The kinetics of industrial flotation are studied with special reference to grain size, chemical conditioning and liberation. Related models are derived for batch flotation in the laboratory and for continuous flow flotation in a plant. For practical testing of their relationships, specimens of regular mineral and samples from the output of an industrial conditioner are floated in a laboratory cell and radioactively labelled specimens of the same mineral in a plant cell. Timed samples of concentrates and tailings are collected and classified, and kinetic coefficients are evaluated in each case for different grain size and conditioning. Use of these data in theoretical models provides consistent results. The quantitative relationships of the kinetics in laboratory and plant delivered by the method have a central role in the scale-up of flotation from the laboratory to a plant cell, including that of the effects of various control inputs. The dynamic flotation models obtained are reduced to steady state and can then be used for model construction and control design of larger flotation plants.