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Recycling old gold


#1

I have recently acquired numerous gold wedding bands and diamond
rings that have been handed down in my family. Most of which I would
never wear so they all sit in a memory box to reflect on. I have
been thinking lately that it would be nice if I could have all the
different golds verified, sorted and refined so I could make myself a
special piece of jewelry that I would wear and have all the memories
with me. does anyone have any advise on how I would go about doing
this? and also where to “sell” the diamonds that I would not be
using?

Rgds, gail


#2

Gail,

Have you thought about using the old jewelry as components of a new
piece?

Bands can be opened, straightened, rolled into wire or sheet. Parts
of old stuff can be cut apart and reassembled into new shapes. Areas
of good texture can be removed and used as accents that still evoke
the “feel” of the original piece. Stones that are left over can be
used in new pieces to sell.

What I’m getting at is, this metal can be made into a new piece that
is your style and still be a “family heirloom” Who cares if a 18k
blob is used with a 14k setting, it’s your piece. Let your
imagination go wild!

Mark Thomas Ruby
SunSpirit Designs


#3

using a loupe or magnifying glass look for the karat / fineness mark
(12,14,18,22 karat or Pt for platinum) on each piece. If large cut
into pieces with sharp french shears, sprue cutters or a bench
shear, then melt them in a crucible glazed with borax to cover all
surfaces then add the scrap (and a pinch of flux) according to each
karat- use one crucible for gold, another for silver, another for Pt-
don’t mix them…once the metal is rolling in the crucible have your
mould ready to pour it into keeping the torch on the molten metal as
you pour (you may use a charcoal block with a well carved into it for
the mould if you haven’t anything else). Then once cooled to a grey
colour you may quench it in water then pickle, neutralize and rinse
well before putting it through your rolling mill or forging it into
a sheet if no rolling mill is available…that’s about it…simple
really. You may mix karats for example mixing 18 and 22 will give
you a new alloy of about 20kt… still quite workable. mixing 14 karat
reduces the gold fineness so i wouldn’t add it to say, 22kt. however
if most of what you have is 14 karat you may want to purchase some
24kt. casting grain to raise the fineness of your scrap to the karat
you wish to work in (18 up to 22). If you were to just melt it all
down you would need a calculator to figure the actual karat based on
the troy weight of each piece and the fineness of the respective
quantities to figure out your result in terms of karat gold. I would
not mix white gold with yellow either as the nickel in the white
gold tends to make any scrap reclaimed brittle…rer


#4

Melting down and creating new stock is definitely an option… But
you can also reconfigure elements of the existing pieces. Check out
the Radical Jewelry Makeover.


http://www.ethicalmetalsmiths.org/RJM.html


#5

Gail,

Tim McCreight’s book, The Complete Metalsmith, has some easy
formulas for converting karats of different kinds of gold. The other
issue, as far as pouring ingots and rolling out these melted down
rings and such, is the alloy in the gold. There are 2 basic types of
alloys used in golds: a rolling alloy and a casting alloy.

You can roll out the softer rolling alloys, and even cast with them,
but the more brittle casting alloys cannot be rolled out, generally.

Dental crowns are an example of a particularly hard alloy. It just
isn’t going to roll out, but just crack up on you.

Good luck!
Jay Whaley


#6

Dear Gail,

I have been using Hoover & Strong for the last 30 years to recycle
gold, silver and platinum, which I get from clients and family. Their
return is very good and you can ask for their HARMONY products which
are recycled and environmentally sustainable.

Otherwise, you can just melt them all down and pour an ingot. Then
roll the ingot out into thin ribbons of metal. Place coils of the
thin ribbons of gold into a beaker with Aqua Regina (nitric acid and
sulfuric acid combined) and heat until the metal dissolves.

Hyper Load the acid with silver ribbons to force the acid to release
the gold molecules. It will look like brow scum floating about a half
inch off the bottom of the beaker.

Decant the acid through lab papers to recover the gold. Rinse well to
remove the acid residue, and remelt the gold powder by burning the
lab paper to get an ingot. This will yield gold that is very close to
24-karat. Pure.

