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