Abstract: An open-cell synthetic-resin foam body is placed in a fluidized bed of conductive metallic particles having a particle size many times smaller than the cell size of the foam. The particles completely permeate the body and adhere to all of the strands thereof. Thereafter the body is vibrated to free from it particles not directly contacting its strands. The thus coated body is then simultaneously pressed and heated so as to reduce its thickness by a factor of at least two and permanently compress it, thereby forcing all of the particles into good contact with each other for good electrical conductivity.