Ruski wrote in message ...
the paint is oil based 'Dulux colour mixing system' suitable for wood and
metal. Both the undercoat and topcoat are mixed colours. The Magnolia is
an 'off the shelf' non drip, again by Dulux.
The bubbling is far better on the woodwork, but I do not understand why the
undercoat does not take care of any 'problem' surfaces, as you rightly
point
out that the 'non-wood' surfaces are worse, even tho the paint is suitable
for wood and metal (or so it claimed on the tin :-( )
Primer/undercoat is usually the same as the topcoat but with a greater ratio
of solids to binder. Its job is to obscure the surface. Topcoat has more
resin and, applied sparingly on the first coat is more likely to bond to a
problem surface.
Exterior metal is invariably damp at this time of year, even if it hasn't
been raining, and, whereas a water based primer can cope with surface
moisture, oil based can't.