Transparent coating on a color surface

When a laminate or transparent coating is applied to the surface of a colored slab, there may be a significant change in the color. A reason for the change in color is internal reflection at the slab surface and thus greater selective absorption. The current work develops a random walk model to calculate the reflectance factor of a slab that includes internal reflection at the slab surface to predict the change in color of the bulk reflectance with application of a laminate. The CIELAB colors are calculated from the reflectance, and the model shows that there is not much change in hue but there is significant change in the saturation and lightness: the saturation increases and the lightness decreases. A comparison of the reflectance factor as predicted by the model is compared to a Monte Carlo simulation and shown to have good agreement.