A method of preparing an aqueous dispersion comprising metal particles of mean diameter from 0.5-200 nm by weight and an aqueous carrier liquid, including the steps of i) providing a mixture comprising at least one metal salt, aqueous carrier liquid and a stabilizer for the particles ii) contacting the mixture with a reducing agent to form a reaction mixture iii) causing the at least one metal salt to react with the reducing agent to form a dispersion comprising metal particles and acid wherein step iii) is partly or completely performed in the presence of anion exchange resin whereby the acid is exchanged for a hydroxide ion from the resin and/or is sorbed by the resin.