Firing Clays
What is the Difference between Low and High Fire Clays?
Various projects will require the use of different types of clay. Low fire clay is fired under lower temperature than high fire clay. Low fire clay is most generally fired between cone 06 and cone 02. Firing of high fire clays is done at cone 6 and above.
This Week's Featured Products in Firing Clays
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Amaco No. 67 Sedona Red Clay Amaco Sedona Red Clay has a rich red color before and after firing. It's excellent for all hand methods of modeling, slab, coil, sculpture, and wheel throwing. Wide firing range of cone 06-02 (1855°F–2052°F). At cone 06, shrinkage is 7% and absorption is 11.7%. At cone 02, shrinkage is 13% and absorption is 9.2%. Sedona Red Clay fires well without slumping. This clay is talc free. Comes in a 50 lb (23 kg) carton which contains two 25 lb (11 kg) bags of moist clay. |
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Amaco No. 46 Buff Stoneware Amaco No. 46 Buff Stoneware Clay is supplied in dry and moist formulas. Fire it at cone 5-10 (2205°F–2381°F). Recommended glaze firing is cone 5 (2205°F). Moist clay is de-aired to ensure a homogenous mixture which needs little or no wedging. The dry clay is finely ground and air-floated before packaging, and ready to be mixed with water to form a smooth clay. No. 46 clay is excellent for all hand methods of building, push and pull, coil, sculpture, and throwing on the wheel. When fired at cone 5, bisque is buff colored with 12% shrinkage and absorption is 1.8%. Clay fired to cone 10 will be a soft gray with 13.2% shrinkage, and 0% absorption. It comes in a 50 lb carton which contains two 25 lb bags. Caution Label — The moist clay is certified non-toxic, but the dry clay bears the ACMI Caution Label. |
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Amaco No. 67-S Sedona Red Casting Slip Amaco Sedona Red Casting Slip has a rich red color before and after firing. It is formulated to fire at Cone 05, but its firing range is cone 06–02 (1855°F–2052°F). The rich red color deepens the higher you fire it, producing a great terra cotta look in whatever you're casting. Many transparent and all opalescent glazes are enriched by the red colored clay. Shrinkage at Cone 06 is 7% and absorption is 11.7% . This slip is not talc free, but is ACMI approved for talc content. Comes in a 1 gallon (3.8 L) plastic jug. |
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Low fire clays are usually available in white, buff or red shades. It is often termed earthenware or terra cotta. Glazes for low fire clay are available in a wide assortment of colors. Bold and vibrant shades are better achieved at low temperature firing. Low fire clay can be fired more rapidly as well.
High fire clays are stronger and less porous. Pieces made of high fire clays will require more time for firing. Stoneware and porcelain are high fire clays. Regardless of the clay that is chosen, it is important to select glazes that are compatible and use appropriate firing temperature.