This part of GB/T 3780 stipulates the method for measuring the coloring strength of carbon black for rubber by using the reflective blackness meter (hereinafter referred to as the blackness meter) compared with the industrial coloring reference carbon black (ITRB), and the standard Reference carbon black 3# (SRB3#) is used as a benchmark for comparison, and the method of measuring the tinting strength of pigment carbon black with a blackness meter. This part applies to various types of carbon black for rubber and various types of pigment carbon black.