As many of you would know Retrobrite is a mixture that can be used to whiten plastics that have yellowed, like Amiga cases and keys. The folks at EAB have an in-depth sticky on it.
Just like to say it works. And how!! Bought some "Creme developer" which contains 12% hydrogen peroxide from cosmetics shop (Priceline ,can also get from any hair dresser), added a pinch of washing powder with Oxy (dissolved first in a bit of water) and then applied the pasty mix to my A1200 case, A4000 front face, A4000 keyboard, with a small paint brush, left it in the sun for 8 hours, and they all ended up looking white. As in "looks new" white. Amazing!!!
The keys I removed individually and put then in a glass jar, added some tap water to the mix and left out in sun. Took longer to whiten-probably because the mixture was diluted. Also came out "as new white".
Really simple, cheap ( $5 for 200 ml of peroxide 12%, $10 for 1 litre, and $5 for 1 litre of oxy washing powder, far more than you'll need), and EFFECTIVE. Kudos to the folks at EAB.
Also did it to a SNES I had, worked a treat.