yellow stain bleeding through newly painted ceiling

[trurle]

hi guys

sorry if the subject sounds familiar, I believe my problem is different from previous posts.

I had a bedroom plasterboard ceiling painted by multiple coats of paint. when I started redecorating, I found out that the old paint was coming off in sheets -- so I took it all off. what I was left with was what looked like a decent plasterboard paper surface (dark yellow in colour for some reason). I smoothed some areas (joints, holes) over with white gypsum-based filler, sanded, but the rest remained this yellow paper.

I painted three coats of Leyland contrace water-based matt emulsion paint and I can still see the yellow bleeding through, but not in the places where I used the filler (there it's properly white).

now, there was never water damage on this ceiling. I don't think it's cigarette stains, because if they were, I would have noticed them on the old ceiling paint. it's the paper! the surface is clean and dry.

as I paint it looks perfect, but as it dries, the yellow starts coming through.

I also noticed that the paint dries very quickly. maybe what's happening is that the water from the paint gets absorbed by plasterboard too quickly for polymerisation to happen in the new coat.

I understand that I need to seal the surface somehow. how do I do it without costing a fortune and doing 10 more coats? it's already three coats, how do I do it so the new coat still sticks? if I have to wash off my three coats I might as well remove that stupid yellow plasterboard altogether and build a new ceiling.

water-proof PVA? undercoat? sealer? acrylic primer?

oil-based primer sounds like overkill TBH.

any advise please.

thanks!

 

[Belboz]

Someone on here may be able to suggest how the stain occurred but, in the meantime, use the forum SEARCH facility and input STAIN BLOCK. There are lots of posts on the subject including a couple on that topic in the last few days. You can narrow your search to this section and to a time frame.

Sadly, AFAIK, you coud paint that ceiling a hundred times with emulsion but the stain will show through unless you use a stain blocker first.

That is IMHO but there are experts out there who may be able to advise you better than I can.

Regards,

B.

 

[blightymam]

Hello!
Have you any photo's? Be interesting to see the stain. Did you mist coat as you were down to the plasterboard?

If you are 100% certain it's the yellow paper and not damp then perhaps use something like zinsser shellac primer (best applied with a roller because it dries very fast). This stuff is excellent for stopping stains etc, and I use it instead of old fashioned knotting.

 

[trurle]

Have you any photo's? Be interesting to see the stain.

I don't think it will be visible on a photograph, too faint. 8( I have a photo of the plasterboard before painting. 8( will this help to identify the problem?

Did you mist coat as you were down to the plasterboard?

by mist coat do you mean diluted paint or diluted paint + PVA? I did not do either. 8(

If you are 100% certain it's the yellow paper and not damp then perhaps use something like zinsser shellac primer (best applied with a roller because it dries very fast). This stuff is excellent for stopping stains etc, and I use it instead of old fashioned knotting.

yes, it's not damp. the ceiling is very dry. also it could not be a water stain, as it's the whole ceiling, and not just in one room (divided by walls). it's some strange old plasterboard.

even a small layer of filler (I used gypsum-based thistle and water-based lightweight filler from SF) stop the stain. so I think even a water-based sealer (whatever) should do the trick, if it's allowed to polymerise.

 

[trurle]

I can see that most stain blocks on the market are oil-based. is applying oil- or solvent-based paint on top of water emulsion not asking for trouble?

 

[trurle]

tried to photograph with two different cameras -- doesn't show.

here's the photo of the original ceiling with the old paint peeling off. you can see that the paint is white and that the plasterboard is dark yellow.

http://s8.postimg.org/iqegugpdh/ceiling.jpg

as I was saying, even with two coats of the new paint on, the paint dries very quickly, like minutes to touch dry. I notices that over the filled patches it's wet much longer.

how do I prevent this old plasterboard sucking the water in so quickly? I assume it's the same as sealing?

thanks again to everyone replying.

 

[JohnD]

I wonder if some idiot might have put glue on the ceiling? Some ignorant people do that with new plaster. It would make sense, with the paint coming off in sheets.

If so, the yellow stain might possibly be the glue dissolving into the water-based paint.

 

[trurle]

good possible explanation JohnD. I guess we will never know.

you would think the glue would penetrate the paper and stop it from absorbing water too fast -- this is contrary to what I am seeing now.

will any water-based primer/undercoat/sealer seal it? how about diluted waterproof PVA?

I just realised: there's a good chance the old paint/undercoat could have been oil-based. what if it's them that stained the plasterboard?

 

[JohnD]

I believe people use Zinsser BN to seal plaster that has been contaminated with PVA, but luckily I have never had to deal with it myself.

Ordinary smooth plaster can be washed and scraped, but with plasterboard, you'd damage the paper surface.

p.s.

DON'T USE PVA!

 

[trurle]

DON'T USE PVA!

JohnD, could you please elaborate why?

 

[geraldthehamster]

how about diluted waterproof PVA?

PVA=glue

PVA should never be used prior to painting as it prevents proper adhesion of the paint.

PVA is used to stabilise plaster and other surfaces that are going to be plastered.

Cheers
Richard

 

[trurle]

any advice on what to use to seal this old plasterboard and prevent staining of new paint?

 

[misterhelpful]

Zinsser Coverstain is best for water/smoke/nicotine stains on that type of surface and will work out the quickest, easiest and cheapest. B-I-N will be a nightmare to apply to a large area but would be required if the stain was tar/asphalt/creosote (unlikely in this situation). Of course, if the staining is something else altogether it might not work but Coverstain is pretty reliable for most stains.

Also:

Untitled

• misterhelpful
• 24 Jul 2014
• 1

 

[trurle]

bought a water-based stain blocking undercoat for just over £20 per 2.5L.
one coat, followed by one coat of the same emulsion as before -- perfect results.

clearly not all water-based paints are the same. the undercoat is so tough, it took me a number of scrubs to wash the dried paint off my hands, while the emulsion washes off instantly.

 

[JohnD]

that's great news. What brand was it?