Everyday Science

Why don't trick birthday candles go out?
Answered by Science Channel
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    Science Channel

  1. Burning candles as tributes is a tradition that could date back to the ancient Greeks, who baked round cakes as symbols of the moon and added candles to represent moonlight [source: Wonderopolis]. Ancient Egyptians had candles, too, probably as early as 3000 B.C. The Egyptians' candles weren't designed with wicks like modern birthday candles, however. The Romans (ever heard the term "Roman candle?") were credited with creating the wick design [source: National Candle Association]. Candles also played an important role in early Jewish religious celebrations. The wax creations always have served as more than household helpers. It's possible that the birthday/make-a-wish tradition started with the belief that candles' smoke carried wishes to the sky, and to the gods.

    At some point, however, just singing and making wishes from blown-out candles wasn't enough fun. Friends, family members and co-workers decided to up the bar on birthday boys and girls with trick, or magic relighting, candles. Technically speaking, trick birthday candles go out when you blow on them, but they relight themselves so quickly that they appear to never extinguish.

    When you blow out a normal candle, there's still a little burning ember in the wick that vaporizes the paraffin and creates a ribbon of smoke. But that ember isn't hot enough to actually ignite the paraffin vapor. Manufacturers add substances to the wicks of trick candles that are flammable enough for the embers to light and then ignite the paraffin vapor. Often, this substance is magnesium, which ignites at just 800 degrees Fahrenheit (430 degrees Celsius). Once the magnesium dust catches fire, it gets hot enough to light the paraffin vapor and the candle starts to quickly burn again. So just adding extra air to the mix -- usually enough to take out the flame -- doesn't get the job done on relighting candles. Birthday celebrants (and usually a few kids who join in) can keep on blowing, but the darn candles keep on relighting.

    The good news is that paraffin and other common candle waxes -- though not as tasty as cream cheese frosting -- are not toxic. So there's no need to worry about how long it takes while everyone gets their laughs and the relighting candles melt onto that yummy homemade carrot cake.

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