Strange crystal like furry stuff & blistering paint? pic

[doogyscoot]

Hi all,

I'm hoping someone can help to identify this. It has appeared as a line on our kitchen wall which was plastered just over a year ago and then painted in standard white kitchen paint. There was nothing coming up until a few weeks ago. I scraped it all off, presuming it was a splatter of bleach or similar that had caused the paint to bubble but there was a weird crystal type of furr within it. It follows an off path which I think may follow where cables were originally raggled into the wall and where the plasterer would have used browning t o fill before doing the top coat. Seems odd for it to be damp and just have sprung up over a few weeks. Any thoughts? It just came back twice after sanding, plaster sealing and repainting the affected area. If you can think of the most effective stuff I could use to seal this in I would appreciate your recommendation as it is ruining how the kitchen looks.
I can get better pics tomorrow if these aren't clear enough.

Thanks in advance!

 

[JohnD]

It will be efflorescence. Scrape the paint off and let the wall dry. Don't try to seal it in.

Drop the crystals in vinegar and see if they fizz. Is it a new wall? how long did the wall and/or plaster dry before painting?

what sort of paint is it?

Is there a source of water in the wall, for example a leaky pipe, or bad pointing on the outside?

 

[Robbie uk]

John is right. Its salts in the plaster. The wall needs to be completely dry and sand the affected area. Use a thinned down oil based undercoat to cover it then use the emulsion to finish. Just using emulsion wont cover it properly.

 

[doogyscoot]

Thanks lads, it is an internal wall between our block of tenements and the block next door do shouldn't be the pointing. Not exposed to the outside and no plumbing running through it. Could possibly be moisture getting through from the old chimney breast from next door but I doubt it. More likely to have come up from under the floor as we are ground floor and it's been hellishly wet this summer. Strange thing is the wall was plastered over a year ago and painted after a few weeks. It only just came on about a month ago. Could it be whatever the plasterer used to fill the old cable raggles as I think that is the only area it is an issue? Will try the vinegar thing with it. Have stripped and sanded it twice and both times it came back after it had been repainted. Any good suggestions how to dry it out? Say leave it a few weeks then use the oil based stuff?

Thanks again!

 

[dcdec]

When plaster gets wet the dampness is drawn to the surface, it brings with it salts from the plaster and they form on the wall. This is efflorescence.

There will 100% be a source of damp coming from somewhere, its just finding the source.
Personally i wouldn't put OB u/c on the wall, this can cause problems as well because if the u/c comes into contact with damp plaster it can cause saponification. If you stop the damp, brush off the fluffy stuff (do not wash), make any repairs to the wall and paint as normal, no sealer is required. Obviously let it all dry out first.

 

[ic1927]

Scrape it off, sand it down, brush on methylated spirit a few times as this will evaporate any moisture it comes into contact with, then apply either Glutenglass or alkali resisting primer before decorating.

 

[JohnD]

I'm still wondering where the damp is coming from. It doesn't look like condensation or rising damp (if it exists). It looks like a wet wall, like from a leak.

 

[TheDec]

Scrape it off, sand it down, brush on methylated spirit a few times as this will evaporate any moisture it comes into contact with, then apply either Glutenglass or alkali resisting primer before decorating.

ic1927,

Two words from me, [/b]Spot On

Dec