A dark powdery deposit of unburned fuel residues, composed mainly of amorphous CARBON and some hydrocarbons, that accumulates in chimneys, automobile mufflers and other surfaces exposed to smoke. It is the product of incomplete combustion of carbon-rich organic fuels in low oxygen conditions. It is sometimes called lampblack or carbon black and is used in ink, in rubber tires, and to prepare CARBON nanotubes.