How do you whiten the case plastic?
I would like to renew old case.
I use the hair care product method similar to the one described by HanJammer above.
Salon Care makes a product called "20 Volume Creme Developer". I think the number, in this particular product, 20, refers to its strength. Salon Care makes a 10, and a 30.
I paint it on in liberal amounts caring only slightly to how even I get it. Cover in clear plastic wrap, set it under some UV lights and come back in about 3 days. I got 3 $10 cheapo UV lights off Amazon and set them up to provide 128 degree coverage on the product. I've done two cases and a keyboard to great effect.
One of my cases I forgot about and came back like 5 or 6 days later. Most of the product had dried or turned in to a thick viscus mess. I just rinsed it off and it was fine. I know some people complain about "marbling" or inconsistency if not done correctly. But with this product, in my hands, it was pretty idiot proof.