Sieving

Sieving is a mechanical separation process that uses a sieve, a device containing a mesh of defined openings, to separate particles according to size. When a sample is passed over or through the sieve, particles larger than the mesh are retained while smaller particles pass through. A common laboratory setup uses a stack of sieves with progressively smaller openings placed over a collection pan; the sample is placed on the top sieve and subjected to vibration or shaking. Dry sieving is most common, though wet sieving is used for sticky or cohesive materials and can improve separation by reducing static or clogging.

Standard practice often records the distribution of particle sizes by weighing the material retained on each sieve, yielding a particle-size distribution. The terminology is tied to the sieve sizes, often described by sieve indices (such as No. 8 or 200) or by pore size in millimeters or micrometers. Sieve analyses are widely used in geology (grain-size distribution of soils and sediments), civil engineering (quality control of aggregates for concrete and asphalt), and materials science (powder characterization), as well as in food and pharmaceutical manufacturing for quality control.

The term sieving also appears in mathematics as a different concept—the sieve methods, notably the Sieve of Eratosthenes, used to identify prime numbers.