Soot

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(Redirected from Lampblack)

This article is about the powdery substance. For the language framework, see Soot (computer science).

Soot, also called lampblack or carbon black, is a dark powdery deposit of unburned fuel residues, usually composed mainly of amorphous carbon, that accumulates in chimneys, automobile mufflers insides of smoke saunas and other surfaces exposed to smoke—especially from the combustion of carbon-rich organic fuels in the lack of sufficient oxygen. The combustion is thus incomplete. Lampblack is sometimes used only to refer to carbon deposited from incomplete burning of liquid hydrocarbons, while carbon black may be used to refer to carbon deposited from incomplete burning or pyrolysis of gaseous hydrocarbons such as natural gas.

Lampblack has been used since prehistoric times as the source for Carbon Black, a common pigment used in paints and inks. It is still widely used in printing inks, toners for xerography, laser printers, and in the chemical industry. It is also used as food colouring, e.g. in liquorice sweets. The black colour of rubber tires is due to the use of lampblack as an ingredient in their vulcanisation; this use accounts for around 85% of the market use of carbon black.

Lampblack is easily produced experimentally by passing some noncombustible surface, such as a tin can lid or glass, closely through a candle flame. Lampblack produced in this way is among the darkest and least reflective substances known^{[citation needed]}.

Lampblack is also used to coat aluminium foil that has been previously attached to a recording drum for use in a recording barograph or other instrument. The surface is scratched clear by a pointed stylus. In this case, the sooty smoke is produced by burning a small amount of camphor. After recording the image is fixed by spraying the surface with a clear lacquer. Similar coatings were used in direct recording pendulum seismometers. While not a sensitive instrument, these were capable of directly recording the direction of significant horizontal shocks upon a smoked glass plate.

Soot is in the general category of airborne particulate matter, and as such is considered hazardous to the lungs and general health when the particles are less than 5 micrometres in diameter, as such particles are not filtered out by the upper respiratory tract. Smoke from diesel engines, while composed mostly of carbon soot, is considered especially dangerous owing to both its particulate size and the many other chemical compounds present.

[edit] Soot production

Soot production can be complex. It can depend not only on the oxygen supply but the existing wind or uplift, as well as convection. Soot can also be reoxidised during production, depending on the manner in which its flow is routed through an industrial process.

Soot tends to rise to the top of a flame, such as in a candle in normal gravity conditions, making it yellow. In microgravity or zero gravity, such as an environment in outer space, convection no longer occurs, and such flames tend to become more blue and more efficient, producing much less soot. [1] Experiments by NASA reveal that diffusion flames in microgravity allow more soot to be completely oxidised than in conditions on Earth, because of a series of mechanisms that differ from those in normal gravity conditions. [2] Can also stain clothing and/or cause illness if inhealed by persons with lung disorders or difficulty breathing.identified by Irum S. of Alabama.