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18k Rose gold, to anneal or not to anneal


#1

I am working on an 18k rose gold ring. It was cast but still needs to
be hammered for design and stretched a full size. Some people told me
I should do the work cold to avoid fractures others have told me to
anneal it. Quench it in water, alcohol and oil. ANy advice.

Thanks Adam


#2

Adam-- you must quench rose gold while it’s still hot-- just as it
loses red, water quench is fine. If you let the metal cool without
quenching, it will become so brittle that it can break into pieces
when you hammer it. 18K is more prone to this problem than 14K–
just the way the molecules line up in the alloy. If you are not sure
if it was quenched properly, suggest reheating it to red hot, quench
when the color disappears.

Jim Sweaney
mardonjewelers.com


#3

The real question here is what’s in your rose gold alloy? Is it rosy
with maybe a little silver in it? Or is it a full on 18kt. red gold
alloy with no silver or alloy constituents other than copper and Fine
gold?

18k red golds with little to no silver in the alloy can and do
develop an array structure or arrangement in the metal crystal
lattice if allowed to air cool from a soldering/ annealing
temperatures. AS I understand it the copper and gold atoms organize
themselves in segregated layers along grain boundaries during slow
cooling and apparently no longer like to share electrons with each
other. Selfish of them don’t you think! The net result is a red gold
object which can just crack apart in little expensive large grained
pieces. In my own case I had the misfortune to solder two such side
bands onto a diamond eternity ring( slow air cooling required). This
unsatisfying experience spurred my own research into this very topic
here on orchid. I recommend you do an archive search here on orchid.
Pay attention to the posts by James Binnion and Peter Rowe for more
accurate and less anthropomorphic characterizations of this alloy.
You should also follow the annealing and quenching recommendations
of your metal supplier (they should know what is in the metal you
purchased from them).If you mixed it yourself and its only got
copper and gold in it you’ll need to quench at a dull red heat after
annealing or soldering… no slow cooling! Repair work on this alloy
is a pia and any time I see 18k red I explain the situation to the
customer and ask for liability waiver on this problem. The entire
problem can be avoided if the alloy has a small percentage of silver
in it. I don’t know if other alloy additives will ameliorate this
characteristic.

I’ve also seen what appeared to be excessive grain growth in 18kt.
Nickel white alloys resulting in cracking and mounting failure. This
was on a cast piece set with large diamonds that had been sized a
few times and had had the center head replaced at least once. I
wonder if that alloy was having a similar issue or if the mounting
was only suffering excessive grain growth from slow cooling.

Good luck,
mike


#4
I am working on an 18k rose gold ring. It was cast but still needs
to be hammered for design and stretched a full size. Some people
told me I should do the work cold to avoid fractures others have
told me to anneal it. Quench it in water, alcohol and oil. ANy
advice. 

Your as cast ring will definitely be fully hard. Anneal and quench
before trying to hammer or stretch 18k red. Water or alcohol doesn’t
really matter. What you do not want is a slow cool from above 770 F
(410 C) to room temp. So heat and quench. Alcohol will be a gentler
quench but will still be fast enough.

Jim

James Binnion
James Binnion Metal Arts


#5
I am working on an 18k rose gold ring. It was cast but still needs
to be hammered for design and stretched a full size. Some people
told me I should do the work cold to avoid fractures others have
told me to anneal it. Quench it in water, alcohol and oil. ANy
advice. 

18K rose gold, especially the redder versions with pretty much just
gold and copper, are subject to an unusual behavior where, if the
alloy is cooled too slowly through around the 750F range, it can form
a layered structure with layers of copper and gold atoms alternating,
rather than the usual cubic crystal structure. This "ordered array"
structure is highly brittle. An item in this alloy, where that
structure has formed, can litterally shatter if just dropped on the
floor, much less actually worked in any way. Castings, if quenched
after they’ve cooled a bit, often are harder because of this
structure having formed, so the raw castings must be annealed
properly to ensure good workability. And the metal needs to be cooled
quickly enough from annealing temperature so as to not allow the
metal enough time to form an ordered array structure. Usually, this
means quenching. However, quenching rose golds from the annealing
temps in water, can sometimes be too much for the metal, leading to
stress cracks from the quenching. So a somewhat more gentle quench is
useful. The traditional answer is to quench rose golds in alcohol,
rather than water. The alcohol more easily forms a vapor layer around
the hot metal (water does this too, initially), and that layer stays
there longer, so the finaly quench when liquid actually wets the
metal occurs at a lower temp. Be careful not to have flame near the
alchol, of course, and quickly and fully immerse the gold, so there’s
not hot ignition source at the alcohol/air interface. Done that way,
it’s safe. Be sure the alcohol is in an appropriat container (not
plastic), with a lid that can be put on it if by chance it should
ignite.

