Painting a Skim Coat too Early

13 Oct 2007
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United Kingdom

I have left my skim coat of plaster to dry for a week and was sure it was ready to paint as it had turned pale pink. I have applied most of my mist coat today (80% Dulux Matt + 20% water) but have noticed that some small sections look a bit blotchy.

I'm presuming this means that the plaster under these patches is not completely dry.

If I leave it for another week or so will the plaster continue to dry underneath the mist coat or should I scrape the paint off these patches?

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You'll probably be OK. Ideally you should have used a non-vinyl matt such as a contract matt emulsion, but it should still dry out in time.

If it doesn't dry out even after a few weeks it probably means that there is damp coming through from somewhere behind the new plaster - is it an outside wall?
So the darker coloured spots/patches are appearing on the inside walls as well as the outside ones?
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Were the walls lined with sheets of plasterboard stuck to the walls before skimming, by any chance?
Do the patches look like they are drying out yet?

A mist coat doesn't always look perfectly even and some darker patches, which look like the paint hasn't covered properly, can be because the plaster has been over-polished. This will usually cover after a couple of topcoats, but you do need to ensure that it isn't damp plaster that is the root cause before applying your finish paint.

Any chance of a pic or two so we can see the problem better?
Hi Misterhelpful

It is all looking a lot better today, thanks. The patchy bits are much more even. To be on the safe side I'm going to leave the room as it is for the next 3 to 4 weeks before painting.

Thanks everyone for your help!

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