Gypsum board, which is also referred to as drywall, is a common ceiling material used for its durability and ease of installation. Water stains on gypsum board ceilings can be frustrating for homeowners because they tend to bleed through regular wall paint, no matter how many coats you apply over them. You aren't stuck with an unsightly water stain on your gypsum board ceiling, however. While the stains can't usually be literally removed, you can conceal them with the right products.
Address the source of the water stain before you begin to repair the ceiling. Leaky pipes or roofs will only produce more stains or damage the entire ceiling if they are not repaired.
Touch the stained area of gypsum board gently. If it feels spongy or wet, leave the stain to dry completely.
Lay a drop cloth or plastic sheeting on the floor beneath the stain to protect your flooring and furniture. Wear rubber gloves and safety glasses as you work.
Set up a ladder so that you can reach the ceiling easily, and have a helper nearby to hand materials to you.
Scrape off loose drywall mud and paint with a putty knife. Scrape outward until you reach beyond the stain to coatings that are solidly attached.
Sand the area with fine-grit sandpaper, such as 220-grit, to blend the edges of the stain and wipe with a dry cloth to remove sanding dust. When you finish, the area should be smooth, with no visible edges to show where paint or drywall mud was removed from the ceiling.
Apply a thin coat of drywall mud over any exposed fasteners -- or to smooth depressions in the stained area -- using a putty knife. Allow the mud to dry and then sand lightly to smooth the patch.
Dip a clean cloth in alcohol or undiluted household bleach and wipe the surface of the stain to kill mold and mildew. This may also lighten the stain, which will make covering it easier.
Leave the ceiling to dry thoroughly. Sealer may not adhere to wet gypsum board.
Brush or roll on a sealer labeled for covering water stains, such as an oil-based stain-blocking primer, or shellac, which is an alcohol-based sealer.
Leave the sealer to dry overnight and then apply a second coat.