Paint bubbles, also known as blisters, occur when there is a lack of adhesion between the paint and the surface beneath it. Factors that can prevent adhesion include wet, grimy or hot surfaces as well as moisture seeping through walls.
Other factors that sometimes cause a lack of adhesion between paint and a surface include improper surface preparation and applying oil-based or alkyd paint over latex paint. While bubbles are capable of appearing in any kind of paint, they occur more often in latex and acrylic paint.
Humidity caused by a lack of ventilation is another factor that sometimes contributes to paint bubbles occurring. Experts recommend installing vents or exhaust fans in a room in which a person plans to paint to ensure conditions are sufficiently dry. It is best to avoid painting when a storm is due or when it is foggy or raining, as such conditions increase humidity.
In some cases paint bubbles exist only on the surface of the paint and not in the actual substrate. In these instances bubbles may be scraped away and then the surface sanded to create a new, smooth surface and the area covered with primer and then a quality acrylic latex paint.