A High-Fire Reduction Potter Develops Great Glaze Recipes for Oxidation Firing to Cone 6 in Electric Kilns Jayne Shatz

With an initial impetus in the energy crisis of the 1970s, Jayne Shatz began exploring options for translating her high-fire reduction glazes into cone 6 oxidation glazes for electric kiln firing. While the exact results were not possible, she learned a lot about glazes and came up with some nice results.

In today's post, Jayne passes those recipes on to you. - Jennifer Poellot Harnetty, editor

In 1976, I was forced to “go electric” when a cooperative studio I was a member of closed because of the energy crisis. At that time, my contemporaries looked down on electric kilns and oxidation glazes. After all, we were hurly-burly, brick-and-burner, reduction-?red gas guzzlers! But all that was changing. I had to make my way in a strange new world.

Having built three large outdoor brick kilns, I felt I was committing a despicable act by purchasing an electric kiln. It was stainless steel, shiny and fit into a corner of my basement studio. I had no clay bodies, glazes or low-temperature experience. I bought this kiln because it had the potential of ?ring up to Cone 10. But I soon asked myself, “Why bother ?ring up to Cone 10 when Cone 6 would be more cost effective?” After all, it wasn’t the temperature range that was so cataclysmic; it was the fact that I was switching over from reduction to oxidation. That was the whole ballgame. Ultimately, I committed to working at Cone 6 in oxidation, and recreating the glazes I was accustomed to using at Cone 10 in reduction.

I surveyed this problem in its most rudimentary components. Simply speaking, a reduction clay body develops its toasty warm color when the oxygen entering the kiln is reduced by closing down the kiln’s dampers. This reduction of oxygen and increase in carbon creates the autumnal colors of reduction stoneware.

I read everything I could on clay bodies and clay chemistry. I finally developed a Cone 6 clay body that was rich in iron and would develop into a toasty warm color in oxidation.

Painstakingly, I developed a white porcelain clay body with which I was satis?ed. It was not translucent, but that was not a quality I was pursuing. Because of this characteristic, and the midrange temperature, there is some debate over whether or not it is truly porcelain. For me, it is a clay body that is beautifully white, dense, nonbrittle and throws fantastically. The body contains bentonite, enabling it to be plastic and very strong. It even can be once fired. I found out years after I developed the body that my clay distributor believed it to be one of the best slip-casting bodies he had ever used. It is now used by several tile and slip-casting companies for industry. I can be very casual with it, due to its plasticity and strength, and it is fabulous for large sculptural pieces. With the addition of sand, it becomes an excellent white raku body.

Then I began bringing down the melting temperatures of my glazes to Cone 6. I delved further into chemistry, learning the various effects oxides produced in an oxidizing atmosphere. Very slowly, and with many glaze tests, I began to obtain the colors I was seeking. My ?rst success was to duplicate an iron saturated glaze from my college days, Ketchup Red [see recipe]. I then continued down my palette of glazes. This process took two years. I continued selling pottery during this time, which meant that, for a long time, I was working with only one glaze. Fortunately, people were buying my pots.

After much work, I produced a wonderful clear glaze for my porcelain. It was very clean on the surface and pooled into crevices, where it transformed into a lovely robin’s egg blue. It reminded me of the beautiful “Scarab Vase” by Adelaide Alsop Robineau. If you look closely at that pot, the pooled areas are a lovely soft blue. This realization hit me like a thunderbolt! What I should have done so many years ago was research the glazes of American Art Pottery. Ironically, many of those potteries worked in oxidation. The answers were there; I just didn’t know where to look.

I discovered that, by layering glazes, I could achieve certain Cone 10 reduction effects. I learned to work with base glazes, varying the oxides to make additional glazes.

The years progressed and it seemed the entire country was firing electric. Kilns got better, clay and glaze recipes filled books and publications, and the Internet was born. Oxidation firing in American ceramics flourished—and here we are.

For further information on the work of Jayne Shatz, see www.jayneshatzpottery.com.