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Carbon black is a pigment made of carbon formed by the pyrolysis of gaseous hydrocarbons in a minimum of oxygen. In short, they burn natural gas, crude oil residues, what have you, without enough air so it makes a lot of soot (although carbon black is created under much more controlled circumstances than soot, so it doesn't have any of the impurities of soot). It comes as a fine black powder, in the form of spheres and their fused aggregates with particle sizes below 1000 nanometers (1000*10-9 meters, 0.000001 m), and as small as 8 nanometers.

It is also known as noir de carbone and lampblack. Lampblack is, however, is not "carbon black", as it is created from a different process: the sooty burning of liquid hydrocarbons, such as kerosene. Varieties include acetylene black, channel black, furnace black, and thermal black, and these vary by the exact process used in their manufacture, and subsequently have differences in their particle size, structure, etc.

http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/carbonbl/basic_cb.html has this to say about its uses (links added for convenience):

It is used mainly as a reinforcing agent in rubber products such as tires, tubes, conveyor belts, cables and other mechanical rubber goods; used as a black pigment in printing, lithographic, letterpress, carbon paper and typewriter ribbon inks, paints, coatings, lacquers, plastics, fibres, ceramics, enamels, paper, record discs and photocopier toner; leather finishes; manufacture of dry-cell batteries, electrodes and carbon brushes; electrical conductors; conductive and antistatic rubber and plastic products; electromagnetic interference shielding; videodiscs and tapes; UV stabilization of polyolefins; and high temperature insulating material.

The process for its manufacture was invented by J. K. Wright, a Philadelphia ink maker, in 1864, though it wasn't mass produced until the 20th century with more advanced technology making it profitable. Because of its many oil fields, Texas lead the nation for many years in carbon black production, peaking in 1973 with 1,511,127,000 pounds (686,876,000 kilograms), valued at $128,144,000. World supply is now dominated by three companies: Cabot Corp., Degussa AG and Columbian Carbon (Part of Phelps Dodge).

According to a fine table on the brochure located here on the Columbian Carbon website http://www.columbianchemicals.com/Markets_Applications/IndustrialCarbonBlack/, these properties of carbon black have these effects (my annotations in parentheses):

Smaller Particle Size 
(Higher Surface Area)

   Increases        Blackness
   Increases        Tint
   Increases        UV Protection
   Increases        Electrical Conductivity
   Increases        Vehicle Demand and Viscosity
   Reduces          Dispersibility

Higher Structure 
(larger aggregates of spheres, as opposed to smaller, or lone spheres)

   Reduces          Blackness and Tint Dispersibility
   Improves         Vehicle Demand and Viscosity
   Increases        Electrical Conductivity

Higher Porosity  
(more pores in the aggregates)
   Increases        Vehicle Demand and Viscosity
   Increases        Electrical Conductivity
   Enables          Reduced Loadings in Conductive Applications

Higher Surface Functionality  
(more chemical hooks on the surface of the spheres to bind with)

   Improves         Vehicle Wetting
   Reduces          Viscosity of Liquid Systems
   Lowers           Electrical Conductivity

Sources include:

Everything noder wrinkly (thanks much!)

Handbook of Texas Online, s.v. "CARBON BLACK INDUSTRY,"
http://www.tsha.utexas.edu/handbook/online/articles/CC/doc1.html (accessed May 18, 2005).

Canadian Centre for Occupational Health and Safety, s.v "OSH Answers: Basic Information on Carbon Black"
http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/carbonbl/basic_cb.html (accessed May 18, 2005).

IUPAC Compendium of Chemical Terminology
http://www.iupac.org/goldbook/C00824.pdf (accessed May 18, 2005).

Columbian Chemicals, s.v. "Brochure: RAVEN BLACKS, Industrial Applications Require Powerful Solutions"
http://www.columbianchemicals.com/Markets_Applications/IndustrialCarbonBlack/ (accessed May 18, 2005)

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