Carbon black is a powdered form of elemental carbon in the form of near‐spherical colloidal particles and coalesced particle aggregates of colloidal size, obtained by partial combustion or thermal decomposition of hydrocarbons. It is distinguishable from other commercial carbons, such as charcoal, by its fine particulate nature and the shape, structure, and degree of fusion of the particles observed with the electron microscope. The fundamental unit of a carbon black particle is the aggregate. Although carbon black is often equated with soot, it differs markedly from the unwanted, uncontrolled by‐products of combustion found in chimneys and the ambient air. The contrast between carbon blacks, soots, and diesel particulate is discussed in more detail in the following.
Carbon black is the earliest known synthetic pigment, having been produced by the Chinese more than 1500 years ago. They made the ink pigment lampblack by burning purified animal or vegetable oils in small lamps with the flames impinging on cool porcelain surfaces on which the carbon black collected.
Carbon black has been commercially produced in the United States for more than 100 years. Although it is still used as a pigment in printing inks, paints, and lacquers, its major use over the past 50 years has been as a reinforcing agent in rubber, particularly in tires. It is also used in plastics, to which it imparts weathering resistance, antistatic, and electrically conductive properties.