The NIST Reference Materials, #30 to #325, is a set of three 150g bottles of different sands for use in sieving. Material A is the coarsest for testing sieves from No.30-No.100. Material C is for No.70-No.200 sieves and Material D is for finer sieves, No.100-No.325.
Percent of glass beads retained on each sieve is calculated, and effective opening of each of the sieves is determined from calibration data on the NIST Certificate supplied with the bead set.
