How pigments are made

People were grinding color 350,000 years ago. Titanium dioxide now goes into about two-thirds of all pigments.

stations: 8
things upstream: 14
raw sources: 8
steps from the ground: 4

The short version

Pigment plants make colored powders that will not dissolve. Red iron oxide mostly comes from two routes, Laux and Penniman. Organic colors leave synthesis as coarse crude crystals that need milling and finishing with water, solvents, acids or alkalis. Fine grinding sets how well the powder spreads, and each lot is tested against a standard before sale to paint, ink and plastic makers.

Dig the earth colors

Iron oxide minerals give red and yellow ochre, the oldest colors people have used. Iron-rich earth is dug, cleaned and sorted before any processing.

Goes in
Iron ore
Bring in white and black

Two pigments make up a huge share of the market and have lines of their own. Titanium dioxide gives white and opacity, and carbon black gives the darkest tones.

Goes in
Titanium dioxide Carbon black
React iron into reds

The Laux and Penniman processes together meet more than 90% of demand for synthetic red iron oxide. Laux oxidizes iron with aromatic nitro compounds and forms its reds by calcining. Penniman can give very bright reds with a yellow undertone.
Synthesize the bright colors

Chemical reactions build colors nature supplies poorly. Ultramarine, once made from lapis lazuli, is made by treating aluminum silicate with sulfur. Phthalo blue is a metal and organic compound created in the early 20th century.

Goes in
Sulfur
Mill the crude crystals

Many organic colors come out of synthesis coarse and crystalline. Patents describe dry milling, sometimes with salt, often followed by wet milling in a stirred ball mill with very small grinding media.
Finish the color

A later treatment using water, solvents, or weak acids and alkalis turns crude crystals into the usable pigment form. Any milling salts have to be extracted, which leaves waste water to deal with.
Micronize the powder

Downstream grinding raises the share of primary particles, so the pigment stirs into liquids more easily. Bayer introduced this micronization in Germany in 1964.
Test against standards

Each batch is checked by general ISO test methods for pigments and dispersion. Makers identify the color by a Colour Index number, so buyers can get the same chemical whatever the trade name.

End of the linePigment Next it goes into toothbrush, lipstick, nail polish and 20 more.

Worth repeating

Prussian blue, the oldest modern synthetic color, turned up by accident in 1704.
The Colour Index catalogs over 27,000 products under over 13,000 generic names.
Egyptian blue, the first known synthetic pigment, dates to around 3250 BC.