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Woodfired Clay Colors
Owen Rye reviews a woodfire/salt glaze body

long with clay body experiments I have for many years investigated details of the firing process, and it is clear to me that the best clays in the world will not respond with good color if fired inappropriately. An oxidising fire, for example, produces no flashing (except an occasional slight coloration where works are touching during firing). My early experiments showed that RSF develops color when oxidation and reduction are alternated during firing, as can happen quite naturally during woodfiring if stoking is delayed until only brightly glowing ember is left. This helps temperature rise.

Better results later came from consistently reducing up to (and maintaining) top temperature, followed by reduction during cooling down to around 1100 Centigrade (1832 Fahrenheit). This procedure gives orange/apricot flashing colours. The strongest colors have developed since I started introducing water into the kiln during firing and cooling. Water in the kiln during cooling seems to give the strongest colors, which move towards pinks and reds. There is no final word on these experiments, which continue with each firing. And just in case anyone thinks that color development is only possible in long duration firings, I have seen strong flashing on RSF fired over six hours in a fast-fire kiln, followed by appropriate cooling techniques.

The next stage in experimentation will be to develop a higher-iron woodfire clay. The aim here will be to develop rich red colors as seen in some Bizen ware in Japan, notably developed under wads in work by Kei Fujiwara. We are planning that the new clay body will be available later this year.

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