Simon wrote in message ...
That's quite a definitive statement. Not at all porous would mean that it
didn't soak water at all, glass is not porous. MDF is most definitely
porous, though maybe not as much on the face as it is on the edge as the
face is tighter packed. Try leaving a puddle of water on the face of a
piece
of MDF ............ and watch it bloom.
Neither pva nor mdf will withstand "prolonged exposure" to water. Sure, I
wouldn't line a pond with it, but it's a good enough base for tile adhesive,
and superior to plaster and most ply.