Painting over plaster (old plaster that's just been exposed)

[stuey2]

Hi,

I've moved into my house and decided to paint over the walls with emulsion. The existing paint is emulsion too, so I thought I'd sand the walls, fill in any cracks with polyfilla - sand again and overpaint.

However after filling, sanding and filling and sanding I started to apply paint to the existing paint, and the paint underneath (not my layer, the layer below) in areas, started blistering and when I went round to reapply (via roller) the paint underneath started to wrap itself around the roller (fantastic!).

So after trying to pain with a brush etc etc and dab it down I decided to scrape off the paint underneath (terrible job). Which I've now done. I then got some emulsion and watered down 1/4 water 3/4 emulsion (dulux trade vinyl matt) and started to apply it, however I'm getting the same problem again and the paint has started to lift/blister again! (arrrggghh). It had tiny pin prics in some areas (or like tiny pinhole bubbles) and then started to 'blister again' in areas.

Please see image (click to enlarge)



Can someone please advise as to what I'm doing wrong?

Regards

S2

 

[Zampa]

The same thing has happened to me this week...stripping a wall in my hallway (busmans holiday!!! )...loads of paint came off leaving the bare plaster behind then the paint that was on the plaster bubbled so I had to take a load of that off too..Im not 100% sure why it blistered, but of got a sneaky feeling the original painter didnt thin the first coat out)

I dont think your really doing anything wrong..that could have happened to anyone, you took a straightforward wall at face value and painted it..nothing unusual their.

I could be blstering for many reasons...my guess is the plaster below was polished up to much thus making the surface virutally impervious to moisture..add to that the possiblility that the existing coat is non vinyl emulsion...possibly not thinned out enough/at all...and youve got a serious problem to sort.

The damage has been done so lets forget about the cause..

I think the wall needs the existing lose stuff scraped off first..then apply a coat of zinseer bin primer sealer..to a small sample area first..theres no point in doing the whole wall, because if it bubbles again your going to find it really hard to get off

If it works coat the whole wall with it

Then fill the damaged areas

Rub down and emulsion..id suggest a brush for the first coat just in case

 

[Zampa]

Yeh thanks...