Short answer
Carbon black is almost pure elemental carbon made by controlled incomplete combustion or thermal decomposition of hydrocarbons, formed as nanometre-scale particles fused into aggregates. It absorbs light across the whole visible spectrum and scatters very little, so even a fraction of a per cent in a white paint pulls lightness down steeply — the strongest tinting effect of any common colourant.
Commercial carbon black is more than 97% elemental carbon in grape-like aggregates: primary particles, generally 10–300 nm across, fused together, and in the product as sold further clustered into agglomerates of roughly 100–1000 nm. Nearly all of it is made by one of two routes. In the furnace-black process, the most common, a heavy aromatic oil is atomised into a hot gas stream in a closed reactor, where it pyrolyses into carbon particles that are cooled and collected on filters. The thermal-black process decomposes natural gas or oil in a hot refractory furnace in the absence of air. Older routes gave lamp black and channel black, names that survive as grades. The industry association stresses that carbon black is chemically and physically distinct from soot, and that activated carbon and bone black, often confused with it, are different products made by different processes.
Carbon's electronic structure absorbs strongly and fairly evenly across the visible spectrum, and the particles are small enough that almost none of the light entering a carbon-black film escapes by scattering. In Kubelka–Munk terms it has an enormous absorption coefficient and a tiny scattering coefficient. Two consequences follow. First, a well-dispersed carbon black in a glossy binder gives a very deep masstone, and the industry grades blacks for coatings largely on this jetness. Second, when it is let down into a white — where scattering is supplied by titanium dioxide — each small addition of black removes a large share of the light the white would otherwise return. The table shows how steep that curve is.
Only a small share of carbon black goes into inks, coatings and plastics as a pigment — about 9% according to the industry association, against roughly 90% in rubber, where it reinforces tyres and belts. Its pigment uses include printing inks, toners, automotive and industrial coatings, and coloured plastics. In plastics and cables it does a second job: absorbing ultraviolet at the surface and protecting the polymer beneath, which is why black versions of outdoor plastic parts often outlast pale ones. The same near-total absorption makes carbon-black plastics hard for near-infrared sorting machines to see, a problem covered on the recycling pages.
Not all blacks look alike. Different grades and different black pigments — carbon blacks, bone and ivory blacks, iron oxide black, mixed blacks — give different masstone depth and a slightly different hue when greyed with white, which painters and paint makers describe as a bluish or brownish undertone. The industry association lists colour and undertone among what carbon black contributes to inks. For anyone mixing greys this is the practical point: a grey made from one black and white is not the same grey as one made from another black, and a dark grey that looks neutral in the tin may lean warm or cool once it is on a large wall beside other colours.
| Black in the pigment mix | Reflectance (thick film) | CIE L* |
|---|---|---|
| 0.05% | 72.8% | 88 |
| 0.10% | 64.0% | 84 |
| 0.20% | 53.6% | 78 |
| 0.50% | 38.1% | 68 |
| 1.00% | 26.6% | 59 |
| 2.00% | 16.9% | 48 |
| 5.00% | 8.1% | 34 |
Why: Carbon black's absorption is so high that tiny additions dominate the mixture.
Fix: Tint in very small, measured steps, or pre-mix a weak grey and add that instead.
Why: Black pigments differ in masstone and undertone when let down with white.
Fix: Use one black for a whole scheme, and compare greys in a let-down with white, not as masstones.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactModerate evidence
Most carbon black types contain more than 97% elemental carbon as aggregates of primary particles generally 10–300 nm in diameter, sold as agglomerates of about 100–1000 nm.
Caveat: Industry-association figures describing the product class, not a specific grade.
Source: What are the Physical & Chemical Properties of Carbon Black?
Observed market dataModerate evidence· Worldwide
About 90% of carbon black is used in rubber, about 9% as a pigment, and the rest in other applications; world production is about 8.1 million tonnes a year.
Measured: Global carbon black production.
Caveat: Industry-association figures without a stated year or method.
Source: What is Carbon Black?
FactModerate evidence
The furnace-black process, which pyrolyses atomised heavy aromatic oil in a hot gas stream, is the most common way carbon black is made; the thermal-black process decomposes gas or oil in a preheated furnace without air.
Source: How is Carbon Black Produced? / Uses of Carbon Black
Colourwise analysisLimited evidence
In an illustrative Kubelka–Munk model, 0.5% of a strongly absorbing, weakly scattering black in a white pulls the white’s reflectance from about 96% to about 38%, a drop of roughly 30 L* units.
Based on: Colourwise calculation using Kubelka–Munk mixing with illustrative absorption and scattering coefficients; see the table.
Caveat: Coefficients are illustrative, not measured for any product; the shape of the curve, not the exact values, is the point.
Source: New Contributions to the Optics of Intensely Light-Scattering Materials. Part I (Journal of the Optical Society of America, 1948); Kubelka–Munk theory
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.