Patchy paint

[Steve Maskery]

OK, so I've painted a wall red. Not one of my best life decisions, but not one of my worst either.
I have a pale patch about the size of a saucer and it has resisted about 6 coats of paint so far. I've painted it out with a darker shade and then overpainted and it still shows pale. What on earth is happening?
It's a recently modified chimney breast (i.e it was bricked up, has been opened up and re-plastered).
Any painting and decorating experts out there?
S

 

[cutting42]

Use a stain blocker style paint, usually white and in a spray can. They are very good, this is one I have used: http://www.screwfix.com/p/no-nonsense-s ... 00ml/40126

 

[Mike.S]

Damp perhaps?

Has the chimney been swept? Accumulated soot, fallen debris/nests etc combined with rainfall can provide a near constant source of damp - which migrates through the chimney breast, impacting your paint finish. Absent a damp meter try leaving some newspaper (or similar) propped against the wall overnight (ensure full contact with wall) - both at the 'patchy paint' site and elsewhere. Then compare the two in the a.m. If that confirms damp then need to address source, allow to dry out and then seal with suitable sealer/primer - Zinsser do a good range - before re-painting.

I think if it is damp and you apply a blocker before source is addressed the damp will just surface elsewhere.

 

[Steve Maskery]

Thanks guys.
The obvious thought is that it must be damp, but I would expect it to be darker, not lighter. Plus the spot where it is has just been rebuilt, it's old bricks but new brickwork
It's not as bad as it was so I think I shall just live with it. If I takes my contact lenses out I can't see it at all, anyway.
S

 

[Random Orbital Bob]

Might be that there is some of that silicon vapour barrier additive in some of the reclaimed stocks. We used it in a 400 year old cottage with walls like a sponge and it repels water like a ducks back. Perhaps just in that patch, the stocks were once in a wall that was injected?

 

[Steve Maskery]

I don't think so, Bob. They came from the chimney breast in the first place. They had to come out to clear the path for the new flue, then got put back afterwards.

 

[kostello]

Hang a picture over it[SMILING FACE WITH OPEN MOUTH]

 

[Steve Maskery]

If it wasn't in such an inconvenient position that is just what I would do.
S

 

[disco_monkey79]

Have you tried covering it with an oil-based paint, then going back over that with your emulsion? Had to do that previously where someone had written on (unpainted) lining paper with a permanent marker, which once painted, kept grinning through the white emulsion.

Painted over the area with some white gloss, then over that with emulsion again.

It was in a discrete area, and it was a few years ago, so I can't remember whether the end texture looked the same of different to the surrounding area.

 

[Random Orbital Bob]

I called my paint expert who runs a commercial decorators merchants and that's exactly the advice he gives ie cover with an oil based paint first (to seal in the stain) and then emulsion over the top when its really dry. Apparently oil based paints are much more robust.

 

[petermillard]

If all else fails, use Zinnser Coverstain - absolutely brilliant stuff, very thick 'gloopy' oil-based primer that I've used very successfully on difficult surfaces. Better than BIN or 123 IHMO, though they both have their place in the toolkit