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Remelting old gold jewelry


#1

I am trying to move slowly over to more gold and less silver,
but slowly due to cost. I also have a large handful of gold
rings, necklaces, and pendants which are gold and I am thinking
of re using in mine. I can’t send it out to be re-melted…for
obvious reasons! Security and honesty… So I am considering
trying to re melt and roll it my self on a charcoal shaped
block. NOW my question is: How do I calculate the final carat
of the new gold?? I have 24 K. chains and 18 K. rings and a
little 12 and 14 K. Is there some way I can weigh and then
calculate the balance between them and come up with a
total? Or should I keep them all together and just have
several pieces of different carat?? All help very appreciated!
Sharron in hotter and hotter by the day Saigon (dry + hot
season is coming!)


#2

Sharon, your biggest problem with remelting and using old gold
is the solder content, especially with chains. In the US at
least, the amount of solder allowed in chains is greater than in
other jewelry. It is especially significant in plat chains. So
your 24 karat gold chain, depending of the type of link could be
as low as 22 K with the solder content. The quality of your
final product will be greatly diminished, as well, forging and
fabricating will be much more difficult due to cracking and the
lower than normal melting point.

So even though it is possible to calculate the final karat of
gold you would have if you mix it together, It’s not something I
would recommend doing.

Larry Seiger


#3
I also have a large handful of gold rings, necklaces, and
pendants which are gold and I am thinking of re using in mine.
  I can't send it out to be re-melted..for obvious reasons!
Security and honesty..... So I am considering trying to re melt
and roll it my self on a charcoal shaped block. NOW  my
question is:  How do I calculate the final carat of the new
gold?? I have 24 K. chains and 18 K. rings and a little 12 and
14 K.  

Sharron -

Not to be discouraging, but re-using prevoiusly worked gold ia
always a thorny problem. Besides having to trust the original
markings, you are faced with the question of “how much of what
sort of solder did whoever put this piece together use?” And how
much of the alloys am I going to lose in the re-melting process?
There really are excellent reasons for finding an able and
trustworthy refiner - are you telling us there are none such in
sunny Saigon or environs? as fro determining the carat of the
resultant melt - how good are your assaying skills? This is
another job better left to the professsionals and the experts.
How stringent are Viet Nam’s precious metal marking /
trademarking laws? If they’re anything like the US, you have a
very narrow window (+/- 3%) of accuracy before you can get into
big trouble for mismarking - including confiscation/destruction
of mismarked pieces and hefty fines - so even keeping only
similarly stamped old jewelry in a melt can be problematical.

Besides, fresh, new, just-refined gold is so wonderful to work
with, and just so darned PRETTY!! that its worth the extra
expense - not to mention avoiding the grainy, brittle,
cantankerous hassle some remelted golds can be.

Good Luck, Mike


#4

I can’t send it out to be re-melted…for obvious reasons!
Security and honesty…

Sharron, Around 250 B.C., Archimedes had the same problem and
became famous for solving it. You can use the same method today
and get pretty close to the correct answer. It seems that
Archimedes was hired by a nobleman to find out if the local
goldsmiths were ripping him off when they made pieces for him.
He would weigh out a certain amount of gold, send it to the
goldsmith for fabrication, then weigh it when it was returned. If
it weighed the same he was happy. But then it occurred to him
that the goldsmith MAY be substituting a few units of base metal
for an equal amount of gold. He brought in Archimedes as a
consultant. Without going into the now familiar (Eureka!) bathtub
story, Archimedes realized that a mixture of gold with any base
metal would have a lower density (Specific Gravity) than pure
gold. So, rather than simply weighing the object, he measured
its specific gravity. If it wasn’t 19.3, the goldsmith was in
BIIGGG trouble. Your problem is a little more complex because you
need to know what percentage of Gold is in the alloy. However,
the approach is the same. Measure the Specific Gravity. (There
has been a recent thread on the subject, but I’ll give you an
equation to use.) First, we will have to make some reasonable
assumptions about what the adulterants are the relative
quantities of each . Let’s assume that the adulterants are
primarily silver and copper. Let’s also assume that the
copper/silver ratio is about 60% copper and 40% silver. (The
actual ratio isn’t all that critical) This adulterant mixture
would have a S.G. of about 9.52 and gold has a S.G. of 19.3 Once
you measure the S.G. of your ingot, you can calculate the % gold
with the following formula. % GOLD = 197.4 - 1880/S.G. For
instance, if your ingot had a S.G. of 15.4, the gold content
would be: % GOLD = 197.4 - 1880/15.4; or 197.4 - 122 or 75.4%
(Approx. 18K) The math involved in getting this little "plug-in"
equation is a bit too involved to describe here but if you are
interested, contact me off-line Also, if you need help in
determining S.G. contact me off-line.
Go for it!..Bob Williams


