GB/T 3780.17 - 2008 is a standard for indirect measurement of carbon black particle size, using the reflectance method. The standard specifies the steps from sample preparation, instrument calibrating to reflectance measurement and particle size calculation. Particle size is an important parameter of carbon black, which affects its performance and application. This standard provides carbon black production, testing and use enterprises with a unified and convenient indirect particle size measurement method. Without complicated direct measurement methods, particle size data can be accurately obtained, helping to control carbon black mass and promote the efficient application of carbon black in rubber, inks and other industries and product mass improvement.