Gavin Stairs on wed 4 oct 00
Hi All,
I was rereading my flux post, to see what I said, and I noted something
which is not quite right. It concerns the order of melting of a
flux-refractory mix. I say that the fluxes first flux each other, and then
the refractories. This is true of the silicate and borate fluxes, but not
of the pure oxides and carbonates, like soda ash, lime and dolomite. These
fluxes are pretty good at attacking silica, but not much use on each
other. So a pure oxide system is most likely to begin by melting silica
with one or more of the oxide fluxes. A silicate flux, like talc,
wollastonite, various feldspars, etc., will likely begin by melting with
adjacent silicates, and then they will attack the silica. The borates melt
at such low temperatures that they become quite liquid all by themselves,
before melting much silicate of any sort. The rates at which all of these
things take place is highly dependent on the local concentrations of the
various components.
I was going to re-post the entire note, but I think we've had enough flux
talk for the moment. I can feel the eyes glazing over.
Gavin
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