To use PVA in paint or not? That is the question.

Painting and decorating, plaster mouldings, Artexing questions

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GC2decor8
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To use PVA in paint or not? That is the question.

Post by GC2decor8 » Fri Mar 20, 2009 10:22 pm

Hi guys & gals who are into painting rooms, ceilings and such like. Sorry to sound bard-ish, but I would like to hear your opinions on mixing PVA with the first base layer of paint.

I am painting my house from freshly plastered walls. Was considering using lining paper, but decided to go straight for paint onto the walls. As you all know on the paint pot it says mix with water (20%) to form the base layer and seal the plaster, then on my own assumptions apply a second coat (undercoat) then finish with a top coat. Pretty simple really.

Some people have been telling me to mix PVA with the first base watered down coat, others have said don't bother.

For PVA: Have been told forms a more solid protection on the wall and seals the plaster better. Could have used a plaster sealer, but a friend of mine never trusted a B&Q/Wickes sales person. (Sorry if there are any out there.) Others have said that painting onto PVA painted walls the paint will not 'spread right' because of the smoothness that the PVA gives when dried.

Against PVA: Have been told not really needed as the watered down paint forms the seal and as long as your undercoat is good will provide a good base for the top coat.

Although I have now painted 2 rooms with a PVA painted base I have also done a room without the PVA. Am reasonably happy with both results. However, can anyone shed some light if mixing PVA with paint is a good idea or not. Am starting to get a bad headache on this. ::b

Looking forward to your suggestions/opinions......
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fordy
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Post by fordy » Sat Mar 21, 2009 2:29 am

Dont put pva in paint ( with water)

Thin paint down for mist coat to seal plaster thats it


Do not add pva
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Post by gmoore » Sat Mar 21, 2009 9:07 am

Never put PVA in paint. It will make the paint perform differently than it should. As Fordy says on good sound plaster thin the first coat down. If the plaster is very porous then you could use a purpose made primer sealer.
Do not use PVA as a primer sealer under paint. The paint could react to it and pickle up creating an orange peel effect.
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fordy
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Post by fordy » Sat Mar 21, 2009 9:27 am

gmoore wrote:Never put PVA in paint. It will make the paint perform differently than it should. As Fordy says on good sound plaster thin the first coat down. If the plaster is very porous then you could use a purpose made primer sealer.
Do not use PVA as a primer sealer under paint. The paint could react to it and pickle up creating an orange peel effect.
To be honest m8 when i was a bit more naive i used pva in paint when painting over paper! Idea being to give it more sticking power on paper.
It didnt do much to paint performance at all.

PVA is in paint anyway but manafacturers obviously know correct amount etc.

if you have done a room in system you have mentioned i wanted but if you have i wouldnt panic to much.

Never use it as a primer though. PVA sits on surface and doesnt really get absorb say like size.

Paint could eventually flake off, noit neccessarily str8 away but maybe after being decorated 2 or 3 times as the pva wont be able to take the weight of the added coats!!
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Post by darrenc » Sat Mar 21, 2009 11:39 am

No, No, No and No again.

If you size the walls with pva, yes it seals the plaster, but you are then painting onto the pva and not the wall, creating a permanent problem.

As mentioned a thinned coat of a non vinyl matt emulsion will seal bare plaster nicely, give it a rub down to de-nib etc then a couple of full coats.

Staff in B&Q and Wickes etc rarely know what they`re talking about.
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Post by diybelle » Tue Mar 24, 2009 12:05 am

I have in the past used for newly plastered ceilings and walls a Dulux Trade emulsion which is suitable for painting directly onto new plaster and found it to be really good and works well giving a lovely finish. It is slightly more expensive than the ordinary emulsions but works a treat and saves a lot of hassle. Actually bought it in B & Q after doing a search myself - given up asking! I can't remember the name off-hand but will find the tin and post the name tomorrow.

