Ivor and Olive Lewis on fri 12 jan 07
My suggestion is to regard this as a Lime Magnesia glaze. I say because =
of the Dolomite, Talc and Whiting components. These together, with the =
Zircopax (how would it look without this ingredient?) give opacity.
BUTTERMILK ^9-10
Gerstley Borate-----10.5
Dolomite------------ 6.8
Whiting--------------9.0
Custer Feldspar----29.3
EPK--------------- -6.8
Talc----------------13.5
Flint----------------24.1
Zircopax-------------8.0
To reduce the maturity cone value to coincide with the energy load =
needed by your other glazes I would try to convert as much of the Kaolin =
and Flint into Custer Felspar and juggle the remainders of Alumina and =
Silica. This adds in more alkali metal oxide which should give that =
extra addition of a melting agent to enhance melting as temperature =
passes through the 1250 Deg C mark. This should ensure there is a large =
enough volume of vitreous fluid to encourage dissolution of the more =
refractory ingredients and is preferable to adding more Boron.
Regarding technique: I would like to slow the rate of heating as firing =
nears maturity temperature. Slow things down when the first witness cone =
starts to set. Slowing the cooling slightly might also encourage the =
crystallisation of those minerals that cause translucency or opacity.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
| |
|
