Ever heard of reduction? It's a complex sort of subject, which can best be summed up as complex sulfur compound chemistry. (here's an article on it, if you are curious.) Anyway, I opened an organic Soave the other day that was a perfect example of reduction, with a slightly acrid, smoky, flinty, rubbery sort of stink to it. It's the sort of thing that once you've spotted it, you are better at identifying it on future occasions. It's not like cork taint, which means you really can't drink the wine; in many cases reduction is a little more subtle, and spoils the fruit quality a bit without making the wine foul.
So I tried an experiment. You can fine out some of the stinky sulfur compounds using copper. So I went to my old coin collection (it was a sort of hobby I had when I was a kid) and picked out an old copper penny (you won't find much copper in present-day pennies). It turned out to be from 1966, when England last won the world cup. I plopped it in a glass of the wine and swirled it around a bit. The transformation was remarkable. The fruit was back, the stink had gone. Interesting, eh?