These filter papers are a little thicker than Grade No. 1. Medium crystalline precipitates (8 µm) are retained. Initial filtration speed (ASTM)* is 55 seconds. Surface is smooth with normal hardness. Loading capacity is normal. 0.7 mg of ash content per 12.5 cm circle. (For cost savings, see Ahlstrom equivalent, 446-200-10 Series)

*Time for 100 ml clean (prefiltered) water to pass through a 15 cm quadrant folded circle.