A non-thermostatic heating device is provided with temperature range control whereby materials may be heated and melted to a safe or desired temperature and maintained, particularly soy based non-candle formulated waxes for skin therapy as well as aromatherapy waxes generally. The device is vented and comprises a non flammable insulative container such as treated paper tubing and semi insulative elements, particularly one or more enclosed air pockets which are predetermined in dimension or movable for change in volume to provide a desired equilibrium temperature range.