Pigmentum

Pigmentum, from Latin pigmentum, refers to a substance that provides color to a material by absorbing and scattering light. In art, industry, and biology, pigments are typically insoluble powders dispersed in a medium rather than dissolved.

Pigments are broadly categorized as inorganic or organic. Inorganic pigments include iron oxides (red, yellow, brown), titanium dioxide (white), chromium oxides (greens), and ultramarine. Organic pigments include phthalocyanines, quinacridones, and diketopyrrolopyrrole reds; they offer a wide range of hues and high color strength but can vary in lightfastness. Pigments differ from dyes in being insoluble and dispersed as particles rather than dissolved.

Key properties include particle size, dispersion stability, opacity or transparency, tinting strength, and lightfastness. Compatibility with binders and carriers affects film formation and durability. Pigments are milled or formulated into pastes and concentrates for use in paints, plastics, inks, cosmetics, and coatings.

History and safety: pigments range from natural earth colors to synthetic inorganic and organic forms. Some historic pigments, such as lead white and vermilion, are toxic and controlled or replaced today. Modern regulations govern composition and labeling of pigments in consumer products, especially cosmetics and toys.

In biology, pigments such as chlorophyll, carotenoids, and melanins color organisms and participate in photosynthesis, photoprotection, and signaling. The term pigmentum is also used in Latin texts as a general word for colorant.