I’ve some of my clay graphite crucibles break down also, but these
were the cheaper crucibles, currently I only use gas to melt metal
and a direct gas flame onto the side of a crucible is far harsher
than electric melters. In the larger furnace when I used a cheaper
crucible, the outside of the crucible would crack, but thus far have
remained intact. The smaller micro furnace, where I’ve only used a
good quality crucible, there are no problems.
I don’t get graphite in my melts at all.
This is my procedure for a melt.
1)* Fill the crucible to the brim with a high quality flux, not
borax (I have 80 kg of flux used for an aluminium pot line, seems to
work well). Then empty the crucible.
Place in your charge of metal (or alloy components in the correct
order). Sprinkle in some more flux.
Melt your metal.
4)* Before you pour, stir the metal with a green stick.
- Pour the metal.
Thus far my castings are porosity free, and clean.
The * next to the step above represents a trick given to me by an
Regards Charles A.