My wife and I were on a trip recently, and we had the pleasure of hanging out with and observing an expert blacksmith.

He was working on crafting these iron rods into a decorative “track” on which you could slide a barn door. He was spending most of his time working on hammering out the end of the rod to create an end piece that looked like a leaf. This required a lot of precise hammering, which meant he was constantly going back and forth between the fire and the anvil. In talking to him we learned all about melting point temperature and the methods of heating up the fire over the years. We learned about anvils and their importance in metal-craft, and we even talked about how an anvil is often used as a percussion instrument in orchestral music from time to time.

But I noticed something in particular that the blacksmith kept doing over and over that fascinated me.

Every time after he struck the iron rod he was crafting, he’d let his mallet bounce off onto the...