Abstract: A method and apparatus for controlling the rate of operation of a glassware forming system including a temperature sensing device positioned in the blank and blow molds of an I.S. machine. The mean temperature over a period of time is derived for each of the molds. The mean temperature is compared to a predetermined optimum temperature. The optimum temperature is chosen to be the highest desirable temperature at which the corresponding molds should operate. In response to the comparison of the detected and optimum temperatures, the speed of the I.S. machine is varied to increase or decrease machine speed depending upon which the mean mold temperature is, greater than or less than the optimum temperature, respectively. However, before the speed is changed, if the detected and mean mold temperatures are greater than the optimum temperature, the amount of cooling air is increased until it reaches a maximum.