There has been some debate on what Greek Fire actually was. Most historians agree that it made use of petroleum and others throw around combinations of pine resin, quicklime, calcium phosphide, sulfur, or niter. So then let us briefly examine some of these components to the best of my ability, bearing in mind that chemistry has never one of my strong subjects!
Pine Resin This seems like a likely enough candidate. It is certainly a substance prone to inflame, particularly the sticky resin used to make turpentine and obtained from the low growing terebinth tree of the Mediterranean. Pine resin likely also thickened the mixture, helping it to cling to armor, skin and the sides of wooden sea going vessels.
Naphtha would have been the petroleum component in the mixture. Also flammable, it forms part of the word for Napalm, probably one of the world’s best known incendiaries. The word is derived from Persian and comes to us in the Latin and Greek. However then it would have simply been a term for crude oil and was probably what was referred to when used in Greek fire.
Quicklime From what I have studied, the use of quick lime, or calcium oxide, in actual application for the liquid is highly probable, though there are those who would disagree with me. When calcium oxide makes contact with water, it increases its temperature above 150°C. In addition, the fumes from burning this substance are irritants to the skin and mucous membranes. Not a nice thing to be hit with when the wind isn’t favoring you. It certainly speaks on Greek’s Fire’s notorious reputation for the flames increasing in intensity when water was poured on it.
Calcium Phosphide This, like quicklime is known to react with water. Historically, it was made by boiling bones with charcoal and lime in a closed container, possibly made of clay. When put in contact with water calcium phosphide releases phosphine, which is actually explosive. Calcium phosphide is used in modern times in incendiary weapons and in fireworks and torpedoes. It has also been used as a rodenticide, reacting with the acids in the animals’ digestive systems.
Niter is the mineral form of potassium nitrate, also known as saltpeter and commonly an ingredient of gunpowder. During the American Revolution, back country caves in Kentucky were a common source for saltpeter needed for gunpowder. Niter as well as sulfur have both been disputed as actually having any actual bearing in the formula. For one thing, saltpeter was not supposed to have been known in the West before 1125.
Sulfur would have been well known all the way back to ancient times and was known then as brimstone. There is no doubt it was used by itself or with bitumen hurled in clay pots as an incendiary weapon. As a component for Greek fire, however, many experts seem to be unconvinced.
So do we know what Greek Fire was really composed of? Have all attempts to reconstruct this substance failed? Perhaps not. Watch this documentary showing how Greek Fire may have been sprayed using a sort of ancient flame thrower.
For more information, see also:
A History of Greek Fire and Gunpowder
By J. R. Partington
Greek Fire, Poison Arrows, and Scorpion Bombs: Biological & Chemical Warfare …
By Adrienne Mayor