Abstract: Warped, spread apart, graphite enclosures of the type used with crucibles for "pulling" crystalline bodies, and the like are restored substantially to original "set" condition by compressing them and holding them in substantially their original shape while heating them to temperatures which result in vaporization of the crystalline material and the carbon compounds which have deposited or formed on the enclosure, holding them at the elevated temperatures for a period of time sufficient to volatilize, and permit removal of all, save perhaps a minor residuum, of these materials, and then cooling the enclosure. Alternatively, the heating can be accomplished in a reactive furnace which also reacts a halogen or the like with the material to be removed.