sand back how far before re-painting?

[The Night Tripper]

Hi all I have some yellowed white paintwork that I want to refresh. I was planning to lightly sand back the surface and then repaint the gloss. But given that most of the pigment in paint is in the primer & undercoat, is it worth sanding back to the undercoat and re-coating that before re-glossing?

Thanks J^n

[Stuart Noble]

If the surface is smooth and still basically white after your light sanding, then just a coat of gloss should be fine. Otherwise a coat of primer/undercoat first. No need to over sand if it's sound

[The Night Tripper]

Thanks Stuart, that's useful

J^n