William J. Marshall

A surface in Colour Space representing equal depth at all points (a Control Depth) is defined by a constant value of Integ – an integration of a weighted function of the measured reflectance values of a dyeing throughout the range of visible wavelengths. The amount of a dye that must be applied to a particular substrate by a specified dyeing method to give this Integ value may be determined by experiment, and is called the Control Strength of the dye. Extensive checks made by matching colours with various ternary combinations of dyes have shown that Control Strengths give a reliable indication of the relative strengths of different dyes, even when these differ very widely in colour. The position of dyeings at a Control Depth in ANLAB 40 Colour Space may be projected on to the A, B plane to produce the ICI Colour Map. This indicates quantitatively the relative hue and brightness of the dyeings, and displays the total gamut of shades attainable by combinations of dyes at the Control Depth. By combining this information from the Colour Map with Control Strength and selling price data, a very complete and quantitative description is obtained of the coloristic value of different dyes. This is a powerful tool in the selection of dyes for particular purposes.