Hairline cracks in plaster. Best Filler?

[Peterade]

Hello,

I'm wondering if anyone can help with hairline cracks in 4 year old plaster painted with Dulux Trade Matt.

I thought they may have settled down by now but they almost vanish in winter but have reappeared now. Very very fine, smaller than a hair but curved lengths of 4 feet or so on the walls. I have tried TOUPRET which worked well but lines have re-appeared.
Paint itself seems to fill but only lasts for a few days.

Are there any flexible fillers that work?

Thanks for any ideas.

Peter

 

[Grenage]

You'll probably want to rake out the crack so it's more substantial, then fill; that should sort it.

 

[Peterade]

So here is what I did.

Didn't rake out fine hairline cracks. I filled with "Red Devil One Time lightweight ready mixed filler". Let dry and sanded.
Then touched up with two coats flexible polycell paint with a 1/2 " brush.

Looks great even before I repaint whole area. Time will tell weather they re-appear.