Applicable to ceramic, glass and glass-ceramic materials to be used for electrical insulation purposes. Specifies methods of test. Intended to provide test results typical of the material from which the test pieces are processed. Since, in the majority of cases, ceramic components for insulating purposes are of rather different size and shape to test pieces, the results of such tests provide only a guide to the actual properties of components. The limitations imposed by the method of forming and processing are discussed where relevant.