Methods for estimation or measurement of particle loading on bubbles in the flotation process are reviewed. The paper focuses on direct measurement methods developed under the direction of Moys at the University of the Witwatersrand and by Seaman and co-workers at the JKMRC, Brisbane, Australia. Deficiencies in both designs are identified and a new design which deals with all these deficiencies is proposed. A hydrodynamic model for this version is developed and tested in a water-only environment, then tested on the copper flotation plant at El Teniente. It was found that the new design had successfully dealt with prior method deficiencies and provided a very precise (relative standard deviation equal to 0.72%) measurement of the loading on the bubbles in five tests. (C) 2009 Elsevier Ltd. All rights reserved.