... , air heating, heating a surfaceCeramic shellCeramic shell, with wire and ceramicinsulationLow cost, small bulk, insulating shellNot ... for very small bulk, low powerPlastic shellPlastic shell, with wire and plasticinsulationLow cost, small bulk, insulating ... such as aluminum plate coated with ceramic paint, aluminum plate oxygenated, aluminum plate coated with teflon, aluminum plate electroplated, ...