Filter Paper, Qualitative, Grade 1, 185 mm Pack of 100 sheets. Supertek Qualitative filter papers are made from virgin cellulose fiber. Grade 1 filter papers are suitable for medium flow rate and medium retention applications. Grade 1 filter papers are the most widely used in general laboratory use. They are frequently used to purify or clarify liquids. They are frequently used to separate precipitates or sediment from liquid for further analysis. Supertek Grade 1 Filter Paper will retain particles down to 9 nanometers in size. Very useful in waste water treatment, soil analysis or seed testing, education and in the commercial food industry,