Bubbling paint

  johndrew 22:16 14 Nov 2010

An interesting/annoying problem.

My daughter has bought her first house and stripped many layers of wallpaper to get back to plaster for painting.

Having cleaned the walls a coat of standard Dulux matt emulsion paint was applied with a roller. Most of the wall area was fine but in certain areas the paint bubbled. When the first coat was dry (nearly a week due to work) a second coat was applied and again the paint bubbled in the same areas.

Whilst I am aware that applying some paints (such as cellulose over synthetic) can cause this effect I have never seen emulsion react in this manner. The only material likely to be on the wall after stripping is wallpaper paste (probably from the 1960s) and perhaps a sealer such as a PVA type adhesive (often used to bind plaster to brickwork); there would also be standard filler used for the odd crack/score/hole.

Has anyone any experience of this type of reaction with emulsion paint applied to walls or can suggest what may be happening as emulsion paint is (to my knowledge) pretty stable normally?

Many thanks in anticipation.

  Forum Editor 22:24 14 Nov 2010

if applied over an impervious surface, such as old glue size.

I suggest that the affected areas are rubbed back with sandpaper, and then treated with a good spray coat of stain-block. When the blocking coat has dried, repaint with the emulsion and all should be well.

  onionskin 22:26 14 Nov 2010

Don't know why it happens. A coat of universal primer, thinned right down to a milky consistency with white spirit stops it though.

  onionskin 22:32 14 Nov 2010

When you have these bubbles, sanding down the emulsion isn't easy, it tends to peel so that you cant feather the edge. I'd dig out the bubble with a pointed knife, fill the (small) hole with pollyfilla, sand the filler down lightly then repaint the affected area.

  Forum Editor 23:09 14 Nov 2010

if you give it time to harden properly.

To get rid of a proud edge, use fine sprackle filler applied with a steel plate filler tool.

  johndrew 09:52 15 Nov 2010

The day isn't wasted if you learn something - at least that's what I was taught at school.

Many thanks for coming back people.

Looks as if I'm going to get my daughter to 'damage' her great new paint job by rubbing it down, washing thoroughly and applying an impervious finish. (I wonder if she would like gloss white walls???)

A further thought; would a coat of PVA adhesive be likely to seal the area? The reason I ask is because I already have some and it appears cheaper than stain-block having done a quick search.

  ella33 11:08 15 Nov 2010

I am wondering about a nice picture, mirror, or book shelf in the affected area, as it is harmless and just doesnt look good. I remember having a similar type of problem years ago, after using brown putty, insted of white filler, to fill in holes where there had been nails, screws. So we ended up with a picture where there had been one before! But corrected it the next time we needed to decorate, rather than do the whole thing again straight away.

  Covergirl 12:19 15 Nov 2010

. . . but in the bathroom. It's a vinyl silk applied directly onto plaster, although there may have been a size coat applied first.

Ours only happens during/after a shower, so it is probably something to do with the moisture in the air and possibly heat too.

  peter99co 12:47 15 Nov 2010

Use stain-block. A job worth doing is worth doing well!

  sunnystaines 13:27 15 Nov 2010

use a two coats of stain block, buy from a paint merchant rather than a retail outlet, as the quality is ofter far better.

  johndrew 14:09 15 Nov 2010

Unfortunately there are several areas at various heights across the wall - don't need that many mirrors.

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