I have some 24K gold coins that I want to reduce to 14K and some to
18K. I will be working with small amounts and am considering pouring
the molten gold into a shallow depression in a charcoal block,
rather than into an ingot mold.
I will be using a new, freshly prepared crucible to avoid any
contamination of the metal.
Also, I will be using rolling alloy, as I will not be using the
alloyed metal for casting. I have the charts giving the proportions
of gold to alloy, and will be careful with my measuring.
However, after consulting various sources on the internet, I have
become quite apprehensive about doing any alloying as I understand
that there are a number of problems, such as brittleness, cracking
of the gold when it is being rolled, as well as spots and other
impurities contaminating it. Also it must be properly quenched before
it has a chance to cool, but no as to how long to let it
cool before quenching.
With all these dire predictions, I am beginning to wonder if I
should forget doing any alloying, and just trade the coins for some
sheet metal, in which case I would be losing money on the exchange.
Am I being unduly fearful of the undertaking, or should I just
proceed to do my own alloying.
Alma- We alloy our own all the time. I prefer to melt the 24 kt 1st.
Then add the alloy. The 24 kt takes a long time to melt. I like to
add the alloy after it melts so that I don’t burn the lower melting
temp alloy while trying to get the 24 kt hot enough.
When your alloyed metal is well melted and mixed, pour into a bucket
of water. Then drain and dry off the alloyed metal before you start
to make ingots.
Forge your ingot on sides before rolling.
If it is pink or red gold be sure to quench while hot.
Am I being unduly fearful of the undertaking, or should I just
proceed to do my own alloying.
Yes. don’t believe all the dire stuff (about all sorts of topics,
not just this) you find on the net. Remember, any 10 year old who can
type can post stuff on the net, and by age 12, they can make it look
like a pro. Doesn’t mean there isn’t good info there too, but it
takes some discerning reading to find it sometimes. It’s really easy
to find “how to” info posted on some subject by someone who decided
to try and figure out how to do something, without any prior
experience. The results can be entertaining, and sometimes are
really creative thinking by creative beginners. That doesn’t mean
what they’ve come up with is the easiest or best answer.
I’d suggest your ingot molds are a better idea than pouring into
charcoal, if you’re planning to roll the metal. You’ll get smoother
more uniform ingots, easier to roll. And they ingot molds will chill
the metal quicker, which reduces any problems with uneven alloys that
can (occasionally) happen with some alloys segretating as they cool
slowly.
Alloying isn’t much different from any other melting metal task. Put
the more reactive elements on the bottom, to minimize undue
oxidation. Stir the melted metal to be sure they’re fully melted all
the way to the bottom. Use flux. etc.
If you’re worried that you may not have a fully uniform alloy, then
simply do the whole thing twice. melt, pour your ingot. Clean/pickle,
then remelt and pour again. Be sure your melting flame is suitably
set, ie at least slightly reducing, not oxidizing, but also not
excessively so. Just a nice moderate, slightly reducing flame. Flux.
Go for it. It’s not complex.
Don’t be too worried about alloying your metal. I have alloyed all
my yellow golds for the last 30 years without any major problems. I
am no expert but I can explain the process I use.
Make sure all of your metal is uncontaminated. I alloy from fine
gold granules and have never tried using coins. I use copper foil I
purchase froma chemical company and fine silver granules. I was told
not to use copper from electrical wire as it has too many
impurities.
I melt the metal in a standard ceramic crucible using oxy/ Propane.
The18ct alloy I use consist of copper / Silver/ Gold and the 14 ct
has a smallamount of zinc as well.
I start by melting the fine silver in the crucible. When this is
molten Iadd a very small amount of copper and stir the molten metal
with a quartz rod to mix in the copper. Use small amounts of copper
to start with andmix in well. Using large amount of copper first
makes it difficult to get the copper to mix well with the silver.
Add the copper faster as you get more of the copper mixed with the
silver. Once you have all the copper mixed in start adding small
amounts the fine gold (coin)as you did with the copper. When you
have all the gold mixed in pour the metal into whatever you are
using as a mold. I remove the bar of gold from the mold once it has
solidified, before it has a chance to cool, and anneal it. Annealing
the metal removes any stresses from the pour and give the bar a
uniformhardness. I generally let the metal cool for a minute or so
before I quench it. The thicker the bar the longer I let it cool.
If the alloy has zinc in the mix I add this last. If you just drop
the zinc on top of the molten metal it just burns away. I take the
torch off the the metal in the crucible long enough for it start to
start to solidify. I then lift the metal off the bottom of the
crucible some tongs and place the zinc under the alloy. Melt the
metal again using the solidifiedmetal to shield the zinc. Mix the
metal again when it is molten and pour.
I hope this helps.
I’ll be interested to see what methods other people use.
I have been melting and alloying gold in charcoal blocks In small
quantities for many years with no problems I do not pour the molten
metal into a depression in the block however, but melt it directly
intoa trench or slot cut in the block. I then roll, forge or draw the
metal into the desired form. You should have no problems.
Thank you for all the responses to my query about alloying my gold
coins. I feel much more confident now that you have demystified the
process.
