I've read here that after annealing, quenching white gold in
denatured alcohol is recommended. I was wondering why denatured
By now you’ll have noticed a distinct variety in the answers you get
to this question.
White golds can be tricky, as different alloys, even those not all
that different from each other, can require different annealing temps
and procedures. But in general, more of the nickle white golds are
best annealed, than those that should slow cool. Nickle white gold is
one of those alloys that can be heat treated to harden it, making it
possible to harden a piece without work hardening. The process is
called age hardening or precipitation hardening, and relies on a
somewhat extended heating at a temperature just below the annealing
Because of this ability of some of the nickel white gold alloys,
annealing and then slow cooling can allow the metal to cool slowly
enough through that age hardeing temperature range, that it then gets
a bit harder again, harder than it would have been if quenched. But
again, the alloys vary, sometimes inexplicably.
Ask your metals supplier what they recommend for their alloy.
Palladium white golds, by the way, can be either quenched, or not.
Makes no difference. They don’t age harden, so once annealed, the
speed of cooling doesn’t have a noticable effect.
Rose golds, especially 18K rose golds, are another example of this.
Rose golds in this alloy range, when age hardened, form a quite
unique structure, unlike the normal one for gold alloys, that is not
only very hard, but also very brittle, and easily cracked. For this
reason, annealing rose golds requires that you quench, so it doesn’t
have a chance for form those hardened structures, which risks
cracking the piece, either during cooling itself, or subsequent
handling and working. Done wrong (the most common victims of this,
are rose gold castings where the flask is allowed to cool too much.
In this situation, the casting can cool much more slowly than in a
normal air cool, being still insulated in the investment. I’ve seen
castings like this, removed from the investment and accidentally
dropped, that literally shattered on hitting the floor…
And some white golds, like that rose gold, can also be a bit weak or
brittle, both when at annealing temperatures, and if cooled/quenched
One occasional culprit is that quenching in water is a pretty rapid
chilling. The outside layer of the metal cools fast while the
interior cools more slowly.
Greater shrinkage of the outside layer before the interior cools and
shrinks, can cause cracks in a piece, if it’s not got the strength to
hold together through quenching, so for those alloys, and rose gold,
it’s often (depending on who you ask. The German schools all teach
this, while here in the U. S., it may be less known or practiced)
suggested that you quench in alcohol. Denatured, or grain or
whatever, doesn’t matter, but most of us are more likely to have
denatured around, as we mix it with our boric acid, use it to
dissolve shellac, and more.
The difference between quenching in alcohol and doing so in water is
that when you quench in water, initially there’s a layer of steam
formed at the metal surface that limits how fast the metal cools.
When the temp gets low enough, that layer collapses, and you hear
that distinct quenching noise, at which time the metal cools very
quickly in actual contact with the water. When quenching in alcohol,
the same thing happens, but that vapor layer lasts much longer, and
the “quench” happens at a distinctly lower temperature. So while the
work is indeed being cooled (by that active vapor layer), it cools at
the initial slower rate longer, and by the time it actually makes
that quench sound, that last bit of rapid cooling is at a lower temp,
so there’s less stress on the metal. The slower alcohol quench is
gentler to the metal, with less heat shock, yet still fast enough to
avoid problems with age hardening. For my part, by the way, I don’t
bother with a seperate container of just alcohol. I just use my
boric acid and alcohol container. The boric acid in the mix doesn’t
affect the quenching action.
And to those who worry that the alcohol may ignite, it just doesn’t.
You quickly immerse the work under the surface of the alcohol, and
there, no oxygen is present to combine with the alcohol. Even doing
it slowly, it’s very rare for anything to ignite. If it does,
continue to drop the work into the jar, and calmly put the lid on the
jar. puts the fire right out. In some 40 years of doing this on and
off, I think I’ve set the alcohol on fire maybe twice. No biggie.
I should mention that in general, quenching metal after annealing
(except for steel, when you’re hardening the metal), you quench only
after any red glow is gone, or almost so. Quenching hotter than this
is a good way to crack your metal. But even this can be useful. I
once did a series of pieces that relied on this. Using old scrap
silver, solder and all, I made up a bunch of not very good sheet
metal (the sort of junk that blisters when you anneal it). Worked,
shaped, textured via roll printing, and then annealed quite a bit
too hot, and quenched from a good red heat. The result was a bunch of
really neat cracking, in patterns a bit like lightening bolts or
tree/twig like patterns sometimes. No way could I have gotten that
effect with just a saw blade. Lots of cool warping and distortion,
along with the cracking, and I ended up with a bunch of really
organic looking metal to work with. That was cool because that was
what I was hoping would happen. Not so cool if it’s just happened to
your carefully made piece that you did not want to crack or distort.
So don’t quench from a red heat (you want the work to be around 900 F
when you quench it, for most precious metals.)
Hope that’s useful