Casting, models and molds

Jewelry Discussion
1

Two more questions I forgot to ask:

  1. What are the best flask temperatures to cast ? It is my
    understanding that silver is cast at 800 - 950 F depending on
    size of models and that gold is a cast at a higher temperature
    than silver ( increasing as karat goes up ). Is there nothing
    more specific than this? I’m referring to centrifical casting.

  2. What is the preferred metal to make molds of? When I mold a
    silver casting the mold reacts with t he silver and discolors
    both. Does this reaction harm the subsequent waxes pulled from
    the mold thereby hurting the end result - the finished castings?
    I’ve been told to rhodium plate the silver model before I mold it
    but I don’t like the Idea of plating and

would not sell such so I would then keep the model. Is it common
practice among the brethren to keep all original models rather
than just the molds?

Thank you for any answers,

Slone

2 
 I've been told to rhodium plate the silver model before I
mold it but I don't like the Idea of plating and               
would not sell such so I would then keep the model.  Is it
common practice among the brethren to keep all original models
rather than just the molds?

Molds don’t always last forever. Your models are best made in
silver, and kept after molding. If you don’t keep them, and the
mold is damaged, then you’re left with taking a mold from perhaps
some used piece, or a second generation casting or some such.
Obviously, this doesn’t apply all the time. If you’ve made a
custom piece from gold or silver and need to deliver it, then
that’s that. Taking a mold of the thing before you let it out of
your shop is a decent policy, even though the original has been
sold. Never know when you might need to do another. For those
models made for that use, which you can keep, then a nickel
plate, followed by rhodium (directly plating silver in your
rhodium will contaminate your rhodium solution) will lead to a
slightly smoother mold. The difference is slight though, and the
discoloration left by the silver on the rubber won’t have a great
effect, though waxes may stick just a little bit more. Usually,
you won’t find much difference. Your silver is discolored by
the sulfur in the rubber. It’s no different than ordinary
tarnish, and a good polishing will take it back off. It’s
surface discoloration only, and the silver itself has not been
harmed.

Peter Rowe