Bisque firing, or the first firing, is the process of transforming dry clay (bone dry) into a piece that is strong enough to handle but still porous enough to absorb glaze well.
What temperature should bisque firing be?
There is no single temperature that works for all types of work, but generally, it is fired within the range of Cone 08 – Cone 04
- Cone 08 (≈ 955°C): The clay body is quite porous and absorbs water very well.
- Cone 07 (≈ 975°C): Good porosity, suitable for glazing.
- Cone 06 (≈ 999°C): The most popular range. Balanced in both strength and absorption.
- Cone 05 (≈ 1,046°C): The piece becomes stronger, and porosity begins to decrease.
- Cone 04 (≈ 1,063°C): The bisque is hard and dense. The piece is durable for handling.
Note: The Cone number measures accumulated heatwork, not a single temperature. You should primarily follow the clay manufacturer's recommendations.
What is the difference between Cone 06 and Cone 04?
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Cone 06 (Lower Bisque):
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Pros: Highly porous, excellent glaze absorption, suitable for dip glazing.
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Cons: The piece is still fragile and prone to breaking during handling.
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Cone 04 (Higher Bisque):
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Pros: The piece is stronger, more durable, and resistant to decoration.
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Cons: Less glaze absorption. You may need to adjust the glaze thickness or application method.
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4 precautions before putting pieces in the kiln
- Clay must be bone dry: If moisture remains, water will turn into steam and cause the piece to explode or crack.
- Be careful with thick pieces: The temperature should be ramped up slowly at the beginning, not too quickly.
- Arrange the kiln properly: Pieces can be stacked partially, but they must not be pressed down to the point of warping or breaking.
- Check clay specifications before firing: Always check the Recommended Bisque Temperature from the manufacturer, as each stoneware or porcelain formula has a different maturation point.