AbstractWhen mechanical foambreakers are used in chemical engineering processes to control an undesired primary foam, a secondary foam is often produced. Secondary foams consist of small bubbles, have a high liquid hold‐up, and cannot be condensed further by mechanical foambreakers. Secondary foams can be converted into liquid and gas in a coalescence column by drainage, diffusion, and breakage of the lamellas. This paper presents a new model to determine the velocity of bubble growth and the time of coalescence of secondary foams. The experimental investigations have been carried out with surfactants in aqueous solutions.