Efficiency of sieving is indicated by the percentage of finer near-mesh particles that fail to pass through any sieve. The percentage of finer particles retained is a function of the load on the sieve and the length of time of sieving. A graph shows maximum loads for 3-inch diameter sieves at one-fourth and one-half phi intervals. The maximum load is set at five particles per aperture. Sieving time is ten minutes.