A series of paints at varying pigment volume concentration (PVC) has been prepared in several vehicles to demonstrate the general principle that the lightness or darkness of a paint varies widely depending upon the PVC. The change is most noticeable at the critical PVC (CPVC) below which all of the air pockets in the pigment-vehicle mass are filled with vehicle and the paint is usually in a dark condition, and above which the lightness of the paint in creases with PVC, owing largely to the presence of increasing amounts of void-space.