What applications are the Gardner, Yellowness index, and CIE L*a*b color scales used in?
Gardner, yellowness index, and CIE L*a*b color scales
Gardner Color and Yellowness Index are typically used for non-aqueous non-turbid liquids such as resins and rosins and directly follow ASTM Methods (American Society for Testing Materials https://www.astm.org). The color method using Tristimulus Values and Chromaticity Coordinates can be used for any liquid sample. In all of these methods, the wavelength is scanned in specified increments and converted to tristimulus values. The software for the Gardner and Yellowness Index programs uses the tristimulus values in calculations for Gardner Color and YI. Tristimulus values and chromaticity coordinates are somewhat of a three-dimensional representation of color that in general describe the basic color, the purity or amount of that color, and the amount of white or black in the color. These values can in turn be converted into various "color spaces" such as Hunter or CIE L*a*b used by various industries for use in defining and controlling product color. If interested the ASTM color methods referenced in the non-aqueous methods can be found in the "ASTM Standards on Color and Appearance Measurement" reference book.