Properly annealed, rose golds are wonderfully workable. And if you
like, once completed, heat treating to precipitation harden the metal
can produce amazingly hard metal, in part because some of the
hardening is due to that ordered array structure forming in small
areas. The main thing with annealing though, is not to neglect it. If
the metal starts out hard (a slowly cooled item or casting), then any
working can cause tiny cracks, if not obvious ones. These then are
not healed by subsequent annealing, so it’s important to prevent
their forming in the first place, by not working the metal at all
before annealing it. If small cracks are allowed to form at any
stage, then further working will make them show up as defects in the
item, or maybe even allow them to destroy the item. So yes, anneal
rose golds.

By the way, if alcohol as a quench is not something you’re
comfortable with, you can also quench the hot metal with a blast of
compressed air, if you’ve got a compressor handy. Cools the metal the
same as a torch flame heats it…

hope this helps.
Peter Rowe


#6

we sometimes work in 18K rose and when soldering it we quench it
immediately. If you fail to do this and let it air cool, it will
often result in cracking. Rose also seems to work harden faster than
it’s yellow brothers so you will more than likely have to anneal
frequently, just remember to quench right after it is annealed. Good
luck, let us know how it works out.


#7
What you do not want is a slow cool from above 770 F (410 C) to
room temp. So heat and quench. Alcohol will be a gentler quench but
will still be fast enough. 

Let me put it in practical terms. Use reducing (yellowish) flame.
Constantly move the torch. Only outside of flame envelope should be
used. Metal should be clean, scrub it if you have to. Watch metal
closely. At first you should see oxides forming on the surface.
Continue heating. The moment will come, if everything gone well,
when oxides will disappear and there will be clean metal under the
flame. Stop and quench immediately. Every part must reach that
temperature when metal appears clean, so use big enough torch and
move it all the time to equalize temperature through out the ring. If
metal is taken to the read heat by mistake, do not quench until the
metal will go black. The results will not be as good, but usable.
This only applies to gold - copper alloys.

Leonid Surpin
www.studioarete.com


#8
If you mixed it yourself and its only got copper and gold in it
you'll need to quench at a dull red heat after annealing or
soldering... no slow cooling! 

You absolutely should not do that ! No gold - copper alloy should
ever be quenched at quenched or even attempted to be handled in any
way if the slightest signs of red heat are present. These alloys are
very fragile at that stage. You must quench them when they cooled to
when they look black.

Leonid Surpin
www.studioarete.com


#9

I had a question arise in the casting class I teach as to whether
there is a time when it is too late to quench the casting. We cast
in sterling, and quench in water when the button has just lost its
redness and is a dull grey. Is this the best time to quench for
sterling? Is there a time when it is too late to quench, i.e., the
metal is too cool to be properly annealed? Thanks!


#10
In my own case I had the misfortune to solder two such side bands
onto a diamond eternity ring( slow air cooling required). 

This is the sort of situation where using compressed air to cool the
piece quickly can be useful. Gentler than a quench that can damage
the stones, yet still can cool the metal quickly enough to avoid most
of the hardening and formation of that nasty ordered array structure.
You kind of need three hands, though, one for the piece in tweezers
etc, one for the torch you’re trying to hang onto or hang up on it’s
hook or holder, and one for the air gun which needs to be activated
to cool the work before it’s been away from the torch flame too
long… And if the work is held in a third hand tweezer on your
bench, of course then murphy’s law will see to it that the air blast
will unintentionally manage to send all sorts of small stuff
(diamonds, solder pieces, small tools, and who knows what all else)
on your bench top flying… ) Try it. it’s fun, and a sure cure for
the bordom that comes with nothing lost and in need of searching
around on the floor for… (grin)

Peter


#11
Your as cast ring will definitely be fully hard. Anneal and quench
before trying to hammer or stretch 18k red. Water or alcohol
doesn't really matter. 

Once the metal has been worked a bit, so the grain size is smaller
and more uniform, I’d agree with you that water or alcohol both are
fine. But though it’s not common, I HAVE had unworked red gold (only
gold./copper) castings crack when quenched in water. Generally
heavier weight castings, with larger grain sizes. It’s that
possibility, even though not common, that leads me to suggest
alcohol as the quench if in doubt. I’ve not had any problems with
water quenching once the metal has been worked.

Peter


#12
In my own case I had the misfortune to solder two such side bands
onto a diamond eternity ring( slow air cooling required). 

It’s been so long now that I forget the whole story, but it’s GIA -
the properties of diamond relating to heat expansion and such mean
that at least theoretically a diamond can be heated to it’s maximum
safe temperature and quenched in liquid nitrogen without harm. I
have quenched many a diamond from 1000 or 1200F without ill effects.
I agree that it’s prudent to cool them, and I also do that most of
the time, but it’s not ~required~. The biggest problem with
soldering eternity rings and similar is when the stones are touching
(though they shouldn’t be) and chip each other when they expand and
contract - but that damage is already done whether you quench or
not…

http://www.donivanandmaggiora.com


#13

The 18k Gold-Copper alloy forms the intermetallic or ordered alloy
AuCu. Even though the weight composition is 75 gold and 25 copper the
atomic composition is Au 50% - Cu 50%. The lattice structure does not
change it is still a FCC (Face Centered Cubic) lattice but the
position of the atoms in the lattice becomes fixed into alternating
planes along the Z axis. You can see a diagram of the structure of
this ordered alloy at

http://cst-www.nrl.navy.mil/lattice/struk.picts/l1_0.s.png

It indeed forms alternating layers of copper and gold atoms as
opposed to the random distribution of atoms in a non ordered alloy.
This regular ordered formation means it is not ductile at all so like
a mineral crystal once you push on it hard enough to cause the bonds
to shift it fractures rather than forming slip planes and plasticly
deforming like a typical gold alloy would.

