Abstract: The invention provides a method for washing, with a water-based system, reusable molds for making silicone hydrogel contact lenses. The water-based washing system comprises a solvo-surfactant which is an alkyl (propylene glycol)n ether wherein alkyl is a linear alkyl group having 2 to 5 carbon atoms and n is the integer 1, 2 or 3. The water-based system of the invention can effectively wash away silicone-containing components and other components of a lens formulation left behind on the molding surfaces of a reusable mold, after removing a silicone hydrogel contact lens cast molded in the reusable mold.