How Matches Work

posted: 04/11/12
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A match will start a fire.

Unlike most of our ancestors throughout history, making fire is a snap for us. Ever since the match was invented in 1827, most people take it for granted and never bother to learn how this magical little stick can conjure up fire. Let's dissect the chemical reactions going on inside a match.

The Ingredients for Fire

Although they're made from different materials than gunpowder, matches contain the same kinds of ingredients necessary for fire, which explains why (in the right quantities) they can be as explosive. Specifically, these ingredients are an igniter, a fuel and an oxidizer. In a match, these roles are played by red phosphorus, sulfur and potassium chlorate, respectively.

But before we explain the purpose of each of these, we should mention a few other supporting elements. Ammonium phosphate, for instance, is impregnated into the matchstick wood to stifle afterglow when the flame dies. The stick is bathed in hot paraffin wax, which ensures the flame burns down past the head to the stick. Animal glue in the head has a dual purpose: It binds the materials and serves as extra fuel. Another important element is the powdered glass inside the head, which provides the friction that aids striking but also helps bind the materials and creates an even burn.

Lighting Up

Phosphorus is the star of the show when it comes to igniting a match. And like many Hollywood starlets, it's unstable, sensitive and volatile. This is especially true for white phosphorus, which can ignite spontaneously in the air and was used in early matches. Modern matches use an allotrope of the same element called red phosphorus. But the white variety still makes a cameo: The friction that results from striking against powdered glass generates enough heat to convert some of the red phosphorus to white phosphorus.

Adding Fuel to the Fire

Phosphorus alone would make a spectacular (but brief) one-man show. To sustain itself, the flame needs something to burn and more oxygen than it can get from the air. The fuel, sulfur and the oxidizing agent, potassium chlorate, work together in their capacities. The heat generated from the phosphorus is enough to break down potassium chlorate, and in the process, it releases oxygen. This oxygen combines with sulfur, allowing the flame to thrive long enough for us to light a candle or barbecue.

We've described what's called a strike-anywhere match -- in which all these reactive components are packed together in its head. In safety matches, the phosphorus is contained in a separate strip.

And in case you're wondering, the matchstick isn't a natural redhead: Red dye is added to the tip to lend a dash of drama to the ensemble.

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