It does not just form at the crystal boundaries as some have
suggested. Each crystal in the whole mass of the item will develop
this structure if allowed to spend any time at 600-800 F so it is
imperative that you cool it rapidly between these points. If there is
another metal in the alloy like a small amount of silver it will
break up the ordered structure to some degree but there will still
be areas of ordered formations in the crystals. This is why you can
heat treat gold alloys with enough copper in them to make them
harder. This ordering makes the crystal matrix stiffer or harder i.e.
less likely to deform.

James Binnion
James Binnion Metal Arts


#14
You kind of need three hands, though, one for the piece in
tweezers etc, one for the torch you're trying to hang onto or hang
up on it's hook or holder, and one for the air gun which needs to
be activated to cool the work before it's been away from the torch
flame too long... 

Couldn’t you just turn off the feul and use the oxygen to blow on
the piece?

Noel


#15
You absolutely should not do that ! No gold - copper alloy should
ever be quenched at quenched or even attempted to be handled in
any way if the slightest signs of red heat are present. These
alloys are very fragile at that stage. You must quench them when
they cooled to when they look black. 

Hogwash, I hot forge laminates of red, yellow and palladium white at
1450F all the time. Nickel whites are a different story as they can
fire crack.

James Binnion
James Binnion Metal Arts


#16

Leonard is absolutely right about this.

Also, removal of the fire scale and burnishing between repeated
steps of this process will result in fire gilding the metal to a
very high, yet very hard 22K look. Even fine details will last for
many years of wear. It’s tricky the first couple of times.

Wayne Emery
www.thelittlecameras.com


#17
Couldn't you just turn off the feul and use the oxygen to blow on
the piece? 

Compare the volume and speed of the air jet from your typical
compressor driven compressed air gun, versus what you get from the
oxygen line on a typical torch, and you’ll see why not. A gentle
cooling breeze isn’t what’s required. It needs a high speed, high
volume blast of cold gas to chill the metal quickly enough to equal a
"quench".

At least, that’s been my experience with my torches…

Peter


#18
I hot forge laminates of red, yellow and palladium white at 1450F
all the time. Nickel whites are a different story as they can fire
crack. 

I limit my comments to general gold - copper alloys.

Gold-copper alloy above “black heat” are fragile, which is not the
same as brittle. Since you mentioned “fire crack”, I assume that you
took fragile to mean brittle. Fragile in this case means very little
resistance to plastic deformation as your experience with forging
laminates demonstrates.

Handling gold - copper alloy above black heat could result in loss of
shape, and could leave marks on the surface. Depending on a stage of
completion, the piece been worked on may or may not be ruined.

Leonid Surpin
www.studioarete.com


#19
Gold-copper alloy above "black heat" are fragile, which is not the
same as brittle. Since you mentioned "fire crack", I assume that
you took fragile to mean brittle. Fragile in this case means very
little resistance to plastic deformation as your experience with
forging laminates demonstrates. 
Handling gold - copper alloy above black heat could result in loss
of shape, and could leave marks on the surface. Depending on a
stage of completion, the piece been worked on may or may not be
ruined. 

Again I strongly disagree, while gold alloys are softer at heat the
main benefit of hot forging is that there is no work hardening while
reducing in section not the reduction in hardness. I also hot forge
ingot materials to reshape for further processing. Gold copper
alloys are is still strong enough to resist casual deformation like
gently picking up with tongs or tweezers even at a red heat. I know
it is foreign for a modern goldsmith to hot work gold alloys but the
majority of them are not all that fragile even at red heat. Poorly
made gold alloys that have even trace amounts of lead or other
contaminates in them can indeed be hot short but if your alloy is
clean, copper gold alloys are good hot work alloys.

James Binnion
James Binnion Metal Arts


#20
Again I strongly disagree, while gold alloys are softer at heat
the main benefit of hot forging is that there is no work hardening
while reducing in section not the reduction in hardness. I also hot
forge ingot materials to reshape for further processing. 

It would be nice if strong disagreement is based on other experience
than forging.

I think that I would be justified in saying that I handled more rose
(red) gold than anybody on this forum, except members who were
trained and worked in Russia, because it was the only alloy that was
used. Fitted parts do not fit anymore if annealing or soldering done
incorrectly, and just because you can swing a hammer at it, does not
change that. It is important fact to be aware of if one’s practice
done on fractions of millimeter scale. Not everything is judged by
"Can I hit it with a hammer".

Leonid Surpin
www.studioarete.com