Potters & Sculptors - Making Rock from Mud
Gas kilns use hard fire-brick which cool far more slowly than the foam-core brick used in electric kilns. Many here have suggested this is one major difference in the "cone 10" look of a gas kiln.
Using our Cress E23 computerized kiln controller we slow the rate of cooling between 1,800F and 1,500F.
Over the past two years I have used three different cooling rates: 185F per hour, as suggested in "Mastering Cone 6 Glazes"; 100F per hour; and 50F per hour. We finally settled on 50F as the rate we preferred.
Some glazes become so crystallized and matte at 50F cooling I need to add 10% Ferro Frit 3268, or slightly more, to give them enough flux and silica to retain their look.
These are photos of Ron Roy's Sapphire cooled at 185F, 100F, and 50F.
Kathryn - All of the recipes for the glazes I use are available on George Lewter's Insight Live Users Group. Send George an email to join at this link, and he'll send you a log-in ID.
This is the website of Jayne Shatz, whose glaze this is. - http://www.jayneshatzpottery.com/
And this is the recipe in Insight Live
Kathryn Reedy said: