optical brightener

Optical brighteners, also known as fluorescent brighteners, are chemical compounds that make materials appear whiter. They are not true bleaches. These compounds absorb ultraviolet light and emit blue visible light, counteracting the natural yellowish tint of materials like fibers, paper, and plastics.123

While bleaching can reduce yellowness, it must be done carefully to avoid damaging the material. Optical brighteners offer an alternative by masking this tint. They were first used by banknote printers in 1927 for security purposes but are now widely applied in the textile industry, as paper brighteners, and as additives in detergents and polymers.2