Is it possible to ignite flesh?

[Elfdart]

One factor in burning human bodies in so-called spontaneous human combustion is air supply. In order for the bodies to do a slow burn that reduces the corpse to a charred skeleton (if that much), a steady supply of oxygen is necessary. So it either has to happen outdoors (think of Viking funerals) or under special conditions indoors. Many cases involve apartments, trailers or houses with open spaces under the location of the burning corpse. This creates a "chimney effect" as cooler air from below is sucked into the fire as the hot air and smoke flow upward.

These types of burnings often start as little things like a drunk, sick or elderly person falling asleep with a lit cigarette. The clothes or furniture or carpet catch fire, then the human fat and flesh burns and if left alone, the only things left are the bones and a greasy spot. The burn is often very slow and low-temperature, so the rest of the room is more or less undamaged. This is why people thought something eerie or supernatural was going on.

[Broomstick]

It was most likely liquid oxygen.

Yes, that would make more sense. Actually, I don't think they ever said what they dipped the twinky in, just that they froze it down...

Here's a tip:

Liquid oxygen is light blue. Sky blue, in fact. Pretty neat looking stuff.

[tharkûn]

As the thread title says. I'm not that familiar with the chemistry of the human body except for the fact that it's hydrocarbon-based and mostly water. I know that fats can burn (anyone who's ever BBQ'd something will know that), but what about flesh itself? And if it's possible, what would it take in order to make this happen?

Yes you can ignite flesh. What would it take? High fat content and a source of ignition (the hotter the better, but at least 250 C). Numerous cases of alleged spontaneous human combustion resulted from elderly smokers and prolonged human combustion has been oberserved in numerous fire investigations.

I'm asking because of the way General Grievous got burned to a crisp in ROTS.

Did the fire burn just upward or downward as well, I cannot recall? Presumably a collection of organs would not make all that impressive of candidate for human combustion, fat content would be low. If the fire burns downward you are dealing with very high heats, far greater than required to simply ignite flesh - assuming you don't have something else propogating ignition.

In the case of Grievous, Aunt Beru, and Uncle Owen, the flames destroyed the bulk of their flesh but were insufficient to destroy the skeletal structure (although in the case of Grievous, that's meaningless since his skeleton is metal).

No it is not. Any element not in its highest oxidation state can combust if oxygen is present and the temperature is hot enough. The atoms in metal are never in their highest oxidation state, otherwise you have something else like say a salt or ceramic, so if a metal doesn't ignite you know something about the temperature and something about heat exchange.

If the fireball Grevious becomes burns downward then the combustion is being driven by something other than stock fat combustion (which virtually never burns downward, often leaving the feet unconsumed). That could be a polymer casing on his organs which is exothermicly decomposing or the intitial heat source creating a ludicriously hot zone of ambient heat or other more screwy things. If the metal doesn't combust then the ambient temperature never reached the ignition point.

Getting numbers out requires knowledge of the all aspects of the problem:
total ambient pressure, partial pressure of oxygen, metal surface area to volume ratio, geometry of the ignition source, etc. We simply know he was likely burning at well over 700 C (that takes about 15 minutes to char away flesh to the bone) and somewhere under 4000 C (where you kiss all the metals goodbye).

What you can get out is materials his skeleton wasn't composed of: magnesium, aluminium, tin, bismuth, zinc, or alloys of these metals. Chromium and tungston would be extremely good candidates for him to made of.

In the case of Beru and Owen they might simply have not had sufficient time to burn to completion. At 1000 C it takes about an hour to completely cremate the body, though temperatures as low as 500 C work with wick effect.

[nickolay1]

It was most likely liquid oxygen.

Yes, that would make more sense. Actually, I don't think they ever said what they dipped the twinky in, just that they froze it down...

Here's a tip:

Liquid oxygen is light blue. Sky blue, in fact. Pretty neat looking stuff.

If it was liquid nitrogen or any other inert gas, the twinkie would not burn too well (it'd be very cold and hard to ignite). However, liquid oxigen allows for rapid oxidation (combustion) of the twinkie, enough to overcome the low temperature.