Experimental methods based on light beam deflection for the determination of surface stress change of electrodes are critically revisited. Expressions for the evaluation of data from electrochemical bending beam experiments with non-normal light incidence are derived. Consequences of neglecting the refraction at the optical window or at the air/solution boundary are discussed. It is shown that the data analysis in previous work needs revision, since neglecting the refraction may introduce severe errors in the calculations, and this can lead to inconsistencies in the interpretation of the experimental results. (C) 2005 Elsevier Ltd. All rights reserved.