Constitution of Fireclays at High Temperatures: III, Deformation Characteristics

The hot‐pressing characteristics of kaolin, fireclay, and plastic fireclay were determined between 1150° and 155O°C at 3000 to 10,000 psi under oxidizing conditions. Each clay could be pressed to near its true density at an optimum temperature. Insufficient temperature produced low bulk density; excessive temperature caused bloating. Synthetic glasses were prepared to represent the composition of the liquid phase estimated to be present at the optimum pressing temperature. Viscosities of the synthetic glasses were measured, and those of the optimum pressing temperature were estimated. The deformation characteristics are in reasonable accord with the Mackenzie and Shuttleworth hot‐pressing equation for viscous flow.