Made of pure cellulose treated with hydrochloric and hydrofluoric acid, filter papers are used for straining with good retention and flow rates. These cellulose filters create a semi-permeable barrier perpendicular to a liquid or airflow in order to separate fine substances from liquids or air. Different grades of filter paper are available for performing various laboratory applications including routine lab work, ranging from coarse to fine filtration of particulates. VWR offers a wide range of qualitative and quantitative filter papers with varying pore size, particle retention, flow rate and filtration times.