Painted plaster has pitted rough marks any ideas why?

[america]

I have painted new dried plaster with a watered down matt base paint a couple of weeks after I painted the wall with Wickes matt paint. When it dried out there was rough patches/pitt marks. Any ideas why? I have tried a different paint and roller, but the problem is still there. I rubbed down the rough parts and as the paint shop told me to put a 10% watered down matt paint on over the top, but the problem is still there. I have tried another room wall and I am still having the same problem. It's not orange peel affect, which you can get if the paint isn't watered down enough and it not indented into the wall like you get if the plaster isn't dry.

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  Thank you.

 

[misterhelpful]

I have come across this problem myself when using Wickes' paint and believe it is due to the consistency of it combined with the pile of your roller. The paint covers quite well but gives nowhere near the finish of better quality products.

Many colleagues of mine are happy using it but I can always see the marks you have described. Perhaps we are just too fussy!

 

[Richard C]

10% thinning is way too thick for new plaster; when priming/misting new plaster, use a either a proprietary primer (waste of money) or plain old cheapo white matt emulsion; thin 25-30% & apply 2/3 coats in quick succession to give good paint adhesion; finish with your chosen paint after 12 hours. If you fail to prime new plaster as described, the paint won’t stick & may eventually fall off; even if it doesn’t, it will certainly come off with the wall paper some other poor soul tries to strip in the future.

Of course you could just have a crap plaster finish. A good plaster finish will never need sanding; unlike filler, its not designed/meant to be sanded for anything other than minor blemishes.

 

[america]

Thank you for your replies. The primer cheapo Wickes white paint was watered down 4 to 1 cup consistency. The primer coat went on okay. It was when I put the Wickes Magnola paint not watered down a couple of weeks later that the pitt/rough marks appeared. Its not an artex look, which you will get if you use a long haired roller, but rough patches with small holes in. You notice it more when you first walk into the room and can see the rough patches.

I went to a good paint shop who told me that they had never seen it before and could only suggest changing the roller to a small pile and changing the paint from Wickes to one of theirs which the painters and decorators come in to buy.

Any suggestions please on how to put the problem right and what to do with the other rooms as I noticed it today on another room wall.

Thanks.

 

[Richard C]

You said 10% that's not a 4:1 ratio still a little thick but not that far off. I’m not strictly a pro dec but never use paint “out of the tin” on my building renovation work. The holes have got to be air bubbles I would think, could be a crap roller but I’m no expert on rollers. Try thinning the top coats around 5% or so, depending on paint thickness, I find it goes on much easier & gives a better finish. I also prefer & mostly use a 4” brush rather than a roller. I know rollers save time but not much & time is not a major priority for me; quality of finish is what I’m after.