The Mills bomb design for grenades was used until the 1980s.
According to the Spiritus-Temporis website, the most widely known and manufactured grenades are the pin and pineapple types. The first version of the pin and pineapple grenade was the British designed Mills bomb, created by William Mills in 1915.
Spiritus-Temporis reports that the early history of grenades is filled with simple versions made from paper, ceramics or glass containing dangerous substances that broke apart when thrown at an enemy. Included in the early grenades was the use of eggs of parasites, such as fleas and lice to infect an enemy camp. The English Civil War in the 17th century saw the first use of primitive metal casings filled with gunpowder and fitted with slow-burning fuses to ignite the gunpowder in the case. These primitive grenades were not seen as effective and the use of grenades did not become widespread until the outbreak of World War I.
According to Spiritus-Temporis, an early grenade still in use as a homemade grenade is the Molotov cocktail. This grenade is made by pouring gasoline or another explosive substance into a bottle, placing a cloth in the bottle and lighting it. The Molotov cocktail is then thrown and ignites when the bottle breaks.
World War I saw the grenade become an important weapon with the German army leaping ahead in early development before quickly being caught by allied forces using versions such as the Mills bomb. The Mills bomb was created with a serrated casing that broke apart during the explosion to become a fragmentation bomb. Spiritus-Temporis explains that the German army developed the stielhandgranate, or stick grenade. The stick grenade was made up of an explosive charge encased in a metal can, which in turn was attached to a wooden stick for easy throwing.
The Inert Ord website reports that grenades such as the Mills bomb were designed with a water-tight centerpiece inside the metal casing. The centerpiece held the fuse mechanism, detonator and the explosive. The explosive was poured into the grenade via a plug on the top side of the casing.
There are two types of detonator used in grenades, according to the First World War website-an impact or percussion detonator and a timed fuse. During World War I the use of a pin to hold the striking pin in place became commonplace to avoid accidental detonation of grenades. Stick grenades were activated with the fuse being lit by friction as the can holding the explosives left the stick. In the pin and pineapple grenade the strike lever is released when the grenade is thrown, releasing a four-second fuse, which makes the explosives within the grenade ignite after four seconds.