How can people walk barefoot on hot coals?

Answer 1

During a fire-walking event, you almost always see a large, glowing bed of burning coals. The bed may be 10 feet long or so. And the glowing coals are real. People actually do walk across the red-hot coals in bare feet.

The trick comes from the weird physics of the coals themselves. Think about this. Let's say you took a 10-foot long iron plate and heated it up red-hot with blow torches. Now you walk across that. What would happen? Walking across a red-hot metal plate would be insane. Imagine a hamburger patty when it hits a hot iron skillet. Now think about your bare feet being the hamburger! Bare feet on red-hot metal would give you third-degree burns in milliseconds.

So what is going on? There are a couple of things to notice about any fire-walking event:

1. Firewalkers are not actually firewalkers. They are really coal walkers. Someone lights the fire well ahead of time to allow the wood to burn down to non-flaming coals.
2. The event is always held at night. If it were done during daylight, the bed of coals would look instead like a bed of ashes. There is always a layer of ash covering the coals. By doing it at night, the glowing red light is still visible through this layer of ash.
3. The firewalker never dawdles. No self-respecting firewalker would run across the coals -- that would be undignified. But firewalkers certainly are walking briskly. You never see firewalkers just standing around on the coals.

The coals start out as pieces of wood. But because they've been burning for a while before the stunt, the coals have burned down to nearly pure carbon, like charcoal. If you were to pick up one of these pure-carbon coals, you would notice that it is extremely light. Carbon is a lightweight element -- that's why carbon-fiber bike frames and tennis rackets don't weigh very much.

This lightweight carbon structure is a poor conductor of heat. It takes a relatively long time for heat to transfer from the glowing coal to your skin. Now, add to that the fact that ash is a very good insulator. People actually used to use ash to insulate iceboxes. The red-hot coals covered with ash transfer their heat even more slowly because the ash acts as a layer of insulation.

Then there is the short time span. Heat transfer from a red-hot coal is slow, but it still happens. If you were to stand still on the coals for several seconds, you would definitely get a burn. By walking quickly, you keep your contact with individual coals very short. You also get across the bed of coals fast, and that limits your total amount of coal time. So, your foot never gets hot enough to burn.

Do not try this at home! If you fall, it is going to burn you badly. But, the next time you see a fire-walking event, you will know exactly what's going on.