I have a shelf in my bathroom that was painted with white gloss. Part of
this bubbled up exactly as if it had been treated with paint stripper only
much more gradually (it took a few weeks or so to go ). Can anyone suggest
why?

This may be sheer coincidence but it happened just after I fitted a new
mirror and the bubbling occurred underneath the mirror, dead center and
about 10cm wide. chauvinist And, contrary to my first thought, SWMBO
hasn't been cleaning the mirror with anything except mild
detergent./chauvinist

I have now stripped it back to bear wood and I'm about to repaint. I don't
want it to happen again.

Any advice would be much appreciated.

A.