I've been asked to sort out a ceiling that has brown stains from there having been a leak from the room above.
My experience of stains like this is that however many coats of emulsion you apply it still ends up brown. I remember there being an aerosol called Stain Block or some such - is it still available and does it work?
I just use shellac.
Yes, you can still get something similar. But white oil-based undercoat is just as effective. Then re-coat it with emulsion when dry.
There are a number of aerosol preparations, I used two, but have no recollection of the name. I used two because I dumped the first thinking I would never need it again :-) I would guess that they are all of a similar mix.
Standard bedroom ceiling, I noticed a brown patchon the plasterboard around 20years back. Did nothing apart from inspect the loft [Dry]. Patch darkened and spread at around 0.7m^2, I bought my first spray a couple of years after the first sighting.
Job done, cured, for two years then a respray was needed.
Over 10 years it has had around five treatments [10 minute job]
The brown stain is just starting to reapear now.
The return is now more sluggish and only noticeable I am sure because I look for it.
Probably the best solution would be to remove the plasterboard and replace.
I don't regret using the spray, even if the occasional recoat is needed, replacing the plasterboard wouldnt be fun.
Incidentally, the stain looks like a damp patch, but the loft is bone dry and the wall in contact with the dicoloured ceiling is plasterboard also and isn't stained.
Maybe the stuff was contaminated with something during manufacture.
In my case I was happy. A quick squirt over the years was a small effort considering the result.
AB
+1 Thats all I have ever done.
A Dulux water based, white stain block paint gave me good results. TW
there are several things you can use to block stains. Most work most of the time, none work all the time. Undercoat for woodwork, the alkyd solvent sort PVA diluted shellac in solvent shellac flakes dissolved in alcohol commercial stain block paints eggshell paint
I'd seldom recommend sprays, sprays tend to get everywhere and don't keep well. In the worst cases it can be necessary to keep alternating spirit based & water based layers several times, but usually one layer does the job.
NT
Something like Zinsser B.I.N is a shellac based primer / undercoat that will prime and seal pretty much anything, and is an effective stain block:
They also have another product called 123 which is water based (hence fast drying, and easy to clean brushes etc) that is nearly as good IME.
+2
+1.
Yes, and yes.
Be 'generous' with it. Not so much in terms of applying thickly but do cover a decent area around the stain.
For, say, a 2" ring (diameter), I'd apply stain block over 6" dia min. I've not used it for some time but, as I recall, you apply a couple of coats.
Thanks for the advice everyone, I like the sound of the Zinisser stuff
Dunno but something made by unibond fixed my stains from a loft tank leak. It was on poly tiles and it seems to have lasted after a couple of coats of emulsion on the ceiling, but sorry cannt recall the product it was some years back and suggested by a bloke in b/q, the stuff dried a kind of crackl hard shell on the times as I recall. Brian
Most of us have got an old tin of solvent based paint lying around. One coat is enough
Available from Toolstation and works a treat, use it often.
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