Quote Originally Posted by dmanb2b View Post
If you suspect it is metals, rub the area with a vit C tablet and see if it improves.
If a stain is metal you do not need to RUB with a vitamin c. Ascorbic acid (vitamin C) is a reducing agent and just by holding the tablet on the stain the chemical reaction will lift it in less than a minute, If it does not the stain is not metal (or at least a metal that is easily treated with ascorbic, citric, or oxalic acid).