What increases when you coil a wire. 40931 DB-9DD 1" (25mm) DropOn™ Bit - DoubleDiamond - How to Make Refractory Cement. Fire clay. Fire clay is a term applied to a range of refractory clays used in the manufacture of ceramics, especially fire brick.
The United States Environmental Protection Agency defines fire clay very generally as a "mineral aggregate composed of hydrous silicates of aluminium (Al2O3.2SiO2.2H2O) with or without free silica. "[1] Properties[edit]