Predicting the spectral reflectance factor of translucent paints using Kubelka‐Munk turbid media theory: Review and evaluation

The use of Kubelka‐Munk (K‐M) turbid media theory in predicting the spectral reflectance factor of an opaque specimen from the specimen's constituent optical constants is well established in practice and well described in the literature. For translucent samples, there is a paucity of published results and the approaches are disparate. Accordingly, a review of K‐M theory and its application for predicting the spectral reflectance factor of translucent samples is presented and tested. Four methods for determining the absorption and scattering coefficients with respect to a certain film thickness are described: the black‐white method, the infinite method, the masstone‐tint method, and the two‐region method. The black‐white and infinite methods use the general form of the K‐M equation. The masstone‐tint method can be used for both the general form and the opaque simplification. The two‐region method, combining opaque and translucent approaches, was enhanced in this research and included an opacity calculation to automatically differentiate opaque and translucent spectral regions and a smoothing technique to combine both spectral regions. The two‐region method was tested using a set of acrylic‐emulsion artist paints and glazes spanning a range of opacities from opaque to nearly transparent. The results were reasonable and provided statistically significant improvement compared with the opaque simplification, commonly used in art conservation science and industrial color matching. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 417–431, 2009