Fire piston

Hmm, is so fun to play with this device known as fire piston. However you need a great strength to push the piston in order for the cotton wool (or any combustible material) to ignite. Above is the video of fire piston.

A fire piston is a device of ancient origin which is used to kindle fire. It consists of a hollow cylinder ranged in size from around 7.5 cm to 15 cm long, sealed at one end and open at the other. A piston which is about 1-2cm in diameter, can slide into the cylinder forming an airtight seal with the cylinder wall. The piston has a handle on the end to allow a firm grip to be applied to it and can be completely withdrawn from the cylinder.

The piston must be rammed quickly into the sealed cylinder with a single stroke. The compression of the air causes the temperature to rise rapidly to 260 degrees Celsius. This is hot enough for the cotton wool inside the piston to ignite. It can then be withdrawn and transferred to a larger mass of kindling to create a fire.

The principle of fire piston works based on rapid compression of the air (known as adiabatic compression) increases its pressure and its temperature at the same time. If this compression is done too slowly the heat will leak away to the surroundings as the gas returns to equilibrium with them. If the compression is done quickly enough then there is no time for equilibrium to be achieved and the absolute temperature of the air can suddenly become several times that of its surroundings, increasing the original room temperature of the air to a temperature hot enough to set the cotton wool alight. The air in the cylinder acts both as a source of heat and an oxidizer for the cotton wool.