Sifting

Sieving of granular material is limited by the availability of mesh sizes and by the particle's ability to pass through them voluntarily. Once particle size drops below around 50 µm (0.050 mm), conventional sieving becomes technically impossible.

The 'micro grain range' refers to grain sizes finer than 58 µm. These can no longer be determined using vibrating sieves, but rather through methods such as sedimentation or laser diffraction (laboratory analysis). During production, the grains are fractionated using air classification techniques (sifting). The grain size distribution is specified by the 50% value (D50) as well as the 3% (D3) and 94% (D94) values.