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The wick drinks its own fuel

Why Does a Candle Burn for Hours?

A candle makes its own fuel supply: the flame melts the wax, the wick draws it up, and the heat turns it to gas.

The flame gives heat Wax meltsinto a pool The wick draws it up It turns togas and burnsCandle
Every part of the loop feeds the next one.

  1. Step 1 of 5

    Wax molecules are middle-sized chains.

    Gas — very short chainsmethane, propaneWax — middle chainsmelts around55-60°CPlastic — very long chainsmelts far hotter

    Short carbon chains are gases, long ones are hard plastics. Wax sits in between — solid when cool, but melting at a temperature a small flame can reach.

  2. Step 2 of 5

    The wick is not the fuel.

    The wick Gaps that draw liquidupward

    The wick is a bundle of twisted cotton fibres. Its job is to carry liquid wax upward into the flame, which it does through the gaps between its fibres.

  3. Step 3 of 5

    It is the wax gas that burns.

    1 Solid wax2 Melted bythe flame3 Turned togas at thewick tip4 The gasburns

    Liquid wax reaching the top gets hot enough to become a gas, and it is that gas which meets the air and lights. Solid wax will not catch at all.

  4. Step 4 of 5

    The loop keeps itself in balance.

    The flame's sizeMore heat melts more waxThe wick can only carry so much

    A bigger flame melts more wax, and the wick can only draw so much. That limit is what keeps a candle burning at a steady size for hours.

  5. Step 5 of 5

    The wick curls into the flame and burns away.

    The wick curls outwardIts tip reaches thehottest edgeThere it burns awaySo it stays the rightlength

    A well-made wick bends outward as it burns, into the hottest, most oxygen-rich edge, where its tip is burnt off. That is why it never needs trimming.

    A household candle gives off roughly 80 watts of heat — about the same as a person sitting still, and about a tenth of it as light.

The short version

A candle works as a loop: the flame melts wax, the wick draws it up, the heat turns it to gas, and the gas feeds the flame.

Try it yourself

Blow a candle out and watch the wick smoke. That white trail is wax gas the wick is still making, with nothing left to light it.

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