Bl This standard establishes the requirements that light and dark oven-drying insulating varnishes must meet. Clear ones are appropriate when an oil-resistant varnish is required. B-2 The dark insulating varnishes established in this standard are intended for the impregnation of windings and mainly for use in electrical traction equipment and in devices that are subject to mechanical vibrations when used. B-3 The clear insulating varnishes established in this standard are intended for the insulation by immersion or by impregnation of coils of transformers, motors, generators and similar materials that must be completely impregnated with insulating varnish. B-4 Clear insulating varnishes are also intended to be used to form the protective layer on varnished papers and to be applied on metallic surfaces, such as magnetic plates for transformers, interior varnishing of tanks, etc.