Sodium zinco/stanno/titano-silicate is synthesized by mixing a concentrated aqueous sodium zincate, stannate or titanate solution with a source of silica (e.g. powdered glass or sodium metasilicate solution) in the ratio 60 g sodium silicate to sodium zincate equivalent to 8.1 g zinc oxide, keeping the temperature at 40.degree. C. for 1/2 hour, diluting threefold with water of 20.degree. C., allowing a precipitate to form overnight, and filtering and drying the residue at 110.degree. C.The resulting sodium zincosilicate may be used in its own right as a water softener or may be converted by cation exchange into any other desired zincosilicate.