Plainsman Fireclay

Plainsman Fireclay fires buff to yellowish at cone 10 with fine iron speckles. Added to a clay body it raises the body's resistance to heat without darkening the fired colour much. On its own it has an absorption of 4.5 to 5.5 percent at cone 10, a drying shrinkage of 7.6 percent and a fired shrinkage of 5.6 percent at cone 10, and it is supplied dry, ground to 42 mesh. For a refractory mix it is combined with an aggregate such as silica sand, kyanite or molochite and as little water as practical, given room to shrink as it dries, and dried slowly before the first firing so the water can leave. It is a clay and shrinks as it dries, so on its own it is not a cement or a ready to use castable, and ordinary construction sand is avoided as an aggregate because it can contain lower melting minerals. Its coarser particles can release gas in the firing, so a glaze is tested on it before production, and a surface left wet while it is stretched on the wheel can crack, so water is kept off stretched surfaces.