method by which the temperature of an electrically nonconducting (insulating) material can be raised by subjecting the material to a high-frequency electromagnetic field. The method is widely employed industrially for heating thermosetting glues, for drying lumber and other fibrous materials, for preheating plastics before molding, and for fast jelling and drying of foam rubber.

The material to be heated is placed between two metal plates, called electrodes, to which a source of high-frequency energy is connected. The resultant heating, in homogeneous materials, occurs throughout the material.