the effect of sun light on yellowed decals

[Massimo Tessitori]

Hi,
I have decided to try a trick that I've read somewhere to improve the yellowed decals sheets of very old kits: I've fixed them inside a window exposed to south with some adhesive tape.
After few days, I see that the yellow shade of old films has strongly reduced, and I hope to turn those old decals into new ones within further few days.
Pity that I've decided to do this only when the summer is turning to its end.
I wonder if the same could happen on already built old models with yellowed decals; if so, some days of summer holidays to the sun could improve the health of them.
I've a MiG-25 of Hasegawa, for example, whose decals have yellowed after its completion despite the layer of trasparent matt paint protecting them.
Apart for the modelistic advantage, this fact could be taken into account when observing the shades of the paint of other exhibits: it is likely that many bonders of the paints age differently if exposed to the sun or if preserved in shadow. While parts in open air become light and chalky, the chips preserved in close places could turn to yellow, and this could be particularly noticeable on light grey and light blue ones.
Regards
Massimo