What causes paint to crack, bubble, or peel?
Why Does Paint Crack?
Painters use a wide lexicon to describe common paint cracks. Some examples and causes:
• Mud cracks. Paint was applied too thick; surface was dirty.
• Hairline cracks. Paint was over-spread; paint was cheap and had low adhesion and flexibility.
• Alligator cracks. Paint was applied over a wet base coat or a glossy finish; a stiff coating, such as an oil-based enamel, was buttered over something with a higher expansion rate, like plaster.
Why Does Paint Bubble?
Small Bubbles: Shaking a can of paint introduces excess air. Rolling on the paint too quickly can whip bubbles into the paint. High-gloss paints are particularly sensitive to this. So, slow down!
Another culprit is a porous surface like plywood, brick or sheetrock. A sealant or primer will help.
Big Bubbles: Blisters often result when using latex and acrylic interior and exterior finishes. It happens when the paint separates from its base, a result of the application temperature being too cold, too hot, or a damp base.
Painting during a humid evening often results in blisters. Painting during hot, sunny afternoons may result in the upper stratum of the coat drying too quickly, making the solvents vaporize and expand into unsightly boils.
Huge Bubbles: You didn’t paint a coat of oil-based paint over latex, did you? Yes, you did.
Why Does Paint Peel?
Paint peels because it cannot adhere to the underlying layer.
The simplest solution is to sand. Sandpaper roughens the base surface creating tiny peaks and valleys onto which paint molecules can adhere. Trying to paint a glassy, smooth surface is like trying to walk on ice.
Most paint-on-paint peeling comes from high humidity or surface moisture. Chemical incompatibility is another common cause. You can daub oil-based paints on galvanized metal all day, but it won’t stick.
Fact is, paint can be a real pain in the wallet. You need to choose the right paint or you'll be doing the same job over and over again. Choose right the first time.