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Casting rose gold


#1

Hi everybody. So I have started casting my own wire today (lost wax)
with some wax I bought. I tried first with some plain copper - it
was almost impossible for me to melt! It took a long time and would
adjust to room temperature super fast. I have to cast a rose gold
ring for my sister’s birthday (March 20th) and I am FREAKING OUT
because she pretty much only likes rose gold. I am using a
Bernzomatic TS4000 if it helps. I will probably need to buy a new
torch I am guessing. What do you suggest? Thank you all!


#2

Jane- It is much harder to melt copper than gold. We don’t even try.
Beware when casting with rose gold. It must be handled very
carefully to ensure that it will not get brittle. The alloy we use
must be quenched while hot. Please be sure to talk to your metal
supplier about how to handle the particular alloy they will be
selling you. Seriously.

Have fun and make lots of jewelry.
Jo Haemer
www.timothywgreen.com


#3
Bernzomatic TS4000 if it helps. I will probably need to buy a new
torch I am guessing. What do you suggest?

I hate to say something’s impossible, but casting ~anything~ but
pewter with that torch just might be. If you’re going to take up
casting, you’ll need a big, hot torch any and all the time anyway.
BTW, there are those who say that casting copper is not possible.
That’s not entirely true, but it’s not a good metal for casting
either, that’s for sure.


#4

Hi John et al,

I hate to say something's impossible, but casting ~anything~ but
pewter with that torch just might be. If you're going to take up
casting, you'll need a big, hot torch any and all the time anyway.
BTW, there are those who say that casting copper is not possible.
That's not entirely true, but it's not a good metal for casting
either, that's for sure. 

Well not exactly impossible, but I wouldn’t use that model torch.

That TS4000 will melt gold, silver and copper, but not in an open
crucible, this will work :-

http://www.ganoksin.com/gnkurl/ak

I use an earlier model of the BZ8250HT (the JTH-7 Bernzomatic hose
torch), and I use use propane.

I melt gold, silver, copper, bronze, and various other mixtures of
those with no problems at all.

The secret (and it’s not a secret at all) is to contain the heat
long enough to melt the metal.

There is no chance in hell that a JTH-7 will melt precious metals in
an open crucible.

Regards Charles A.
P.S. Platinum in definitely out with the micro furnace setup.


#5

I have already received the casting grain but I really should have
asked everyone about casting rose gold before I would have even
attempted it. To be honest, I am just casting wire which I will use
to make the ring, not the ring itself. I just want to make sure that
I am right with this? From my understanding, I need to treat it like
regular yellow gold for quenching at first but be careful not to
crack it. I then heat it up to ~900 degrees and quench it in alcohol?
That’s what I read somewhere. I bought an oxygen propane torch and
have been able to melt copper with it pretty easily. I haven’t tried
any casting with it, though so I am a little worried. To be fully
honest, I have only just “started” lost wax casting.

All my castings have been silver and have turned out just fine - but
I am starting to worry about working with this metal. I didn’t buy
much moneys worth of it as I am going to make a ring with rose gold
bands but also other metals (I only got $50 worth - very little, I
know but I want thin bands for a rolling ring). Maybe I should just
return the casting grain and try to think of something else. Does
anyone have any opinions? Thanks so much for all your help!

Jane


#6

Jane,

In my experience you ALWAYS have to quench red golds from a near red
heat.

Water is just fine, alcohol is just too exciting for my tastes. Let
it air cool and drop it on the floor and you may never find all the
pieces :slight_smile: It will work harden faster than yellow or even Ni white
golds. A slightly different alloy but not enough to be scared of.

Alloys have a range and are much more forgiving. I'm not saying
that you can't do it but it just might not be fun.

PS: copper is not nice to cast, pure metals tend to have the same
liquid and solid temps.

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


#7

Hi,

You may want to know that RED GOLD has two phase while other metals
have only one which means that at red hot it is call “red gold” but
if you let it cools down (double phase) it becomes “rich in copper”
(copper ends up on the surface of the metal)that explain it crack
into pieces or break often Red gold can be age hardening

stepfan chong


#8
You may want to know that RED GOLD has two phase while other
metals have only one which means that at red hot it is call "red
gold" but if you let it cools down (double phase) it becomes "rich
in copper" (copper ends up on the surface of the metal)that explain
it crack into pieces or break often Red gold can be age hardening20 

This is not correct. The gold copper system is not two phase like
silver copper where you would end up with a combination of copper
rich (beta phase) an silver rich (alpha phase) crystal structures
who’s ratio depends on the ratio of silver to copper in the alloy.
However what can form in the gold copper system is an ordered
crystal structure that is sometimes referred to as an intermetallic
or ordered phase but it is different from a two phase alloy in that
ordering only occurs in very limited areas of the gold copper system
(around 18k and 12k) and only if the alloy is allowed to dwell in a
particular temperature range where the ordering occurs. In a two
phase alloy there would be clumps of the two different phases
present but in a random distribution. In an ordered structure there
is a very specific position for the copper and gold in the crystal
and this is what induces the hardness and brittle nature of an
ordered structure it more resembles a mineral crystal than a metal.
In mineral crystals each type of atom has a specific position in the
crystal lattice like in say salt NaCl the sodium and chlorine atoms
can only be in specific positions in the lattice where in a typical
metal alloy the atoms are able to be in random locations in the
lattice but when you have an ordered structure in an alloy then the
atoms line up in very specific positions in the lattice and are even
referred to like other compounds so in the gold copper system you
have Au3Cu AuCu and AuCu3 depending on the percentage of gold to
copper in the alloy. At 18k even though the weight percentage is 75
gold 25 copper the atomic percentage 50 gold 50 copper and if it is
allowed to dwell in the neighborhood of 350 C to 450 C the atoms will
align in alternating planes of copper and gold in the crystal lattice
and it will end up as brittle as glass. But if you rapidly quench
through this temperature zone the atoms will not have time to order
and the alloy will remain ductile. If it ever happens that you allow
the AuCu structure to form it can easily be gotten rid of by heating
the alloy to 500C and then rapidly quenching it. And when heat
treating red golds to harden them the mechanics are different than
precipitation hardening of silver copper (Standard sterling or
Argentium for example) with a two phase alloy you need to heat it to
a point where you dissolve all the second phase and are only left
with a single phase then quench this is called solution annealing.
You then follow with a controlled heating that allows the second
phase to precipitate out and pin the crystal lattice. With a ordered
crystal lattice like gold copper can form you only need to heat to
the ordering temperature and hold it for a while. There is no need
for the solution annealing step.

James Binnion
James Binnion Metal Arts