Continuity and extensibility of insulating varnishes

One of the important, functions of insulating varnishes is to provide protection against the entrance of moisture and dirt within the insulation system of electrical apparatus. A considerable amount of effort has been spent in studying the effect of moisture on the electrical properties of insulating varnishes as well as the moisture transmissivity of perfect varnish films. However, to be effective in the practical application, the varnish must provide an initially continuous film which maintains its integrity under operating conditions.