Paint bubbling commonly occurs in kitchen and bathroom ceilings where high concentrations of moisture accumulate. When the moisture evaporates, it leaves behind whatever was in it. Soap scum, cooking grease films and minerals are among the main bubble-causing culprits. These paint-bubblers are often invisible to the eye, and many homeowners often paint right over them without thinking about it. A few weeks go by and what do you know -- bubbles begin appearing. The cause of the bubbles must be corrected before painting again or it will just keep happening.
Inspect the ceiling for the general area where the bubbles are occurring. Draw an imaginary line around this problem area. Put on a pair of eye goggles. Lay a piece of painter's plastic beneath the work area. Set a ladder up on top of the plastic.
Climb the ladder with a putty knife and a piece of 120-grit sanding paper. Scrape away the loose and peeling paint with the knife and then sand all of the paint off the ceiling within the problem area circle. Use 100-grit if 120-grit doesn't rip through it.
Spray the sanded area with an all-purpose cleaner and scrub it with a non-abrasive scrub pad. Wipe the area down with a wet painter's rag to remove all grime and then with a dry rag. Allow the area to dry for 24 hours.
Pour a stain-blocking primer paint into a hand-held paint holder and dip a mini roller into the paint. Roll the problem area with a layer of primer. Wait 24 to 72 hours for it to dry. Watch for bubbling paint during this time. If no bubbling occurs, then you've fixed the problem. If bubbling recurs then you'll need to strip the primer and paint beneath it with a chemical paint stripper.
Apply a skim coat of drywall joint compound over the problem area to level the paint edges where the bubbles were removed and sanded. Use a 25-centimetre (10-inch) drywall mudding knife to apply the mud; it should be only 1.5 mm (1/16 inch) thick at the most. Allow it to dry for 24 hours and then sand the area smooth with a piece of 150-grit sandpaper mounted on a pole sander. You can just use a 150-grit sanding block on small areas. Dust the area with a dust brush and then prime again. Apply a finish coat of paint 24 hours after the primer has dried.
Use a semigloss finish paint for high-moisture areas for easier cleaning.