Abstract: The rotary furnace has a generally cylindrical rotatable outer member that is driven by a belt and pulley arrangement. An inner member that defines the confines of the heating chamber is freely supported on the outer member to permit free expansion and contraction of the inner member with respect to the outer member. Insulating material disposed between the inner and outer members also joins the inner and outer members together during rotation of the outer member. The insulating material thus transmits the driving force from the outer member to the inner member to thereby cause rotation of the inner member. A cantilevered, non-rotatable heat supply structure extends into the inner member from one end thereof. An access opening to the heating chamber, that is normally sealed during furnace operation, is provided at the opposite end of the inner member.