Tom Buck on mon 19 mar 07
For a Cone 6 oxidation firing, the actual coeff. of
expansion (CTE/COE) value depends on the claybody you use. if you
are firing a "standard" stoneware body then perhaps 73-75 will not lead to
crazing. but that is a bit high for a porcellaineous stoneware...then you
as for SiO2 & Al2O3 values, Doc Carty at Louisville reported that
the important value is SiO2 and it determines largely how things go. so I
would suggest you target the SiO2 from 2.5/.8 - 3.5 moles, going to a max
of 4.0 moles. The Al2O3 controls the runoff..so you set it to give a
SiO2/Al2O3 ratio of 7 - 10 for a gloss without running (we hope), and 5-7
for a satin matt, and below 5 for a dryish matt.
good glazes. peace Tom
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