The EPA concluded that tarnish does not reduce the effectiveness of copper against germs. The change in color is natural and called Patina. As long as the Copper piece is free of debris, it will continue to be effective . If you would like your copper to remain shiny, you can clean your CopperTouch piece with the chemical free home recipes provided or with a store bought copper cleaner. With all cleaners, be sure to rinse the product thoroughly after cleaning and rub with a soft cloth.