The internal porosity of ceramics shaped before fusion has been improved by three firing techniques: (1) firing in wcuo, (2) firing in diffusible gas, and (3) finish firing and cooling under pressure. A method of measuring pore volume and texture has contributed to understanding the operating mechanics of these processes. This has led to recognition of the firing-process requirements for different porcelains depending on their crystalline content, matured viscosity, service conditions, and performance specifications.

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A review 01 various types 01 cracking, primarily in metals, revea/s that tension is developed by a variety of mechanisms. Fundamentally, tension, leading to cracking (with or without applied tension), originates in volume changes, particularly in the surface layers. The volume changes in turn originate in temperature change, in phase change, or by loss of mobile constituents. The tension theory of cracking includes the thought that exploration of the source of tension is likely to provide clues as to the detailed mechanism.

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