PVA or not

[Gall.B]

:lol: :lol: cut down in his primer was he.

 

[White Room]

Be sensible

 

[Gall.B]

????????

 

[White Room]

????????

Not your post Brian

 

[Gall.B]

Sorry :smilewinkgrin:

 

[One Day]

Sorry! :smilewinkgrin:

 

[Neill1]

Shame. 13 replies and only two sensible answers, what am I supposeto think of that? And no, luck does not come into it, obviously the job was done well for it to last as long as it was needed.

 

[DHTiling]

Shame. 13 replies and only two sensible answers, what am I supposeto think of that? And no, luck does not come into it, obviously the job was done well for it to last as long as it was needed.

If you wish to continue to use PVA then go ahead.. you have been told it is not suitable as a tiling primer and all you want is to be told other wise.. PVA does not prevent Etterignite failure and can become live again with moisture from the adhesive or water ingression, so why take the risk no matter how long it was tiled before..?

I cannot see why you persist in this matter.


This info might help you,, who knows..

PVA stands for polyvinyl acetate, and it is a rubbery synthetic polymer. It is commonly emulsified in water and used as glue. Many know it simply as "wood glue", or "carpenter's glue".

Cementious materials, such as many tile adhesives and grouts, or other materials which contain cement, such as concrete, are alkaline. Simplified, that means they have a high pH.

Alkali slowly attacks polyvinyl acetate, forming acetic acid, which has a low pH. Cement doesn't dry per se; it cures through hydration, which means it binds the water you mix it with chemically. This causes the pH of the substance to rise dramatically. Introducing an acid negates that process to some extent, preventing the cement or conrete from binding all the water it needs to harden properly.

It is hydrolysis which gives cement and concrete products strength, and holds them together. Without this process, it would merely be the powder you started with.

The acetic acid which is formed when cement and PVA comes into contact, either through mixing them, or "priming" with PVA, will continually free the water bound in the cement, and that will weaken the bond and/or integrity of the material. The effect is accelerated if the material is subjected to moisture, which is more or less always the case.

PVA isn't water resistant. It becomes slightly live when exposed to moisture, and this in combination with the exposure to alkali, accelerates the forming of acetic acid. PVA which is marketed as "water resistant" or "exterior grade", has additives which makes them water resistant, but they're not alkali-resistant.

 

[user123]

I thought impish's pva poisoning reply was funny :lol: But on a serious note, I really like the chapter above, Dave, can I quote this to my mosaic artist friends? Did you write it or someone else? There are still too many who seal garden pots with pva, then using cement to fix the mosaics and then are surprised when stuff falls off. This would be perfect to send out....

 

[DHTiling]

Yes use it.. it was part of sWe's guides..