In order to simplify things, and assure greater success I will not
be making my own alloy, but will be using one I got from Stuller
which is alreadymixed for 18K rolling, got it a number of years ago,
and just was too reluctant to just wade in and do it. Call it fear
of gold. It is the high price of the metal that is so intimidating.
Now with all the kind suggestions and recommendations you have all
given me, I shall get busy and reduce my 24k coins to 18, and some
14 karet ones.
I have a couple of questions too as I have a lot of metal to melt
down but am fearful…
Jo. why drop in water instead of the charcoal block or an ingot
mold?
If using an ingot mold, how fast is quenching done? I assume you
remove the mold first.
Should the metal be tarnish free and right out (so to speak) of
the pickle?
When is it necessary to forge the ingot and when not?
I believe I was told that plumbing copper was ok to use but not
the stuff we buy to make copper jewelry with. Is that so?
As you are stirring the metal with the quartz stick, and schmutz
(technical jewelry term, I believe) comes to the surface, what do
you do with the schmutz?
Thanks for info, Esta Jo on her way to Paris! Thanks for all the
advice everyone!
Jo. why drop in water instead of the charcoal block or an ingot
mold?
I leave this to Jo. I have only ever done this to granulate metal.
If using an ingot mold, how fast is quenching done? I assume you
remove the mold first.
The metal mold takes heat way quickly. You can quench it straight
away or leave it for a minute or two. I let my white gold cool
longer than the yellow golds. I let my gold air cool when I first
started alloying with no problems.
The metal was slightly harder and needed annealing sooner but other
than that no problems.
DEFINATLY remove the metal from the mold.
HEAT THE METAL MOLD BEFORE POURING ANY HOT ALLOY INTO IT. If you
don’t it is very likely the molten metal will explode due to
difference in temperature and possible moisture in the mold.
WEAR EYE PROTECTION AND GLOVES.
I use a thin layer of oil in the bottom of the mold. This form a
barrier that helps the metal flow by slowing the cooling process.
Should the metal be tarnish free and right out (so to speak) of
the pickle?
Fine gold, yes. 18 ct, less so. 14 ct even less so. The less pure
the alloy the more tarnish. I use a brass brush to remove ant
tarnish left after it is pickled.
As you are stirring the metal with the quartz stick, and schmutz
(technical jewelry term, I believe) comes to the surface, what doyou
do with the schmutz?
If melting in a ceramic melting pot I sprinkle borax onto the metal.
The pot is already glazed with borax. Remove the flame from the ball
of metal for a couple of seconds. This causes the ?schmutz? to run
to the edge of the ball of metal and stick to the pot.
Before pouring, or if there is a lot of ?schmutz?, I use a metal bar
(usually the tang of an old bench file) to run around the edge of
the ball of metal to collect the excess flux.
Use at turning action as if you were picking up honey with a knife.
I cool the flux on the file between scoops by then twisting it
across a metal block. This makes the flux into a cone shape and
cools it so it doesn’t melt off the file back into the melting pot
on the next scoop.
Use quick scoops to prevent the flux melting as you try to scoop
more flux out of the pot before you pour.
Dean- The reason I pour into water before pouring into the ingot
mold is to assure a complete mix of the alloy and pure gold. I have
tried alloying in the crucible and then casting or pouring straight
from the crucible and had a left over puddle of pure gold in the
bottom. The result is a perfect casting or ingot of 8 kt gold rather
than 18kt.
You have to screw up a lot to get good at this jewelry biz. I’m
whatcha call an expert.
Under the heading of TMI…
Another piece of advice is to be sure to pee before you start. It
takes forever to get the iron ingot mold hot enough as well as
melting the metal.
There is something about the sound of a casting torch that makes me
want to pee every time. Go figure.
Dean- The reason I pour into water before pouring into the ingot
mold is to assure a complete mix of the alloy and pure gold. I
have tried alloying in the crucible and then casting or pouring
straight from the crucible and had a left over puddle of pure gold
in the bottom. The result is a perfect casting or ingot of 8 kt
gold rather than 18kt.
I do pretty much the same thing for the same reason, but after
mixing I allow the metal to cool in the dish style ceramic crucible
until it’s hardened and then quench the metal button still in the
crucible under a slow-flowing faucet of cold water. You can also just
dunk the whole thing in a bucket of water which works just as well,
but is more wasteful of water. I’m sure someone will scream out that
everything will shatter, explode or otherwise fly apart when the
water hits it or if you ever try to use the crucible again, but in
thirty-plus years of doing it exactly like this at least once a week
(frequently several times a day), no such thing has ever happened.
I’ve never even seen a crucible crack. In about ten seconds, the
button just falls out and the crucible steams and hisses for a minute
or two. As soon as it stops hissing, it’s ready for action again.
It’s easier doing it this way as you end up with a round, flat button
instead of wet grain, and it’s a bit easier to handle.
Under the heading of TMI......
Another piece of advice is to be sure to pee before you start. It
takes forever to get the iron ingot mold hot enough as well as
melting the metal.
There is something about the sound of a casting torch that makes
me want to pee every time. Go figure.
Obviously the advice of a highly experienced professional. The lady
knows what she’s talking about. This also applies to investing and
pretty much any other casting procedure.
