use chemical means that actually dissolve it in acids, or in
cyanide solutions, rather than anything having to do with fire. If it was
pure silver to begin with, and was polished to begin with, then even with
heating, if the flames are a reducing atmosphere, one will still be able to see
a reflection in the silver. But commonly, silver is mixed with copper, which
causes the silver, if not protected with flux or something, to usually blacken
with the formation of copper oxide on the surface, or at least, to dull down as
the crystal structure at the surface changes some. If the silver is dirty, or
covered with something like pitch (A tar like materials used to support silver
in sime types of work, which then has to be cleaned off again), then of course
one might be able to burn off the surface dirt, but this is just cleaning, not
refining.

Now, the description is closer to the process of annealing. If that is what's
being described, then the level of error on the part of the story teller is
much smaller, a mistake in terms (and probably, the meaning of those terms),
and perhaps a bit of stretching of the truth a bit. Annealing is not
refining, as it does not affect the purity or composition of the metal, and has
nothing to do with burning out impurities. But, when silver (or gold, and many
other metals) are worked, they get harder from working and distortion of the
crystal structure. Heating the metal allows the crystals to "relax", and
reform new crystals that are then capable of more deformation, and the process
is used frequently in metalwork as one works the metal by forging, hammering,
etc, in order to keep the metal soft enough to work withough cracking. In
this process, one heats the silver to just below, or just near, the lowest temp
at which it is slightly glowing. As I stated earlier, normally, heating
silver in a fire will tend to oxidize the copper in the surface, and this can
cause problems, as well as additional work and clean up. One solution is to
coat the silver with a flux, such as borax, boric acid, or various more complex
mixes, which as the silver heats, melt to a glaze on the surface that protects
the surface from the oxygen in the air. And, one way to tell if your metal has
gotton hot enough to be annealed is when the initially crusty white coating of
flux fully melts and becomes fluid, at which point it is mostly clear. So if
your fictional silversmith is annealing, perhaps he's telling the observer that
he knows the silver has gotton hot enough to be annealed because, since the
flux coating has become clear and mostly transparent, he can now once again see
the metallic reflective surface of the metal, and perhaps some bit of his own
reflection (though that's stretching it a bit).

that's my bet for your story.

anyone else?

Peter

Peter,
Anyone else you say?
Yes me.
The news article is a load of rubbish as any practicing silversmith will
know. Also if it really worked then all the professional refiners would
be using it.
So with that out of the way, there is just a minute grain of truth there
albeit very little.
This is based on the principle of zone refining , a technique used in
titaniun production metallurgy.
This, under a high vacumn in a watercooled copper cylinder, is melted
by high frequency induction heating . As the melted zone proceeds up
the column of metal the impurities being lighter move up with the
molten area. When cold the impure top area is cut off and the metal is
processed further into other sections like rod sheet tube etc.
Not for the medieval alchemists level of technology to which the news
item refers.
Ted Frater.

On Thu, 04 Mar 2004 02:23:09 -0800, in rec.crafts.jewelry "ted.frater"
wrote:

Peter,
Anyone else you say?
Yes me.
The news article is a load of rubbish as any practicing silversmith will
know. Also if it really worked then all the professional refiners would
be using it.

That's sorta what i told him too, isnt' it.

So with that out of the way, there is just a minute grain of truth there
albeit very little.
This is based on the principle of zone refining , a technique used in
titaniun production metallurgy.
This, under a high vacumn in a watercooled copper cylinder, is melted
by high frequency induction heating . As the melted zone proceeds up
the column of metal the impurities being lighter move up with the
molten area. When cold the impure top area is cut off and the metal is
processed further into other sections like rod sheet tube etc.
Not for the medieval alchemists level of technology to which the news
item refers.
Ted Frater.

I rather figured zone refining would be a bit beyond the scope of what needed
to be brought up. Besides, though it seems to resemble his description
slightly more than normal methods of refining, it still, as i noted, requires
the metal being refined to be molten. In zone refining, it's just a very
small, travelling, portion of the rod. And as you so correctly point out,
controlling this rather exacting process isn't quite in the realm of medeival
technology. Heck, it's beyond the means of many modern refiners too, who are
set up to just actually melt the whole batch.

Also, while zone refining is used with titanium and a few similar metals, it's
not generally used with most precious metals, which are such good conductors of
heat that it's more difficult, and takes a lot more power, to establish the
needed small traveling melt zone. The method, however, IS one of the
preferred means of achieving ultra pure crystals of some of the semiconductor
or laser rod materials. works quite well, if I remember right, to turn
things like an ordinary quartz rod into an ultrapure one.

Peter

TL wrote:
=

Peter, thanks for your response. This story told in the first person
is hwat inspired me to ask my question. do you think there is any
truth in this story?
=

BEGIN QUOTE FROM A STORY I FOUND_____________________
As I watched the silversmith, he held a piece of silver over the fire
and let it heat up. He explained that in refining silver, one needed
to hold the silver in the middle of the fire where the flames were
hottest, so as to burn away all the impurities.
=

I asked the silversmith if it was true that he had to sit there in
front of the fire the whole time the silver was being refined.
=

The man answered that yes, he not only had to sit there holding the
silver, but he had to keep his eyes on the silver the entire time it
was in the fire. If the silver was left a moment too long in the
flames, it would be destroyed.
=

I was silent for a moment. Then I asked the silversmith, "How do you
know when the silver is fully refined?" He smiled at me and answered,
"Oh, that's easy =96 when I see my reflection in it."
BEGIN QUOTE FROM A STORY I FOUND_____________________
=


What a crock!

Abrasha
http://www.abrasha.com

Hi Peter,
Thanks for filling in some more of the background on this.
Ted