Is there a way to make vintage Star Wars toys White again?

Although heat could be a factor, it was not in my case. They've been stored at room temp.

Clutch said:

Although heat could be a factor, it was not in my case. They've been stored at room temp.

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The plastics were of lower quality, IIRC, a common problem for some trilogo toys, too. IIRC the Trilogo Sand Skimmers bubble that I have in my collection has turned so dark that you could use it as sunglasses

For white toys, such as stormtroopers etc.. the best results for me have been simply sitting the items in the sunlight and turning them over and over.
dealing with pigmented plastics is a whole new game. the oils in many plastic toys will evaporate from the surface, over time.. the only way I think that may work for some items, is to lift the deeper remaining pigment up to the surface with a blow-dryer or heat gun. an oven, or the sun. Please see some of the youtoob vids about restoring or reclaiming car plastics bumper and dashboard colors with a heat-gun before attempting to reclaim colors on toys!!
and always practice on a test subject, so you don't do damage to your good items.

Vintage carded figure bubble yellowing and staining are impurities in the plastic formulation and as I understand it, these can never be cleaned or reclaimed.

Good Luck !

Let's also face the fact that these toys and bubbles weren't meant to last forever. You make something out of oil based material, it WILL break down sooner or later.