How Do Safety Matches Work?

I really can’t imagine how primitive men, who first made fire by rubbing stones together, would feel if they were shown a few matches. They probably wouldn’t even know what they were looking at! A couple of tiny twigs with colored tips!?

As it is, we have to give our ancient ancestors some credit for introducing us to the idea of how rubbing things together – or in technical terms, friction – could get things hot and ready to burn… which is the basic principle behind how matchsticks work.

Composition of matches

Parts of a safety match (Image Source: commons.wikimedia.org)

Matchsticks, as you have surely noticed, consist of a head and a wooden stick. The head usually contains potassium chlorate, an oxidizing agent, a small quantity of powdered glass that provides the essential friction while striking, animal glue to bind some other abrasives, and additive compounds like sulphur or antimony (III) sulfide that act as fuel. The wooden stick also has a certain substance, typically ammonium phosphate, impregnated in its composition to suppress the afterglow once the flame dies. The other part is the striking surface, which usually consists of red phosphorus, powdered glass (or silica), binder and filler.

Now, let’s go a bit deeper…

What really happens when you strike a match?

Safety matches

Rubbing the match against the striking surface provides the necessary friction (Image Source: commons.wikimedia.org)

When you rub the stick against the striking surface, the friction generated causes some of the red phosphorus present to turn into white phosphorus. Now, white phosphorus is highly sensitive and volatile; it ignites spontaneously in the air, making a flame. Once the stick has a flame at one end, all it needs to do is sustain it by providing it with more oxygen (oxidizing agent) than it can get from the air directly, and by giving it something to burn.

The heat released during ignition breaks down potassium chlorate, releasing a lot of oxygen for the flame to become larger. This oxygen combines with the sulphur contained in the head to sustain the miniature fire. Once the flame lives through its eventful initial phase, all it has to do is burn up the length of the wooden stick in the presence of atmospheric oxygen.

Strike-anywhere matches

A strike-anywhere match

The process we’ve discussed here is how safety matches burn; however, there is another variant of matches, known as ‘strike-anywhere’ matches, that are slightly different. As opposed to the former, these matches pack all the reactive components, such as sulphur, potassium chlorate, etc. in the head of the matchstick. Also, they usually have phosphorus sesquisulfide included in the matchheads, as it is easier to ignite with friction than red phosphorus. Also, unlike safety matches, these matches don’t need any specific striking surface; the phosphorus sesquisulfide that is present packs enough of a punch to ignite even with the help of a little friction.

If someone who has never lit a match in their lifetime were to read through the details of the process of lighting a match, they would undoubtedly believe that lighting a match is a long-winded process, but in reality, it’s far from it – provided the matches aren’t wet and it isn’t a windy day.