Painting new plaster?

helpwithdiy · 17 Sep 2010

I know it's not the done thing to paint vinyl silk directly over new plaster but if a thin coat of vinyl silk was applied to dry plaster, would it inevitably flake off eventually, or might it actually be O.K.?

I know that the received wisdom is to mist coat the plaster first but i spoke to someone in the trade who said that whilst the standard procedure is to apply a mist coat first, in fact there shouldn't really be any problems painting vinyl silk directly onto new plaster, providing that the plaster is dry.

Richard C · 17 Sep 2010

Your trade man doesn’t know what he’s talking about & I wouldn’t like to buy a new/renovated house that he’s decorated further down the line. New plaster is extremely porous & if you don’t mist coat or prime it, the paint won’t stick. In time it will start peeling/blistering & if you wall paper over it, the paint is very likely to come off in sheets with the wall paper the first time it’s stripped.

My preference is to use cheap own brand matt thinned 25-30% & 2-3 coats in quick succession, this keeps it moist & allows the pigment to be drawn into the pores of the plaster giving good adhesion; leave 24 hours & then apply your chosen finish. Don’t use vinyl silk to prime, it traps moisture in the plaster, preventing it drying out properly & reduces paint adherence; never use PVA.

helpwithdiy · 17 Sep 2010

He didn't say you shouldn't apply a mist coat, just that it wasn't strictly necessary.

He actually said that it's a common misconception to suggest that the paint will start to flake off if it's applied directly to plaster. In fact the real problem is moisture and that providing the plaster has thoroughly dried out, it shouldn't really matter what paint is applied directly onto it.

He also said that by applying a mist coat you are actually adding new moisture to dry plaster and unless you ensure that the mist coat has dried thoroughly, you will still have problems with peeling paint.

Richard C · 17 Sep 2010

This statement merely confirms your guy doesn’t know what he’s talking about, especially the "adding new moisture" bit. New plaster has to be allowed to dry out thoroughly before painting so you don’t trap moisture (Vinyl silk will trap moisture); this takes between 10 days & 4 weeks depending if just a skim or ful float & set/base + skim. Adding moisture to the top of the plaster when misting is essential so that the pigment gets sucked into the plaster pores providing adhesion, it’s only the very top layer of the plaster that absorbs this moisture & it will fully dry out again after 24 hours - unless you use Vinyl silk.

Do a search on the forum & you will find numerous disaster threads about paint falling off due to lack of misting or the use of PVA. But, hey, being a plaster I most likely don’t understand the materials I'm using or have a clue what I'm talking about so I’d go with your trade deco, he obviously does; does he put PVA in his paint as well

helpwithdiy · 17 Sep 2010

Richard C said:
New plaster has to be allowed to dry out thoroughly before painting so you don’t trap moisture (Vinyl silk will trap moisture)

Didn't i just emphasise that he said the plaster must be completely dry before painting? I am aware that plaster continues to absorb moisture but i have been told that the problem of vinyl silk flaking after being applied directly to plaster is exaggerated.

Richard C said:
Do a search on the forum & you will find numerous disaster threads about paint falling off due to lack of misting or the use of PVA.

...and you will also find a number of people on both this and other sites, who say that it's a GOOD idea to use PVA. There are conflicting opinions. It doesn't necessarily mean that you are right and they are wrong.

Richard C · 17 Sep 2010

Unfortunately they are wrong & will find out to their cost (or someone elses most likely) sooner or later. You obviously have no intention of listening to sound advice from someone with experience in the trade but I’m not here to argue with trolls. If you want an argument, try posting something controversial in the General Forum, there are several regulars on there who will be only too pleased to oblige

goodbye

joe-90 · 17 Sep 2010

It's amazing isn't it Richard. Someone gives them duff information and they preach it like it's Gospel. I guess that's how religion works too.

Growler · 17 Sep 2010

Nothing, but nothing, causes more confusion and aggro, than painting new plaster.

Nothing.

http://www.icipaints.co.uk/products/info/dulux_trade_vinyl_silk.jsp

Becka · 17 Sep 2010

I am about to repaint my bathroom ceiling because I slapped on PVA followed by vinyl silk. The paint has vein like carcks and is now peeling off in very large patches. I'm going to have to start again javascript:emoticon('

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Nige F · 18 Sep 2010

helpwithdiy said:
. I know that the received wisdom is to mist coat the plaster first but i spoke to someone in the trade who said .

I spoke to someone in the trade who said " if you can ****, you can paint" - I have 2 ancestors that were in the trade ( Dad+ Grandad) so some knowlege of painting

. When I went to my Spiritualist Church meeting last night I had a message ( not unusual there) but it was from the clairvoyant. He said . " Nige, your folks are interrupting the others getting through- They are

so loud in my psychic ear "Didn`t say why - now I know .

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Painting new plaster?

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