The aperture tells us the diameter of the largest sample that would pass through the mesh; it is important to take into account the shape of the hole, as the results will be different if we use a mesh with a 212µm square hole compared to a 212µm perforated round plate. To pass through the sieve, particles must be smaller than the mesh openings. The particle may have another dimension longer than the aperture and still pass through, but if it is too long, it may take longer to pass through the sieve.
Types of sieves
Sieves are classified into 3 different groups:
- Woven Wire Sieves: Composed of a wire mesh welded to a frame, this is the "classic sieve." They can be identified by the sieve aperture (in mm (when it is greater than or equal to 1.00 mm) or in µm (when it is less than 1.00 mm)). Also known by the term "Mesh," it tells us the number of openings per English inch (1" = 25.44 mm.).
- Perforated Plate Sieves:Consist of a perforated metal plate, which can have a square, round, or rectangular aperture (welded to a frame). They are used from a 4.00 mm aperture upwards.
- Electroformed Plate Sieves: In this group of sieves, the plate is usually made of nickel. The aperture ranges for these sieves include from 2.00 mm down to 3µm. They are characterized by their superior precision, in addition to offering non-standardized aperture dimensions.