PVA or not ?

[Leatherface]

Hi
I have seen much talk about the use of PVA as a primer. The one aspect that does concern me is the use of PVA as a sealer, prior to the application of cement based advesives onto gypsum plaster walls. I know of many tillers who use PVA as a matter of course.
I instead prefer to use Mapei Primer G.
Here is an extract from the official data sheet -

" Technical Characteristics
Primer G is a water dispersion of special synthetic resins which, once applied to any surface, dries to form a flexible, compact, shiny film.
This film protects porous substrates from damp penetration, consolidates their surfaces and improves the adhesion of paint, adhesive for wall paper, adhesive for tiles and mortar for renders.
The film of Primer G on the surface of gypsum prevents any chemical reaction between sulphates and the cement alluminates of the tile adhesives which, in the presence of moisture, leads to the formation of a salt named "ettingrette" which is the cause of tiles breaking away from the gypsum substrate"

Does the use of PVA really have the same effect ? Just because many tilers use PVA does not necessarily mean that this is the correct method. I would appreciate some clarification ( backed up by some real facts, if PVA is deemed to be ok )
Thanks

 

[Dan]

From a guarantee point of view, most adhesive manufacturers will make a primer so it's probably best to use thew one that's compatable with your adhesives. PVA is sometimes used as a primer but in nearly every case it's used, there's probably a propper primer made for the job.

BAL say that a PVA will simply break back down with water, that's why when you were at school and you got your hands all mucky, you used to just wash them with warm water and they'd clean off.

Try that with BAL primer, no chance of just warm water getting it off, so it has to be different.

I've never used a PVA on my jobs, always used BAL Primer.

 

[Varley]

Pva is nothing more that a sealer, it is in no way a bonding agent, therefore all it does is seal in dust, it does not aid the tile in sticking to the surface. The only time imo that you could ever use pva is to prep a concrete floor, but personally i would always stick to acrylic primer m8, why take unnecessary risks. Hope this helps a little.