Save the Acid and then hyper-load it with copper to get it to drop
the silver molecules. Sound like fun? Make sure you have all the
protective clothing, ventilation, and gear possible.

Good luck.
Nanz Aalund
www.nanzaalund.com


#7
Place coils of the thin ribbons of gold into a beaker with Aqua
Regina (nitric acid and sulfuric acid combined) and heat until the
metal dissolves. 

Almost. It’s called Aqua Regia (no N.) And the formula is nitric
acid with Hydrochloric acid, not Sulphuric. 3 parts HCl to one part
Nitric. Nitric and sulphuric will not dissolve gold.

Also, what’s with that “Hyper load” with silver to drop out the
gold. Have you actually done this, Nanz? When gold dissolves in aqua
regia, it forms a gold chloride (the reason gold does not dissolve in
nitric plus sulphuric is that gold forms neither a gold nitrate, nore
a gold sulphate). To drop the gold out of the solution, you have to
get that chloride ion to jump to something else. The trouble with
suggesting silver, is that silver isn’t very soluable in hydrochloric
acid (or aqua regia). The reason is that silver chloride is not water
soluable Put silver in the acid, and it forms an impervious layer of
silver chloride on the surface, and the reaction stops. Normally,
when acid refining gold alloys, the acid dissolves the gold and the
copper and the platinum metals, but the silver componant of the
alloys remains behind in the sludge as silver chloride. It’s not
dissolved in the aqua regia.

The process of “dropping” the gold out of the solution by adding a
more reactive metal is, I think, called “cementation”. You can do it
with copper directly, or even easier and cheaper, with steel wool.
The trouble with cementation is that if not every bit of the new more
reactive metal dissolves, then you end up with a mix of pure gold AND
the remains of your other metal. If you use little enough so all the
(steel or whatever) DOES dissolve, then likely, you’ve still got
some gold remaining in the solution. So you have to use more steel
wool than needed, so there’s still some left mixed with the gold. So
then you neutralize all acid, and wash the mix. Now add sulphuric
acid to dissolve the iron without bothering the gold. It’s this part,
where sulphuric is added, that may have led to your confusion with
the aqua regia mix. You can also use nitric to get rid of the iron,
but if there is any trace of chloride iol left (traces of
hydrochloric acid), then adding nitric will not only get rid of the
iron, but it will also redissolve traces of your gold as well,
depending on how much HCl or chloride ion is present. So sulphuric is
safer for this part. But overall, dropping the metal out of solution
with steel wool, while it sounds easy, is a bit of a mess to do.
There’s an easier and cleaner way.

Better than using another metal to precipitate the gold out of the
solution, is to use a liquid agent. Ferrous sulphate, a pale green
crystaline chemical that’s rather inexpensive is a good and common
choice. Dissolve it in water, and add this to the gold bearing acid
until no more gold comes out of solution. Let it settle, decant, and
filter to get your gold (be sure to check the remaining liquid with a
bit more ferrous sulphate just to be sure you’ve got it all)

If you’re original alloy had any of the platinum group metals, then
you’ve got a problem, because the platinum metals will have come out
of solution at the same time as the gold. To prevent this, you have
to remove the platinum first. Oxalic acid is the agent added to
precipitate the platinum metals, without bothering the gold. Then,
after filtering out the platinum sludge, you can recover the gold.
Wash, dry, mix with a bit of boric acid, and melt. Done right, you
can get very close to 24K. Want to get to laboratory standards of
pure gold, then repeat the process, redissolving your precipitated
gold in new acid.

