Paint not adhering to new plaster - ideas?

[moogdroog]

Any ideas on this one? I've given it a mist coat, now on first coat and there's patches where it's just not covering well, mostly around the edges of window frames and outside corners (where there's beading underneath - sorry bit rubbish at explaining). Should I just persist? Or is there something else I need to be doing?

Dp is a plasterer, we always water the first coat down (when painting fresh plaster) and then put two full coats over that. It depends on the quality of your paint though, could need more coats if it's a bit thin.

If you have a mist coat on, think you just need to persevere.

Thanks for replying both. Yes, we did mist coat (50-50 water and leyland trade) and I'm now putting on trade again, watered down just a tiny bit as I was finding it hard to work with. I wonder if the plaster is just a bit too polished, as on the rest it's fine, problem patches are just where it's been worked to get the smooth edges.
Will rock on and prepare myself for a few more coats than I was anticipating.

Plaster is very porous, so I think you have to put a primer on it first, and at least once - or you can use watered down emulsion for this.

I'm sure that we painted our new plaster with a PVA and water mix.

It stopped the plaster soaking up the coats of paint.

Our plasterer told me...

First coat 50% paint / 50% water
Second coat 70% paint / 30% water
Third and fourth coat 100% paint

never put PVA on a wall that you hope one day to paint.

There are still a few people who recommend it, but most of them have been killed by angry decorators.

Oh no, don't listen to me op

Piglet just out of interest, why not?

PVA prevents the paint touching the wall. As PVA is water-soluble, it softens and tends to bubble or lift when you put (water-based) emulsion on it, even on subsequent coats or if sponging marks off or wallpapering over the paint.

Applying emulsion thinned with water, it soaks into the wall and grips well. Diluting the first coats means the dry plaster sucks it off the brush and into the plaster. You know when you have primed the wall with enough mist coats, because you feel it no longer sucking at your brush. Then you can finish unthinned and use a roller.

Masonry paint is the same. thinned coats soak in and give a longer-lasting finish to the subsequent unthinned thicker coats.

Unthinned paint on dry plaster, the liquid is sucked out and the solods lie on the surface, not adhering well, and may not be smooth.

If the plasterer has polished the surface like glass (usually done to annoy the decorator) you need to take the shine off. very very fine sandpaper will do, wipe all dust off with a moist sponge afterwards. If there are dark brown patches showing, they are not yet dry enough.

Ah, Piglet John! Was hoping you might be along with your wisdom.
I've done it all by the book with regard to the mist coats etc, so it must be too polished. Plaster been on for months, so it's not still wet.
Bit of light sandpapering sounds like to might be the key.

Thanks everyone for your input!