Mist Painting

27 Mar 2008
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United Kingdom

I'm applying a coat of mist paint to a recently plastered wall that has been drying for a couple of weeks. Mostly the paint has gone on nicely, a very even white finish, but in a couple of places it has gone on with a blotchy finish.
Is this because the wall has not yet dried fully ?
If this is the case what do I need to do, do I just leave it or should I rub the paint off in the blotchy parts ?

many thanks.
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If the walls were skim over render two weeks would not be enough time to allow the skim to dry out so if this is the case then probably.

What sort of plastering was it, a skim coat of a full base & skim? If it’s a mist coat (matt emulsion thinned 25-30%) it will look blotchy. I apply 2-3 coats in quick succession as I’m convinced it helps paint adhesion but others will disagree!
Yes, skim over render, I've stopped painting and am leaving it to dry further. Is there anything I should be doing to the part of the wall where it is a patchy finish please ?
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And the mist coat I'm applying is a 50/50 paint / water mix, dulux trade matt white.
Yes, skim over render
You’ve rushed it; skim over render needs 28 days to dry unless you use special breathable paint finish. Leave another couple of weeks & try again but check the paint you’ve already applied isn’t starting to blister & peel; if it has it'll have to come off or you’ll just create an even worse disaster later on.

50/50 is too thin for mist coats IMO but at least it's trade matt!
Thanks for the advice Richard, I really appreciate it. I'll give it more time. The colour of the plaster has gone very light compared to what it looked like when it was put on which is why I gave it a go. Is there any way, either visual or testing, that will allow me to tell when the plaster is sufficently dry ?
The simple answer is no, you can if you wish purchase a damp meter to keep a check on the moisture content yet you would be far better off to follow the advice offered by Richard. Give the walls more time to dry and do not apply anymore paint, then post back with more information regarding the degredation of your applied paint system.

A skim will go light pink (or grey) & look dry in just a few hours & even skim over base will look dry within a couple of days but will will still have a relatively high residual moisture content which must be allowed to evaporate or it’ll create problems.

Plaster with high moisture content will be very cold to touch which can be a clue but is hardly scientific. Drying time is usually 10-14 days for a skim over & up to 4 weeks for a base coat & skim but if you want to rush it, the only way to tell is to test with a damp meter or splash out on rather expensive breathable primer & paint finish; don’t be tempted to force dry it using heaters or you could ruin the plaster.
I think you would be better to give the wall time to dry out before you consider applying anymore paint.

Thank you Dec, thank you Richard.
I'll be patient and give it the full 28 days before applying any more paint. If the paint I have put on this week has gone wrong in any way I'll add a reply to this post.
Once again many thanks.
The best paint for the new plaster IMO is macphersons eclipse as it's breathable and suited to the new plaster. Wall stills needs to be dry though.
Hi gents,

Nearly 5 weeks, the mist paint I put on earlier was still on the wall OK so I painted the remaining wall today, it went on a lot better, many thanks for all your advice.


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