In Section 3.1, the problems of “tape separation” or “girth cracks” developing during service with high-voltage asphalt mica flake groundwall insulation were introduced. The softening temperature of the asphaltic resins used by various manufacturers was dependent on the percentage of drying oils used in their preparation. Insulation, containing the most weakly thermoset formulations, could only withstand a small amount of shearing loads from thermal cycling (Section 8.2) before the layers of insulating mica-splitting tape began to separate. Both the generator slot length and the service temperature were important factors in determining the shear loads within the insulation. Other factors included the tightness of fit of the coils in their slots, the duty cycle of the generator, and the degree of cumulative heat exposure in air before cyclic duty was started.