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Charcoal casting flux


#1
Hi Dave, Try some powdered charcoal casting flux.  It will usually
clean the metal and the porosity right up. Skip

– What is powdered charcoal casting flux and where can it be
obtained? ==Pisces @mbm


#2

Skip I know you are very experienced in very precise technical casting
and would not use too much of the charcoal flux. But if too much
were used I would be concerned about causing more problems than the
flux solves. Adding excess carbon(charcoal) to a investment casting
melt is not a good idea. If it does not burn up before pouring and
gets into the mold cavity and ends up in close proximity to the
investment it will lower the investment breakdown temperature and
cause more porosity from the sulfur dioxide gas released by the
investment breakdown. I also have seen carbon inclusions in castings
done with graphite crucibles that are not in good repair and would
worry about the same kind of inclusion from unburnt charcoal.

Jim


@jbin
James Binnion Metal Arts
4701 San Leandro St #18
Oakland, CA 94601
510-533-5108


#3

Charcoal is not a flux . It will only serve to make a cover by
making a carbon monoxide reducing atmosphere over the metal. It won’t
combine with impurities or remove much oxygen from the metal. Jesse


#4

The flux comes in a cylindrical ‘can’ about 4 1/2" tall x 1 3/4"
dia. I have had mine for 12 years (about 5000 casting melts) and
there is about 1/3 of a ‘can’ left, so I don’t use very much (three
quick shakes per oz. of metal). This flux also has borax in it. The
residue from the ‘cleansing’ ends up as a ‘glass’ on the bottom of
the button. Pickle removes it. I can’t remember the particulars of
what the Ney metalurgist told me a zillion years ago, but I can even
use this casting flux on my high heat gold alloys which are used for
dental ceramic application. ANY contamination, even finger (body)
oils, is a delayed ‘death sentence’ which interferes with the
ceramics chemically bonding to the metallic oxide layer. This
usually appears as a large ‘air’ bubble on the final glaze bake, as a
’crater’ through the porcelain down to bare metal, OR is one of the
problems that causes the ceramics to shear cleanly off down to the
metal substructure after the crown is cemented into the mouth.

Regards,

Skip

Skip Meister
@Skip_Meister
Orchid Jewelry Listserve Member
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