Bathrooms, with their typically high humidity levels, present some painting challenges. Excess moisture under the paint film causes bubbles and blistering and, left unattended, will eventually lead to damp, rotted drywall. Before you attempt to repair bubbled paint, address the moisture issue, if possible. Install a fan, open windows frequently to vent humid air or run a small humidifier in the bathroom. If the dampness continues, your repair work and repainting will be in vain because the paint will most likely bubble again. Keeping your bathroom as dry as possible will ensure your repair job will last a long time.
Clear the countertops and any areas beneath the work area. Cover counters, bathroom fixtures and the floor with dust sheets.
Remove mildew by spraying it with 1-part household bleach to 3 parts water. Let it sit on the surface for 20 minutes, then rinse thoroughly.
Scrape away bubbled and loose paint with a rigid paint scraper. Use 50- or 80-grit sandpaper to remove small bubbles and flaking paint.
Repair gouges, cracks and ridges in the paint with joint compound. Spread the compound beyond the damaged areas by 1 to 2 inches with a drywall knife, and allow it to dry.
Sand the repaired areas smooth, and lightly sand the rest of the area you will be repainting so primer and paint will adhere properly. Wipe down the surface with a damp, lint-free rag.
Prime the surface with stain-blocking oil- or water-based primer.
Caulk around the shower enclosure, tub and countertops, especially if any of the paint near these areas has bubbled. Allow the caulk to dry for at least four hours.
Paint the surface with two coats of acrylic paint in a satin or semigloss finish. Use paint formulated especially for bathrooms if mould or mildew is a problem; this paint has mildewcide added.
Open windows or utilise fans to dissipate paint fumes and speed drying while you work.
Never mix bleach with other cleaning agents, especially those containing ammonia. This creates a toxic chlorine gas.