A process for preparing a dispersion of a particulate solid comprising: dispersing a particulate solid with a dispersant and a liquid medium, wherein the dispersant is a random copolymer obtained or obtainable from the copolymerisation of a composition comprising: i) one or more monoethylenically unsaturated hydrophilic monomers, ii) one or more monoethylenically unsaturated hydrophobic monomers, iii) one or more di- and/or higher-ethylenically unsaturated monomers, and iv) one or more chain transfer agents; wherein the dispersion step is effected by a mechanical treatment which reduces the particle size of the particulate solid.