Painting problem

TKK

I'm currently attempting to finish painting my hallway...I'm on the final coat and ready to tear my hair out...

Right I've stripped back any loose paint and filled cracks/screw heads/etc. and washed the whole place down. Then I started with a watered down (10%) Crown matt white as the original paint scheme had a very dark red over some of it and, due to other renovations, there was also some fresh plaster (many many weeks of drying). Then I put a coat of Crown matt emulsion on and all seemed well. Until, that is, I started on the final coat of matt...

In some places I'm getting blisters 2-6mm when I put on the final coat. I had no problems with any of the other coats. In most cases it's around places that were the original paintwork with some minor filling/sanding (filled nail holes and sanded back raised original paint etc.) due to the original dado rail that has been removed.

What could be causing this? Is there a solution that doesn't involve stripping the entire wall back?

Help.

chiefwiggum

sounds like dust under your paint..did you dust down the wall after sanding?

Baldie

Potential causes of blistering could be:
1) Painting in direct sunlight on a hot surface, which traps solvent vapor as the paint dries too quickly.
2) Painting when the wood is damp causing trapped moisture to expand the paint film.
3) Dew, rain or very high humidity after latex paint has dried if the latex paint is of lower quality or the surface preparation was inadequate.
4) House moisture escaping through the walls due to improper house ventilation.

Possible repairs are:
1) Scrape away blistered paint and sand to bare wood.
2) Let wood completely dry.
3) Sand, prime and paint in non-direct sunlight and non-humid conditions.
4) Use high quality latex paint.
5) If due to lack of home ventilation, corrective repairs must be made to properly ventilate the home's walls, roof and eaves, bathrooms, etc.
6) Check and repair any loose or missing caulking around windows and doors.
7) Consider providing siding ventilation.

Link

Wertz

Is the blistering mainly occuring where the new skimcoat meets the old paintwork? This is a common problem caused by dust and poorly adhering skimcoat. As the previous coat(s) of paint dried they "pulled" the loose material from the wall and when you apply your final coat, the finish blisters as it "pulls".
Ways to avoid this were to sand down the edge of the new skimcoat thoroughly and dust off, and/or to apply some polybond to the edge of the skimcoat.
To fix it now? Scrape back any of the loose stuff to a sound surface...mix up some polyfilla (the real stuff not the cheap chalky crap), flush fill the area(s), allow to dry fully, sand smooth, touch up with matt or water based primer allowing full drying, then touch up with your finish colour and finally finish coat the wall(s).
At those problem areas try to avoid backrolling too much (running back over the surface with the roller that has already had paint applied to it) as this can still pull paint off.
Best of luck with it. Nothing more headwrecking that this crap starting on your finish coats...