I'm using 40% H2O2 right now. Remember this is only one day job! More a couple of days and the keys will become minty again (I hope).
Sorry for the joke, I can't help myself.
But for all matters, this experiment is now done.
Now I will start with real needed hardware. I have one A600 and one 1200D with slightly yellow key caps.
My other A1200 is in a DIY tower, using a mint A2000 keyboard.