Examples of surfactants which can be added to the aggregates before coalescence is initiated are anionic surfactants such as sodium dodecylbenzene sulfonate, sodium dodecylnaphthalene sulfate, dialkyl benzenealkyl, sulfates and sulfonates, abitic acid, available from Aldrich, NEOGEN R???, NEOGEN SC??? obtained from Kao, Biosoft D-40??? obtained from Stepan, and the like; nonionic surfactants such