There are a number of factors that would cause the paint on a surface to bubble, such as if paint is applied to a hot, damp or moist surface. The mistake of painting over a dirty surface may also cause paint to bubble. Another possibility is if an oil-based paint or an alkyd paint is applied on top of a latex painted surface. Bubbling can also result when moisture gets behind the paint, or if latex paint gets wet before the paint has had a chance to cure on the surface.
There are ways to prevent the bubbling of paint. All surfaces that are to be painted should be cleaned and dried before any application. After the cleaning process, the surface should be primed appropriately, especially if there are any stains on the surface. Finally, painting should be performed optimally in dry conditions and walls should never be exposed to moisture before the paint dries.
In the event the painter needs to fix a surface that has shown bubbling, the painter should scrape the paint areas clean and then use a primer over the spots. After the primer dries, the painter is free to re-paint the spots.