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A new method and associated equipment has been developed for non-destructively following the progress of the cure of thermoset phenolic molding materials, during a molding operation. It is based on passing an ultrasonic pulse signal through the material as it is curing. The velocity of sound in the material increases monotonically with increases in modulus. Modulus, in turn, increases with increasing degree of cure. Through this method, it is possible to determine when a molded part is sufficiently cured to be removed from the mold. Cure development during compression molding is reported on four phenolic molding compounds, at three different cure temperatures.