Production of an electrosuspension of particles (5), comprising an insulating container (3) fitted with two spaced apart electrodes (2, 4) between which a high electrical potential is applied. At least one of the electrodes (2) is mounted for rotation by an associated electric motor (20). The electrode mounted for rotation preferably has a drum like configuration formed by a plurality of circumferentially spaced apart conductors (6). In a second aspect the invention produces an electrosuspension of micronised particles where one of the electrodes is in contact with a bed of particles and a second electrode is spaced above the particles. Field concentrating conductors are connected with the second electrode to generate ions and irradiate the surface of the particulate material with ions of opposite polarity to the first electrode.