Organic solvents were evaluated through the determination of froth volume and bubble collapse rate in a froth column meter under various solvent dosages and aeration rate levels. There is a non-linear relationship between the froth volume and the gas flow rate for polyglycol ether type solvents. It is inappropriate to apply the concept of linearity retention time to describe the frothing characteristics of polyglycol ethers. Two new parameters are derived to characterize the foam stability and non-persistency of the frothers. The new parameters are initial dynamic froth index (IDFI) and initial dynamic froth collapse rate (IDCR). IDFI represents the froth volume formation properties, and can be used to relate to the ultimate recovery, Rm, and the flotation rate constant, K. IDCR describes the non-persistency of the froth, and can be used to relate to the quality of flotation concentrates. IDFI value depends on chemical structure and molecular weight of a solvent. Increasing solvent molecular weight and number of hydrophobic groups increases the IDFI value. Both ultimate recovery and flotation rate constant can be maintained at a desirable level, if the solvent dosage is applied in the amount to give the same product value of IDFI and solvent dosage. The selection of potential frothers from solvents tested is made by using IDFI and IDCR and comparing with laboratory fine coal flotation performance. (C) 2006 Elsevier Ltd. All rights reserved.