I have used PVA in the past and didn't like it and wouldn't use again. I have also watered down emulsion and it works okay but still feel the above paint I have mentioned works better.
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Post by fordy » Tue Mar 24, 2009 9:17 am

diybelle wrote:I have in the past used for newly plastered ceilings and walls a Dulux Trade emulsion which is suitable for painting directly onto new plaster and found it to be really good and works well giving a lovely finish. It is slightly more expensive than the ordinary emulsions but works a treat and saves a lot of hassle. Actually bought it in B & Q after doing a search myself - given up asking! I can't remember the name off-hand but will find the tin and post the name tomorrow.

I have used PVA in the past and didn't like it and wouldn't use again. I have also watered down emulsion and it works okay but still feel the above paint I have mentioned works better.

A contract matt thinned down will suffice on new palster, be it crown dulux or johnstones or any other brand.

End of the day its a seal coat so i wouldnt wanna be spunking money on something i dont need to!

Money you save could get something else like a new scraper to de nib your new plaster, :lol:
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Post by handyman » Tue Mar 24, 2009 12:38 pm

email i got from dulux trade asking them for their opinion on the matter (previous thread)




Thank you for your E-mail I can categorically confirm we DON'T Recommend using PVA to seal new or bare plaster.This is because the PVA will seal any residual moisture on the plaster and may cause bubbling when it dries.This is also stated in the BS 6150 and our ICI site work instruction.

Hope this helps.

Omar Amjad, ICI Paints Technical Advice CentreICI Paints, Wexham Road, SLOUGH, Berkshire. SL2 5DSPhone: +44 (0) 870 242 1100Visit our web site at http://www.duluxtrade.co.uk



There you go
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Post by inverdecor » Tue Mar 24, 2009 4:42 pm

I dont know where this all started about PVA, I had a customer who just had all his walls skimmed and said he was gonna PVA them all before I came to emulsion them, when I told him not to bother and explained the reasons why he took offence and said I was talking rubbish, I knew he thought he was the Diy king and knew it all but he was not happy at my objections. Needless to say I never done the job, often wondered if the dec he got had the same objections or just went ahead and emulsioned the walls. :scratch:
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Post by darrenc » Tue Mar 24, 2009 5:14 pm

I was wondering the same inver, probably started by a company that makes PVA! It must be one of the most common fallacies in painting, be nice if they could put on the tin something like ' not for sealing walls prior to painting ', would save alot of people alot of hassle, dont think it`ll happen tho :cb
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Post by paint in my hair » Tue Mar 24, 2009 5:22 pm

the Dulux non vinyl paint is called supermatt, but any cheaper brand of non vinyl.

ive just had to sand down and redo a bathroom ceiling for a customer, as someone had used vinyl paint as a mistcoat on the new plaster. after about 2 to 3 years it had started peeling and flaking. think it was caused by the moisture, ventilation in there wasnt too good.
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Post by handyman » Tue Mar 24, 2009 5:23 pm

could this thread be a sticky? It gets asked a lot
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Post by handyman » Tue Mar 24, 2009 6:02 pm

ask and it will be done :thumbright:
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Post by Welsh Decorator » Tue Mar 24, 2009 9:35 pm

I'd love to know just who and where this boswellox started.

Still don't know why people insist on use the crap, it's a wood working adhesive after all, sure plasters use it to 'bond' between old and new coats, but dec's and paint! :? :roll:
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Post by diybelle » Wed Mar 25, 2009 12:46 am

From talking to friends and from my own experience it is the plasterers that recommend sealing new plasterwork with PVA prior to painting so this is where it probably starts.

The reason I stopped using PVA was that I read somewhere that it is actually a moisture barrier and can cause the paint to eventually peel off especially if used in the likes of a bathroom ceiling. From reading the same article I learned that it should be a non-vinyl matt emulsion that should be used on new plaster.

It's good to know that watered down emulsion just works the same as the Dulux trade paint suitable for new plaster. Anything that saves money is always worthwhile :thumbright: Perhaps I got the mixture wrong and that's why I preferred the Dulux paint. Is there a mixture that the professionals use when mixing water and emulsion for sealing plaster eg so many parts water to emulsion?
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