I bought this keycaps from Tai Hao. The keycaps have this "Anti Nano-biosis" thingy indicated on the box. How do I get rid of this? After using for 1 year, the keycaps turned yellow. I really wanna get rid of this coating that my keycaps have. I have read that the 99% isopropyl alcohol would get rid of the coating. But there are no available 99% isopropyl alcohol in my country. Does it work with 70%?