Decorator-PVA-plaster dilhemma. Help!!!

misgrace

Penny_Farthing wrote: »

Thanks, doesn't look like any has been painted on. Plus OH opened tin and discovered it was quite old. He had to break a seal to get in so looks like we're saved.
Thanks.

Thank goodness he realised it was quite old and no good, but I would be a tad concerned as to why the PVA was doing sitting in your hall, was someone going to use it? :eek:

roddydogs

Why do they PVA the plaster? what benefit does it bring?

sodamnfunky

It brings no benefit at all. The only time it can help and personally I never do this is when they want to tile it. Its far better in that case to fit exterior plywood in its place.

Think about what happens to pva when it dries, now even if its watered down its still going to seal the plaster, therefore how is the paint going to take to the wall?

Pretani

Penny_Farthing wrote: »

I've been reading up about decorating here and the pva debate. Returned home today to see an empty tin of unibond pva in my hall and I think the decorator has used it on my newly plastered wall prior to doing a mist coat.

Penny_Farthing wrote: »

Thanks, doesn't look like any has been painted on. Plus OH opened tin and discovered it was quite old. He had to break a seal to get in so looks like we're saved.
Thanks.

Is it possible that the plasterers left it? They would use unibond before applying the cement.

catamite

sodamnfunky wrote: »

It brings no benefit at all. The only time it can help and personally I never do this is when they want to tile it. Its far better in that case to fit exterior plywood in its place.

Think about what happens to pva when it dries, now even if its watered down its still going to seal the plaster, therefore how is the paint going to take to the wall?

Yest Sodamite-Funky, think about it why don't you. Maybe the ethylene vinyl acetate in the matt emulsion is chemically compatible with, and indeed will bond nicely to, the PolyVinylAcetate substrate? Maybe dry plaster isn't the only thing that paint can stick to? Possibly the "shiny" surface is really at a microscopic level gasping for a compatible polymer to bond with? Now that I think about it, maybe being a chemical engineer helps - or having painted countless walls and ceilings on rented properties after sealing them with 5:1 PVA. Muppet - Sodomite

Flyfisher_2

I have read somewhere that you should never use it to seal a wall when tiling?

What kind of disasters can happen if you seal the walls with PVA before painting ?

catamite

Flyfisher wrote: »

I have read somewhere that you should never use it to seal a wall when tiling?

What kind of disasters can happen if you seal the walls with PVA before painting ?

No need to use PVA for tiling - the tile adhesive will bond to dry plaster no problem and in fact wull usually rip the plasterboard off in chunks when you try to rmove the tiles. For painting as far as I'm aware any good water-based matt will go down great onto PVA, no need to thin. Of course if you use faeces there will be a great deal of hairline cracks appearing (and the room will smell something awful, but just for a few days)

yours
The Cat

catamite

Flyfisher wrote: »

I have read somewhere that you should never use it to seal a wall when tiling?

What kind of disasters can happen if you seal the walls with PVA before painting ?

No need to use PVA for tiling - the tile adhesive will bond to dry plaster no problem and in fact wull usually rip the plasterboard off in chunks when you try to rmove the tiles. For painting as far as I'm aware any good water-based matt will go down great onto PVA, no need to thin. Of course if you use faeces there will be a great deal of hairline cracks appearing (and the room will smell something awful, but just for a few days)

yours
The Cat

rjm2k1

Wonder why B&Q paint says walls should be sealed using plaster sealer (watered down PVA) before painting, wonder what the consequences of not doing so before using their paint are if it goes wrong and you complain to them?

Wondering why after following the instructions on the tin and using plaster sealer recently on fresh plaster it all looks great and worked fine? Given how absorbent my ceiling was (skimmed over artex) I daren't think how many coats of watered down paint would have been needed had I not followed the instructions onthe tin and used plaster sealer.

catamite

rjm2k1 wrote: »

Wonder why B&Q paint says walls should be sealed using plaster sealer (watered down PVA) ............coats of watered down paint would have been needed had I not followed the instructions onthe tin and used plaster sealer.

Bravo Rimj*b2k1

Excellent points and most articulately put.

I'm afraid that SodomFlunky has yet to reply with his pearls of wisdom (that unfortunately conflict with the chemistry no doubt); I await, like the cheese-gobbling cat outside the mousehole, with "baited" breath.

The Cat