Wet-strengthened, very slow filtration, smooth. These wet-strengthened hard filter papers are manufactured from refined pulp and linters and have a low ash content of < 0.01 %. They are often used for quantitative routine procedures and for analytical gravimetric applications. Due to their high mechanical strength in wet condition they are particularly suited for applications, where the residue is removed from the filter e.g. with a spatula or a jet of water.