A study of the gas motion through the froth of a prototype bi-dimensional flotation cell was performed. Using video and image analysis techniques, surface velocity data measured with a Visiofroth system were validated by comparing those results with estimations from manually tracking the motion of the bubbles on the froth surface. Images used to manually track the bubbles were recorded using a high-speed video camera. In addition, discharge velocity profiles were measured as a function of the froth height over the launder lip for two froth crowder angles and two superficial air rates. An increasing froth discharge velocity from the lip level up to the top of the froth was observed. Based on these results, the air recovery was estimated using the velocity profile and these values were compared with those obtained using the surface velocity estimation. Results showed differences from 24% to 47% in the air recovery when the froth flow area at lip was employed. However, both approaches presented the same trend when the J(G) and the froth crowder angle were changed. Using the top-of-froth velocity along with the froth flow area at the Visiofroth location allows air recoveries to be closer to those obtained from the discharge velocity profile at lip. The water flowrate in concentrate was estimated from operational variables and compared with the water flowrate measured in the concentrate stream. A good agreement was observed when the discharge velocities obtained from the Visiofroth measurements along with the froth height over the lip at the measurement point were employed. Similar results were obtained when the water flowrate was estimated using the discharge velocity profile at lip. An increase in the air recovery as a function of the froth crowder angle and the JG value was observed. Also, the combined effect of these variables showed a significant impact on the air recovery. A higher concentrate water flowrate was observed when a higher air recovery was obtained. This result favours the concentrate grade decreasing due to the entrainment of non-valuable fine particles. A proper flotation equipment design along with an optimizing control system can improve the metallurgical results in terms of mineral recovery and concentrate grade. (C) 2012 Elsevier Ltd. All rights reserved.