pigments

Pigments are insoluble colored solids used to impart color to materials such as paints, inks, plastics, cosmetics, and ceramics. Unlike dyes, which dissolve in their medium, pigments impart color by scattering light and by selective absorption of wavelengths when dispersed as fine particles within a binder. The appearance of a pigment depends on its intrinsic color, particle size, and the interactions with the surrounding matrix, which affect opacity, brightness, and dispersion.

Pigments are broadly categorized as inorganic or organic, and as natural or synthetic. Inorganic pigments, include iron oxides, titanium dioxide (white), chromium oxide green, and cobalt or nickel pigments, which often exhibit high opacity and excellent lightfastness. Organic pigments, derived from carbon-rich molecules, can provide vivid red, blue, and green hues but vary in lightfastness and heat resistance. Natural pigments come from minerals, plants, and animals and include ochre, sienna, charcoal, and ultramarine historically sourced from lapis lazuli; synthetic forms now exist for many of these colors. Pigments are further described by properties such as opacity (covering power), tinting strength, transparency, heat stability, and resistance to weathering.

Applications span art, automotive and architectural coatings, plastics, inks, cosmetics, and ceramics. Pigments are produced as powders and are dispersed in a binder to form pastes or slurries for paint, or compounded into polymers or ceramic glazes. In conservation, pigment stability and purity are critical for matching historical colors and ensuring longevity.

Safety and environmental considerations influence pigment choice. Historic pigments based on lead, cadmium, mercury, or arsenic have been restricted or replaced due to toxicity. Modern pigment manufacture emphasizes low toxicity, lower environmental impact, and regulatory compliance across industries.