Froth stability plays a major role in determining the mineral grade and recovery in flotation operations, and it depends on the type and amount of both frother and suspended particles. Furthermore, there are other parameters such as quality of the process water which may affect the froth stability. In plant practice, the recycling of process water instead of using fresh water is increasingly being common. However, using recycled water normally leads to building up salts and surfactants in solution. Therefore, the effect of the process water chemistry on froth stability and metallurgical performance is important. In this study, the effect of water quality, including pH, and type and concentration of salts (CaCl2, AlCl3 and NaCl) on froth stability and its relationship with mineral particles zeta potential and slurry viscosity was studied. It was found that the forth stability is higher in the presence of multivalent metal ions. Addition of CaCl2 and AlCl3 considerably increased both froth stability and pulp viscosity. This may be due to bridging effect of polyvalent metal ions between the ore particles. (C) 2012 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.