This study addressed conceptually the formation of foams in coatings and polymer formulations that are often formed from pigment clusters as a result of not having enough dispersing compound. This study introduced several new models relating to cluster sizes and cluster size distributions that resulted from combinations of existing models in the literature. Critical pigment volume concentration values were evaluated both experimentally and theoretically to try to elucidate new ways to evaluate and control the formation of foams formed from pigment clusters in both coatings and polymer formulations. The control of pigment cluster foams appears to be most easily achieved by minimizing the ultimate critical pigment volume concentration and optimizing the amount of dispersing agent added to the formulation. The ultimate critical pigment volume concentration was proposed to be optimized by blending pigment particles with different particle shapes and different random packing fractions. Minimizing the cluster dispersion coefficient, Cq, was found to be very important to keep the viscosity within controllable limits. Although experimental measurement of the parameters to isolate the clustering concepts introduced in this study may be difficult, it is expected that better quantitative measurement of clustering concepts will eventually prove to be very beneficial to providing improved suspension applications involving pigment cluster foams. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012