This study concerns aerosol particles of mixed composition. The particles contain a water insoluble core (polystyrene latex), surrounded by a water soluble shell (various fluorescent dyes). A Collison nebulizer and an electrostatic aerosol classifier are used to prepare the aerosol; its critical supersaturation spectrum is measured with a diffusion cloud chamber. Experiments were done using four different dyes (disodium fluorescein, sulforhodamine 640, sulforhodamine B and rhodamine 560 chloride) with five different polystyrene latex sphere sizes. The results indicate that a Kohler-type behavior is obeyed. This technique of putting a soluble coating onto an insoluble core is found to be a successful method for generating particles with relatively high critical supersaturations. © 1992.