After trying working with my deep red clay at cone 9/10, I am moving back to cone 6. At least for the time being.
I knew when I moved to cone 9/10 that I might have problems. The iron content in my clays is high. I had one beautiful test and got very excited, but after that first test all I got was slumping. I think, that first test just happened to hit the sweet with the perfect amount of reduction. I don’t have a fancy computer controlled gas kiln, I can’t control the reduction as well as I would like. Iron is a stabilizer in oxidation and a flux in reduction. Therefore, amount of reduction can seriously affect the vitrification of a high iron body. Too little reduction, and it’s underfired, too much and it slumps.
I did get some really beautiful clay body tests using 50% local materials. However, the whole point of moving to a higher firing temp was to use more, not less. So…back to cone 6 oxidation I go. The foray wasn’t a complete waste of time. I learned a tremendous amount about alumina:silica ratios, as well as the amount of iron in a body.
It’s amazing looking back 7 years, that my first clay body worked as well as it did. Pic of my temperamental red clay.
