Weber PVA!?!

[Dan]

I'm on the understanding that the primers most firms make, are close to the liquid polymers you'd put in a standard adhesive to make it flexible. And more of the polymer stuff is in the types that are two-part mixes.

So I've always been told if you need primer, you need primer, not PVA.

Though reading those, perhaps they're selling it as a simple solution that helps limit the substrate from soaking up all the moisture, when using adhesives that require curing by hydration (so being wet).

Might be worth us looking into this with the firms to clear it up a bit.

 

[DHTiling]

The thing is also dan...that acrylic primers prevent the portland in the adhesive from adversley reacting with the gypsum plaster and PVA does not help with that...

Primers impregnate where as PVA simply sits on the surface and skins...and can also hinder dispersion adhesives from gripping onto the cappilaries of the plaster surface...

SAY NO TO PVA...:ban:within the tiling trade..

 

[smurf21]

Weber are part of the Saint Gobain group of companies as is C.T.D

 

[DHTiling]

Weber are part of the Saint Gobain group of companies as is C.T.D

Yep.. i know...same as sontex is made for them as well....still doesn't say advice is right..lol lol...

 

[Dan]

Oh I don't know then.

And yeah, you're right. Though don't let that make you assume they're a big brand. Saint Gobain are massive. CTD are quite big, Weber I didn't hear of until running the forum to be honest with you. Though we never had CTD stores where I am based, still haven't now even.

Mapei, being the worlds most used, and BAL, being (what was, not now) the UK's most used brand, all quote Primer, NOT PVA.

I know of other lesser brands quoting PVA but never knew Weber did. I had them on a higher pedestal until reading this topic.

 

[smurf21]

Not saying its right i know it isnt just pointing out that weber is assosciated to ctd who are supposed to be a reputable force in the tiling industry yet still their other members advocate the use of PVA as a pre tiling primer.

 

[DHTiling]

ye i know mate.......A few comps have changed there spec sheets etc to say primer now and not pva....so hopefully others will follow suit...

 

[smurf21]

I Know we have done the PVA thing to death.lol but got bored waiting for new posts and eastenders aint on yet so i found this on another site:yikes: i know i shouldnt have left but needed the exercise.

Ardex, BAL and Nicobond are the three suppliers I use most. Their products are similar in many respects, sometimes one will make products the other don't, and I also find some of there products more useful in different applications. All three of them have one thing in common, they all specifiy that under no circumstances may PVA be used before using any of their adhesives. If you do all guarantees are void.

OK why then? Well I asked this question to Ardex when I once had problem, I'd tiled a bathroom that had been constructed in 25mm Marine ply. Thinking he was doing the right thing, the builder got his guys to seal the ply with unibond PVA...I wasn't aware of this.

I tiled it and 6 months later every single tile fell off the ply, the adhesive solidly stuck to the tile but came clean a whistle off the ply.

We had Ardex Technical down to the site to compile a report, the basis of which was it's the PVA that causes the problem.

When you treat a surface with PVA it partly soaks in and parlty sits on the surface of the substrate much in the same way as wallpaper paste.

If PVA gets wet it becomes slightly live again, it doesn't completely return to it's liquid state but it becomes sticky.

When you spread tile adhesive onto the wall, the water in the adhesive makes the PVA live and stops the adhesive from penetrating the substrate and providing a mechanical grip.

Most tile adhesive works by crystalising when it sets (some are slightly different such as epoxy based ones) but generally they all work the same way. Once the adhesive starts to set crystals from and expand into any imperfections in the substrate surface (at a microscopic level) to create a grip. PVA stops this process by creating a barrier between the substrate and the tile adhesive. Basically a moist layer of PVA is then holding the enitre weight of the tiles, grout and adhesive and stopping a great deal fo the mechanical grip occuring.

Ok so whats the difference between this and Ardex or BAL primer, well basically the tile manufacturers primers are generally acrylic (such as BAL APD- Acrylic Polymer Dispersant), the chemicals don't become "Live" when a tile adhesive is applied to it and stop the mechanical crystallisation of the adhesive gripping the substrate itself. They also stop a chemical reaction occuring between the cement based adhesive and a plaster substrate, a known problem know as "Ettringite failure"

BAL and some other manufacturers also produce SBR primers, these are slurry primers for flooring, so if you're about to tile a dusty sand/cement screed, a thin coat of SBR will bond all the surface dust together and allow the adhesive to bond to the screed correctly, SBR shouldn't be used as a wall plaster primer as a replacement of APD.

I hope this clears up any misunderstandings.
_________________

 

[DHTiling]

Thats already posted on here smurf...:smilewinkgrin:..check the stickies in the adhesive forum..

 

[Spud]

smoke and mirrors from the adhesive manufacturers imo they all claim to have super dooper wonder products that are way ahead of their competitors but the bottom line is they are selling cement blended with silica based aggregates (sand)

 

[Ajax123]

Oh I don't know then.

And yeah, you're right. Though don't let that make you assume they're a big brand. Saint Gobain are massive. CTD are quite big, Weber I didn't hear of until running the forum to be honest with you. Though we never had CTD stores where I am based, still haven't now even.

Mapei, being the worlds most used, and BAL, being (what was, not now) the UK's most used brand, all quote Primer, NOT PVA.

I know of other lesser brands quoting PVA but never knew Weber did. I had them on a higher pedestal until reading this topic.

weber actually bigger outfit in uk than mapei. Weber 180 employees, mapei only 111.

 

[smurf21]

k thats me done on the PVA discussion nothig more to be said on the subject