This method describes a technique for evaluating the ability of an insulating material to resist electrical breakdown perpendicular to the plane of the material when subjected to short term@ high voltages at standard AC power frequencies of 50-60 Hz. Applicability and Use of Data This method may be used on material of any thickness up to approximately 0.125 inch@ however@ for material over 0.020 inch@ other methods such as dielectric breakdown are normally used to characterize a material's electrical integrity. Results of this test may be drastically affected by moisture content@ and results obtained using different preconditioning may not be comparable. This method uses an oil medium to prevent flashover on a small specimen and results may not be comparable to tests run in air. Values obtained using this method should not be used for predicting the insulating ability of ultra thin metal clad laminates. The values determined by this method generally decrease with increasing specimen thickness for otherwise identical material. This method is based on the techniques described in ASTM D149.