Dark-burning, plastic cone 6 clay.
The body is made from 60% of Plainsman’s native A3 stoneware clay; to that they add kaolin, silica, bentonite, raw umber and talc. Raw umber is a natural soil/clay, so it has the same handling precautions as other clays.
Coffee contains approximately 0.5% of MnO. Maximum firing is cone 6, 2200F, beyond that manganese fumes will be released as raw umber decomposes, this will cause glaze pinholing (also, the fumes are hazardous, be sure to use proper kiln ventilation). Use cones to verify that your electronic controller or kiln sitter is not firing beyond cone 6.
For more information, please visit Plainsman’s website.