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Sizing by sifting with screens. Viewed physically, screening comprises superposition of segregation, diffusion, and passage through the screen. Frictional and cohesive forces have to be overcome and the coarse feed material transported over the screen, primarlily by circular, elliptical, or linear vibration. The specific screening performance and the sharpness of separation prove to be a measure for the quality of screening. There are three uses for screening: protective screening with mean particle size D m ≪ mesh w with a simultaneous wish for high screen performance; classification with D m ≈ w with a desire for greater sharpness of separation; and dust removal with D m ≫ w and the problem of deagglomeration, i. e. separation of fines from the screened material. The maximum screen performance can be calculated for the coarse range; it is attainable with most screening machines. A problem encountered in the medium to fine size range is prevention of blinding of the screening machine and deagglomeration of sieved material, with attrition phenomena deserving attention. A range of machines is available: casting, planar, tumble, agitator screening machines are available, as are those with deforming screens, those utilizing centrifugal forces, and, as the latest addition, flow screening. New developments concentrate on fine screening, e. g. screening machines with direct activation of the screen fabric, tumble screening machines, combinations of mechanical and pneumatic screening extending through to pure flow screening. Plastic screens made of polyurethane are of advantage for wet screening; they exhibit greatly reduced wear. Safety requirements are met by silenced and explosion‐proof‐screening machines.