Is is better to prime or sand existing semi-gloss paint?
You can paint over a semi-gloss paint as long as you are using paint of the same kind, i.e., paint over an oil base with only an oil base, paint over latex with only latex. The surface must be clean, and the new paint will take better if you lightly sand the old with a fine grit (120 or 150) paper. It is possible to get good results if you don’t sand, but if you do, you’ll have a nicer finish. It will smooth out any blemishes in the old surface. You should not need to prime unless you are going to paint over a dark color with a light one. That always presents a problem. Talk to the guys at the paint store if you are going to do this; they will be able to recommend the right kind of primer for your project. I have had good results with a product called Kilz. It’s meant to cover water stains and other blemishes, but it’s a good all-around primer for any project.
