Pigment

Pigment is a substance that provides color by selectively absorbing visible light. Unlike dyes, pigments are typically insoluble in the medium in which they are dispersed, and they impart color through solid particles that scatter and reflect light rather than dissolve.

Pigments are classified by origin as inorganic or organic, and by source as natural or synthetic. Inorganic pigments include iron oxides (reds, yellows, browns), titanium dioxide (white), and ultramarine (blue). Organic pigments include carbon black, phthalocyanine blues and greens, quinacridones, and other synthetic colors. Natural pigments are obtained from minerals, plants, or animals, such as ochres, umbers, madder, and indigo, though many are now replaced by synthetic alternatives.

Important properties include lightfastness (resistance to fading), tinting strength, opacity, and heat stability. Some pigments are opaque and cover underlying layers, while others are transparent. In paints and inks, pigments are dispersed with binders and sometimes processed as dispersions to achieve consistent color and stability. Lakes are pigment-like colors produced by precipitating dyes as insoluble metallic salts; they are widely used in cosmetics and food applications.

Applications span art and illustration, printing, plastics, coatings, cosmetics, and food coloring in some cases. Safety and environmental concerns drive regulation, labeling, and handling requirements, including toxicity assessments for certain inorganic pigments and restrictions on toxic elements. Advances continue in pigment chemistry to improve color range, durability, and sustainability.