Segregation is a major problem for many solid processing industries. Differences in particle size or density lead to flow-induced segregation within the surface layer. Here we examine methods of avoiding radial segregation in a horizontal drum mixer. Recently, it has been suggested that segregation in this type of particle mixer can be thwarted if the sheared (surface) regions of the bed are inverted at a rate above some critical frequency. Further, it has been hypothesized that the effectiveness of this technique can be linked to the probability distribution of the number of surface layer "passes" a particle takes per rotation of the drum. In this article, various baffle configurations are numerically and experimentally studied to investigate the efficacy of this measure as a design heuristic for the development of improved drum mixing devices. We choose the horizontal drum geometry as it represents the simplest possible example of a tumbler-type mixer, however, we expect the results found here regarding the efficacy of our design heuristic to be generic for any surface-dominated mixing device. (C) 2013 Elsevier B.V. All rights reserved.