This paper describes in terms of the mass of the solvents in the oil, water, and distillate phases the curing process of highly spheric monodispersed 4-mm-in-diameter polystyrene capsules of a uniform thickness. It was determined that the water solubility of the solvents is crucial in the solvent selection in order to prepare the capsules by this method. The curing process started from the water/oil/water emulsions, where the boiling temperature and the densities of the oil were well matched by mixing benzene and 1,2-dichloroethane. The masses of the solvents were measured for the oil phases and the distillate and then calculated for the water phase. The analysis of the solvents in the water phase indicated that the process was governed by the kinetics of their dissolving from the oil phase to the outer water phase rather than by the vapor pressure of the solvents in the early stage before the oil phase lost its fluidity.