Suitable for filtering are common coffee filters or blotting paper, which reliably retain the solid clumps. A light powder sediment of pigments may well remain desirable after filtering. In general, manufacturers advise against mixing different inks, since chemical reactions can occur; with old iron-gall inks, the deposits are typical components that have thickened over time and are usually not mould. With filtered old IG ink, good writing results can still be achieved on suitable paper.