Additives Optical Brightening Agent (OBA) are colorless dyes that work by emitting visible light when exposed to invisible ultra-violet light.

The brighteners are usually fluorescent dyes or pigments that absorb UV radiation and re-emit it as violet-blue light that gives yellowish-white coatings a brighter, whiter appearance. They are used to increase the luminance factor and to remove the yellow undertone of white or off white materials. Small amounts of blue dyes are also used to achieve the same result.

The optical brighteners or fluorescent whitening agents (FWA) are colorless to weakly colored organic compounds. In solution or applied to a substrate they impart bluish-white effects, have good light fastness and excellent heat resistance and chemical stability