I have experimented with reduction atmospheres since school, but it was friend and master crystalline potter Peter Ilsley who started me on his own method during a workshop in Palm Springs, CA.
Since then, I’ve developed my own techniques -but I owe much to this wonderful artist for inspiring me and pointing me in several right directions.
In this case, post-firing reduction defines a second firing used to bring the glaze up to a lower temperature (between 1350-1750°F) than my initial crystalline firings (^11-12). This temperature does not induce a complete melt, but “softens” the glaze. At critical temperatures, the gas/air mixture is adjusted to create an oxygen-reduced atmosphere. The resulting Carbon Monoxide is hungry for oxygen and takes it from the glaze matrix. This thermal/chemical shift alters the metallic coloring oxides in the glaze and changes the color.
A strike firing denotes a similar technique, with the name deriving from a glass-blowing term. The glaze is reheated to a certain point in a neutral or low reduction atmosphere. This can cause subtle changes in the color, sometimes creating iridescent qualities.
For both of these firings, I employ a kiln that I built on site at Wiseman Ceramics Studio. It consists of an old electric kiln, turned on it’s side, to which a burner, chimney, and damper was added.
I have seen potters try similar approaches with old electric kiln shells, but all those were made into updraft kilns. I’ve always found updrafts to be inefficient, uneven, and provide spotty reduction effects. In order to get the atmosphere to move both around and through the work, this kiln was designed to act as a combination cross/downdraft. It works remarkably well!
To be honest, I built this kiln for the fun of it, in wait for the new Geil JH-10 … and, I’ve got to admit that at first it seemed a bit hokey. But the results that come out of it continue to amaze and inspire me onward:
So I’ve been firing in it pretty steady for about 2 years now, and made some modifications to the kiln this past summer.
I learned to fire electric and larger gas kilns manually in school, so although I look forward to exploring glazes with the oxy-probe automated Geil, I have to say that I really value the experience gained by firing a manual reduction kiln in achieving these effects.