Women Painters.com: Paint Issues and Fixes:
Yellowing
Development of a yellow cast in aging paint; most noticeable in the dried films of white paints or clear varnishes.
Possible Causes:
- Oxidation of alkyd or oil-based paint or varnish.
- Heat from stoves, radiators and heating ducts.
- Lack of light (e.g., behind pictures or appliances, inside closets, etc.).
Solution
Top quality latex paints do not tend to yellow, nor does non-yellowing varnish. Alkyd paints, because of their curing mechanism, do tend to yellow, particularly in areas that are protected from sunlight.