The interaction forces between "particles" present in Bayer liquors have a major influence on the mechanism(s) underlying seeding, precipitation and coagulation. To date these forces have not been explored in the Bayer process. However there is a strong quantitative base for interparticle forces and they have been successfully measured in other systems. The origin of these forces, whether they be electrostatic, van der Waals, or structural, is identified, several mathematical forms quantified and selected measurement techniques are discussed. Examples drawn from the literature, as well as from systems studied in the Ian Wark Research Institute are examined. The significance of the results obtained and their relevance to the Bayer process are highlighted.