The adhesion phenomena of monodispersed barium sulfate (BaSO4) particles on gelatin-coated glass beads were evaluated using the packed column technique and compared with the same system in the absence of the protein. Multilayer deposition was observed with the uncoated glass beads at pH 4, 5 and 6, while at pH 9, which is above the isoelectric point (pH similar to 6) of BaSO4 particles, monolayer deposition took place, even though the BaSO4 particles and glass beads bore the same sign of charge. At pH = 10, no uptake was observed on the glass beads, but the addition of 10(-4) mol dm(-3) BaCl2 induced multilayer deposition due to the adsorption of the Ba2+ cation on BaSO4 particles, which causes a reversal of their charge to positive. The formation of multilayers was found to occur over a much wider pH range on the gelatin coated glass beads. BaSO4 particles deposited in multilayers could not be removed from either glass beads or gelatin-coated glass beads by rinsing the loaded column with solutions of pH 11.5, but could be detached from monolayers on glass beads only.