Ruski wrote in message ...
Advice/thoughts/reasons please

I've recently been doing the mother in laws exterior woodwork painting, rub
down, undercoat and top coat on facia, guttering/downpipes, window frames
and garage doors with brushes, not rollers.

Although it's taken a long time and it looked top-job when completed, a
fortnight later the topcoat has developed miniscule bubbles, about a
quarter
of a mm across over all the surfaces. I'm led to believe that this is
normally due the undercoat not being dry before coating, but I can pledge
that it was... 3 or four days in some cases, 24 hours in other cases.

There is a slight twist to this tale though.... MIL wanted a two tone
colour
scheme, magnolia and green. The magnolia hasn't bubbled, the green has.
The green was a Dulux mixed product bought from the local shed, along with
a
mixed undercoat to match. Could it be a fault in the mixing process? Am I
being paranoid?

I'm left with the God awful feeling that I'm going to have to recoat it all
again (come better weather)... bless my mother-in-law ;-(

IME this can happen when oil paint is applied to either damp surfaces or
things it doesn't bond to vey well (e.g. plastic). You don't mention what
type of paint(s) you're using. Are the magnolia and green the same type? Is
the bubbling better or worse on the woodwork?
..