1.1 Standard test sieves that conform to ASTM Specification E ll (Table 1) are referred to as U.S. Standard Testing Sieves and should always be used in a test sieve-based particle size measurement program. This series of test sieves, based on the principle of a fixed ratio of 4√2:1 between the sieve openings, was first introduced in the United States in 1910 and since has achieved worldwide use. The concept was pioneered by Peter Ritter von Rittinger of Austria in 1867. The number of sieves in the series and the spacing of the openings in the scale have been proved, by over 90 years experience, to be ideal for the separation of particulate materials according to designated size analysis using sieves. Since 1910, many countries have adopted national sieve standards based on the same fixed ratio as the U.S. Series