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.

In message
"A.T." wrote:

[snip]

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

If you've stripped it back then you've probably eliminated a recurrence.

Steve.


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A.T. wrote

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

Loss of adhesion in this form really only occurs when something is
trying to escape from the substrate through the paint coating film. This
is usually moisture, but can also be natural resins and/or solvents
still present after treatment.

The fact that you have noticed a relationship between the mirror
position and the shelf looks like a reasonable area for investigation.
It's difficult to diagnose without seeing the problem, but I would guess
that the problem is moisture related, and that condensation could
possibly be forming on the mirror and running off directly onto the
shelf. Constant exposure to water lying on the horizontal shelf will
shorten the effective life of the coating.

However if the shelf is fitted flush with the wall, its more likely that
condensation is running down the mirror and either down the wall or
dripping onto the back of the shelf, and the rear of the shelf (where it
is fitted to the wall) has not been properly painted/sealed. Moisture is
probably getting into the timber at this point, then trying to escape...
with the consequent loss of adhesion you have seen.

Make sure the shelf is properly painted all over, even the parts that
you can't see... if necessary remove from the wall and paint. You could
also run a thin bead of white sanitary silicone along the rear of the
shelf where it joins the wall for additional protection.

Regards
--
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http://www.decoratingdirect.co.uk/
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In article ,
"A.T." writes:

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?

Was this on old gloss? Some of the manufacturers at least used to
include a silicone compound of some sort (remember SILthane?) to
try to make soiling not stick to the paint. Of course this made
new paint not stick, and although I do not know how exactly they
managed this, the silicone migrated out to the surface with time,
so that the initial two coats bonded together. Sanding, followed
by sugar soap ought to get adhesion.

John Schmitt


--
If you have nothing to say, or rather, something extremely stupid
and obvious, say it, but in a 'plonking' tone of voice - i.e.
roundly, but hollowly and dogmatically. - Stephen Potter

A.T. wrote:

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.

Is the new mirror reflecting bright sunlight directly onto the affected
area ?