Abstract: Used foundry sand is reclaimed by crushing the sand and separating both metallic material and at least a portion of the unwanted non-metallic portion of the sand, then heating the sand to a temperature of about 1400.degree. F. for burning off the foreign material and causing the sand particles to pass through a strong expansion phase somewhere above 1000.degree. F. and passing through a contractual phase at a higher temperature to thereby cause the foreign material to be cracked or otherwise parted from the particles and the sand particles become increasingly thermally stable from subsequent reuse as clean sand. The heated sand is then cooled to about 400.degree.-500.degree. F. The process includes the utilization of some of the heat of the thermal furnace for a shell coating operation.