Polymeric depressants (modified guars and carboxy methyl celluloses) are used in the flotation of platinum-bearing ores in South Africa to reduce the recovery of naturally floatable gangue minerals such as talc. These polymers have always been considered to weakly adsorb (via physical adsorption forces) on gangue minerals and consequently the adsorption is considered to be an equilibrium process and therefore reversible. Micro-scale flotation tests on a talc sample showed that the floatability of the talc could be completely reduced by the adsorption of these polysaccharides but could be restored, depending on the conditions, by washing with water showing that the adsorption is reversible in a pure water system. (c) 2005 Elsevier Ltd. All rights reserved.