Do we know exactly what Greek fire was?

Nope. And neither does anyone else, apparently:


http://en.wikipedia.org/wiki/Greek_fire

Greek fire was a burning-liquid weapon used by the Byzantine Greeks, typically in naval battles to great effect as it could continue burning even on water. "Byzantine fire" was largely responsible for many Byzantine military victories, and partly the reason for the Byzantine Empire surviving as long as it did. The formula was a secret and remains a mystery to this day.

Do we know exactly what Greek fire was?

Not really. It was probably similar to naphtha or naphtha was a component. Interesting topic, I wouldn't mind knowing the true answer.

It's not a secret. I have a book of formulas from the 30's which gives the recipe. Perhaps the actual recipe that the Greeks used is a mystery, but the same effects can be replicated with modern chemicals.

Wait, I have it. The Colonel's secret recipe.


http://www.hypatia-lovers.com/footnotes/Section10.pdf

Fortunately for us, a formula for Greek Fire has survived through a passagefrom the Eighth Century* book of Marcus Graecus, Liber Ignium ad Comburendos Hostes — a passage which has come down to us through a quotation by the Ninth Century Arabian physician, Mesue: "Greek Fire is made as follows: take sulfur, tartar, sarcocolla, pitch, melted saltpeter, petroleum oil, and oil of gum, boil all these together, impregnate tow [i.e., the coarse or broken part of flax orhemp, prepared for spinning] with the mixture, and the material is ready to be set on fire. This fire cannot be extinguished by urine, or by vinegar, or by sand ... Flying fire may be obtained in the following manner: take one part of colophony [rosin], the same of sulfur, and two parts of saltpeter. Dissolve the pulverized mixture in linseed oil, or better in oil oflamium. Finally, the mixture is placed in a reed or a piece of wood which has been hollowed out.When it is set on fire, it will fly in whatever direction one wishes, there to set everything on fire.
There, will that do? He's probably just guessing though, obviously.

The formula I saw is a clear liquid that catches fire spontaneously when it evaporates.

"Greek Fire is made as follows: take sulfur, tartar, sarcocolla, pitch, melted saltpeter, petroleum oil, and oil of gum, boil all these together, impregnate tow [i.e., the coarse or broken part of flax orhemp, prepared for spinning] with the mixture, and the material is ready to be set on fire. This fire cannot be extinguished by urine, or by vinegar, or by sand

Anyone wanna explain to me why they tried urine and vinegar before they tried WATER!

They tried water first but it made the fire spread even more.

Actually, what I found in -at least two- greek sites was that vinegar and urine did extingush the fire. I also read that the exact nature of greek fire is not known even today only some substances mentioned by the other members. That is because the officers (in Byzantium) responsible for the production would talk about it to the emperor only and no one else.

In Greek it is called liquid fire -igron pyr. The English called it Greek fire when Richard I found the secret formula in about 1194.

Part of the legend one learns at Johns Hopkins concerns one of JHU's great early physicists, R W Wood. It is said that occasionally after rains, he would go into the slums of Baltimore with some small chunks of Sodium (under oil, of course) and toss them into puddles. (I do not recall if that alone is enough to cause the water to appear to burn as hydrogen is released or a lit match was tossed in soon afterwards.) Legend has it that he dressed appropriately in black etc.