METHODS OF TESTING and THE PHYSICAL PROPERTIES OF WET‐PROCESS ELECTRICAL PORCELAIN 1

Data are given for the compressive, transverse, and tensile strengths of wet‐process electrical porcelain. Compressive Strength The height of the sample is an important variable. Initial failure and ultimate failure are discussed and it is suggested that as the latter is the more definite and constant of the two, the, ultimate failure be always determined and recorded as the “compressive crushing strength.” The cylindrical specimen 1 sq. in. in area (11/8 in. diameter) and 11/8 in. high is recommended. Transverse Strength The load applied to cause rupture is directly proportional to the cube of the diameter of the cylinder over a wide range of diameters. A cylinder with an area of 1sq. in is suggested. Cylindrical specimens give constant and high values. Tensile Strength As the area of minimum cross‐section increases the tensile strength decreases rapidly. The diameter should be given with determined values. An apparatus for making tensile strength determinations on a specimen with conically shaped ends and minimum area of 1sq. in is described. Relationship of specimen size and effective dimensions to the average general dimensions of the wale and their methods of manufacture is discussed.