You've probably heard the old proverb about how 'rubbing salt into one's (no offence to enthu) wounds' is a bad idea. Well. My doctor did just this. He rubbed Copper Sulphate into an open wound in my thumb. He's not a maniac or anything (despite the fact that he rides a red bike with the registration number painted in a manner akin to dripping blood ). I've had this weird muscle growth around my thumb, and he used the blue vitriol to kill the growth. Now, having rubbed CuSO4 rubbed into my wounds, I am officially the coolest person on the planet. MUHAHA!