Reconditioning Used Crucibles

Jewelry Discussion
1

I am in the process of acquiring a used casting machines that
include with it two used crucibles that have a heavy coating of flux
glass on them from use. How would one go about removing said flux
glass and reconditioning the crucible for use?

2 
I am in the process of acquiring a used casting machines that
include with it two used crucibles that have a heavy coating of
flux glass on them from use. How would one go about removing said
flux glass and reconditioning the crucible for use?

Put the crucible on a good fireproof surface, and bring out your
casting torch. Add lots of borax to the crucible as you heat, and
more as what you’ve added melts, until you’ve got a pretty good fluid
mass of melted borax. It’s nice and fluid because you’ve heated it
probably a good deal hotter than normally needed for melting your
silver or gold, and stirred it around with an appropriate carbon rod
or the like, so it’s picked up the dirty flux glass from the
crucible. Now just pour it out. If it’s hot enough, it will pretty
much all pour out leaving only a thin layer of borax glass, which
should be fairly clean. The clay won’t be it’s original pristine
white, of course, but you should now have a quite usable crucible. A
thin coating of that sort is normally how one preps a new crucible
for use in any case, so this ends up being pretty close. When you get
too much spalling of the surface of the crucible, leaving you with
bits of ceramic junk floating around on the surface, or the crucible
actually cracks, well then it’s time to replace it.

Peter

3

to all-you can put the crucibles in sodium bisulate (sp?) pickle
soloution until the flux dissolves usually takes about a week. then
soak them in clean water for a few days then dry them out in a nice
warm spot i usally put them on top of the steamer for about a week.
reglaze and you are ready to go. ive been doing this for years works
every time - goo

4

A friend had the same problem (over fluxed) and I solved it by
grinding off the accumulated flux with an abrasive stone and that
refluxed it with plain borax.

Ronald Neldner

5

Dear Alex

I am in the process of acquiring a used casting machines that
include with it two used crucibles that have a heavy coating of
flux glass on them from use. How would one go about removing said
flux glass and reconditioning the crucible for use?

Heat the inner of the crucibles with a torchwhile holding it so that
the flux glass can run out, help it out with a piece of steel rod or
the like. I also learned from an old master goldsmith that putting
half a teaspoon of common table salt makes the melted flux glass
easier flowing, at least this little trick has helped me.

Kind regards
Niels Lovschal, Bornholm, Denmark