Abstract: A method and device (20) for spraying particulate materials in which a high voltage is applied to a mass of the particulate material so as to cause particles to issue from the mass. High voltage from a source (16) is applied to a mass of material (36) stored in a container. A surface of the mass (36) is exposed to the surroundings and the applied voltage is conducted through the bulk material to particles located at the exposed surface which are thereby projected as an electrically charged spray from the mass under the influence of the electric field substantially without any accompanying corona discharge.

Abstract: A high voltage generator is provided for use in applications where current demand is low but a high voltage is required. The generator comprises an array of photosensitive elements, such as an array of photovoltaic elements produced by laser scribing or etching of a wafer of material conventionally used for solar cells, the number of elements employed and their interconnection being such that a high voltage output of at least 1 kV is obtained.

Abstract: An electrostatic spraying device for spraying liquids comprises a hollow capillary structure having a convoluted inner surface, one end of which contacts a reservoir of an electrostatically sprayable liquid preferably having a viscosity from 1 to 20.times.10.sup.-6 m.sup.2 /s and a volume resistivity from 2.5.times.10.sup.6 to 5.times.10.sup.8 ohm cm, the other end of which terminates in an atomization tip, and means for applying high voltage to the liquid in order to cause the liquid at the atomization tip to break up into a plurality of electrostatically charged droplets. Cartridges for use in the electrostatic spraying device are also described.