Abstract This work describes the effect of flotation operational variables on the solids loading in bubble lamellae on the surface of flotation froths. For this purpose, a series of industrial experiments in two copper concentrators were carried out to sample the solids in the bubble films under different steady state operating conditions. Samples of the lamellae were taken by touching the top surface of the bubbles with a glass slide. The amount of solids per unit area in the bubble lamellae was determined gravimetrically and by image analysis. Also, the grade of the solids in the bubble lamellae was measured. The operational variables under study were air flowrate, froth depth and frother concentration and were varied to allow statistical interpretation of the results. It was found that the solids loading in bubble lamellae decreases when increasing the air flowrate and increases with an increase in the froth depth. There were no clear trends in the solids loading when varying frother concentration alone although its interaction with other variables is statistically significant. The grade of the bubble lamellae measured was almost constant under different operating conditions.