The collection of hydrophobic particles in the froth phase in flotation has been studied. A continuous flotation cell was developed, in which the froth phase could be isolated from the pulp zone. Hematite particles, d(80) = 87 mum, were floated in the pulp, using a conventional oleate collector, while glass particles of similar diameter, d(80) = 82 mum, were introduced in wash water added to the froth. Four samples of glass particles, with contact angles between 0degrees and 82degrees, were used. The results indicate that the efficiency of collection of the hydrophobic particles in the froth can be very high. The process is strongly influenced by the hydrophobicity of the particles and the surface area available for attachment in the froth. Recommendations for the flotation of particles in the froth phase are made, especially regarding the desirable hydrophobicity as reflected in the contact angle, the froth depth, the solids concentration in the feed to the froth, the air rate and wash water rate. (C) 2002 Elsevier Science B.V. All rights reserved.