A method of manufacturing a tire is provided that includes curing the tire (10) in a curing press (12) and applying microwave energy at a given frequency band into the tire. The interaction between the microwave energy and the tire is monitored to obtain a complex reflection coefficient. A root-mean-squared error is calculated using the measured complex reflection coefficient and a reference reflection coefficient. The reference reflection coefficient is from a fully cured tire made from the same material as the tire. Continuous monitoring of the interaction takes place to obtain the complex reflection coefficient along with continuous calculation of the root-mean-squared error at different times during the curing of the tire in the curing press. The calculated root-mean-squared errors are used to determine whether to stop the curing of the tire in the curing press.