Hi, can anyone tell me why I have these patches in my paintwork? The wall was new plaster but completely dry. How can I rectify it? It looks a mess. Thanks.
Patchy paintwork query
- Thread starter Murdoch77
- Start date
Hard to tell from the photo if it was bad plastering or not. Did you paint it?
It looks (to me) like someone forgot to the thin the first coat of emulsion and then applied the second coat which then pulled the first coat off.
Personally, I would use a DA (random orbital) sander (with 100 grit paper) connected to a dust extractor and sand it flat.
If you paid someone else to paint it, get them to sort it out.
As a decorator, I routinely sand new plaster skim coats. It makes my life easier.
Image 1, you seem to have vertical lines running down the wall. V odd. It makes me wonder it they used long straight edges rather than floats after. When a plasterer uses a float after using a derby (a long edge), I would expect to see curved float marks (the result of the swing of their arm as they run the float over the wall).
Sorry, I appreciate that I have not explained that very well.
More info will hopefully help to give you more definitive advice.
It looks (to me) like someone forgot to the thin the first coat of emulsion and then applied the second coat which then pulled the first coat off.
Personally, I would use a DA (random orbital) sander (with 100 grit paper) connected to a dust extractor and sand it flat.
If you paid someone else to paint it, get them to sort it out.
As a decorator, I routinely sand new plaster skim coats. It makes my life easier.
Image 1, you seem to have vertical lines running down the wall. V odd. It makes me wonder it they used long straight edges rather than floats after. When a plasterer uses a float after using a derby (a long edge), I would expect to see curved float marks (the result of the swing of their arm as they run the float over the wall).
Sorry, I appreciate that I have not explained that very well.
More info will hopefully help to give you more definitive advice.
Sanding will rectify it but I still think it looks like the first coat of paint pulled off because it wasn't diluted properly.
New plaster is very porous. If you do not thin the first coat (as per the directions on the tin) the water in the paint is sucked into the plaster rather than evaporating into the room. Water based paints cure via a process called coalescence. As the water evaporates off, the molecules bond down to create a film. If the first coat isn't thinned, the paint pretty much just sits on the surface rather than bonding with the plaster. When you apply the second coat, the first coat is partially reactivated by the new coat. If brushing the paint on, the problem is less obvious. However, when you use a roller, the roller has a vacuum effect when in use and may pull the first coat off (as it starts to soften).
Did you paint the new plaster? And if yes, did you thin it?
If it wasn't you, again, yeah, feather out the ridges by sanding... but there is a risk of the same thing happening again unless you seal the whole surface/wall.
In the past, I have had customers who tried to "help" me by applying the first coat (without thinning it). I ended up soaking the paint and scraping it off.
Sanding matt emulsion is pretty easy, sanding vinyl silk is more problematic. It tends to overheat and gum up.
Thank you for the detailed replies. It's matt emulsion and it was done by a decorator. He's already been back to sort issues out once so I really don't trust him to come back again. I'm just trying to work out how I can rectify it. Thanks.
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