Real history question: Greek fire

[Ser Lepus]

i have read a lot of books about medieval warfare, and many of them mention the legendary Greek fire.

 

Most modern reconstructions of the weapon describe a metal chamber of pot with a mix of flammable substances that is heated (to keep the oils in liquid state) and has air pumped to create pressure. I often think that the air pump is an unnecessary complication, when there is an easier, less complex solution:

 

I have always wondered... since olive oil has a boiling point of 300º C/570ºC and an autoignition point of around 400º C/ 750º C, while and ethanol (which was discovered around the Middle Ages) has a boiling point of 79º C/172.4º F...why not using olive oil as base and adding the right amount of ethanol?

 

You heat the mix up to around 100º C, the ethanol component becames gaseous (while the oil remains in liquid state), and you have the required pressure without the need of adding a pump.

 

You could add some outer tin plating to the bronze chamber as a security measure: If the tin starts to melt, that means that you have reached 232ºC / 449.4º F, which means you are going dangerously close to oil's boiling point and should stop adding heat.

 

Would that work? Or would it explode? I have little knowledge of engineering, chemistry or explosives, so it may as well be a stupid idea.

[White Walker Texas Ranger]

I think that modern chemists know a number of different techniques that could recreate the general effects of Greek Fire, but historians have no idea which one the Greeks used, or if it's even one of the ways the proposed.

[maarsen]

Greek fire was supposed to ignite when exposed to air. GRRM uses wildfire as an analogue to Greek fire as both of them worked the same way. The Greeks did not have phosphorus, or any method of extracting it, as far as we know, so auto ignition is the real mystery.

[sologdin]

historians have no idea which one the Greeks used

grecians very plainly had domesticated ignivomous reptilians that they put in cages for use as anti-vessel ballistics. endemic warfare sadly led to the extinction of same.

[SkynJay]

My sologdin is a bit rusty. Did we just learn the Greeks used domesticated dragons?

[Lykos]

Greek fire was supposed to ignite when exposed to air. GRRM uses wildfire as an analogue to Greek fire as both of them worked the same way. The Greeks did not have phosphorus, or any method of extracting it, as far as we know, so auto ignition is the real mystery.

 

Quicklime

[Ser Lepus]

Actually, the question was specifically about what would happen if you mixed olive oil and alcohol in a chamber and heated it to 100º C in order to create pressure for the flamethrower. Any idea?

[Lykos]

Ser Lepus, I don't really know, but I think it would only have worked in times when better more effective solutions were available.

 

The first problem is the availability of distilled alcohol, which was first done either in 900 by Muhammad ibn Zakariyā Rāzī (german wiki) or in 1200 at the School of Salerno, though the principle of distillation was known much earlier. 

 

The other problem is the mass production of a portable devise with a controlled heating mechanism. I think they could have built something like the Aolipile  for alcohol, where the expanding ethanol gas passes by or through a second oil container and carries that through a nozzle where the stream of gas and droplets of oil are ignited. 

 

I don't think the solution with a mix of alcohol and oil in one container would work, wouldn't they seperate and the gas go either off without carrying any oil with it or in case the outlet is below the level of the oil, just press out pure oil that wouldn't ignite?

 

And to make it an effective weapon you need to make the oil stick to the target.

[Ser Lepus]

Ser Lepus, I don't really know, but I think it would only have worked in times when better more effective solutions were available.

 

The first problem is the availability of distilled alcohol, which was first done either in 900 by Muhammad ibn Zakariyā Rāzī (german wiki) or in 1200 at the School of Salerno, though the principle of distillation was known much earlier. 

 

The other problem is the mass production of a portable devise with a controlled heating mechanism. I think they could have built something like the Aolipile  for alcohol, where the expanding ethanol gas passes by or through a second oil container and carries that through a nozzle where the stream of gas and droplets of oil are ignited. 

 

I don't think the solution with a mix of alcohol and oil in one container would work, wouldn't they seperate and the gas go either off without carrying any oil with it or in case the outlet is below the level of the oil, just press out pure oil that wouldn't ignite?

 

And to make it an effective weapon you need to make the oil stick to the target.

 

The creation of Greek Fire was a secret procedure; maybe the Byzantines learnt to distill alcohol first but the procedure was lost due to secrecy and rediscovered later by Muhammad ibn Zakariyā Rāzī. Or they might have used some other substance than alcohol.

 

The exit tube for the oil could come out from the lower part of the bronze chamber, that way the oil in the lower part of the chamber would come out before the gaseous alcohol in the higher part of the chamber.

 

Greek fire flamethrowers came in several versions, some smaller, portable versions were like our watergun toys, while others where huge and were carried in dromons. I think a dromon could easily carry a big bronze chamber or pot, and something like a brick forge to put the chamber on.

 

The main reason I am asking this is because this solution seems less technically complicated than the use of an air pump.