Skimming onto dryed PVA

[MFW]

Did a small set this afternoon, onto a couple of small walls that had a coat of PVA that had dried.

Now, I know that most of us on here would agree that 'best practice' is to skim onto PVA whilst tacky, and not dry.

And I also know that most of us on here will agree that PVA is used to control suction, and not to actually 'glue' the plaster onto the wall. And I'm also pretty sure that a dried coat of PVA controls suction just the same as a tacky coat, and in any case, dry PVA will liven up when in contact with water.

So my question is, how come, given the choice, we would rather skim onto tacky PVA, and not dry PVA?

Apologies for what might be a boring question, just interested in your opinions!

 

[kebab king]

cos it also sticking to the pva to.

 

[twitcher]

yeah i think there's some truth in this. There's some adhesion or bond going on too as well as controlling the suction.

I was thinking about this the other day when I was patching some channels. I pva'd around the patches with neat pva and let it dry as usual. When I was blending in the finish, it occurred to me that the pva not only controlled the suction but it was also enabling the finish to bond into the wall. It has to be dry though so it doesn't slip about. Which makes me think it might bond more when it's dry.

 

[countyfinishings]

i often skim onto dried pva... never noticed any difference

 

[S a plastering]

i often skim onto dried pva... never noticed any difference

i know what your saying mate but on the tub why do they say hit it when tacky

 

[spunky]

because both materials gel together and you dont get a sheen that provides no key

 

[gps]

The reason I do it tacky is so that if for what ever reason the plaster blows in places after a few day or weeks usually when the painter is painting then you can see on the blown plaster the pva where if it wasnt tacky when skimmed then it would be obviously just plaster and therefore you will get the blame where as with traces of the pva not your problem.

 

[bodplasterer]

BG recommend you dont use pva at all, but we all been using it for years, but it is strange that BG dont make a pva and only recommend thistle bond-it.

 

[Pug]

i often skim onto dry pva. never had any comebacks

 

[del]

i often skim onto dry pva. never had any comebacks

Agree, never had a problem.

 

[markyspread]

i normally skim over dry pva aswell, like said previously it re- emulsifies on contact with water, and does not slip all over the place!

 

[murplastering]

if i can its tacky but if its dry and last hit its going on cos im not waiting for pva to go tacky and skimabubble

 

[FreeD]

same as marky

 

[Removed_101]

dry pva>>>>>>>>>>>>>>tacky pva

 

[twitcher]

it does spread different on dry pva...

 

[iain_flanagan]

skimmned over dried pva for years never had any comebacks

 

[Removed_101]

BG recommend you dont use pva at all, but we all been using it for years, but it is strange that BG dont make a pva and only recommend thistle bond-it.

gypbond is too dear and too much hassle.

Pva>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>gypbond

 

[lewisricekrispy]

When doing several hits at once (especialy in the summer) I find it imposible to have them all tacky. I hate it when you start to skim and only realise after laying on that a few patches were to wet and started to crack and slip down the wall.

 

[bubbles65]

So - if you want to f**k up someones' wall you could splash parts of it and some would be fine and the wet bits would slide......

 

[FreeD]

just chuck some rubble in with the skim that will f**k it up for sure lol

 

[spunky]

how do you lot know it remulsifys ?........did you skim it then quicly take the skim off to see the pva ???.........i always try and skim it tacky

 

[Chris W]

try getting pva off a laminate floor spunky, it turns white again when you mop it... ;D

 

[spunky]

the lime in multi makes pva set rock hard ;D ;D.........trust me i took some off and had a look :