DIY Repair Paint Bubbles
Also see:
About Paint Bubbling
Bubbling or blistering in newly applied paint is an indication of a problem with the bond between the paint film and the painted surface. This is usually a problem with latex paints more than with alkyd or oil. In addition, shiny finishes like semi–gloss and eggshell are more likely to bubble than flat latex.
The paint bond can be ruined by a variety of causes. Dust, oil, water or any number of other contaminants can be covering wall, ceiling and trim surfaces. Moisture in concrete and masonry walls, wood, drywall or plaster will also cause this problem. Failure to sand shiny, slick surfaces or failure to prime them may also be to blame for bubbling paint. When doing new wall repairs, failure to remove all joint compound dust may cause the paint to bubble.
In some cases blistering may not appear in a new paint coat for a couple of hours or not until the next day. In other cases it will appear immediately after the paint is applied. The blisters may shrink as the paint dries and disappear all together. This will sometimes be the last you see of the problem. In other cases the paint bubbles will begin to crack as they dry further and over time, the paint will peel.
Preventing Paint Blisters
The best way to cure this problem is to prevent it before it happens. Trying to fix the bubbling by scraping and patching immediately after it occurs will not work. You will have to wait a couple of weeks for latex paint to cure and a couple of days or more for alkyd and oil to dry, before doing repairs.
To avoid bubbling in a new paint coat, prepare the surface properly. First, look for stains and dirt where you plan to paint and wipe them off if possible. If necessary, wash the surface with soap and water or mineral spirits to remove any contamination. Rinse off any soap or other cleanser and let the surface dry. Prime all other stains with primer–sealer and let the primer dry completely before painting. Remove any sanding dust with a damp rag or sponge wiping gently to avoid marring the smooth surface. Prime new joint compound with flat latex paint or latex primer.
Repairing Paint Blisters
Remove all loose paint and wall material. Pop the blisters with the edge of a putty knife and slip the blade under the surrounding paint coat to peel all the loose material away.
Remove the dust and seal the surface with a primer–sealer. Stir the paint well or shake the can to be sure it is mixed thoroughly. Apply a thick coat over the whole area with a brush and let it dry for about 30 minutes.
Apply a second coat if the surface has been wet or you are repairing bubbling in newly applied paint. Let the final coat of primer dry for about an hour.
Skim Coat the Damage
If the surface you are dealing with has a chronic bubbling problem, or you are repairing bubbling in newly applied paint, using setting–type joint compound for this repair will minimize the chance of the blisters recurring. Ready–mixed compound tends to add too much moisture to the surface and can induce bubbling in the finish paint.
Mix some mud and apply a skim coat over the damaged area. Use a joint knife held at an angle to "butter" the surface with back and forth strokes, leaving about 1|8in. of mud over the damage.
Immediately skim the excess mud from the surface to leave a thin covering over the damage. Hold the knife at about a 30° angle and press down hard, but not hard enough to dig into the surface, as you skim from one side to the other, without stopping. Scrape the collected mud from the knife onto the rim of a mud pan and continue skimming the remaining mud in parallel strokes, cleaning the knife after each stroke.
Ignore any ridges left between the rows by the edges of the knife blade. Around the perimeter of the patch, skim the mud as thin as possible to help blend it into the surrounding wall. Let the mud set for about 30 minutes. Ready–mixed should dry until the mud gets hard.
Apply a Second Skim Coat
When the mud is dry, scrape off any ridges using the joint knife to cut them off with upward strokes of the blade. Use medium grit sandpaper to lightly sand the whole patch if necessary to smooth out any other bumps or protrusions. At the edges of the patch, sand to feather the mud with the surrounding surface.
Wipe the sanding dust off with a damp rag and apply a second coat of mud, skimming in the opposite direction from the first coat. If you skimmed the first coat horizontally, apply the next with vertical strokes. This will help to level out an irregular surface.
Let the mud dry and if necessary, apply another coat to build up the patch until it hides the damage and smoothes out the wall. As before, skim the mud stroking in the opposite direction from the previous coat.
Sand and Touch Up the Paint
Let the patch dry well and then sand it using light pressure, in wide back and forth strokes, to smooth and blend the surfaces. Along the edges, sand harder to help feather the patch into the surrounding surface. Wipe the sanding dust away with a damp rag or sponge. Be careful not to dig into the new joint compound.
Let any moisture from the rag dry before priming. If you are repairing bubbling in a new paint coat or a water damaged surface, prime with primer–sealer to be sure the problem doesn't recure, otherwise use flat latex paint or latex primer. Let the primer dry for an hour or so before touching up the finish paint.
