The recovery and grades of a coal flotation concentrate are significantly dependant on the water content of the overflowing froth. The drainage of water from the froth is associated with the coalescence and bursting of bubbles in the froth. This work was undertaken to investigate the possibility of regulating the performance of a flotation cell by using Image Analysis to define a desired bubble size in the concentrate, and subsequently to use measured deviations to control bubble coalescence by the compensating addition of surfactants. The image analysis was done on a transputer-enhanced Micro Var computer off-line, using video images of experimental semi-batch runs. Individual runs were done using a single surfactant which had to act both as a frother and collector, two surfactants 2-ethyl hexanol and Triton X-405 being used. Data from the image analysis was interpreted together with experimental measurements of particle and water recoveries in terms of a previously formulated froth kinetic model. Correlation of the point rates of overflow of dry-mineral-matter-free (dmmf) coal in terms of the model produced physically plausible parameters.