This work is a study of the effect of liquid properties and pore size on the initial bubble size distribution of a bubble column equipped with fine pore sparger. Various liquids covering a wide range of surface tension and viscosity values are employed, while the gas phase is atmospheric air. A fast video recording technique is used for both the visual observations of the phenomena occurring onto the sparger and the bubble size measurements. A new correlation regarding the prediction of the initial mean Sauter diameter of bubbles formed from porous spargers at the homogeneous regime has been formulated and found to be in good agreement with available data. The experiments show that the mechanisms of bubble formation as well as the initial bubble size distribution depend strongly on the liquid properties, the sparger design and the gas flow rate. (c) 2007 Elsevier B.V. All rights reserved.