How Do Trick Candles Work?


Trick candles re-light themselves after you blow them out.
Trick candles re-light themselves after you blow them out.

If you celebrate your birthday by blowing out the candles and making a wish, you’ll face a challenge using trick candles. Trick candles are novelty candles that relight themselves a few seconds after being blown out. Here’s a look at how trick candles work and why they aren’t legal everywhere.

Trick Candles vs Normal Candles

Both trick candles and normal candles work by burning candle wax. Wax combustion is a chemical reaction that produces carbon dioxide and water. The burning wick supplies the activation energy to support wax combustion.

When you extinguish a normal candle, you’ll see a thin ribbon of vapor rise from the wick. This is vaporized paraffin wax. If you’re quick enough, you can hold another lit candle a short distance from the extinguished one and relight it by igniting the vapor trail. Otherwise, blowing on the wick of a freshly-extinguished candle makes the wick glow red-hot, but won’t get it hot enough to relight the flame.

Trick candles are just like normal candles, except fine flakes of magnesium are embedded in the wick. Magnesium is a metal that ignites at a relatively low ignition temperature (800 ºF or 430 ºC) and combines with oxygen to release light and heat. It releases enough heat that it’s used in fire starters and fireworks fuses. As a trick candle burns, the wax shields the magnesium further inside the wick from the oxygen in air. But, exposed magnesium near the flame produces telltale sparks. When the flame goes out, the wick ember remains hot enough to ignite the magnesium. The heat of burning magnesium ignites the paraffin vapor right above a freshly-extinguished candle and rekindles the wick.

Watch a trick candle relight itself.

Using Trick Candles Safely

Trick candles aren’t available everywhere. For example, they have been banned in Canada since 1977. The reason is that an unsuspecting person might discard hot trick candles and accidentally start a fire.

When you are finished using trick candles, extinguish them by dousing them in water. Don’t throw away the candle until it’s completely cool and you’re certain it won’t relight.

Who Invented Trick Candles?

Novelty candles have been around for decades, while people have known about magnesium’s pyrophoric properties since the 19th century. So, identifying the inventor of the trick candle is… well… tricky. However, there are a couple of patents that describe products similar to trick candles. Japanese inventor Toshio Takahashi invented a “self-ignited candle” in 1983 using a wick containing aluminum, iron, magnesium, or an alloy of the metals. In 2003, Earl M. Stenger filed a U.S. patent for a wind-resistant candle with a wick containing magnesium or a magnesium-aluminum blend.

References

  • Dreizin, Edward L.; Berman, Charles H.; Vicenzi, Edward P. (2000). “Condensed-phase modifications in magnesium particle combustion in air”. Scripta Materialia. 122 (1–2): 30–42. doi:10.1016/S0010-2180(00)00101-2
  • Government of Canada.”Prohibited Products.” Information for Canadians Travelling Outside of Canada.
  • Wang, Linda (2010). “Why are trick candle flames so impossible to blow out?”. C&EN Vol. 88, 32. ISSN 0009-2347.

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