[MichaelDD]

I am painting a stairwell wall and large bubbles are forming almost instantly. When I cut away the bubbles the existing paint has bubbled up as well and the wall is very soft and sandy in texture. What could cause this?

 

[housepaintingny]

Are you using a waterbase paint? Are the walls drywall or plaster? Has wallpaper recently been removed?

 

[mustangmike3789]

the existing paint/old paint bubbles or is it the new paint? what paint are you using now.

 

[user1007]

Anxious to hear answers to other questions posed but it sounds like you have a plaster fail situation if you are getting sand when you go down through the paint. You are going to have to source where that is happening and coming from.

Where in the room is this happening? Fireplace? Window AC installed? Leaky windows?

More clues please and pictures if you can take them.

 

[Gymschu]

Plaster walls can be tricky to paint. The surface is so hard that paint does not penetrate the substrate to form a cohesive bond. Also, because plaster is so hard, the paint basically lays on the surface and dries more slowly. With it staying wet so long, it can bubble up all the way down to the original plaster. I'm sure there is some chemistry going on there, but I really can't explain it as well as someone else could. It's also possible that it was patched with durabond joint compound which also can react with the paint. Anyway, pics would help.

 

[jsheridan]

I'm betting that the existing paint is a flat, and the vehicle, the water, of the new paint is penetrating the old finish and down to the substrate where it is vaporizing. Your going to have to put an oil base barrier between the coats of latex. You can do an entire oil prime, or do it in spots. Finish the first coat of latex. Never mess with blisters, leave them alone. Most will mostly go down as the paint dries. After the paint dries, sand out the remaining blisters, prime with oil, patch, oil prime, then touch up. The problem with this method is that once you start the second coat, you may activate areas that previously didn't blister, you'll have new problems, and you'll have to repeat the earlier steps. If the stairway can touch up and not look touched up, you're okay. The only certain way to go is the full oil prime. I've come across this once/twice before, inexplicable blisters. Never found why, just worked around it. These were in older houses, do you have one?