“Residue Wax” or “Foots Oil” is the oil sweated out of slack wax. It takes its name from the fact that it goes to the bottom, or foot, of the pan when sweated.

 Wax sweating was originally used to separate wax fractions with various melting points from the wax obtained from shale oils. Wax sweating is still used to some extent but is being replaced by the more convenient crystallization process. In wax sweating, a cake of slack wax is slowly warmed to a temperature at which the oil in the wax and the lower-melting waxes become fluid and drip (or sweat) from the bottom of the cake, leaving a residue of higher-melting wax (i.e. Foots Oil). 

Sweated waxes generally contain small amounts of unsaturated aromatic and sulfur compounds, which are the source of unwanted color, odor, and taste that reduce the ability of the wax to resist oxidation; the commonly used method of removing these impurities is clay treatment of the molten wax.

 Foots Oil can be used as hydrophobia impregnation material, fuel brick component, raw material for production of grease lubricants, conservation oils and lubricants.