By the way. One final note. dissolving a bunch of gold in aqua regia
is a process you need to do with care. The fumes are toxic as hell,
and can mess up any steel tools in your workshop in addition to your
lungs. Also, the metal dissolving generates heat. So use a large
enough beaker or flask to hold the acid so there’s room for foaming
and the like. If you’re melting rolled out ribbon, as Nanz suggests,
it’s controllable, though you may wish to not add all the metal all
at once, but rather, start with some, add more as the first bunch
dissolves. But if you’re directly adding bench filings or sweeps,
which have a much higher surface area, the reaction can generate so
much heat as to boil the acid. Enough to get it to boil over rather
spectacularly, if you’re unlucky enough. And that, trust me on this,
makes one unholy mess… Fortunately, when I learned this lesson the
hard way, back in the 80s, gold was a lot less expensive, so my
losses weren’t quite as catastrophic. But it was still an expensive
lesson. Oh, and did I mention that the heat of the suddenly boiling
beaker can sometimes crack it? It shouldn’t have, given that it was
pyrex, but dang. It did just that… The plastic bin I had the
beakers in caught most of it, but there’s a house in Detroit where
the soil underneath the back deck probably still has more than a
slight trace of gold chloride in it… I caught most of the overflow,
but not all.

Also, remember where I described how silver does not dissolve well
in aqua regia? If your gold alloy has a high percentage of silver,
you will have the same problem getting the gold to dissolve, since it
can also form that silver chloride layer preventing the acid from
getting to the metal underneath. If your gold does have a lot of
silver, then when you melt it down to make the ingot, add a bunch of
copper to lower the karat as well as the percentage of silver.

All in all, you CAN refine your own gold. Get good at it, and you
can sometimes do it for less money than the pros charge. But in my
experience, you normally are not saving yourself enough money to make
it worth it, and sometimes, inexperience will lead to significant
losses. If you’re fascinated with metal and what you can do, then by
all means, try a small batch just so you’ve experienced it and
learned something abou it. It’s educational, after all. But for best
financial results (including the costs of acids, etc, which
themselves aren’t cheap), I personally recommend that you use a
professional refiner. They earn their fees.

Also, please do not consider this particular posting to be complete.
I no doubt have left out important little details. Do more research
before trying this, if you want good and safe results.

Peter Rowe


#8

Nanz,

Place coils of the thin ribbons of gold into a beaker with Aqua
Regina (nitric acid and sulfuric acid combined) and heat until the
metal dissolves. 

Aqua Regina = nitric and HCl

I guess you don’t go through this circus any more often than I do.
(me never) Considering the time and expense of sourcing the acids and
required equipment refiners are really cheap. Double bubble toil and
trouble, but it should qualify as hand made :slight_smile:

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand


#9
The process of "dropping" the gold out of the solution by adding a
more reactive metal is, I think, called "cementation". You can do
it with copper directly, or even easier and cheaper, with steel
wool. 

I agree. The original recommendation does not make sense. Another
wrinkle is that process is very expensive and goldsmith may actually
spend more on chemicals than save on refining it. With today’s acid
prices, it is cheaper to sell your scrap.

As an intellectual pursuit here is way I had done it:

Alloy your scrap with 3 times amount of silver. Roll out thin and
cover with nitric acid. The thing must be under ventilation hood and
should be heated. Stir from time to time, continue until reaction
stops completely.

Wash remains with water and cover with aqua regia. 3 to 1 is a good
recipe. As before it must be under the hood and heated. When
everything is dissolved you are done.

To drop the gold add, powdered zinc and stir. You should see flakes
of dark brown color forming. Add a little at a time and keep adding
until flake formation stops. Allow to settle over night.

Next day filter the solution, wash the remains and melt it. This is
your gold.

Next step is to recover silver. Prepare highly concentrated solution
of common table salt and add to the filtered solution. Flakes of white
color will form as before. Methodology is the same. Add a little at a
time and continue until formation stops, allow it to settle, filter
and melt.

Remaining solution may contain some platinum group metals, but it is
not practical to recover it in small shop environment.

Dispose of remaining solution in accordance with local regulations.

Leonid Surpin
www.studioarete.com


#10

Leonid,

Next step is to recover silver....... filter and melt. 

My experience with trying to melt silver chloride is that it’s not
that simple. It melts, all right, to a blackish liquid that looks
like molten flux. Breaks down only slowly to silver, and with a lot
of heat, and while doing so, generates enormous amounts of noxious
blue smoke (chlorine?) Was I doing something wrong? Is there some
flux or special means to melt it that I missed? I tried both torch
melting smaller amounts, and a gas melting furnace with graphite
crucible. Similar mess either way…

I recall reading that if one adds zinc (or iron, I think), to the
newly generated and still wet silver chloride, it can be converted
directly to silver this way, and Then melted. Also recall reading
that mixing with corn syrup can also reduce the chloride to silver.
But I’ve not tried it. thoughts?