#5

Sharron, Remelting old gold is what I’m doing for a long time out of
cost reasons . My experience is that every gold above 18K including
solder is not a problem. For melting only 14 K or 12K you have to
remove ( cut, or saw )out al the solder connections. This solder
hardens the alloy fast when you are deforming it. You have to anneal
it a lot and the gold will not be of a fine (meaning ductile)
structure. So I use only clean 14 k gold for making wire and sheet.
The rest, solder, filling scrap and other sjit I only use for casting.
It is handy to use old wedding rings for making high quality wire. jus
anneal the ring to dull red (650 degrees Celsius) roller it to a
smaller diameter, and anneal it again and pull it trough a draw plate.
There are special borax mixture for remelting and cleaning old gold.
Its wise to remelt it a few times with this mixture and stir it with a
graphite stick. The slug (I hope I spell this right) on top of the
melted gold absorbs the pollution.

Martin Niemeijer


#6

I have used the “Magic Cast” product when casting 14k gold using more
scrap gold than new grain. The instructions recommend using 5% Magic
Cast to the melt. It comes out nice and clean with little firescale
and makes the gold a nice yellow color unlike the pinkish color that
can occur using mostly scrap. I wonder if others out there use it and
what everyones thoughts on the product are. NET


#7

Magic cast is a good product…I have used it for many years and it
does a great job. Ron at Mills Gem, Los Osos, CA.


#8

I use the alloy replentisher sold through United, much less
expensive, same results.

JMF


#9

I’ve used Majic Cast and other similar products quite a bit. I often
cast using 100% scrap, and usually just use 3% of the additive, my
casts would almost always come out looking like I used all casting
grain or alloyed down coin. I’ve been told that using a slice of a
penny as an additive will yield a pretty cast also. I haven’t had
the situation present itself where I had to resort to trying the
penny trick yet. With zinc being a major part of the casting
additive, and pennys being made of zinc, I’m sure I’ll end up trying
it one of these days.

Rick Barnes
Gainesville, FL


#10
    I have used the "Magic Cast" product when casting 14k gold
using more scrap gold than new grain. . . . I wonder if others out
there use it and what everyones thoughts on the product are. NET 

I use it, when I have a customer who is willing to risk making a
piece using old chain, or mountings of questionable purity, possibly
having past repair work and subsequent solder. I find it does what
it say, and I’ve been happy with the results. You can even add pure
gold to boost the karat up to 14 again, but usually I don’t. For
those who are interested, there is a unit, for about $300, that will
refine your gold using a salt solution. It would take a lot of nasty
processing to refine sweeps and certainly polishing dust would be
practically out of the question, but for solid material, I hear it
works pretty good. David L. Huffman


#11

Regarding “magic cast”, remember that you’re taking gold which is
already only the karat you wish plus whatever solder may be in that
scrap (if any) which would then lower it’s karat. And then you’re
adding some brass, which is the bulk of the “magic cast volume”, in
order to also add the additional deoxidizers in the product. The
result may cast better than plain scrap, but it is now slightly
underkareted. This product is intended to allow you to get a decent
casting when reusing scrap gold, such as when a customer brings in
their old rings to be made into something else. If you are using it
to produce “new” jewelry, and find the magic cast useful because your
ratio of new grain to old sprues is too low, then weigh the magic cast
you’ll be adding to a melt, and also add an appropriate amount of 24K
grain (or, if you’re up to the slightly more complex math needed to
calculate the required amount, any scrap higher in karat than your
main melt can be used) so that your end karat content is up to the
desired standard. It’s only a small deviation in a single use, but
if you’re in the habit of using this stuff because you’re not adding
enough new metal, than the additions of magic cast will also
accumulate in your old sprues, multiplying the effect each time. It
helps to remember that in times when deoxidizers were mostly just
zinc, melting the gold would burn off the zind and the result would be
slightly higher karat over time. These days, often the deoxidizers
and additions are silicon and other elements added in much smaller
percentages, and which don’t always change the karat too much when
the metal is repeatedly melted. Thus the magic cast’s karat lowering
action can be multiplied.

