The vast majority of my work is ultimately fired to pyrometric cone ten (apx 2345 deg. F) in a reduction atmosphere. Often, additional atmospheric effects such as the use of wood as fuel, or the addition of salt into the kiln chamber at high temperatures, or a combination of the two processes, contributes to the final surface of the piece. Most of my work has applied glazes covering at least a portion of the piece. Some pieces intentionally expose the raw clay body in areas, and the use of metal oxides and commercial underglazes may contribute to the final appearance.
The term “reduction”, when used to describe ceramic firing techniques, refers to the process of “reducing” the iron (and other metallic components) in the clay body and the applied glazes by increasing the fuel-to-oxygen ratio, thereby forcing the combustion process to ‘steal’ free oxygen molecules from all available sources. The most readily available sources of free oxygen molecules are found in red iron particles contained in both clay bodies and most glazes. The red iron readily ‘gives up’ its extra oxygen molecules, ‘reducing’ it to black iron.
Wood ash that accumulates on the shoulders of pots and other protuberances melts at high temperatures, creating a glaze by itself that when combined with applied glazes adds to their fluidity. The same is true for the addition of salt which volatilizes into a vapor at high temperatures forming one of the strongest glazes known. Both the salt vapor and the wood flames create localized effects on the raw clay surfaces and the glazes depending on the placement of the objects in the kiln. This can range from bright orange patches on unglazed surfaces to bleached-out and hyperfluid areas of applied glazes as the wood ash, and/or the salt, combine with the fluxes in the glazes creating drips and runs. The results in these types of firings are never completely predictable and the lack of total control over such a critical aspect of the production process is offset by the often dramatic results.
Firing in wood and salt atmospheres adds complexity not only to the finished results, but also to the firing process itself. A small amount of my work is fired to completion in electric kilns which is a bit like putting it into an oven, setting a timer and heading home to read a good book. Firing with gas requires a bit more attention (though computer controlled gas kilns have become more common). But firing with wood and salt requires far more labor. To start with, because wood ash and salt produce glaze, the pots must be protected from sticking to the shelves. This requires small balls of ‘wadding’, a mixture of alumina and clay, be placed between the shelves and all the work, as well as all of the shelf supports, greatly increasing the amount of time and effort required to load a kiln. Firing a kiln with wood requires constant attention as the wood must be continuously stoked, usually for a period exceeding 24 hours. Some wood firings can last up to a week and require a small crew.
My work is influenced by a wide range of sources. Clearly, German and English salt ware, as well as early North American functional ware, are strongly referenced in much of my work and so it is natural that I would be drawn to similar firing techniques.