Vase (XIV)
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This vase with lid was created in 2025. It is made of crank clay with fine sand and small amounts of coarse sand. It has been fired at cone 10 reduction.
What is Crank Clay?
Crank clay is a mixture of different clay bodies. I use a lot of different clays, from locally dug clays to boxed clays bought at ceramic supply stores.
My crank clay is a mixture of all of the clay bodies I use in various proportions. It is an excellent way of recycling clay, thereby increasing sustainability. I take my recycled clays and wedge in some locally dug Atlantic Silica kaolin to bring the temperature up so I can fire it to 1300 degrees Celsius in a reduction kiln. This brings out the warm colour of the clay.
What is a reduction kiln?
In the context of ceramics, "reduction" refers to a firing process where the amount of oxygen in the kiln is intentionally limited, leading to chemical changes in the clay and glazes. This differs from oxidation firing, where there is sufficient oxygen. Reduction firing is a ceramic firing technique where the oxygen supply to the kiln is restricted creates a “reducing atmosphere” where the fuel (like gas) doesn't have enough oxygen to burn completely. Instead of oxidizing, the carbon in the fuel reacts with the oxygen in the kiln, creating carbon monoxide. This carbon monoxide then pulls oxygen from the clay and glazes, causing chemical reactions that affect the final appearance of the pottery.
The effects of reduction firing include dramatically altering colours of glazes and clays. It can also create unique surface textures and effects, such as speckling caused by iron particles melting and migrating through the glaze. Reduction can also bring out metallic sheens.
Iron particles in the clay body can melt and bleed into the glaze, creating decorative spots or speckles.
In oxidation, there is sufficient oxygen, and the typical chemical reactions of firing occur, leading to predictable color outcomes.
In essence, reduction firing is a controlled way to manipulate the kiln atmosphere to achieve specific aesthetic results in ceramics, offering potters a wide range of possibilities beyond what is achievable in oxidation.
