Deyellowing a turn signal lens

I know it sounds crazy, but soak it in Polident denture cleaner. The kind where you put the tablets into water and they fizz like crazy.

Years ago someone told me about this trick. I tried it on an old, really yellowed and gross coolant tank that I was going to throw out anyway and it did work. It wasn't 100% like new but significantly less yellowed.

For clear lenses, you will probably have to polish them afterwards as I'm sure it will leave a dull finish.