Thursday, February 23, 2012

CONE 1 REDUCTION - New firing method

More FUN at Lillstreet Art Center!

Cone 1 (2039 F to 2109 F) Reduction Firing is an alternative method of firing Terra Cotta or other clays such as Stoneware. Because of the reduction firing and unusual ending temperature, unique surfaces develop.

The gas kiln is fired slowly to Bisk temperature and then “reduced” to Cone 1. The work goes into the kiln as greenware, fired slowly with an abundance of oxygen over about 12 hours. At Cone 04 (1915 F to 1971 F), the atmosphere is changed to a reduction firing, when the fuel seeks oxygen on a microscopic level inside the clay body.

The Red Iron Oxide in Terra Cotta is changed to Black Iron Oxide resulting in variations of color from burnt orange to black. Terra Sigilata brushed on greenware, with or without buffing it, enhances the bronze or dark walnut color with sheen.

Stonewares will have gone thru Body Reduction whereby the iron in the claybody is brought to the surface giving a warm tone. The clay is stronger than merely going to the bisk temperature and the reduction makes it harder as well. You may experiment with B Clay or Porcelain too. This could be appropriate for sculptures destined to be left as is or in conjunction with other alternate finishing techniques.

Underglazes may be used for color. The Low Fire Glazes may be used on the inside only and are not tested for food safety. Cone 10 Glazes and Stains will not melt and should not be used.

We will be offering Cone 1 Reduction Firings when we have enough work to fire the kiln, which is located on the second floor. It is about half the size of the Bailey kilns. We will find places to store the greenware here and there. We will teach students to load it. Sculpture students: think about how you will safely get your piece to the kiln without damage before you attempt to make a piece for this firing.

Additionally, please note that after the Cone 1 firing, Terra Cotta pieces will be vitrified, but are not meant to be left outdoors in winter. Stoneware will be harder and more sturdy than bisqued pieces and alternative finishes could be done on Stoneware pieces after the Cone 1 firing.

For more information, please talk to your teacher or Karen. You may also email Karen at

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