why does my white paint quickly turn yellow

Hi This is due to use of vegetable oils to reduce the VOC content in the paint,in an attempt to make it less toxic. If you want white paint then acrylic "waterbased" is your answer as it does not turn yellow but on the down side does not have same finish as oil based paint. It's all about sustainability and water based paints conform to this and they are getting much better application and finish wise. Oil based paints are the past, there are very good oil based paints such as "sikkens satura", little green, but they all yellow eventually. Hope this as helped. Chris spence

A few queries: I'm guessing they were already primed. You say you applied undercoat & topcoat, but what type? water based or oil? I would still recommend Dulux oil based undercoat followed by an oil based gloss. I find water based sometimes snag easily when applying & are not as hard wearing & have a much lower sheen. Best o luck Paul

Where the doors previously stained or varnished? if so they need to be Alliminium primered or zinzerr cover stain blocked first.