On 2007-01-03 14:40:50 +0000, Grunff said:

The Natural Philosopher wrote:
Grunff wrote:
PVA them first.


Don;t bother. Waster of time. Makes the adhesive take longer to set as well.

Well, although I can't say I've tried with and without, my reason for
always PVAing is to provide a dust-free surface. Both ply and PB tend
to be quite dusty, especially if you've been plastering/filling in the
room. A coat of PVA provides a sound, dust-free surface to tile onto.

I was curious about this one, so I contacted the technical departments
of three leading adhesives companies - BAL, Dunlop and Ardex.

One said yes and the second said no and the third said that it didn't
matter. I haven't got my notes with me and can't remember who said
which. Either way, I'm no further forward.

Then I discovered that they are all owned by the same company.