Filter papers with medium size are available in a wide range of diameters, including small sizes from 65 mm to 115 mm, specifically suited for laboratory soil testing applications such as triaxial testing, consolidation, or one-dimensional swelling test with filtration during sample preparation, and geotechnical testing procedures. The consistent quality and dimensional accuracy ensure reliable performance in routine and research-based soil testing workflows.
Note that the filtration speed of the filter papers is defined by the time required for 10 mL of distilled water to pass through a 10 cm² effective filtration area at a controlled temperature of 23 ± 1 °C. Based on this standard test condition, the filter papers are classified into three grades: slow filtration (3–4 µm) with a filtration time of less than 35 seconds, medium filtration (7–8 µm) with a filtration time of 35–70 seconds, and fast filtration (10–12 µm) with a filtration time of 70–140 seconds.
