Binder distribution onto binary mixtures of glass spheres.

Glass spheres (0-8 and 0-4 cm diam.) in differing weight ratios were treated in a rotating pan with four pharmaceutical binder fluids. Binder uptake for a sphere of 1 g was greater onto the smaller spheres irrespective of binder or wt ratio used. There were differences in uniformity of uptake, the solution binders (PVP and gelatin) being more evenly distributed than the mucilaginous binders (starch and methylcellulose). Binder distribution on the basis of unit surface area showed less obvious differences between the sphere sizes. Possible consequences of such binder distribution through powder aggregates are discussed.