Martin Pentreath wrote:
Interestingly the Dulux Weathershield instructions expressly say:

"If the surface is still powdery after thorough preparation, seal it
with a coat of Weathershield Stabilising Primer, but do not seal
sound, new or bare surfaces."


Slightly ambiguous! Good old Dulux. It's really a question of how porous
your new render is rather than how it looks or feels. I suppose if the
stabiliser couldn't penetrate, and formed a clear film on the surface,
you might have trouble getting the paint to cover well i.e. you'd see
brush strokes, but I can't see that happening on normal render. Also,
bear in mind that stabiliser is much more penetrative than water.

The problem with all water based paints is that they contain solvents
which evaporate after the water phase so, although the paint is touch
dry, they are still hanging around ensuring proper film formation. If
they get sucked into the substrate, you tend to end up with a coating
that looks fine but isn't continuous at a microscopic level.