Speaker 1: Welcome to Brainstuff front house storks dot com where smart happens.
Speaker 1: Hi am Marshall Brain with today's question, how do trick
Speaker 1: birthday candles work? You know the kind that relight themselves
Speaker 1: after you blow them out. You have to imagine a
Speaker 1: birthday party with the poor guy turning forty years old.
Speaker 1: Here's his cake and it's beautiful. It comes complete with
Speaker 1: forty candles and they're all burning brightly, and now it's
Speaker 1: time for him to blow the candles out. He makes
Speaker 1: his first attempt, and then he realizes the agony of
Speaker 1: what he faces because their trick candles. He can't blow
Speaker 1: them out because they relight themselves automatically. This brings up
Speaker 1: a good question, how do those trick candles work? And
Speaker 1: what about normal candles? Candles are actually pretty amazing devices.
Speaker 1: A candle has only two pieces. It has a solid
Speaker 1: fuel made of paraffin wax or bees wax, and a wick.
Speaker 1: But talk about something being greater than the sum of
Speaker 1: its parts. A block of wax by itself is pretty useless,
Speaker 1: and a wick by itself will burn in just a
Speaker 1: few seconds. But when you put them together, you have
Speaker 1: something that will provide a source of steady light and
Speaker 1: heat for many hours. The wick of a candle actually
Speaker 1: has two jobs. It's a pump and it's a fuel vaporizer.
Speaker 1: When the wax melts, capillary action in the fibers of
Speaker 1: the wick pumps the liquid wax upward. There, the heat
Speaker 1: of the flame vaporizes the wax so it can burn. Meanwhile,
Speaker 1: the top of the candle forms a small cup that
Speaker 1: holds the liquid wax so it can enter the pump.
Speaker 1: This brings up an obvious question, what is paraffin wax?
Speaker 1: It's actually a hydrocarbon, just like gasoline or kerosene. In fact,
Speaker 1: paraffin wax comes from crude oil, just like gasoline and
Speaker 1: kerosene do. The reason why paraffin wax is a solid
Speaker 1: while gasoline is a liquid has to do with the
Speaker 1: length of the carbon chains in the fuel. In gasoline,
Speaker 1: the carbon chains are eight carbons long. In kerosene, which
Speaker 1: is a little thicker and oilier, there are twelve carbons long.
Speaker 1: Paraffin wax has carbon chains thirty carbons long, long enough
Speaker 1: to solidify it room temperature. The paraffin wax liquefies due
Speaker 1: to the heat of the flame. The wick pumps the
Speaker 1: wax upwards into the flame. The wax then turns to
Speaker 1: a vapor that is quite flammable. To see how flammable
Speaker 1: it is, try this experiment. Light a candle and after
Speaker 1: it has been burning for a minute or two, blow
Speaker 1: it out. You will see a stream of white smoke
Speaker 1: rising from the wick. There is a tiny glowing ember
Speaker 1: in the wick, and it's hot enough to keep vaporizing
Speaker 1: the wax until the ember goes out. That white smoke
Speaker 1: is actually paraffin wax vapor. If you touch a lit
Speaker 1: match to the vapor right after you blow out the candle,
Speaker 1: the flame will shoot down the stream of vapor like
Speaker 1: a fuse and relight the wick. You can light the
Speaker 1: stream as much as twelve inches away from the wick,
Speaker 1: and the flame will travel down and light the candle.
Speaker 1: It's a fun trick to show your friends. Now you
Speaker 1: can see all the working parts in a normal candle.
Speaker 1: There's the cup of liquid wax at the base of
Speaker 1: the wick, the wick acting as a pump and vaporizer,
Speaker 1: and the wax vapor that's actually burning in the flame.
Speaker 1: The flame provides the heat to do the vaporizing, as
Speaker 1: well as the heat to create the liquid in the cup.
Speaker 1: It's genius. So how does a trick candle work? You
Speaker 1: need to add one more thing to the wick. We
Speaker 1: need something that the glowing ember can ignite so that
Speaker 1: its ignition can relight the stream of vapor. That's something
Speaker 1: is normally magnesium powder. The ember can light the specks
Speaker 1: of magnesium. If you care only watch the wick of
Speaker 1: a trick candle, you can see the specs bursting into
Speaker 1: minuscule explosions of flame every few seconds. Those little explosions
Speaker 1: of flame are enough to light the vapor, which relights
Speaker 1: the wick, and the candle keeps burning. The addition of
Speaker 1: that magnesium dust to the wick is all you need
Speaker 1: to create a trick candle. It's simple but quite effective.
Speaker 1: Try one of these trick candles at your next birthday party,
Speaker 1: but not forty they'll ruin the case. For more on
Speaker 1: this and thousands of other topics, is it how staff
Speaker 1: works dot com