The fineness of grinding or the degree of dispersion of the paint can be measured.

One type consists of a steel block having two shallow grooves, the shoulder of which taper from two thousands of an inch to zero. A small blob of the paint under test is placed in the deep end of the groove and drawn down with a scraper blade. The graduation marks at which pigment particles begin to be plainly observed as protruding through the surface of the paint in the groove

is taken as the index of the degree of dispersion. This type of gauge is known 95/5 Hegman gauge.