The present invention is directed to the treatment of skin erythema as exhibited in rosacea and other conditions characterized by increased erythema of the skin. The present invention provides a method for purifying a 3-hydroxyalkanoic acid copolymer produced by a microorganism, which comprises treating an aqueous suspension containing the 3-hydroxyalkanoic acid copolymer separated from a microorganism with a hydrogen peroxide while controlling the pH of said aqueous suspension by adding an alkali either continuously or intermittently. In this way, communications efficiency in wireless communication systems can be improved. A substrate cleaning system and method for cleaning a substrate are also described. The stainless steel component can be a baseplate, load beam, hinge, motor plate, add-on feature or flexure.