White, the symbol of peace and tranquility, isone of the most popular apparently 'achromatic' dyestuff used in textiles.Generally most of the formal wares and summer cool clothing are White or lightpastel shades augmented with Whites. Such Whites obtained by the Optical BrighteningAgents (OBA), also called as 'colorless dyes' are considered to be the secondmost widely used dyes on cellulosic material after Black. The other major nontextile usage of OBA's is in Paper and Detergent industries. Many researchershave published abundant and detailed information on chemistry, principle andmechanism of Optical brightening agents. Generally, the OBA's are organiccompounds possessing property of fluorescence i.e. absorb light of shorter wave-length(invisible ultraviolet rays in 300-400 nm range), convert it in to Bluishviolet light and emit it at longer wavelengths (430-460 nm range of visiblespectrum). Thus, the resultant OBA treated textile material emits more than thetotal amount of light that falls on it, giving brilliant white effect. Theaverage reflectance value measured from the complete range of visible spectrum(400 to 700nm) is called Whiteness and it is commonly measured in terms ofWhiteness Index based on CIE, Ganz, Burger, Hunter, etc. formulae.

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Source:Technical Service, Atul Ltd (Colors Division), Atul - Valsad, Gujarat, India