Hope this helps
Peter Rowe


#12

Peter, thanks for the info on the Magic Cast. I do add some 24k to
the melt. I sometimes have added a tiny bit of Magic Cast to the
already correct ratio of new grain to old buttons just to tweek the
color. I imagine it turns out cleaner looking and yellower instead of
pinker. I am sort of overly sensitive to colors or maybe it’s my
imagination but I think it puts the color back to the color I get
with all new grain. I would really like to be able to fine tune the
colors of gold because I personally see vast differences between 10k,
14k, 18k, 22k and if I cast 14k and it looses some yellow I’m
agravated. I really don’t use scrap, just buttons and new grain. so
why do I see the pink or copper color in the recast buttons with new
grain? (this is very slight really but it’s apparent to me
nonetheless). Maybe I’m crazy. What thoughts do you helpful
Orchidians have on this matter? NET


#13
   I would really like to be able to fine tune the colors of gold
because I personally see vast differences between 10k, 14k, 18k, 22k
and if I cast 14k and it looses some yellow I'm agravated. 

The color differences you’re seeing are due to extended or repeated
melting. It doesn’t matter if this is scrap or a multiply cast button.
It’s the melting cycle, vaporizing some of the zinc deoxidizer, that
changes the color. If you use a gold alloy that uses silicon
deoxidizer, instead of zinc content, then the color won’t change. But
it will still need some sort of replenishment with new metal, simply
because you NEED that deoxidizer for casting alloys, if you’re to
consistently control porosity. Aside from the zinc, which burns out
on repeated meltings, the color is simply a function of the ratio of
copper and silver within the alloy. More silver gives you a less
coppery color. The silver doesn’t burn away on repeated use, so this
color shift is not a problem with non-deoxidized alloys such as one
might use when fabricating pieces, rather than casting them. In that
case, repeated melting may introduce more oxides and other
inclusions/impurities, giving some pits or flaws in the metal, but
you simply don’t use that part of the metal when you make up the
piece, and careful melting technique, with appropriate fluxs etc,
control that sort of flaw pretty well anyway. It should be mentioned
too, that zinc, in addition to giving a gold alloy a less "rose"
color, also tends to just plain “bleach” the color a bit. The yellow
color of a zinc free alloy, even with lots of silver so it’s a paler
yellow, will tend to be richer and more intense than that same hued
alloy that contains zinc. That’s another plus in favor of the silicon
deoxidized alloys. Now if those alloys were only a bit more malleable
and ductile too, we’d all be happy clams. Unfortunately, designing an
alloy for maximum castability isn’t always the same as designing it
for maximum workability in a rolling mill or through a draw plate…

Peter Rowe


#14

I’m getting in late on this thread, but my two-cents is this. I like
to buy 24K from the refiner, or take that in exchange for my sweeps
and scrap. I use United Metals. Then I buy the alloys from Stuller.
Besides having alloys for different colors and karats of gold, they
also supply different alloys for casting and making sheet and wire.
The formula for raising and lowering the karat of gold is in the back
of their findings book too.

David L. Huffman


#15

Can you purchase ‘Zinc’ by itself… and how does this effect the mix
formual… . I guess, being a simple ratio foumula it lowers and then
you have to add pure grain goldto off set the zinc amount??? Jim C


#16

to jim c yes add zinc the amount of zinc [alloying element] is
dependent on the gold karat you want to make . example 14 karat gold
is 14 parts gold and 10 parts alloy9silver,copper,zinc,etc,.white or
yellow ? PHIL.