WEBVTT - How do trick birthday candles work?

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<v Speaker 1>Welcome to Brainstuff front house storks dot com where smart happens.

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<v Speaker 1>Hi am Marshall Brain with today's question, how do trick

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<v Speaker 1>birthday candles work? You know the kind that relight themselves

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<v Speaker 1>after you blow them out. You have to imagine a

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<v Speaker 1>birthday party with the poor guy turning forty years old.

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<v Speaker 1>Here's his cake and it's beautiful. It comes complete with

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<v Speaker 1>forty candles and they're all burning brightly, and now it's

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<v Speaker 1>time for him to blow the candles out. He makes

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<v Speaker 1>his first attempt, and then he realizes the agony of

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<v Speaker 1>what he faces because their trick candles. He can't blow

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<v Speaker 1>them out because they relight themselves automatically. This brings up

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<v Speaker 1>a good question, how do those trick candles work? And

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<v Speaker 1>what about normal candles? Candles are actually pretty amazing devices.

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<v Speaker 1>A candle has only two pieces. It has a solid

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<v Speaker 1>fuel made of paraffin wax or bees wax, and a wick.

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<v Speaker 1>But talk about something being greater than the sum of

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<v Speaker 1>its parts. A block of wax by itself is pretty useless,

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<v Speaker 1>and a wick by itself will burn in just a

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<v Speaker 1>few seconds. But when you put them together, you have

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<v Speaker 1>something that will provide a source of steady light and

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<v Speaker 1>heat for many hours. The wick of a candle actually

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<v Speaker 1>has two jobs. It's a pump and it's a fuel vaporizer.

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<v Speaker 1>When the wax melts, capillary action in the fibers of

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<v Speaker 1>the wick pumps the liquid wax upward. There, the heat

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<v Speaker 1>of the flame vaporizes the wax so it can burn. Meanwhile,

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<v Speaker 1>the top of the candle forms a small cup that

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<v Speaker 1>holds the liquid wax so it can enter the pump.

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<v Speaker 1>This brings up an obvious question, what is paraffin wax?

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<v Speaker 1>It's actually a hydrocarbon, just like gasoline or kerosene. In fact,

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<v Speaker 1>paraffin wax comes from crude oil, just like gasoline and

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<v Speaker 1>kerosene do. The reason why paraffin wax is a solid

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<v Speaker 1>while gasoline is a liquid has to do with the

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<v Speaker 1>length of the carbon chains in the fuel. In gasoline,

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<v Speaker 1>the carbon chains are eight carbons long. In kerosene, which

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<v Speaker 1>is a little thicker and oilier, there are twelve carbons long.

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<v Speaker 1>Paraffin wax has carbon chains thirty carbons long, long enough

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<v Speaker 1>to solidify it room temperature. The paraffin wax liquefies due

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<v Speaker 1>to the heat of the flame. The wick pumps the

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<v Speaker 1>wax upwards into the flame. The wax then turns to

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<v Speaker 1>a vapor that is quite flammable. To see how flammable

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<v Speaker 1>it is, try this experiment. Light a candle and after

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<v Speaker 1>it has been burning for a minute or two, blow

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<v Speaker 1>it out. You will see a stream of white smoke

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<v Speaker 1>rising from the wick. There is a tiny glowing ember

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<v Speaker 1>in the wick, and it's hot enough to keep vaporizing

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<v Speaker 1>the wax until the ember goes out. That white smoke

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<v Speaker 1>is actually paraffin wax vapor. If you touch a lit

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<v Speaker 1>match to the vapor right after you blow out the candle,

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<v Speaker 1>the flame will shoot down the stream of vapor like

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<v Speaker 1>a fuse and relight the wick. You can light the

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<v Speaker 1>stream as much as twelve inches away from the wick,

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<v Speaker 1>and the flame will travel down and light the candle.

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<v Speaker 1>It's a fun trick to show your friends. Now you

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<v Speaker 1>can see all the working parts in a normal candle.

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<v Speaker 1>There's the cup of liquid wax at the base of

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<v Speaker 1>the wick, the wick acting as a pump and vaporizer,

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<v Speaker 1>and the wax vapor that's actually burning in the flame.

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<v Speaker 1>The flame provides the heat to do the vaporizing, as

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<v Speaker 1>well as the heat to create the liquid in the cup.

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<v Speaker 1>It's genius. So how does a trick candle work? You

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<v Speaker 1>need to add one more thing to the wick. We

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<v Speaker 1>need something that the glowing ember can ignite so that

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<v Speaker 1>its ignition can relight the stream of vapor. That's something

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<v Speaker 1>is normally magnesium powder. The ember can light the specks

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<v Speaker 1>of magnesium. If you care only watch the wick of

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<v Speaker 1>a trick candle, you can see the specs bursting into

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<v Speaker 1>minuscule explosions of flame every few seconds. Those little explosions

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<v Speaker 1>of flame are enough to light the vapor, which relights

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<v Speaker 1>the wick, and the candle keeps burning. The addition of

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<v Speaker 1>that magnesium dust to the wick is all you need

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<v Speaker 1>to create a trick candle. It's simple but quite effective.

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<v Speaker 1>Try one of these trick candles at your next birthday party,

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<v Speaker 1>but not forty they'll ruin the case. For more on

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<v Speaker 1>this and thousands of other topics, is it how staff

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<v Speaker 1>works dot com