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> Peter, What is the "desired range" for heat hardening? I have
> experimented with using the cleaning cycle on my oven to do a
> couple of different things. Most ovens hit 800 to 850 degrees
> during the cycle.
Morris, The Handy and Harmon "handy book" states a temperature of 600
F, for 30-50 minutes. I'll confess that in my prior post, I had it in
my head that it was 700, not 600. If your oven reaches 550, I'd bet
that this will do the trick, though slower than 600 would.
If the cleaning cycle is reaching 850, though, then I think that at
that point you're maybe getting uncomfortably close to the annealing
range. Now, I'm not a metallurgist, so I can only go on the temps I
see published. I don't know for sure at what point precipitation
hardening stops and annealing starts instead. But I guess I'd opt for
the lower temperature range instead, or at least test em both and see
which works better.
Also, the handy book suggests that for the highest hardness, you want
to initially anneal the silver at a much hotter than normal
temperature, like up to 1375, for 15 minutes, followed by a water
quench. what that does is to both dissolve the copper rich phase
(sterling is a mix of copper rich, and silver rich crystals, ie copper
dissolved in silver, and silver dissolved in copper), and allow
crystal grain growth to occur. Both will increase the effectiveness
of the age hardening procedure. But I've a problem with these
instructions. Many of the times I've quenched sterling silver from
that high a temperature, I get major cracks forming. In a number of
pieces I did in grad school, I used that propensity of overheated
silver to shatter when quenched to get some interesting effects of
broken and shattered forms. So the handy book's specification for
annealing that high then quenching makes me wonder just how they wish
to do this without destroying the piece... Still, I mention it for
what its worth.
Hope this helps.
Peter Rowe
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