How to clean graphite crucibles

Peter,

I’m having the same problem, I just purchased an old Jelrus
Handy-melt (stamped 1969), similar to the Kerr 30 oz. Unfortunately
the crucibles are slightly different at the bottom from what Kerr
offers.

My first attempt at using it was an attempt to make my own brass
from copper wire and pennies (97% zinc). Not really the best project.
The typed out instructions that came with the unit said not to take
it above 2000 F, which I thought would be high enough to melt the
resultant brass. Trouble is, that copper melts pretty close to 2000
and thus I’m left with a fused bundle of copper pieces stuck at the
bottom of the crucible and a haze of zinc. I’m tempted to melt some
aluminum on top and hope the copper will dissolve into the molten
aluminum so that I can pour it all out, similar to the way in which
salt (high melting temp) dissolves readily into water. Any
metallurgist have a helpful suggestion for this? Would tin be a
better option?

Graphite can be machined readily. You may want to lightly sand/bore
out any contamination that you can’t burn off or pour out. I think
the general practice is to have separate crucibles for each metal
and to replace them regularly. Note, that because graphite produces a
reducing environment you won’t need to use quite as much borax as
you’d expect (if any).

Scott