The purpose of this study is to report several significant findings made during a more comprehensive study of post-reaction changes occurring during cleaning and storage of latices, and the consequent effect of these on the surface characteristics. These relate mostly to the soap-free polymerization technique where conversions of monomer to polymer seldom proceed to 100% and consequently large amounts of reactants and reaction products have to be removed. Polystyrene latices in particular are considered since the great majority of work on 'model' polymer latices is concerned with this polymer.