Why it takes silver to kill a werewolf

Red Riding Hood, a film about a werewolf, comes out today. Werewolves live as humans, only turning into wolves on the night of the full moon. They're strong, vicious, and they can only be killed by silver. But why silver?

So, we're not into the supernatural here. As the great Pythons have showed us, there have to be rational explanations for all phenomena. Both a witch and a duck float in water, so they both must weigh the same amount. And since a werewolf dies when scratched with silver, there has to be something running through the wolf that causes it to expire from just a wee sparkle.

Silver has a few good qualities. It conducts heat better than any other metal. It's incredibly ductile and malleable, which is one of the reasons why it's used for jewelry in the first place. Werewolves are equally malleable — they change shape easily. Although they're usually found in northern woods on cold, misty nights, they might have a problem with heat, but there has never been any mention of having to heat a silver bullet or knife before it's shot into a werewolf. What is it then, what makes silver so bad for werewolves?

There is one quality that silver has that isn't shared by many other decorative metals. It tarnishes. Silver has to be constantly polished or coated with something to protect it from the air. If it's left exposed, it develops a disgusting black crust that ruins the look of the silver. (Some people get silver especially for the disgusting black crust, but they have problems.) It turns out, though, that silver isn't reacting with the air. Silver is pretty nonreactive - staying the same in water, air, and most solvents. But tiny bits of an element suspended in the air combine with silver to make that blackened goop that coats it. What element is it? Sulfur.

Otherwise known as brimstone — that's right — the devil's element. Put together silver and sulfur and you get silver sulfide. Now, silver sulfide is not shown to be toxic to any other animals, but it's not soluble in water, and so can only be ingested. In a werewolf, it would lift from the silver and travel through the bloodstream of the animal, blocking off blood vessels and poisoning cells. And it is this that kills the werewolf.

So clearly, a werewolf is stuffed with sulfur. This can provide other clues to spotting werewolves. Sulfur burns blue, which means that werewolves would, when exposed to flame, emit a blue light. (This could go the way of throwing witches in a pond to see if they float, but remember a werewolf should have sulfur everywhere, so try burning hair or fingernail samples first.)

A werewolf would also emit sulfur through bodily fluids, which would include sweat. So there's no need to stab someone with silver to see if they're a werewolf. You can just try rubbing a silver bracelet on a sweaty werewolf to see if it tarnishes especially quickly. Lastly, we all know the smell of sulfur. It's the odor of rotten eggs (and one of the reasons you shouldn't rub egg yolks on silver jewelry). If you smell rotten eggs around a person, you know that he or she's a werewolf. Or that they have gas. Try to run another test before you stab them.

[Via Chemistry Explained, Salt Lake Metals, Online Library, and Sulfur Chemistry]