PVA
- Thread starter CraigFa
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M
Moz
yeah ..
only kidding no ..lol
only kidding no ..lol
Give your PVA to your kids for their next Blue Peter project.
Keep it well away from any of your walls
Keep it well away from any of your walls
trazor said:
Unless you are leaving a specific brick wall exposed... not trying to be cocky - i've just done this in my loft. The chimney breast wall is being left as a feature, and I have PVA'd this wall to stop loose bits flaking off and causing dust. It also gives it a shony look
P.S. The other walls have been plastered and skimmed.
pva isn't the villain these lot are trying to make it out to be.
it's just the people using it that are the problem.
it is not a miracle binding product that can overcome all cohesion boundaries thrown up by various paints, masonry backgrounds, ply wood surfaces, damp surfaces etc.
but it is a damn good wood glue and connects some water based building products well to one another.
the problem is some people lay it on too thick on very porous surfaces that allows the product to form a skin or a barrier in itself, thus preventing a direct link between a certain adhesive and the recipient.
the lack of direct pressure is also a problem. pva behaves very well when it is connecting products under mechanical pressure i.e. in a clamp. this is hard to replicate when plastering a wall for instance. so timing is important when applying secondary layers to surfaces primed with pva. i'm not a fan of allowing the product to completely dry between coats or before applying a skim coat of plaster.
plain old water is by far the best way to help connect any cement based products to one another.
it's just the people using it that are the problem.
it is not a miracle binding product that can overcome all cohesion boundaries thrown up by various paints, masonry backgrounds, ply wood surfaces, damp surfaces etc.
but it is a damn good wood glue and connects some water based building products well to one another.
the problem is some people lay it on too thick on very porous surfaces that allows the product to form a skin or a barrier in itself, thus preventing a direct link between a certain adhesive and the recipient.
the lack of direct pressure is also a problem. pva behaves very well when it is connecting products under mechanical pressure i.e. in a clamp. this is hard to replicate when plastering a wall for instance. so timing is important when applying secondary layers to surfaces primed with pva. i'm not a fan of allowing the product to completely dry between coats or before applying a skim coat of plaster.
plain old water is by far the best way to help connect any cement based products to one another.
Well said sir.
M
Moz
noseall
with respect
what a load of ******s ...
old mate
...wrote this an Im sharing his Love an saving me tapping away like a monkey here ..
..................................................................................................
"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."
....................................................................................................
I hope to have another good night on the lash with this fella if ever down his way again ...
with respect
what a load of ******s ...
old mate
...wrote this an Im sharing his Love an saving me tapping away like a monkey here ..
..................................................................................................
"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."
....................................................................................................
I hope to have another good night on the lash with this fella if ever down his way again ...
Moz, you've misunderstood noseall's post.
M
Moz
I read what he said ...
an just read the proof ...
been at the Stokes Factory before regarding this ...in my youth ...
NEVER EVER USE BUILDERS PVA AS A BASE TO TILE ON (wet or dry )
get this as a sticky or the above rules
an just read the proof ...
been at the Stokes Factory before regarding this ...in my youth ...
NEVER EVER USE BUILDERS PVA AS A BASE TO TILE ON (wet or dry )
get this as a sticky or the above rules
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