I have tried heat hardening fine silver (after forming and then
soldering on a jump ring), by heating to annealing temperature and
then quenching. No luck
There seem to be many jewelers, especially the “self taught” and the
beginners, who are confused about how precious metals can be
hardened. Everyone is at least vaguely familiar with how steel is
heat treated and hardened, and some people just assume all metals can
be treated this way. (they cannot). And it gets more just assume all
metals can be treated this way. (they cannot). And it gets more
confusing when people like me, or others, point out that SOME of our
jewelry metals can actually be heat treated. But it’s important to
know that this is more the exception, than the rule, and the process
is quite different from what goes on with steel.
In the case of silver, with sterling silver, you take advantage of
the fact that copper is not completely soluable in silver, or vice
versa. So careful heating, below the annealing temperatures, allows a
sort of seperation to take place, with copper moving to the crystal
boundaries between the silver crystals (actually it’s crystals of
mostly copper with a tad of silver, and crystals of mostly silver
with a tad of remaining copper, but that’s being picky), and this
structural change makes the metal harder. Not as much harder as can
be attained by work hardening, but enough so sometimes it’s worth
But it’s the interaction between the silver and the copper in the
alloy that does this. You need both to be there.
In the case of fine silver, there is nothing there but silver. In
that case, the only possible way to harden it is with cold working,
to work hardening. There are no heating processes which will increase
the hardness of fine silver.
This is true, by the way, of all the pure metals, including gold,
platinum, silver, copper, and yes, even iron. Pure iron cannot be
heat treated and hardened. You can anneal it, or work harden it, but
no heat hardening or tempering. For that to happen, you need an
alloy. In the case of iron, it’s an alloy of iron and carbon, rather
than an alloy of iron and another metal, but again, it’s the
structural interactions between the two different componants that
make the heat treatments possible.
As well, just because you may have an alloy of two metals, does not
mean you can get heat treatability out of it. In the case of silver
and gold, both of them can be hardened if they have enough copper
mixed into their alloys, and in both cases, it’s because copper’s
ability to fully dissolve into the other metal varies with the
temprature. Molten, it’s fully soluable, but in the solid form,
niether gold or silver are completely soluable in copper, or copper
in them, thus the ability to induce useful structural changes.
But gold and silver themselves, are completely soluable in each
other. So no matter what ratio of gold and silver you have, that
alloy will not be able to heat treat for increased hardness. You can
only anneal them, or work harden them. They won’t harden if it’s just
an alloy of gold and silver, without copper or other elements.
Hope that helps.