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Valspar WB eggshell flaking off oil based architrave/skirting etc

my daughter had a [nonTP] decorator do her woodwork trim recently; apart from the door linings these were all MDF .
I suggested cover stain on any exposed MDF after sanding , 123 primer then 2 coats of waterbased Valspar eggshell on top
In the end the decorator used MDF primer of some sort and need 3 coats of eggshell to achieve a satisfactory finish
The paint now flakes off with minimum contact , 10 days later

What do contributors think about what has happened & what would they do to remedy it please?
She has been advised by another decorator to leave it for a month /alternate has been to prep any loos e area and reprise/paint
Many thanks for your advice

Sorry to hear of the issue painting MDF which is one of the most straightforward and paintable surfaces!

I would agree on providing an oil based based high adhesion primer coat on the new pre-primed MDF to give the subsequent coats a better chance.

It is not clear what the failure is though.

ie Is the paint flaking off back to the original surface - in which case it is the painter’s primer that has failed to adhere to the factory primer

Or is the eggshell paint flaking back to the painter’s primer coat - in which case the eggshell is not adhering to the painter’s primer.

Issues could be anything from damp conditions delaying the drying times and affecting adhesion between coats. Or they could have over polished (sanded) the primer before topcoating.

You haven’t got too many options beyond sanding the paint back to a solid base and starting with say Tikkurila Otex adhesion primer. Don’t sand the primer too much, it has to grab subsequent coats.

many thanks Andy for that comprehensive answer

The failure seems to be of topcoat to primer-I think that all of the factors-damp unheated conditions /rapid recoating and potentially excess primer prep may have applied .She has decided to leave any restoration for 1 month to optimise paint cure and then proceed as you describe .Would any Zinsser product be suitable for repriming?what are the advantages of the Tikkurila Otex over other high adhesion primers?
Would you spot prime or prime the whole job?

There you go, I missed out “painting with one arm behind their back”. There are so many variables when painting, you can work around one or two issues, but if the whole job is done on a wrong footing, it is hard to come through unscathed.

I wouldnt spot prime, it is likely just as quick if not quicker to recoat all dodgy surfaces, and you will have a lot more peace of mind too.

In general the difference between Otex and Coverstain is down to amount of sanding required. CS grips well, and buffs up like a babby’s bum but you don’t need that degree of work and exercise to get Otex ready for next coats.

No doubt all adhesion primers have hooks, so to speak, but if you use the complete Tikkurila system for instance, the primers and topcoats are formulated to work with each other. Mix and matching brands, you can never be quite sure. That rule of thumb applies across all brands btw, but unfortunately you cannot always get a complete system from one company, especially if you need a stain blocker in the mix.

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many thanks again Andy