Poor water fastness of modern writing materials handicaps the restoration preservation of materials. The most vulnerable are those containing water-soluble ionic dyes (fountain pens, fibre-tipped and liquid ballpoint pens, copy pencils and certain stamping inks). Some dyes, such as the important blue ink types, react relatively quickly with water to form colourless carbinols, even around ph7. Investigations have made it possible to strengthen water soluble ink dyes on paper by using fixing agents. Polycationic and polyanionic compounds which form almost water insoluble complexes with oppositely charged dye ions are especially suitable for this purpose. Waterfastness of ink colourants on paper is improved so that legibility of inscriptions is usually maintained even after deacidification with magnesium bicarbonate. No evidence was found that the treatment increases degradation of the paper. This technique may enable mass treatment of archival materials using aqueous methods.