The size of bubbles in flotation cells was measured using the UCT bubble size meter and the HUT bubble size analyser. While both methods provided similar critical coalescence concentration (CCC) values for the three tested frothers, they also revealed important differences. Using the HUT bubble size analyser, which does not impose any lower bubble size limit, it was possible to find differences in bubble size measured for three frothers at concentrations exceeding the corresponding CCC values. Frothers affect both the break-up phenomena in the impeller/stator zone in flotation cell, and bubble coalescence. While longer chain polyglycols (e.g. DF-1012) are able to produce larger stable bubbles than the short chain DF-250 and DF-200 polyglycols, the CCC values for DF-1012 are lower than those for DF-250 and DF-200. (c) 2005 Elsevier B.V. All rights reserved.