Definition
The whiteness index is a photometric measurement value that describes how strongly a surface reflects white light while being perceived as nearly perfect white. It captures both the brightness and the hue of a specimen, in particular the blue component of the reflected light, since the human eye perceives a slightly bluish white as especially pure. The whiteness index is generally determined using standardized measurement procedures and is expressed as a dimensionless numerical value, with higher values corresponding to a greater perceived whiteness.
Use in the textile industry
In the textile industry, the whiteness index is used to evaluate and quality-control bleached, optically brightened, or greige fibers, yarns, and fabric structures. Optical brightening agents (fluorescent whitening agents) are applied specifically to increase the whiteness index of textiles by converting invisible UV light into visible blue light. The whiteness index is also relevant in textile finishing, because as a baseline value prior to dyeing or printing it affects reproducibility and color fastness.
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