1. Somebody online said that you are not supposed to use silicon
carbide crucibles when melting Argentium for casting. (I am sand
casting). Does anybody know why this is/if this is really true?
No idea if it's true, but I doubt it matters. I challenge you to
find silicon carbide crucibles for sale in any of the regular jewelry
supply catalogs. That's the sort of thing that might be used in
certain very high temperature induction melt machines, but not
generally for lower tech melting, like with a torch.
Silicon carbide, like graphite (more common for crucibles, but still
generally for melting furnaces, not torch melting), is a very good
conductor of heat, so while an external heat source, like a melting
furnace surrounding it, can get heat to the metal, if you were making
a melting dish out of it and torch melting, you'd have a very hard
time getting the metal to melt, as that crucible would be draining
all the heat away. But again, this is probably adademic. I've seen
various silica clay (common gold melting crucibles), fused silica
(higher temp, like for platinum) graphite (like for electromelts) and
ceramic (some casting machines with integral crucibles, like Memco
machines and others) types, but I don't think I've ever seen a
silicon carbide crucible for precious metal melting sold to
2. After I cast an item and age harden it I will need to clean it
up, set stones, etc. Does annealing it in order to do the other
work diminish what was done during the age hardening process?
So lets see. You're going to age harden it in order to harden and
stiffen the metal, but then you want to anneal it to soften it so you
can set stones. How would you expect the two processes to coexist?
Annealing the metal will soften it again. If you need the additional
hardness and stiffness of age hardening (which you CAN do, but are
not obligated to do. It's optional, not required if you don't want.
Not essential, especially for smaller pieces like most jewelry), then
age harden it, but it means stone setting will have to be done with
the metal in it's harder state. This means setting work will be in
metal that's a bit harder, perhaps like yellow gold in workability
instead of dead soft silver.
If you're reasonably experienced in stone setting, this won't bother
you at all.
If you need both hard and soft, then make the bezels or settings
from fine silver instead of argentium. They won't harden when the
rest of the piece is hardened.