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Annealing gold


#1

Maybe this is one for Peter RoweI can’t find any info in my
tons of books on annealing 18kt gold, and only vague information
on annealing 14kt. I mostly work in silver but slowly working my
way into gold work. How do you really tell if you annealed 14kt
or 18kt correctly? In silver work when you anneal there is a
marked difference in how soft the metal gets versus hardened
silver. I anneal the 14kt by heating until slightly reddish and
the let it cool till it doesn’t show in the dark then quench in
water then into the pickle. Is this correct, and whats the
differenece for 18kt? Thanks in advance as usual…Dave

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#2

You’ve got it right. As with silver, the actual annealing temp
is slightly below a red heat, and you use that red glow to tell
you you’ve reached a sufficient temp. Plus, at a low red heat,
annealing is almost immediate, without needing to soak for a bit.
Too high and you start to get increased grain size, which is
counterproductive. 14K yellows can be quenched when they’re
still faintly red, but it’s better not to, since occasionaly
that will cause warpage or even (rarely) cracking. Similar with
18K yellows and greens, but they are even more forgiving about
quenching while still faintly red. Both qualities, in white,
MUST be allowed to cool below low red heat (about 900 F) before
quenching. All colors will be softer if quenched instead of
allowing them to completely air cool. A major exception is 18K
red gold (only gold and copper). It MUST be quenched above about
800 to avoid the formation of an ordered array structure which
will lead to cracky brittle metal. 800F is below red heat, but
hard to judge, so it’s best to quench at just that last trace of
red color.

If you work mostly in silver, then the hardness of fully
annealed gold will still seem hard. Annealed silver, to a
goldsmith, resembles soft butter. Some 18K greenish alloys will
come close to sterling silver, but even they are a bit stiffer.
22K yellow golds are perhaps close to silver…

But rest assured, there is a great difference between annealed
and work hardened gold in both stiffness and hardness…

Peter Rowe


#3

A slight correction, Peter. You wrote ‘As with silver, the
actual annealing temp is slightly below a red heat’. I assume you
meant to say sterling silver. Fine silver anneals way below that.
I say about 350 C (660 F) which is just after it looks pale. We
use mostly fine silver in this workshop - always annealing it -
often just a wave with the flame for 0.25mm fine.

Just a small point.

Brian
B r i a n =A0 A d a m J e w e l l e r y E y e w e a r =A0
@Brian_Adam1 ph/fx +64 9 817 6816 NEW ZEALAND
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