You're disappointed to find that your new paint layers have either peeled, blistered or cracked after the paint has dried. I’d like to share some information that might help you understand why this happened, what you need to do to make repairs, and how you can avoid these types of problems in the future.
Peeling / Blistering
This is commonly due to improper surface treatment before your application of paint (for example, cleaning with harsh cleaners and failure to rinse well afterwards), or inherent moisture/dampness being present in either the substrate or environment.
Cracks forming in the paint are due to the unequal expansion or contraction of paint coats. It usually happens when coats of paint are not allowed to dry completely before the next coat is applied, or the surface of the paint is exposed to strong sunshine or the drying process is accelerated with the use of a high heat source (such as a blow dryer), or close exposure to an operating heat vent.
There are still more reasons why cracks can form. A common cause in the United States is the surface was previously cleaned with a spray furniture polish that contains dimethicone, a silicone which can cause cracks to appear in the paint layers, especially along edges. Yet another reason is the surface was first sealed with shellac that was either past its shelf life or applied too thickly (care should always be taken to use the freshest shellac and to apply it in thin layers; too thick layers can cause your new paint layers to crack or even peel away).
Regardless of the reason, the fix remains the same in all cases. You will need to sand the affected areas with medium or fine grit sandpaper to remove the defects and smooth the surface. Ensure that the underlying substrate is completely dry; if moisture is present allow it to evaporate. Then seal those areas, including the remaining paint, by wiping on one or two coats of clear shellac. Finally, once the shellac is dry, reapply your paint. Basically, you’re removing the damage and starting over, but don’t panic, these are all quick steps!
Here are a few tips to help you avoid these defects from happening in the future:
Make sure the surface is clean and dry. Avoid using caustic cleaners, such as TSP, and solvents. Use a biodegradable cleaner and warm water. A Scotch-Brite™ pad can make the job go easier and also scuffs the surface, making it ready for a new paint coat. Be sure to rinse well with clean warm water (don’t skip this very important step) and then let the piece dry completely.
Remove any spray furniture polish with mineral spirits. Dampen a shop towel with a small amount of low-odor mineral spirits and repeatedly wipe the surface until the shop towel remains clean (you may need several shop towels for this). Follow by wiping with a shop towel dampened with clean warm water and let dry completely.
Enjoy your painting but take your time. Allow each paint layer to dry completely before applying the next.
Avoid painting in directly sunlight or near an operating heat or air vent, and don’t rush the drying process by using a blow dryer.
Always use the freshest shellac and wipe it on in thin layers using a cloth pad.
Follow these tips and you should enjoy stress-free painting in the future.