June Perry on wed 20 dec 00
Mel, going through my glaze notes for my glaze group last night, I realized,
after looking at my scratch sheet, that I gave you the untested revision for
that blue. :-(Here's the recipe for the one I described and tested!
JP#2501 Cone 10
31.3 Kona F-4 Sodaspar
15.24 Whiting
15.99 Grolleg
33.17 Silica
4.3 Strontium Carb.
A: Dark blue- Add: 5 % rutile (dark), 2 copper oxide, 2 cobalt oxide.
If you want it a hair lighter try using copper carb and cobalt carb instead
of the oxides.
This SiO2:Al2O3 ratio is 8.38 Expansion 6.98 The glaze is within cone 10
limits for a copper bearing glaze with just a hair less alumina that is asked
for. Adding 1 more gram of grolleg would bring it up to the .45 Alumina that
Insight calls for in a copper bearing cone 10 glaze.
If you want it shinier and want to up the silica, just add the 1 more grolleg
and 6 more silica and that will give you an 8.96 ratio and an expansion of
6.72.
I'm guessing that this should be able to fire to a flat cone 10-cone 11.
Regards,
June
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