This work presents experiments and theory describing a mechanism for how brighteners in electrolytes function. The mechanism involves change of local coverage of a deposition rate-enhancing catalyst adsorbed on the surface through change of local surface area during growth as well as accumulation and consumption. A first-order perturbation analysis shows the surface is stable against growth of perturbations for all wavelengths below a critical value that is deposition-condition dependent. The model predictions are shown to be consistent with the experimental results. (C) 2003 The Electrochemical Society.