Meaning
Mathematical models describe the relationship between the reflectance of a coating and the scattering and absorption properties of its pigments. Applying kubelka munk theory allows paint manufacturers to predict the color of a final product based on the concentrations of different colorants. This approach is widely used in the production of automotive coatings and industrial plastics.
Optical Modeling
Light traveling through a translucent layer interacts with particles that either absorb its energy or change its direction. The kubelka munk theory simplifies this complex behavior into two main coefficients that can be measured experimentally. These values allow for the calculation of the hiding power of a specific film thickness.
Pigment Formulation
Color matching software uses these equations to determine the most cost effective blend of dyes to reach a target shade. When using kubelka munk theory a technician first measures the reflectance of individual pigments over black and white backgrounds. This data creates a library that the software uses to simulate thousands of potential mixtures.
Measurement Constraint
Accuracy of the model depends on the assumption that light inside the material is perfectly diffuse. While kubelka munk theory works well for matte finishes, it requires corrections for gloss surfaces where specular reflection is high. The samples must be thick enough to be opaque for the simplest form of the equation to hold true.
In cases where the film is very thin, the reflectance of the underlying substrate must also be included in the calculation.
