Speaker 1: Welcome to Brainstuff from how stuff works dot com where
Speaker 1: smart Happens. Hi Am Marshall Brain with today's question, how
Speaker 1: does a candle work? Candles really are an amazing lighting system.
Speaker 1: The fuel itself is the package. There are two parts
Speaker 1: that work together in a candle. First there's the fuel,
Speaker 1: made of some sort of wax, and then there's the wick,
Speaker 1: made of some sort of absorbent twine. The wick needs
Speaker 1: to be naturally absorbent like a towel, or it needs
Speaker 1: to have a strong capillary action like the glass wicks
Speaker 1: that you see in some oil lamps. If you buy
Speaker 1: a length of unwaxed wick at a craft store and
Speaker 1: play with it, you'll find that it feels like soft
Speaker 1: string and that it absorbs water really well. This absorbancy
Speaker 1: is important in a candle because the wick needs to
Speaker 1: absorb liquid wax and move it upward while the candle
Speaker 1: is burning. Paraffin Wax is a heavy hydrocarbon that comes
Speaker 1: from crude oil. When you light a candle, you melt
Speaker 1: the wax in and near the wick. The wick absorbs
Speaker 1: the liquid wax and pulls it upward. The heat of
Speaker 1: the flame vaporizes that wax and it is the wax
Speaker 1: vapor that burns. You can prove that it's the wax
Speaker 1: vapor rather than the liquid wax that's burning. With this experiment.
Speaker 1: The next time you blow out a candle, notice a
Speaker 1: stream of white smoke leaving the wick. This stream is
Speaker 1: paraffin vapor that's condensed into a visible form. It continues
Speaker 1: to form as long as the wick is hot enough
Speaker 1: to vaporize paraffin. If you touch a lit match to
Speaker 1: the stream, even a foot or two away from the wick,
Speaker 1: a flame will run down the stream and relight the wick.
Speaker 1: The reason the wick doesn't burn is because the vaporizing
Speaker 1: wax cools the exposed wick and protects it. You may
Speaker 1: have seen the camping trick where you put a cup
Speaker 1: of water on a fire, or the paper cup won't
Speaker 1: burn because the water inside it cools it. The liquid
Speaker 1: wax does the same thing for the wick, cooling it
Speaker 1: so it doesn't burn up. Paraffin wax will burn on
Speaker 1: its own, but it's like cooking oil or motor oil.
Speaker 1: You have to get it very hot for combustion to begin.
Speaker 1: An oil fire is intense and very hard to put out.
Speaker 1: Paraffin is the same way. In a candle. This works great,
Speaker 1: though only a tiny amount of wax on the wick
Speaker 1: is hot enough to vaporize and burn. For more on
Speaker 1: this and thousands of other topics, does it, How stuff
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