Keeping Paint Leftovers: Keeping paint leftovers is a good idea; this way, whenever you need to touch up a small area, you have the right color at hand. In order to keep paint in a can that has been opened, you need to ensure good sealing of the lid. To do that, with a wet paper towel, clean paint on the lid and in the groove in the rim of the paint can. Cover the can with plastic wrap and press the lid back into place. If the paint is alkyd based, put a piece of waxed paper directly onto the paint surface before placing the lid back.
This will help remove the film that tends to form on alkyd paint. And don’t forget – latex paint may freeze!
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