Just painted newly plastered walls and on 2 walls the paint has had a reaction and is flaking?

What has caused it and waht can I do to fix it?? The walls were plastered 4 weeks ago.Just painted newly plastered walls and on 2 walls the paint has had a reaction and is flaking?
You do not normally need to buy any special primer for plaster. The accepted way is to apply three coats of water-based emulsion, thinning the first one out to the consistency of semi-skimmed milk - this thinning of the first coat is to allow it to sink in and grip the plaster.





As you thinned your first coat there are a number of possibilities why it has gone wrong.





Sometimes plasterers over polish the plaster making it harder for the paint to grip. Often there are patched of fine powdery residue which stop the paint attaching. But this is usually just in patches, not the whole wall.





Anyway, rectification. You only need a sound surface. So you don't need to take the paint off where it is attached soundly. Use a stripping knife to take back the flaking areas. If the indentations are deep enough that they are going to show through your next coats of paint then you need to sand the edges of the paint (not the bare plaster) with a sanding block and some fine-ish abrasive paper, try a P120 grade first. If they are not to bad, it is easier to apply a couple of extra coats of paint than to spend all day messing around rubbing down.





I always apply my first thinned coat of emulsion with a brush, working it into the plaster and under any residue. Do this on your bare plaster patches when you have finished.





(I have made an assumption that your walls only had a skim finish coat of plaster and did not have a new sand/cement render underneath. If skimmed then they were almost certainly dry under most conditions, if they were rendered also, then it takes 12-18 months to dry out and the moisture of the drying walls is pushing your vinyl matt off the walls. You would have needed a non-vinyl paint).Just painted newly plastered walls and on 2 walls the paint has had a reaction and is flaking?
You need to seal the new plaster with P.V.A. first that will stop it.
you never cut the paint what .the paint was too weak to adhere to the walls you changed the composition of the bonding agents in the paint sand down the walls and start over and use primer this time
sounds like it wasn`t dry..do it again..
PLaster not dry
use sand paper to lightly rough up the surface, its glazed over to the point of being too slippery, your paint will not adhere, then use a good quality primer/preparing solution like KILZ. let it dry over night then repaint the wall, your problems solved
There are a few possibilities:





1) The walls were not settled in and caused them to shift and the paint film on top didn't have the flexibility to withstand that movement and flaked off.





2) There was a large temperature variable that caused thermal expansion of the film and it couldn't withstand the temperature changes.





3) This is the most likely: You bought terrible paint.





4) You didn't prime the plaster wall, although there isn't much excuse nowadays for a paint not adhering to that substrate.





To fix this:





You need to remove any paint that is loose on top. Use a wire brush to remove paint that is not adequately adhered to the plaster.





Go over it with a coat of primer: Preferably Kilz to make sure that you will get good adhesion with the topcoat.





Buy a GOOD paint and repaint the wall.








You NEVER want to cut a paint unless instructed. They are carefully formulated to have the right amount of resin solids in them. You weren't getting good adhesion to the walls.





For example: You probably had around 25% resin solids in the paint. This is what bonds it to the substrate. You cut that in half and only had 12% or so. You just weren't getting adhesion.








(I make paint for a living. Generally you do get what you pay for.)
did you use primer?
sometimes the plaster because its alkali will react you need to seal them with alkali resisting primer (readily available from any diy stores) technical term for this reaction is saponification