Ahlstrom 617 is an extremely fast filtering grade and has a larger particle retention than Grade 631. Grade 617, a thicker filter paper with higher loading capacity, is used for rapid filtration of coarse particles and gelatinous precipitates such as in oils and resin solutions. Grade 617 is also found in construction product testing and is used by students to retain large flocculants and precipitates.

Standard qualitative filter papers are suitable for quadrant folded or gravity flow applications. These grades contain a high level of alpha-cellulose that provides high purity but will weaken when wet. The inherent strength of standard (untreated) grades does not pose a problem when they are used in routine quadrant folded applications. We do not recommend these grades for use in vacuum work or when wet handling is required.