The paper describes the background to development of a methodology to characterize frothers based on two-phase tests using gas holdup and froth height as the hydrodynamic and froth parameters, respectively. The data showed patterns, that frothers could be grouped into classes, and could be moved from one class to another by chemical modification. As a result of this better understanding of the interdependence of hydrodynamic/froth parameters and chemical properties, frothers based on ethoxylated butanol (ButOH-nEO, with n = 1.5-3) were identified as potential substitutes for MIBC. Batch flotation tests and a plant trial showed successful substitution but one application suggested that the new frothers were more sensitive to the contribution of particles in froth stabilization. Inspection showed the new reagents gave a more soap-like froth than MIBC. Ethoxylated butanols offer a range of properties: by changing the number of ethoxy (EO) groups products could be made slightly weaker or stronger than MIBC but the chemistry cannot provide hydrodynamic/froth characteristics similar to frothers like glycols and glycol ethers. (C) 2008 Elsevier Ltd. All rights reserved.