A porous solid product containing 85–98% carbon produced by heating carbonaceous materials such as cellulose, wood, peat, and coals of bituminous or lower rank at 930–1110°F (500–600°C) in the absence of air. Chars or charcoals are rendered more porous and more efficient for sorption by heating in air, carbon dioxide, or steam at 1650°F (900°C) for a brief period. The surface area of activated char produced by this technique is about 800,000 ft²/oz (1000 m²/g). Chars from cellulose or wood are soft and friable. They are used chiefly for decolorizing solutions of sugar and other foodstuffs and for removing objectionable tastes and odors from water. Chars from nutshells and coal are dense, hard carbons. They are used in gas masks and in chemical manufacturing for many mixture separations. Another use is for the tertiary treatment of wastewater. Residual organic matter is adsorbed effectively to improve the water quality.