How To Deal With Hygroscopic Salts In Plaster.

[RATTER15]

We had a leaking roof which led to a few areas of hygroscopic salts leaching through the plaster.
The leaking roof has now been fixed, we have a dehumidifier running in the room and the wall is drying quite rapidly.

The plaster is still in good condition so I don't really want to go knocking it off, I can see the plaster well because it is stripped back bare. You can see where the salts were because of the staining on the plaster.

Is there anything I can apply to the wall to prevent the salts coming back once the wall is dry?

[murraymints]

builder will be here later !

[TonyV]

I would reline it with plasterboard and give it a skim coat. If you don't want to do that and plaster is basically sound wire brush it and coat with kitchen paint - cheapest you can get and paper or paint paint over that

[The Builder]

Migratory salts can be quite difficult to deal with. Once the wall is dry, the salts may disappear, but the staining possibly won't.

Dealing with rising damp (which is much the same process in this case), usually involves removing all affected plaster and replacing it. Tony's idea (plasterboard & skim) is what I would do here. Much less messy, and pretty quick too.

Before you go that far, Ratts, try a couple of coats of something like "Zinsser Stain Blocker" when it's all dry.............

http://www.decoratingdirect.co.uk/viewprod/z/ZINCS/?gclid=COm8xIfX09ACFUHGGwod8qwGZQ

You may be lucky :o)

[ethandron]

We had a leaking overflow pipe which literally ran down an outside wall and leached through into the utility room, wetting and staining the plaster on the wall and ceiling. We were away for two weeks when it happened, goodness knows when the leak started.
We let it dry out and then painted over the stained area with white oil based undercoat. We then put pale blue emulsion over that, to match the rest of the room. That was approx ten years ago and no staining has reappeared, job done.
I don't know if that's any help or what you're calling hygroscopic salts.

[alavahalf]

What .. 10 years and you haven't redecorated, shame on you .. you wouldn't get away with that in our house. The wife has a constant companion ... it's called a colour chart. When I see her collecting them off the shelves in the DIY stores, I then know it's time to say I am thinking of taking up fishing again.. ;-)

[ethandron]

Don't clean it if it isn't dirty, don't decorate it if it doesn't need it. Saves loads of time to spend on things you enjoy doing ;)

[The Builder]

Oil-based undercoat is a good traditional blocker.
I know "Homer" swears by it ;o)

[RATTER15]

Thanks all, Oil based undercoat it will be it will be!