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Burning wood twice

Why Does Charcoal Burn Hotter Than Wood?

Charcoal is wood that has already been half burned, with everything that would make smoke driven out of it.

1 Wood, full ofwater and tar2 Heated in asealed pilewith no air3 Only the carbonis left
The smoky parts are driven off first, on purpose.

  1. Step 1 of 5

    Wood is not just wood.

    Water, sometimes halfthe weightTars that become smokeCarbon, the part thatreally burnsMinerals, which end upas ash

    A log is carbon mixed with a lot of water and tarry compounds. Those are what steam, hiss and pour out as smoke — and boiling them off is where a great deal of a fire's heat goes.

  2. Step 2 of 5

    Charcoal is made by heating without air.

    With air It burns, and is goneWithout air It bakes, and carbon isleft

    Pile wood up, cover it so almost no air gets in, and heat it. It cannot burn without air, so instead the water and tar are driven out as vapour, leaving behind nearly pure carbon.

  3. Step 3 of 5

    Nothing is left to waste the heat.

    A wood fire Much heat goes intoboiling waterA charcoal fire Almost all of it goesinto heat

    A wood fire spends much of its energy boiling off water. Charcoal has none, so all the heat goes into the fire — which is why a barbecue works and a pile of damp logs does not.

  4. Step 4 of 5

    And there is nothing to smoke.

    It glows ratherthan flames Almost no smoke,because no tar

    Smoke is unburned tar. Since the tar was driven out during the making, charcoal glows with barely any smoke at all — which is why it can be used indoors where wood cannot.

  5. Step 5 of 5

    It is full of holes.

    A light black lump A maze of microscopictunnels

    Driving the tar out leaves a maze of microscopic tunnels. That is why charcoal is so light, why it lights easily, and why treated charcoal is used to soak up smells and clean water.

    Charcoal was how people got fires hot enough to melt metal, thousands of years before anyone understood why it worked.

The short version

Charcoal is wood baked without air until only carbon remains, so it burns hotter and cleaner than wood.

Try it yourself

Compare a barbecue and a campfire. One glows quietly; the other spits and smokes. The difference is the water and tar.

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