Painting over watermarks

[KLav]

Our bathroom recently leaked leaving an unsightly watermark (brown staining) on our living room ceiling. We've attempted to paint over this with white ceiling paint but it's still showing through. Any tips for how to get rid?

[Maz123]

You need to use something to block the stain before using emulsion paint or it will keep coming through.
Zinsser do a few products which are great for this, or you can use an oil based undercoat. There are products marketed for damp stain covering specifically but have found they're not as good.

[OchAye]

A "stain blocker". All majors do one but probably zinsser has the edge with (Bin, Bulls Eye 123 Plus, or coverstain, and bin comes in spray form if you have only a small patch). Apply two coats belts and braces approach. And if you only paint the patch (feather the edge) use a quality trade emulsion or else you might see the patch you painted as opposed to the stain or put the stain blocker on the whole ceiling.

Caveat, I never had to block a stain on plasterboard but I had to block "leaking" varnish from wood.

[Tom d'Angler]

As above. My favourite is Zinsser Bulls Eye 123 Plus.

Ensure the stain has completely dried out before you paint on the stain block. I tell my customers it needs to be at least four weeks after the leak has been fixed before painting can commence.

[toolbox]

Another vote for Zinsser, two coats, recoat in about an hour the stain may still show after the first coat but is then locked in second coat will cover it.

[Bob225]

+1 on the Zin Bullseye 123, it covers all sorts of problems

[OchAye]

Pedant alert!!! (Yes, that's me ).

It is zinsser bulls eye 123 plus that is the stain blocker the 123 without the plus is an adhesion promoting primer. All said and done, it is probably the most straightforwd of the 3 zinsser products to use.

[Tom d'Angler]

It is zinsser bulls eye 123 plus that is the stain blocker the 123 without the plus is an adhesion promoting primer. All said and done, it is probably the most straightforwd of the 3 zinsser products to use.

Agree. Zinsser Bulls Eye 123 Plus is much easier to work with than their Cover Stain.

[Bob225]

The plain 123 says on the tin its a stain killer ?

http://www.zinsseruk.com/product/bulls-eye-1-2-3/

I see the plus blocks water stains

http://www.zinsseruk.com/product/bulls-eye-1-2-3-plus/

[gc1967]

Smith and Rodgers blockade stain block is the best on the market goes on easier and has a lot less smell