TABLE OF CONTENTS In the previous section, we briefly discussed how body (subsurface) reflection can be modeled through radiative transfer theory. In fact, this is a topic that is of great interest in the paint, textile, paper, plastic, and publishing industries. The central question is how to mix different amounts of dyes and/or pigments to obtain products of a desired color. This is an important part of a process called colorant formulation, which also includes the selection of dyes and pigments for the application requirement, the study of color matching criteria, and the minimization of production cost. An interesting example of such applications is called shading in paint manufacturing. Pigments are ground and dispersed in the liquid solvent and binder (called the vehicle) by milling equipment to produce paint of the desired color. Because of batch to batch differences, the correct color is reached by successive approximations. First, about 80% of the required pigments is ground into the vehicle. Then the color is measured and the additional amount of each pigment required to match the desired color is calculated. Somewhat less than the calculated amount is added and the color checked again. Using repeated trials with visual inspection and comparison it usually takes as many as ten trials to come up with a good color match. With the help of computational models and color measurement, it is now possible to make the match in one or two trials.
The physics of colorant formulation is also of...
