XDA

Whatever it was, it kept Saracen invaders out of Constantinople for a few centuries. Greek Fire was the Dark Ages secret weapon and the recipe was kept so secret, we don't to this day know what it was really or how it was made. It was invented around 672 AD, during the reign of Emperor Constantine IV, by a Greek architect, Kallinikos, who took refuge in Constantinople when his own town, Heliopolis, in Syria, was overrun by Muslim jihadist. The liquid weapon he invented floated on water, clung to any hard surface, could not be extinguished once started, and burned up everything it came in contact with. Wow. That's a weapon. It was most effective at sea against wooden ships.

More than 580 years later, Albertus Magnus wrote, around 1250 AD, a formula which included resin (colophonium), sulfur, saltpeter and linseed oil. However, this is clearly not the feared Greek Fire. It doesn't cling and and the flame this stuff produces doesn't survive a dousing with water. Phosphorus has to be involved, if only for the cannot be extinguished by water part. A more volatile substance than linseed oil, like naphtha, mixed with the some other secret ingredient could have the cling characteristic that the jellied gasoline we call napalm certainly has. Others have stated, as if a fact, that it was a colloidal suspensions of metallic sodium, lithium, or potassium--or perhaps quicklime--in a petroleum base. A colloidal suspension we have some familiarity with is Hollandaise Sauce. Somehow I can't see ancient Byzantines whipping naphtha and sodium over heat until it thickened. The quicklime mentioned contains calcium phosphide which, when exposed to water, puts off phospine (phosphorus hydride, Ph3), which ignites spontaneously. Hmmm. Quicklime and jelied gasoline--what could be more dangerous?

The recipe, it seems, is to be forever secret. Of course, the inhabitants of Constantinople would not have called it Greek Fire as they considered themselves Roman, which they were.