Soda Ash in Oxidation

Minori Thorpe Ceramics Art + Perception 1109 2018 Technical Home

Since publishing an article titled An Alternative to Wood-firing Using Gas at Cone 6 in Ceramic Technical issue 37, I have been researching and experimenting with soda ash in electric kilns. I am intrigued by the soda effect on pots in reduction firing.

The studio where I work has many electric kilns and I wondered what the effects of the soda ash mixture I use in the reduction kiln would be like in oxidation. I researched some techniques and performed my own experiments and was quite pleased with the outcome. This article explains my process and the effects on the pots as well as addressing some concerns with using an oxidation kiln with these chemicals.

The studio I mainly work in is at the University of Delaware. Here, they mainly do cone 6 oxidation firing. With all the electric kilns and the different glazes producing different effects, I started thinking about my own process using the soda-ash mixture in the reduction kiln and how I could merge these ideas. I started researching different techniques on how to get reduction soda-firing effects on oxidation pieces. After reading a few different techniques such as soaking bisque-ware in a soda solution before glazing, I decided to spray the soda-ash and baking soda solution (1g soda-ash, 1g baking soda, water, and gum solution to homogenize the two sodas) using an atomizer directly onto each oxidation glaze dipped pieces.

A concern that is often brought up when using soda- ash is how the soda-spray would affect the inside of an electric kiln. I discussed this with a chemist, John Koh, and he suggested that I spray the mixture directly on to an element as well as the soft brick.

The first test was carried out on small test tiles where the results included interesting colors and a fluxed surface. I decided to test on a larger, vertical surface as well as several oxidation glazes, with and without the soda spray mixture, on mugs to get a comparison. The mugs that were sprayed with the soda-spray mixture came out beautifully with some distinct color changes and a nice fluxed surface that had minimal running. I was quite pleased and impressed with the results that I was achieving through this experimental process.

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