new paint on newly skimmed wall has not stuck at all


Postby kbain » Wed Jan 28, 2009 2:11 pm

I recently had my bathroom skimmed over and waited about a week to paint over it. I realise now this was probably too soon - but I sealed it with a watered down coat of emulsion and it looked fine for about three weeks and then started to crack and peel. I thought I would take the worst of it off with a scraper then sand down the edges and try again, but I couldnt stop! The scraper has taken off most of the paint on the wall and I realise now that most of the paint was not stuck at all. So I am left with a patchy - but mostly bare plastered wall. Ive had two lots of conflicting advice. One - to seal with oil based undercoat thinned down with white spirit first then a mist coat of emulsion and then a full coat of paint. and two - wait a bit longer, to make sure the plaster is definitely dry, and mist coat like i did before. Which is correct? And should I use the matt again or buy a silk or vinyl emulsion next time? Im confused!
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Postby stoneyboy » Wed Jan 28, 2009 7:05 pm

kbain,
If you throw some water on the wall does it sink in or run down the wall?
If it sinks in recoat the wall with something like dulux supermatt (thinned), if it does not you will have to prime the wall with an oil based undercoat - don't forget to open the window when you are doing this.
end
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Postby steve bain » Tue Feb 17, 2009 9:21 am

i always give it a quick going over with 50/50 mix of emulsion and water. i think it flakes as all the liquid is drawn out of the paint into the plaster. anyway, this was how i was taught and it works. then paint normally. ior paint with watered down pva first to seal it. steve
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Postby rosebery » Tue Feb 17, 2009 8:58 pm

Its flaking for the reason SB says. Paint far too thick on a nice shiny surface - no adhesion.

If the water test results in running off frankly you have to scrape it all off and start again. No amount of remedial work over the top will lessen the fact that the coat of paint nearest the plaster hasn't stuck to it.

50/50 is a bit on the thin side for a mist coat but it depends which paint you are using. Some take more than others. If the second coat is thinned by 10% with the final neat it gives a cracking finish. PVA? Nah!
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Postby rigga » Tue Feb 17, 2009 11:07 pm

kbain, To remove the existing paint from the walls use a tool called a zipper which is used for removing wallpaper it has a sharp blade to the leading edge and the handle should be held as close to the wall as possible. Wet the painted sections first as this will help with the removal. If the sides of the blade are digging into the plaster then turn the tool over take your time. Do not paint with undercoat this is as it says an undercoat not a primer and don’t use contract matt (supermatt) this is slightly under bound and over pigmented manufactured to allow new plaster breath this will lie on the surface and not suitable for a bathroom. If you need to prime any bare plastered surface use a good quality vinyl mat paint thinned by 30 per cent, first coat always matt emulsion if vinyl silk used as a finish. Alternatively use acrylic primer undercoat thinned again by 30 per cent.
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Postby badzim » Tue Mar 17, 2009 7:19 pm

what i have used is 'paint for new plaster'. this is a sort of matt paint. i used one coat of this and after it had dried i used normal emulsion paint. it's been two years now i put the paint on and it is still like new.
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Postby stoneyboy » Tue Mar 17, 2009 9:55 pm

kbain,
Had a look at the dulux web site and they do not recommend either supermatt or vinyl matt for use in a bathroom.
Their recommended paint is diamond matt but this costs about +75% above the other two.
end
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Postby rosebery » Sat Mar 21, 2009 7:52 am

"what i have used is 'paint for new plaster' .... and its is still like new."

Yes it will be. PFNP is aimed at the retail market and is just a fancy name for supermatt. Supermatt contains no vinyl so is eminently suitable for use on plaster which is stil drying out as it lets the moisture through.

Cheers
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Postby rosebery » Sat Mar 21, 2009 7:56 am

"dulux ...................... do not recommend either supermatt or vinyl matt for use in a bathroom.

Their recommended paint is diamond matt but this costs about +75% above the other two."

This is not a technical recommendation - its about finish. The Diamond rang is tougher and far more durable so its suitable for use wetter areas and withstands frequent cleaning. Dulux are promoting their Diamond range just atm. Thats all.

No reason not to use supermatt or trade vinyl matt in a bathroom. Whatever you do, however, don't believe the marketing hype and use paint for bathrooms and kitchens aimed at the retail market. Basically it's carp paint anyway.

Cheers
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Postby rigga » Mon Mar 23, 2009 9:47 pm

I have been using good quality vinyl matt paint in bathrooms and kitchens for years and had no problems as Rosebery has said don’t believe the hype. Dulux would say they recommend diamond matt but go to another manufacturer who does not manufacture diamond matt and what will they recommend “vinyl matt” I rest my case.
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Postby deetem » Sun Mar 29, 2009 1:01 pm

Hi All,

Just discovered this forum and it's really useful...

I'm in the process of having my walls skimmed and intend to paint over the top of them and have just been doing some research online and came across this from the Dulux site which some may find useful....


Sealing new or bare surfaces:
Add up to 1 part clean water to 3 parts paint.

Normal use (not to be exceeded):
Add up to 1 part clean water to 5 parts paint.

SURFACE PREPARATION:
Surfaces must be sound, clean, dry and free from all defective or poorly adhering material, dirt, grease and salts.

Where necessary wash the surface to remove dirt, grease and powdery or dusty residues. Rinse with clean water and allow
to dry.

Seal surfaces that remain powdery after thorough preparation with an appropriate plaster sealer.

Where necessary, rub down and then wipe off with a damp, lint free cloth, to avoid dust. Avoid the inhalation of dust. Wear a
suitable face mask if dry sanding.

Any surface defects should be filled with the appropriate Polycell Trade Polyfilla.

Google "duluxdecoratorcentre.co.uk/wcsstore/DDCUK/en_US/ddc_datasheets/410.pdf"
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Postby redmist » Mon Mar 30, 2009 7:03 pm

leave the walls for a week then use a mixture of 2 parts water to 1 part PVA glue. It seals the plaster & forms a key for your paint.
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Postby rosebery » Mon Mar 30, 2009 9:21 pm

"Sealing new or bare surfaces:
Add up to 1 part clean water to 3 parts paint.

Normal use (not to be exceeded):
Add up to 1 part clean water to 5 parts paint."

But what they don't say is that it depends on the paint. Never ever use Dulux Rich Matt - it doesn't adhere to new plaster. Ordinary "cooking" emulsion shouldn't be thinned more thn 10 - 15% - even for a mist coat. Trade Vinyl Matt is much thicker than most and so can be thinned a lot more.

Cheers
rosebery
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