Rule of thumb, try to never paint over a shiny surface(of any kind) without doing some sort of prep. You have to break the surface sheen by either uniformly sanding with a light grit(220) or priming with a good sandable-type primer. I prefer to use Gripper primer on everything to provide uniformity and adhesion. Plus I ALWAYS prefer to prime vs. sanding (unless there is surface imperfections of some sort)mainly because of cleanliness(because you know that dust will somehow find it's way into your paint finish!!) Gripper is sold at Home Depot, by the way.. --Dave

QUOTE: Do I need to sand before I paint? Or what? The current finish does have a slightly raised texture. Well, if you are wanting a smooth painted wall finish , then yes you would need to sand away "ALL" of the little lumps and bumps of the raised paint. I would suggest using an electric sander. The work would go much faster for you. As far as the grit of paper to use, that would depend on how raised is raised on the finish. I would at least start out with a 180- medium grit. Be careful using the sander . Keep it moving all the time and watch your approach to prevent any gouges. After you have finished sanding, wipe away all of the sanding debris and reprime your walls. Don't forget to wear a mask. For your smooth wall surface, 3/8th would be fine. Purdy dralon ; corona brushes.

Sis, I saw in your other post in home decorating that it had only been a week since you painted when the burnishing occurred. Faron will know more about this than I do, but since latex paint takes around a month to finish "curing" (hardening), it seems likely that it would be more prone to burnishing in that first month. I seem to remember someone else having this problem with moving furniture into a newly painted room, though the paint didn't seem so burnish-prone later on. Still, I tend to think of flat/matte finishes as being for looking pretty in rooms no one touches...not for "real life".

I would figure out how to get a fan installed in there, if your paint is attracting mildew. If you cant get a ceiling fan installed, look into getting a through the wall fan installed. Other than that, the only thing you can do is prime well, with a very good quality oil based primer, and then repaint the ceiling with a mildew resistant bathroom type paint. I have a fan, and also have silver metallic paint in one bathroom. (Martha Stewart brand), and have no problems at all with mildew. Before you paint, or do anything though, use a good cleaner with bleach in it to clean off that mildew. Fumes could be strong, so have good ventilation.