A major challenge in the processing of PGM-bearing UG2 ore is the fact that it is comprised largely of chromite (60-90% by volume). Chromite is generally not naturally floatable but significant quantities report to the concentrate by entrainment. This is a serious problem for the downstream smelting process, which is generally constrained to a grade of about 3% chromite. Four of the most accessible levers for the control of flotation performance which are available to a plant metallurgist are frother and depressant dosage, air flow rate and froth height. The effects of each of these factors on the flotation performance have been extensively studied, but interactive effects are not well understood. This study presents the results of an investigation into the interactive effects of these parameters using a factorial experimental design approach. The flotation tests were carried out using a 2 m high continuous column flotation cell which facilitated the generation of a deep froth, since this was the phase of most interest. The results were analysed using statistical analysis software that fitted a regression model to the data for each of the outputs. These results highlight the interactive effects of these variables on the flotation performance and illustrate the complexity that is required in process control. (C) 2014 Elsevier Ltd. All rights reserved.