Painting newly skimmed ceiling - top coat blistering

[walty666]

Hi,
Had my artex ceiling scraped and skimmed at the end of December. I waited a week with a dehumidifier on in the room before painting first coat with B&Q matt emulsion watered down 2:1 paint:water, then second coat of the same but watered down 3:1 paint:water, then third coat same 3:1 again. I did not paint PVA on to seal the plaster before starting as I read that this is a myth. Yesterday I applied the top coat of Dulux Trade Matt Emulsion undiluted. It's very thick and in a couple of areas seemed to be sucking the other coats off, which is manifesting itself as small wet blisters of paint which when burst showing bare plaster underneath. These two problematic areas started off as about 2" square but when I scraped and sanded them the paint seemed to flake away and now I'm left with a couple of large patches which I fear will grow and grow if I keep sanding to find a sound edge.

I'm finding this very frustrating. It was only a skim and the plasterer said a week should see it dry enough to paint, especially with a dehumidfier on in the meantime. I stuck to the recommendations of watered down matt emulsion to key in the paint, couple of coats to build up and so on. I've waited the required length of time between coats, in fact 24 hours at some points.

For the time being, last night I repainted over the patches of bare plaster with a couple of coats of watered down emulsion to see if this would key in again but it just seems to make the existing paint around the edge of the patch blister initially. It then dries hard without any blistering but I'm sure when I try putting the thick Dulux over it tonight it's going to pull it off again.

HELP! Anybody have any tips?

Thanks in advance.
Ross

 

[joe-90]

Plastering over Artex means quite a thick coat. A week to dry is just silly. At least a month or even 6 weeks. A dehumidifier won't do anything at all.
You've painted a wet ceiling and now you'll have to scrape the whole lot off.

 

[walty666]

Thanks for the respone but it seems a bit alarmist. 99% of the ceiling is OK and the paint has gone on fine. The artex was scraped flat(ish) before plastering so it's not that deep a coat - just a skim. I suspect it may be a bit of PVA has leached through from under the plaster or dust or contaminate/grease on the plaster surface.

 

[jondecs]

Leave blisters alone till fully dry..
If it dries out (24 hrs) without any blemish's then leave it alone.
I suspect the B&Q crap being very porous, is leaving the prime coats in as hot (very porous) state as the bare plaster. The Dulux trade is very thick I suspect you putting it neat ontop of porous crap is part the problem..
So when you do it tonight leave the blisters alone and when you look in morning i think you may find all ok

I usually coat up (prime ) with the one brand... thin first coat then bit thicker next coat = finished in two coats...

Good luck.

 

[walty666]

Thanks. Well I put another top coat on last night. It covered the original patches well. There was one area where a blister came up so I quickly moved on and left it well alone. Looking at it this morning it's a tiny blemish that's only noticeable if you know it's there.