GB/T 3780.21-2016 specifies the method for the determination of carbon black residue on sieve by the water washing method. It details everything from sample preparation and flushing operation process, to sieve selection, flushing time control and residue on sieve collection, and also clarifies the result calculation and reporting requirements. The content of residue on sieve affects the quality and application effect of carbon black. This standard provides a unified specification for carbon black production, testing and use enterprises, which helps to accurately control the carbon black mass, ensure that it meets the needs of downstream industries, promote the stable and efficient application of carbon black in various fields, and promote the standardization of black carbon industry testing.