Ahlstrom’s qualitative grades of filter paper are, by definition, recommended for use in analytical methods, which determine or identify particulate constituents of a mixture irrespective of the amount present. Qualitative filter papers are often used in routine separation work that still requires high purity and consistent performance. Ahlstrom offers a complete range of low ash filter papers for general laboratory work that provides you with the correct combination of particle retention, filtration speed, loading capacity and wet-strength. All our qualitative grades consist of > 95% super refined a-cellulose and linter fibers. Qualitative analysis Low ash content 0.06% Untreated Consistent performance Wet-strengthened grades available Custom cut Bulk packaging Standard Grades (Non Wet-Strengthened) 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. Ahlstrom 617: 35µm – Fast Speed This is an extremely fast filtering grade and has a larger particle retention than Ahlstrom 631. Ahlstrom 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. Ahlstrom 617 is also found in construction product testing and is used by students to retain large flocculents and precipitates.