This paper describes a frit and sleeve sparger designed to control the size of bubbles produced. The design comprises a porous ring (frit) surrounded by a sleeve through which water is passed to generate shear. A prototype is described and results confirm that bubble size can be controlled independent of gas velocity and is governed by the shear in the annular gap between the frit and sleeve independent of gap size. (C) 2007 Elsevier Ltd. All rights reserved.