Henry Langston, of King's High School, asks :-

What is Greek Fire?

Kathryn McGrath, a chemist at the University of Otago, responded.

Greek Fire was first documented as being used by the Byzantines against the Saracens during their siege of Constantinople in 678. A search for the exact recipe of this highly flammable fluid generates a widely varying answer and indeed even after perusal of J.R. Partington's seminal text `A History of Greek Fire and Gunpowder' one must be forgiven for remaining unclear as to its composition.

Many misleading translations from Greek anthologies have Greek Fire ranging from liquid petroleum alone through to it being the first documented use of gunpowder. Indeed neither of these simple answers is the case, gunpowder being invented in much later times. Considerable mystery surrounded the composition of the fiery liquid, with rumours that the composition was passed down from emperor to emperor over several centuries. While in truth Greek fire was probably invented by a chemist in Constantinople, it was said that the recipe had been revealed to Constantine the Great by an angel, and it became regarded as a Byzantine state secret.

The true advantage of the weapon however was its method of delivery rather than its exact formulation, as similar mixtures had been used in warfare previously. First used in Naval warfare, Greek Fire was shot as a burning material from hand held siphons mounted on the prows of the galleys of Byzantine naval ships, causing panic and dread in the Saracen warriors.

The liquid fire could travel large distances, remain burning even on contact with water, and only be extinguished through the use of vinegar, sand or mud, or urine. The hand held pumps, later used ironically in fire extinguishing, were often mistaken as being the precursors to hand grenades. Such munitions did, some centuries later, come into wide spread usage but the pump-action liquid fire of the late seventh century brought terror to the Saracens who later mastered the technology using it during the Crusades in Syria and Egypt.

It is believed that the basic recipe contained liquid petroleum, also known as naphtha (the aromatic solvent extracted from coal tar), sulphur and quicklime (calcium oxide) a caustic white solid. Variants included the addition of pitch, resin and bitumen or asphalt. The inclusion of these ingredients changing the consistency of the fluid allowing the mixture to be tailored for specific use in initially flame-throwing and later hand-thrown fire bombs. Greek Fire remained as a major military aid for several centuries and indeed during the First World War pumps throwing burning petroleum were still in use.