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This part of ISO 105 specifies a method intended for quantifying the whiteness and tint of textiles, including fluorescent materials.

Whiteness as measured by this test method is an indication of how white the textile appears to an average viewer. Tint, if other than zero, is an indication of a reddish or greenish hue having shifted away from a bluish (neutral) hue with a dominant wavelength of 466 nm. The formulae for calculation of whiteness and tint are those recommended by the CIE¹⁾.

Because reflectance is affected by the nature of the surface of the textile, comparisons can be made only between specimens of the same type of textile.

The application of the formulae is restricted to specimens that are called “white” commercially, that do not differ much in colour and fluorescence and that are measured on the same instrument at nearly the same time. Within these restrictions, the formulae provide relative, but not absolute, evaluations of whiteness that are adequate for commercial use when employing measuring instruments having suitable modern and commercially available capabilities.

Many impurities in textiles absorb short wavelength light, resulting in a yellowish appearance to observers. Therefore, a measurement of whiteness may be an indication of the degree to which a textile is free from impurities.

The effect of blueing components or fluorescent whitening agents (FWAs) on the whiteness of textiles may also be determined using the whiteness measurement.

1) International Commission on Illumination, Vienna.