Variations in reflectance of pigmented material with particle size and refractive index: An experimental and theoretical study

Abstract

The multiple-scattering technique proposed by Mudgett and Richards is the first applicable rigorous theory permitting the computations of reflectance of pigmented surfaces from the size and refractive index of pigments. The validity of this theory is established by comparing the experimental values of the reflectance of four paint samples with the theoretically predicted values. A further theoretical study on the variations in reflectance with particle size and refractive index (real and imaginary part of the refractive index) is carried out covering the range of relevance to paint technology. The study revealed that the error in the real part of the refractive index does not introduce a significant error in reflectance values. A small error in the absorption index, however, considerably changes the reflectance values and the error in particle size significantly affects the results in absorbing systems rather than in non- or weakly-absorbing systems.