Paint blisters usually resemble a boil. A pocket of air forms beneath the surface of a fresh coat of paint, causing the paint to swell. In mild cases, the paint will resettle, leaving little or no visible mark. More severe blisters will pop or leave wrinkles in the paint. Two factors can cause this. The first is high heat, typically the result of direct sunlight. The second is moisture, and it can be caused by anything from poor ventilation to a leaky pipe.
Step Two
Scrape off the blister and smooth the surrounding area with sandpaper.
Step Three
Apply a new coat of paint to the affected area. Timing is essential. Wait until the sun has already passed so the paint is not exposed to direct sunlight while it's drying.
Step Four
Moisture Blisters - Identify the source of the moisture. Causes vary, as do solutions. Common causes include leaky pipes and high humidity. To counteract humidity, open windows and doors. You can also direct a fan at the affected spot.
Step Five
Pop the blister. Both thumbtacks and needles work well. If the blister doesn't fully deflate, increase the size of the puncture. Wait for it and the rest of the paint to fully dry, typically at least two days after applying the final coat.
Step Six
Scrape off the blister and smooth the surrounding area with sandpaper.