When you open a half-used can of paint, you’ll typically find a skin of dried paint on the surface. Not only is this annoying to remove, but dried bits can wind up in the paint. You can prevent this by using a two-pronged attack when you close a used paint can: First, put a piece of aluminum foil under the can and trace around it. Cut out the circle and drop the aluminum foil disk onto the paint surface. Then take a deep breath, blow into the can, and quickly put the top in place. The carbon dioxide in your breath replaces some of the oxygen in the can, and helps keep the paint from drying.