The invention involves a method of preparing an alkaline-earth metal oxide-containing polishing pad useful for polishing at least one of semiconductor, magnetic and optical substrates. The method includes introducing a feed stream of gas-filled polymeric microelements into a gas jet, the polymeric microelements having varied density, varied wall thickness and varied particle size. The method passes the polymeric microelements in the gas jet adjacent a Coanda block, the Coanda block having a curved wall for separating the polymeric microelements with Coanda effect, inertia and gas flow resistance. Then it separates various alkaline earth metal oxide constituents from the curved wall of the Coanda block to clean the polymeric microelements.
