-Moisture trapped in the paint
-Painting in temperatures above 90 degrees
-High humidity like rain or dew before the paint dries
-Using oil paints on damp surfaces
-Painting a warm surface in direct sunlight
-Painting over a chalky or dirty surface
Solutions: Remove all blistered areas by scraping, sanding, or power washing for large areas. After removing all the blisters let dry. Before the surface is repainted the surface of the wood should be checked with a moisture meter to ensure that the wood is dry. Any bare wood should not be painted before a minimum of 48 hours of dry weather. When there is high humidity that time could be extended. Control the mositure with adeqaute venting such as, wedges under the shingles or clapboards, vents in eaves. Make sure the gutters are clean and not overflowing. Proper insulation is important so the house can breathe correctly from the inside out. Caulk any gaps and cracks so moisture does not penetrate areas that will cause problems later. To repaint the surface the first coat should be an oil based breathable primer. The finish coat should be an acrylic finish for the best results.