At the hardware megastore, I noticed 2 grades of PVA: interior and exterior. Does the exterior version have some additive? I know that PVA glue can turn white when exposed to high humidity for several hours, presumably it absorbs water.
BTW they also had "craft glue" which is also PVA, but costs twice as much per litre of contents.
The exterior PVA is supposed to be a bit "water resistant". The craft glue is more viscous.
The price of anything is determined by what people are prepared to pay. Nothing to do with what it costs to make.
One of the base rules of capitalism.
No, it's really EVA, rather than PVA, but it tends to be sold as 'Exterior PVA'. It is more water resistant than PVA, but in building processes, it's only really intended to be used as a cement additive in exterior mortars, renders, etc. It's not usually sufficiently waterproof by itself to be used in other potentially damp situations.
It is slowly water soluable.
PVA is dirt cheap - lots of scope for selling it at higher margin. My favorate is by diluting it. OK, it is a bit fiddly doing it yourself and if you are a builder on an hourly rate, then maybe it makes sense to buy it already diluted.
According to "Chemistry in the Marketplace 5th ed":
"PVA formulations with an acid hardener have better water resistance."
Look at the 'D' exposure rating ..........i.e D4 That will tell you its suitability for external use
There are different formulations.
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