Posting in here because I wasn't sure of the best place, not having been here for a long while.
I've used retr0bright a fair bit on my old Macs, and it does the job. Curiosity about the causes of and fixes of yellowing lead me to leave some plastics out in the sun for a bit, to see if I could induce yellowing (and how quickly it might come on).
Turned out a week and a bit in bright summer sun near completely de-yellows old Mac plastics. That was a surprise.
some pics below:
Manufacturer plastics vary of course, so what works on the typical Mac plastics may give a very different result on those used for Amiga cases, but thought I'd share the idea in case anyone wanted to give it a burl. I've only done a few pieces so far, and I've now packed them away with a reminder to check them every month to see if there's any re-yellowing or even extra-yellowing that's yet to show.
The top case in the pics above I just sat on top of a garden shed for 12 days total. I left it out overnight, and all day during midsummer sun and >30C temps (and a couple of thunderstorms). No other treatment than Lots Of Outside.
Dana
