A theoretical model of the production of open-cell microcellular foam is presented. This model allows the prediction of the conditions necessary to produce these materials. Experiments verify the model quite well. The results of the batch processing experiments indicate the processing parameters that promote the development of open-celled microcellular polystyrene foam. A saturation pressure of 17.2 MPa (2500 psig) provides the nucleation density necessary to form an impinged structure with microcellular bubble density. A foaming temperature of 200 degreesC promotes the formation of both internal and surface porosity. A scaled time between 1 and 2.7 seconds develops a foam structure that intrudes a large volume. Samples foamed at 200 degreesC for 1 and 2 seconds possess pores less than 1 mum in diameter. These samples represent scaled times of 1 and 2 seconds. Therefore, to produce open-celled microcellular polystyrene foam with batch processing, samples should be saturated at approximately 17.2 MPa (2500 psig) and foamed for a scaled time between 1 and 2 seconds.