Theoretical aids for the determination of colorimetric curves of binary powder mixtures

Colorimetric assessment of powder mixtures or pigmented specimens can be made by determining CIE color coordinates from sample spectral reflectance curves. The diffuse reflectance spectra of five particulate systems having different hues are determined using modified particle model theory for wavelengths of 400 (20) 700 nm. Six binary powder mixtures are prepared from these particulate systems. The reflectance spectra of binary powder mixtures are then predicted assuming the contribution of each component to be equal to the product of its reflectance and the total surface area of particles. The theoretically predicted diffuse reflectance spectral curves agree well with experimentally measured ones. The evaluation of the theoretical technique is made by determining the color difference between the measured and predicted color coordinates. The color difference calculated for all the samples is <2 CIELAB units. The study establishes a theoretical aid to predict diffuse reflectance spectra of powder mixtures from the fundamental morphological and optical properties of particulate matter.