Blistering paint in bedroom

[CanYouHelpMe]

I am trying to decorate for the first time ever and it seems like one step forward two steps back right now.
The latest problem is blistering paint I scraped off all the lose stuff and it went back to plaster as I couldn’t smooth off the edges I applied some pollyfilla skim which sort of did the trick but as soon as it touched the paint the paint all bubbled up again – eventually I managed to skim over it and leave only a few minor bubbles but closer inspection of the wall showed more ready to pop elsewhere – I have sanded most of these down now.
I thought I was pretty much ready to paint so I washed all the walls down...
Only now the damp (it was only a damp cloth not like I hosed it down) has caused the edges of all the patches I filled in to bubble up again and a few more patches have appeared... I can peel off the paint like a face masque – I probably managed almost a meter square in one go so it comes off really easy.
So what do I do – would the bubbling have happened in the same way if I had just painted the wall instead of wiping it?
Do I need to strip all the paint off?
How do I do this?
Will I need the plaster redone?
If I am painting straight onto plaster is there a special primer I should use first?
Also it would be useful to know what would cause this to start with – it is an upstairs room I don’t think there is any damp – the boiler is in a cupboard in the same room which gets nice and warm but the paint in the cupboard is fine?
Any advice gratefully received I am at a loss – I just hope the rest of the house isn’t this bad!!!
Thanks in advance,
S

Untitled

• CanYouHelpMe
• 28 Sep 2010
• 1

Untitled

• CanYouHelpMe
• 28 Sep 2010
• 1

Untitled

• CanYouHelpMe
• 28 Sep 2010
• 1

 

[Richard C]

It looks like the original paint has not stuck to the plaster & when you put new paint onto it, the water causes the original paint to blister. The plaster looks like it might be fairly new so most likely causes are;

• the bare plaster wasn’t primed or mist coated before un-thinned finishing coats were applied or
• some idiot has primed the plaster with PVA before painting it (never prime with PVA)

Whatever water based paint you put on it now will most likely cause blistering so you will be chasing yourself around in circles, I think your going to have to strip it all off & start again. A steamer will help strip the paint & it will most likely come off very easily but don’t leave the steamer in one place too long or you will overheat the plaster skim & it will blow off the wall as well. Once you’ve got it all stripped back, test a small area for adhesion with ordinary cheap white matt emulsion thinned 25-30%. If it’s OK, go over the rest of the wall with the same paint mix with 2-3 coats in quick succession, leave overnight & then apply your chosen paint finish.

If it’s been PVA’d it will just sit on the surface rather than soak in & you will have to get it all off, lightly sand & then mist coat. An oil based primer may work but I prefer not to go down that route.

 

[CanYouHelpMe]

Thank you Richard,

Sadly that confirms what I thought I would I would need to do sounds like it will be messy! Though I reckon just wiping it with a damp cloth I can peel most off pretty easy as it goes all pliable then just goes brittle again when dry.

I have one more question now though - How would I know if it has been pva'd?

When you say thinned emulsion (thankfully I already got some cheap white emulsion to go over the brighter walls) does that mean I mix 70% emulsion to 30% water and apply that?

Thanks again!

S

 

[Richard C]

How would I know if it has been pva'd?

Once you’ve got it all stripped back, test a small area for adhesion with ordinary cheap white matt emulsion thinned 25-30%. If it’s been PVA’d it will just sit on the surface rather than soak into the plaster.

does that mean I mix 70% emulsion to 30% water and apply that?

Yes, 25-30% water; apply 2-3 coats in quick succession, it keeps the paint moist & helps adhesion then leave over night to dry thoroughly.

 

[OchAye]

Thank you Richard,

I have one more question now though - How would I know if it has been pva'd?

S

The first photo you posted appears to show two different layers of something on the wall (1st layer PVA, second paint).

Charles

 

[CanYouHelpMe]

I think the two layers are the paint that I am now going to get rid of and the polyfilla I originally used to try and smooth the gaps where the paint had come off originally as i was struggling to sand the edges of the paint smooth!

I am still concerned that I won't know if the paint is soaking in or just sitting on the plaster - I think it is soaking in as you can see around the edge of the paint a wet outline which I think means it is soaking in but would I get the same if it had been pva'd?

Also what is a "mist coat"?

 

[1john]

25-30% water; apply 2-3 coats in quick succession, it keeps the paint moist & helps adhesion then leave over night to dry thoroughly.

that is a mist coat.

 

[CanYouHelpMe]

Aha!! Cool I can do that!!

Thank you!

 

[opps]

Hi Canyouhelpme

For future prosperity the easiest way to determine if a wall has been PVA'd is to brush some water on it. If it soaks in immediately then pva has not been used.