On 07/08/2019 10:49, Brian Reay wrote:
Eldest daughter and Son-in-Law have a problem with painting some walls
and a ceiling, mainly the latter.

The room was previously painted- looked like ordinary emulsion.
Condition of walls wasn't great and there was some (non-original) coving
they removed, made good walls, cleaned down etc, and proceeded to paint.

They've used the type of paint before, while they are new to DIY, SIL
has taken to it rather well, the the finish he got on the first room was
darn good. However, this time, the paint has been nothing but trouble.
It has peeled in several places- no obvious reason, some where he'd made
good, some not. They removed the peeling paint, applied sealer*, tried
again, still it peels. Walls had been cleaned so no grease etc. It
wasn't the 'bubbling' you get when there is a solvent issue, this is
peeling. No real evidence the room has been occupied by a smoker etc.
We'd previous checked for damp with a meter- no issues.

The only time I have had bother like that is on very old walls with some
parts being exposed nearly pure white lime mortar rather than plaster.
The emulsion paint refuses to bond to the highly alkaline lime. A litmus
or pH paper will show you if this is the case.


I've run out of suggestions- other than contacting the paint
manufacturer (or of course covering it, which they don't want to do). It
isn't cheap paint, although I forget the make.

I've never had emulsion peel before, in fact I don't recall any real
issues applying it- although I don't pretend to be an expert at it, I
just follow the instructions and use reasonable quality paint- one of
the 'brands' or even B&Q etc, which has always been fine.

*the sealer was in case there was an issue with the previous layers of
paint etc. I thought it may work and a search on the internet confirmed
this. It hasn't made much difference, if any.

Has anyone any ideas, please?

If it is an acrylic based sealer it will fail the same way. You may need
a thin skim of plaster across the whole wall to bury the offending lime.

--
Regards,
Martin Brown