Remaining solution may contain some platinum group metals, but it
is not practical to recover it in small shop environment. 

So the zinc powder doesn’t also remove the platinum group metals? I
would have thought it would do so at the same time as the gold. You
also don’t mention that people would want to add a slight excess of
zinc, to be sure of removing all the gold. And in that case, if the
acid happened by then to be fully used, there might be some zinc
powder remaining, mixed with the gold flake. So after rinsing the
gold powder, one would want to again rinse with a single acid, one
that would remove any traces of zince but not the gold. Or is this
overkill?

Peter


#11
My experience with trying to melt silver chloride is that it's not
that simple. It melts, all right, to a blackish liquid that looks
like molten flux. Breaks down only slowly to silver, and with a
lot of heat, and while doing so, generates enormous amounts of
noxious blue smoke (chlorine?) Was I doing something wrong? Is
there some flux or special means to melt it that I missed? I tried
both torch melting smaller amounts, and a gas melting furnace with
graphite crucible. Similar mess either way... 

There are several ways to recover silver from silver chloride:

  1. Prepare weak solution of sulphuric acid - 1 part acid to 20 parts
    of water Wash silver chloride with hot water. Hot water is important
    because if lead chloride is present it is solvable in hot water but
    not in cold.

Cover silver chloride in weak acid solution and slowly add powered
zinc, or even thin strips. There will be bubbles which is hydrogen
gas. Keep adding zinc until reaction stops. Silver chloride will be
converted to metallic silver which can be easily melted. There are
could be zinc residue on silver, so before melting it, cover with
fresh batch of weak sulphuric acid solution and let it stand. It
should dissolve all the zinc. Wash it well before melting.

  1. Wash chloride as before and dry it. Prepare flux of equal parts
    of borax, powered glass, and soda ash.

Mix equal amounts by weight of silver chloride and flux and melt it
in graphite crucible. Fill crucible to less than half and start
melting. Good ventilation is a must. The mixture will bubble
violently and can even spill if overfilled. Once bubbling is
subsides add more of the mixture, and so on.

So the zinc powder doesn't also remove the platinum group metals?
I would have thought it would do so at the same time as the gold.
You also don't mention that people would want to add a slight
excess of zinc, to be sure of removing all the gold. And in that
case, if the acid happened by then to be fully used, there might be
some zinc powder remaining, mixed with the gold flake. So after
rinsing the gold powder, one would want to again rinse with a
single acid, one that would remove any traces of zince but not the
gold. Or is this overkill? 

No it is not overkill. There are a lot of steps of washing,
filtering, neutralizing and etc.

If anybody wants to get into it, one should seek proper
documentation. Actual process involves more steps than can be
mentioned here.

Few words about platinum group. If platinum is present process is a
bit different. After removing silver and base metals, alloys is
subjected to cold aqua regia. The recipe is slightly different. 1
part of nitric to 4 parts of hydrochloric and 1 part of water. This
acid will dissolve gold and only little amount of platinum. Most of
the platinum will remain undissolved and can be collected from the
bottom. It will also contain some silver chloride which needs to be
removed before melting. Whatever platinum will be dissolved is
precipitated by ammonium chloride prior to precipitation of gold.
Prior to that sulphuric acid is used to drop lead salts which may be
present in the solution.

The process gets very compacted if iridium, and other platinum
metals are present.

What I am trying to say is that nobody should attempt it without
knowledge of correct handling of chemicals and studied the complete
process using books specially published for this purpose, or
unpredictable results will follow.

Leonid Surpin
www.studioarete.com


#12
If anybody wants to get into it, one should seek proper
documentation. Actual process involves more steps than can be
mentioned here

Wise words Leonid, very wise words indead !!

Enjoy and have fun.
Pedro