I left the last buff i found (the one with the green blob on it) soaking in a yogurt cup of soy sauce for two days. It came out with no red color and no green on it. It does look kinda dry (i know that's not possible) and gray. But i could see the date was 1927 on it now. So cheap value soy sauce from wally world will do the trick. Just lean the nickel against the side and pour in the sauce. It'll get both sides.