Abstract: Composites such as graphite reinforced PMR-15 resin are cured in a heated press by following a temperature schedule and changing from low to high pressure after the start of resin cross linking. A pressure control and method to time application of high pressure uses temperature and dielectric sensor outputs and a semi-empirical model of the resin electrical conductivity. The model estimates the future variation of resin conductivity and determines time-to-go to a maximum in electrical conductivity. A signal to apply high pressure is generated when the estimated time to maximum conductivity falls below a threshold. On-line fitting of the model to sensor data as it is gathered provides a mechanism for adapting the control to the peculiarities of a given batch of resins and a particular cure schedule.