An analytical model has been used to describe the composite scale formation of calcium oxalate monohydrate (COM) and amorphous silica (SiO2) in sugar solutions. The model incorporated the effects of the liquid bulk subcooling and deposition consolidation process arising from microlayer evaporation under subcooled nucleate flaw boiling. The proposed model was shown to provide a better fit to the COM-SiO2 composite fouling data than models considering only particulate fouling or silica deposition over a range of process thermal hydraulic parameters which included,surface temperature, fluid velocity and bulk subcooling. For a better description of the composite fouling process in sugar factory, it is suggested that the effects of solution pH and composition on composite fouling be considered in,future work. (c) 2005 American Institute of Chemical Engineers