With a degree in ceramic engineering, as well as a BFA and MFA in ceramics, potter Po-Wen Liu knows a thing or two about glaze chemistry. In today’s post, Po-wen shares his beautiful powder-blue Ru Celadon glaze, and explains the firing process he developed to get it just right.- Jennifer Poellot Harnetty, editor.
My fascination with the pooling effect of celadon glazes has led me to explore a variety of surface designs on my work.
From opalescent blue to cool, transparent green, the celadon glaze has a tendency to play hide-and-seek with light.
The Ru Celadon glaze has a jade-like, powder-blue appearance. It works well with solid shapes and pure lines.
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A darker clay body can enhance the Ru Celadon. I add 0.3% of red iron oxide to my white stoneware clay. Ru Celadon also requires a thick glaze application. A glaze thickness of at least 1⁄16 inch is needed in order to produce the jade-like quality. I spray and kiln-dry the glaze layers repeatedly, applying as many as five coats, when working with this glaze.
The kiln firing is the most critical process when making celadon. I rely on pyrometric cones to control the firing speed. In a gas kiln, I use Orton cones 010, 08, 04, 1, 3, 5, 6, 8, 9, and 10. Each cone should bend in an hour’s time. Body reduction is not required. I begin glaze reduction at Orton cone 010. When the kiln temperature reaches Orton cone 10, I change to a light reduction atmosphere without dropping or increasing the temperature, hold it for 20 minutes, then shut off the kiln.
Make sure to check out the October 2014 issue of Ceramics Monthly to learn more about Po-Wen Liu in Dr. Elizabeth Perill’s article, A Place of Reflection: Po-Wen Liu. Included at the end of the article as part of October’s Monthly Method, Liu shares another one of his favorite celadon recipes, Green Celadon.