GB/T 21868.6-2008 "Dispersion method for evaluating the dispersibility of pigments and extenders, Part 6: Dispersion with a three-roll mill" specifies the method for dispersing pigments and extenders using a three-roll mill. This method is suitable for high viscosity grinding materials, and the test results can reflect the effect of product dispersion in production equipment. This standard needs to be used in conjunction with the assessment method of GB/T 21867 and GB/T 21868.1. The advantages of the three-roll mill are that it is easy to operate, easy to clean, and the dispersion result can correspond to the dispersion effect of the production Machinery. It is an important tool in pigment quality control.