Water, glycerol and their mixtures having viscosities in the range 1-1340 mPas were subjected to electrostatic atomization at a constant applied voltage and flow rate. The conductivity of the liquids were kept approximately equal by adding citric acid and their density, relative permittivity and surface tension values were measured. The electrospray was deposited on silicone release paper and the size of the relics produced were measured. Results show that the increase in viscosity had a significant effect on the mode of atomization and increased the size and size distribution of relics obtained. (C) 2002 Elsevier Science Ltd. All rights reserved.