Even the most nuanced and worldly prankster can still appreciate the simple pleasure of watching someone blow out their birthday candle – and then blow it out again – and again – and again, before finally realizing there is some trickery afoot. Of course, the fun wears thin after Grandma Betty’s sixth wheezing attempt, but all good things must come to an end at some point. But how exactly does the classic trick candle keep relighting itself? At the risk of ruining some of the magic, we’ve got the answer here.
Your average, everyday candle uses a wick made of braided cotton oranother flammable material, usually coated in wax. Once you blow out the flame, the only thing that remains is an ember which dies almost immediately. Despite its short lifespan, the ember can still melt wax, which creates “paraffin vapor”, or a plume of smoke. Once the ember dies, the smoke vanishes, the wax gets hard again, and you no longer have to worry about burning the house down.
A trick candle has a wick, too, but its wick will have magnesium flakes, or flakes from a comparable metal, in it. These metals can autoignite at temperatures of 800 degrees Fahrenheit, which is pretty low, and once they get going they are very hard to extinguish. The ember left behind is hot enough to spark the metal flakes again, which will keep the flame going even after you’ve blown it out. The downside to all this is that while it’s fun, it also means your birthday wish doesn’t have the chance to come true, which means you’re not going to get that pony, Suzy.
The same wicks that are used in trick candles today have historically been used for explosives like dynamite, and as a survival tool for anyone venturing out into the great unknown, but these days they are chiefly used to make people laugh at birthday parties. Sorry, Canadians, but you’re not invited to the party; trick candles are illegal in Canada.