Effervescing, or bubbling plaster walls, can occur from water damage and typically exist in bathrooms where humidity and moisture are most prevalent. The bubbling plaster starts to peel away at the paint and exposes the wall to further damage unless properly repaired with a new sealer. Once the paint deteriorates, the wall is vulnerable to water absorption, potentially causing the wall to crumble. Properly sealing and plastering the wall with primer-sealer and paint prevents water from seeping into the walls and causing the paint to bubble and peel.
Remove damaged and/or peeling plaster and paint from the wall with a putty knife. Scrape off any loose bits surrounding the immediate damaged area.
Wipe off excess debris with a damp cloth.
Apply primer-sealer with a paint brush on the damaged section. Evenly apply primer-sealer to avoid build-up in certain areas. Let it dry for 12 hours.
Spread joint compound with a joint knife on the wall, and butter the surface with 1/4-inch of compound. Immediately skim off the excess compound with the joint knife, and fill in any cavities or shallow depressions with the compound, leaving a thin coat around the edges. Leave any half-filled pits or small ridges left by the first coat as it will smooth out with ensuing skim coats. Let each layer dry for 30 minutes before applying the next coat.
Sand the repair area with medium-course sandpaper between coats. Clean debris with a damp rag.
Apply a final skim coat with a joint knife by applying it perpendicular to the previous coats. For example, if first applied horizontally, apply the final coat vertically.
Let the skim coat dry for an hour, and sand with 120-grit sandpaper.
Prime and paint as needed.