yellow staining on pine doors

[annasuz]

My daughter is trying to paint previously stained and varnished white internal doors and although she sanded them before beginning, yellow staining is coming through the white gloss paint almost immediately. She has given them several coats of paint, both water based gloss and oil-based but it still keeps happening.
Is the only answer to have the doors taken off and stripped?

[zabo]

maybe the doors are possessed. lol

[zabo]

thanks for seeing the humour in my answer and not hurling abuse at me for it. i see i'm rewarded with stars. x

[carrust]

As a decorator I've had this a few times when painting varnished surfaces. I'd try coating them with some aluminium primer (to seal the surface) , then 2 oil-based undercoats, then a coat of gloss.

[ILoveMyHome]

I had this problem with our doors too, in our case it was a layer of nicotine and tar residue from the previous owner's smoking habit!! Copious washing with sugar soap and lots and lots of rinsing before a light sanding finally did the trick.