The variation of air holdup and stability of colloidal gas aphrons (CGAs) with stirring time, surfactant concentration [6, 8.1, 10, and 12 mM sodium lauryl sulfate (SLS)], and stirring speed (3500-7000 rpm) was investigated, and an empirical correlation between the air holdup and stirring time was obtained. A first-order model for the drainage of CGAs was proposed and it correlated very well with the experimental data. A population balance model was proposed and correlated to the first-order drainage model to obtain an expression for the size distribution of CGA bubbles. A narrower size distribution at large stirring times was observed, which was correlated to the stability of CGAs. The stabilization of CGA dispersion with attainment of equilibrium size distribution at longer stirring times, analogous to homogenization of emulsions, was observed and an empirical expression for this time was reported. Mixing of two oppositely charged CGAs, generated using SLS (anionic) and cetyl trimethyl ammonium bromide (CTAB) (cationic), showed no effect on their stability, air holdup, and drainage kinetics. (c) 2005 American Institute of Chemical Engineers.