White paint going yellow!!!

[runnerjp]

Hello guys,

Hello,

I recently had my bedroom re-plastered to find that the lining on the chimney had eroded away and the water was seeping through onto my new plaster wall.
I have had the flashing replaced and this has solved the issue but now i have come to pain the room.
I have used white paint and where the plaster was damp the white paint seems to go yellow.
Is there any advise anyone can give to solve this issue?

Regards,

Jarratt

 

[vibrobullit407]

If you are talking about the water stain coming through and staining the emulsion there are a couple of things you could try. You could try an alkali resisting primer as when damp gets into masonry and plaster it can cause the salts to reactivate. this will show itself as a fluffy white white substance (efflorescence) and makes the paint peel. Or you could try a oil undercoat if you have some lying around or a stain block. I tend to use an alkali resisting primer for this but the other suggestions may work also.

 

[oldgreymouse]

Yes runnerjp, sound advice from vibro. If you only have a small damp stain on the wall problem, I would try a coat of Oil based undercoat, let it dry for at least 24 hours then add a second coat if needed. Then return to using your original paint which I am guessing is just ordinary matt emulsion.

 

[TheDec]

In this type of situation the application of an oil based undercoat can often prove to only offer temporary relief, the only thing that is known regarding the formation of efflorescence is that it is formed after the ingress of moisture.

Efflorescence takes on two forms, either hard or soft, yet the former is more liable to appear on external masonry, the binder of an oil based undercoat is alkyd wheras the binder of an alkali resistant primer is oleoresin.

In situations such as these the element of doubt should be removed and the correct primer needs to be applied.

Dec

 

[oldgreymouse]

Dec, i got the opinion from the original post that this was just a temporary problem that left a damp stain, usually orange in colour, and that no efloresence was showing, a common occurance with some short term water damage. Long term damp does indeed draw out the salts to the surface and for this other solutions or ideas may be suggested.