search  current discussion  categories  glazes - cone 4-7 

c6 glaze calc

updated tue 20 mar 07


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
need 68-70.
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 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

Tom Buck ) -- primary address.
"alias" or secondary address.
tel: 905-389-2339 (westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street, Hamilton ON L8T 3E1 Canada