Forty celadon test tiles and two that worked
Celadon is supposed to be difficult in an electric kiln. The colour comes from a tiny amount of iron reduced in a fuel-fired kiln, and an electric kiln does not reduce. For a long time I accepted that and used other glazes. This summer I decided to find out how close I could get.
The setup
One base recipe, a fairly standard cone 6 clear, and a line blend of red iron oxide from 0.5% to 2.5% in 0.25% steps. Each tile went on two clay bodies, a white porcelain and my usual light stoneware. That gave eighteen tiles. Then I repeated the set with a small addition of a commercial reduction-substitute, another eighteen, plus four tiles of things I tried out of impatience.
| Iron oxide | Porcelain | Stoneware |
|---|---|---|
| 0.5% | almost clear, faint green | clear, a little yellow |
| 1.0% | pale sea green | olive, muddy |
| 1.5% | deeper green, pools nicely | yellow-brown |
| 2.0%+ | amber | honey brown |
What I learned
The clay body matters more than the glaze. Every tile on stoneware went yellow or brown, because the iron in the clay comes up through the glaze. On porcelain, the 1.0% and 1.5% tiles were genuinely lovely: not the blue-green of a reduction celadon, but a soft sea green that breaks lighter over edges and pools darker in carved lines.
The kiln did not need fixing. The clay did.
The platter on the work page is the first real piece from those tests. I'm now throwing a batch of porcelain bowls to try it on curved surfaces, where pooling behaves differently.