Why Do Matches Ignite When Struck?

Daily life often involves the use of matches. When we need to use them, we simply take out a match and strike it against the side of the matchbox. With a soft “swish” sound, the match ignites. Why does a match ignite so easily? We will explain this in detail below.

The combustion principle of safety matches

The entire match ignites easily because its components are combustible: The main ingredients of the match head are antimony (III) sulfide and potassium chlorate, and the matchstick is made of soft and porous wood such as aspen or pine. The front end of the stick is thoroughly treated with paraffin wax and rosin. The side of the matchbox is coated with red phosphorus and glass powder.

When we strike the match against the side of the matchbox, the match head catches some red phosphorus. Upon frictional heating, the red phosphorus ignites. The ignition of red phosphorus generates oxygen from potassium chlorate, which quickly ignites the antimony (III) sulfide. Consequently, the match ignites with a soft “swish” sound. These matches are called safety matches, and will not light up unless the match head is rubbed against the side of the matchbox. In the past, matches made of tetraphosphorus hexoxide ignited easily from friction against a wall, shoe, or even clothing, which was convenient but not secure.

The structure of safety matches

Safety matches consist of three parts: the match head, the matchstick, and the matchbox.

• The match head primarily contains potassium chlorate, manganese dioxide, sulfur, glass powder, glue, and other additives.

• The matchstick is made of a softwood such as pine that is soaked in ammonium phosphate (to prevent the charred remains from falling off and leaving a complete residue during combustion); a small amount of paraffin wax is applied to one end of the matchstick.
  

• The side of the matchbox is coated with red phosphorus, antimony (III) sulfide, glass powder, and glue.
  

The temperature required for objects to burn varies. Starting temperature is called the “ignition point.” The ignition point for paper is 450°C, and for wood is about 400-470°C. In the late 19th century, match heads consisted of white phosphorus, which ignites at 30°C. White phosphorus is a soft, yellowish-white translucent solid that becomes brittle when cold and changes color when exposed to light. It produces greenish phosphorescence and white smoke in the dark in the air. It ignites at approximately 40°C in humid air, and slightly higher in dry air.

Later, red phosphorus used in safety matches had a very low ignition point, albeit only approximately 260°C. However, this significantly improved the safety factor for matches. The temperature generated by friction is sufficient to ignite red phosphorus, which has a low ignition point. Although the starting temperature for ignition is low, the temperature of the match can reach as high as 2500°C at the moment of ignition. In summary, matches can spontaneously ignite when their temperature reaches 260°C.