Does wet PVA weaken bonds?

[twitcher]

Alright, PVA again

This time I wanna ask does anyone know why wet pva seems to weaken bonds?

Think it's already been mentioned on here that wet pva will weaken set board addy. If you brush wet pva on some hardened board addy stuck on a wall, it'll weaken the bond and make it easier to hack off. Whereas if you brush pva on a wall to be dabbed and let it set it'll strengthen the bond of the board addy to the wall.

Also been thinking that the sheets of skim falling off artexed ceilings scenario might relate to this too. It looks like everyone who's had it sheet off has all used PVA on the artex before it was skimmed. So is the wet pva weakening the bond of the artex and causing it to fail? Whereas if you use a polymer based plaster bonding agent like WBA it won't happen. WBA won't weaken the bond like wet pva.

What do you reckon? Am I talking bollox or what?

 

[S a plastering]

its because it creates a bond and not a key wba for thia which i use most of the time esp on painted stuff

 

[Chris W]

here we go again...
pva - relies on suction to pull it into the substrate...
pva will readily stick to itself and the suction is what holds it to the substrate...
stick some pva on glass and it'll come off peice of p'ss..
stick some bonding agent such as wba on glass and your gonna have a game getting it off again if its been allowed to dry...
artex - a lot of it has been painted with silk paint i.e. limited or no suction..
shiny surfaces, again, use gypbond
thats my take on it anyway and im still bleedin well stickin to it.. ;D

as for pva lossening up dried board addy, f'ck knows, something different entirely i reckon...
maybe it gets pulled in by the suction and helps to separate the grains/molecules but thats just a guess..
maybe the apprentice would know?
..

 

[spunky]

did you try it on the board addy?

 

[twitcher]

yeah i tried it on dabs - getting it brushed between the dab (or dot whateva) and the wall and it did loosen it.

when it's sheeted off on artex, does it bring the artex off with it, or is it just the skim?

It's never happened to me, but I've felt the artex kinda move around a bit when I've trowelled it. Stick to a plaster bonding agent innit

 

[beddy]

If the artex moves surely its nothing to do with using pva or wba. Jj had a ceiling come down when he used wba once

 

[irish_spread]

IF YOU PUT PVA ON ARTEX IT SOFTENS THE ARTEX, becomes like butter.
Thats why I always pva, bond then skim artex although I've
had two ceilings on the same job/day sheet off. When the bonding
sets the artex hardens up again (soz caps lock)

 

[skimmin2day]

when the chemical reaction in the plaster heats up as plaster is setting,if the artex is on to thin it comes off no matter what adhesive you use!!!
Overboard is the answer in this case.