Of course, carbohydrates *are* explosive if you finely divide them and mix with air. Hence the general lack of metal parts anywhere near millstones.

Good point; I'd forgotten that.

Yes, I suppose containing its own oxidiser is the other vital component of an explosive, and there's no more reason for lembas to do so than any other food. Fair enough.

(Makes me slightly sad that LotR isn't SF, though; if it had been, someone would probably have solved a problem somewhere along the quest by powdering some lembas and using it as an impromptu bomb. That'd have been fun, if only for the surprised look on Legolas's face.)

Yes, that's exactly it. An oxidising agent in a fine mixture with a fuel. In the case of some explosives such as gunpowder they are different particles in the powder mixture; other explosives (nitroglycerine comes to mind, but I can't remember if I'm right) have one part of the molecule being an oxidising agent and the other the reducing agent. In the case of flour dust, the oxidising agent is the air; if it's not airborne, it's not explosive, hence why flour doesn't have 'CAUTION EXPLOSIVE' written on the bag.

That and the gas thing kaet mentions. Fairly major part really. I suppose once it's started blowing up I stop being involved and don't think of that bit.

Yes, you're right about nitroglycerine.
Actually, nitroglycerine is particularly alarming because (1) it is extremely susceptible to kinetic, rather than thermal or electrical, triggering (2) it contains enough oxygen to completely burn and still release some oxygen to the surroundings.

But Legolas wouldn't look surprised; he'd react in the split second of the instant of the explosion, jump onto his shield and surf on the edge of the blast wave. :-)

And how Jerry Lee Lewis used to make his piano explode in Great Balls of Fire - bag of flour set to burst, and a trigger on the top key so it would go off when he did that long run at the end.