A reusable self-supporting field director for use in a microwave oven is characterized by a plurality of vanes, each extending radially outwardly from a central axis. The vanes are supported in a slotted central support member. Each vane has a predetermined thickness dimension. Each vane comprises a substrate formed from an electrically non-conductive material having a predetermined coefficient of thermal expansion and an electrically conductive wrapper having a predetermined coefficient of thermal expansion that is different from the coefficient of thermal expansion of the substrate. The wrapper wraps the substrate so that a portion of the first and second major surfaces are covered and the radially inner end of each vane is wrapped by an electrically conductive material. The wrapper and the substrate are arranged in a laterally symmetric fashion so that thermal expansion effects due to heating are equalized across the thickness of each vane.