Development of electrostatic images

A developing material for use in the development of electrostatic images comprising toner particles and carrier particles is described wherein the developing material incorporates at least one solid hydrophobic bivalent or trivalent metal salt of a half-ester of a branched-chain or straight-chain aliphatic dicarboxylic acid and/or at least one bivalent or trivalent metal salt of a monoester or diester of a phosphorus oxyacid. The images obtained by means of this developing material have an improved image contrast, solid area coverage and surface smoothness. The toner particles show less tendency to cake and agglomerate and have improved mechanical strength. Cleaning of the imaging surface between use and re-use is also facilitated.