Computer simulation of sieving was done in order to determine the proper amount of time required to completely sieve a sediment sample. The program is based upon an algorithm published by Ludwick and Henderson (1968). The results suggest that the lower bound for the time to completely sieve a sediment sample into 1/4 Phi intervals is 50 min. The upper limit was found to be 109 min. It. is suggested that either new methods or mechanical analysis or better theories of sieving must be developed.