When you paint a plaster ceiling, the paint job can last for years. However, exposure to moisture, whether in the form of a leak or from consistent humidity in rooms like bathrooms, can cause paint on a plaster ceiling to begin to peel. If you have peeling paint on a plaster ceiling, you can repair the paint job by removing the old paint and repainting.
Cover the floor and any fixtures in the room with a dust sheet or plastic sheeting. Secure the dust sheet or sheeting to the walls on all sides with tape to keep the cloth or sheeting from slipping. A dust sheet is preferable because plastic sheeting will stick to your feet as you walk.
Scrape off all of the peeling paint and any loose paint with a paint scraper or a putty knife. Press the scraper or putty knife so that it is in complete contact with the ceiling, and apply pressure to remove all paint that is flaky or loose.
Mix a batch of levelling compound according to the directions on the packaging. Using a putty knife or drywall knife, apply the levelling compound to any area of the ceiling that isn't level with the rest of the ceiling's surface. Gently scrape the knife across the surface once you have added the compound to remove any excess, and allow the compound to dry.
Apply as many coats of compound as necessary to level the surface of the ceiling, allowing each coat to dry between applications. Then sand the compound down so that it feels even with the ceiling and has a slightly rough surface.
Cover the ceiling with an oil-based paint primer. Allow the primer to dry, then spread a second coat. Then paint the plaster ceiling, applying as many coats as necessary to get the look that you want. Choose a moisture-resistant paint to prevent issues with peeling in the future.