Abstract: A method of automatically maintaining a nominal property value of a material near a limiting value in the process of making the material. The method involves the steps of imparting to the material a property that varies about the nominal value, and measuring the varying property, the measured property having positive and negative excursions about the nominal value. Determination is then made of the amplitudes of the excursions, and the nominal value of the property is adjusted to a predetermined limiting value in response to the amplitude of the most recent excursion, i.e., the nominal value is adjusted toward or away from the predetermined limiting value in respective response to any decrease or increase in the amplitude of the most recent excursion relative to the amplitude of the excursion immediately preceding the most recent excursion.