Preparing peeling paintwork - advice?

DO NOT use PVA as a base for any type of paint!

were clearly begging to be removed. It's not quite as bad as I thought in respect of how much paint has easily come away - I think I just started in one of the worse areas.

Overall I reckon about 10% has come off, but with a large variation depending on the location; by the square foot, it's probably anywhere between 2% & 80%.

So I'm looking for some way to patch this up.

Googling turns up a few comments saying don't use pva/water, though I'm not sure why.

I plan on sanding down tomorrow, scraping off any further bits loosened by the sanding, then possibly filling & sanding, before applying a first coat of the Dulux Bathroom paint thinned 10 parts paint to 1 part water. Does that sound ok?

I think I've got that message :)

Can you possibly explain why? Perhaps a better question might be why does it get suggested as a means to seal plaster prior to painting when it's actually such a bad idea?

Cheers,

No. The trouble with PVA is that paint doesnt stick to it. Its ok to use as a stabiliser for friable surface if its well diluted (5:1) and you go easy with it, and only paint the bad bits.

Some info here, but doesnt answer all your qs:

Which bit or did you mean everything?

water, albeit with caveats about paint not adhering if the pva mix slicks.

Fortunately, touch wood, the surface is no longer unsound, though probably does need to be treated in large part as for bare new plaster, which is probably why my original attempt two years ago didn't take properly.

The above url suggests a first coat with paint:water at 50:50 however elsewhere/when on this group I've seen 70:30 & 80:20 recommended. Also claims that Bathroom paints need less dilution. Then there's the back of the tin itself which says to dilute no more than 90:10.

Thanks again for the url btw. The wiki seems to have a lot more info than that in

Hi,

Look into using alkali resisting primer, from a decorators merchant (who can also advise) or maybe a big 'shed', eg:

If you've washed the bare plaster with sugar soap that will leave some alkali behind too.

cheers, Pete.

NT

Of course it does. Emulsion paint is pva based so, if that were true, you couldn't apply more than one coat. What happens is that too much clear pva prevents the paint penetrating the substrate so that the first coat is necessarily thin and a bit washed out. No pva means the paint will penetrate unevenly, depending on the porosity of the plaster, so that the final colour won't be even. Somewhere in between is the way to go.

Hi,

Have a look at the tin to see if there are any VOCs (solvent) If so it's probably oil based in some way and may react with any residual alkali and/or sugar soap that's soaked into the plaster.

You might be able to prime with plain water based matt emulsion first, following directions for bare plaster, but I'd spend a bit extra and use alkali resisting primer instead of matt.

Dulux should have a a good help line, would be well worth giving them a call.

cheers, Pete.

Apparently this came from some of those makeover programs. Paint manufacturers have never suggested or recommended it. They've had so many complaints about the resulting disasters (which are very hard to recover from) that some tins now include explicit instructions not to use PVA.

Special paints are made for priming plaster, but standard practice is to use watered down matt emulsion, which works perfectly. Watering down instructions are on the tin, but typically something between 10% and 30% water added (go higher the more polished the plaster finish is).

It was pretty thoroughly r> Have a look at the tin to see if there are any VOCs (solvent) If so

It's water based & labelled low VOC.

I didn't think of that, having assumed they'd just try to sell me more of their products. Cheers, will bear this in mind :)

Ok, noted.

I'm a bit reluctant to try a method which requires timing the paint application after the first water coat. It just feels like there's a little more to screw up & as I've not had much sleep recently I could easily manage to mess most things up. Also there's the problem that the walls are a patchwork of old paint, filler & plaster with varying degrees of polish.

I'll go with the 1:1. I'm assuming if this is too high on the water I can recoat when dry with a less dilute mix & gradually build up - that being a worst case; hopefully the paint will go on okay over the piss/miscoat (aside: are they both common terms?).

Thanks, that's very interesting to know :)

That last bit is useful info, cheers. Of course the mess which is our bathroom has a high degree of variation in finish.

No instructions on tin re thinning other than upto 10% water for general application if desired & the environment is warm; instead they push their own primer for bare plaster.

Your suggestion of 10% to 30% seems further confirmation that there's a wide variation in practice, even amongst well experienced individuals, as I consistently come across suggestions anywhere from 10% to 50%.

All the more fun to clear up. Oh well, sanding done, time for a tea then the miscoat :)

heh, yes its one more thing, but its uber easy really. if you paint too quick the paint wont go on the wall, its obvious straight away, you just give it a few more mins. I find it a better option, less time & work for the same result.

Shouldnt be a prolbem.

you'll have to, 1:1 is fairly much a waste of time in terms of getting usable density.

no, its what will happen

it always does

mist coat

NT

Yes, sorry, I realise. What I meant was if the unthinned wouldn't go on over the 1:1 mix, then I'd assume I'd need intervening coats first, also diluted, but at lower dilution.

I'm an exceptional individual ;)

Ah yes, many more hits; ta. At least that one doesn't give me the scat references either :)

These things aren't precise, a mix around those rarios is fine.

It doesn't really matter that much, and surfaces vary as to their suction. If you find that the you aren't able to spread the paint smoothly because suction is drying it out too quickly, dilute it a bit more. The only problem with diluting it too much is that it makes more mess as it gets more watery. I usually aim for about 20% water, and then make it more dilute if necessary.

I think that is referring to the proper coats of paint. for the mist coat it doesn't really matter too much, your not aiming for paint coverage, just to seal the plaster surface.

go away and get on with it now.

NT