In my upcoming novel, my protagonist decided to paint every part of his body in mud before engaging with the fire breathing dragon which dwells at the bottom of a dormant volcano. The flame from the dragon can turn sand into glass. Of course, my protagonist will have to keep maintaining the moisture level in the mud, but I'm concerned that the dragon will make a terracotta soldier out of him instead. Is this a good method to go head to head with the vile creature? If not, how can I touch up to give him a fighting chance?
Your protagonist is really going to get burned badly.
The flame from the dragon can turn sand into glass
Glass won't form until you cool molten sand and it won't be molten until about 1600 C which means your protagonist would get a third degree burn easily ( one second at about 160 C is enough ) from contact with molten dirt and sand in mud.
There's simply too much heat coming in to avoid this.
The most vulnerable parts will be any skin that directly contacts the mud. And mud is wet, so unless your chap/lass has a fully covering waterproof layer underneath the mud they're in major trouble. Any wet cloth would be really problematic - it will either burn or become extremely hot and will transmit that direct to the skin underneath.
You not only need a lot of layers, you need to be able to get them off quickly before you're cooked by them.
how can I touch up to give him a fighting chance?
Well unless this is a very conveniently small dragon you have an additional problem : It's going to hit you as soon as it can after it flames you.
Your hero, let's call him/her "Crispee", will first suffer, at best, a very nasty attack from flame which will, at best, act as suppressing "fire" which Crispee can't do much in (probably won't even be able to see the dragon, let alone attack it).
And the second that's over, Crispee will find (if your dragon is of traditional design) a large claw casually slapping Crispee into the next country.
The way to defeat a dragon is clearly to have multiple attackers. So only one survives to claim the hand of the fair princess/burly prince, this is OK and we can remember the sacrifice of Crispee's late friends Burnit and Ashby who were alas killed distracting the dragon while Crispee got close enough to strike at the beast's heart.
If you're planning to use magic at all, the time to use it would be during the dragon killing phase. :-)
You could limit the dragon in some way : exhausted after flaming, so the hero "just" has to dodge (hide) from the first flame and get in quick before it recovers to fry Crispee and/or thump Crispee so hard that parts land in different places. So you need Crispee to get close enough to antagonize the dragon into flaming, but to choose a spot that provides quick cover (a prepared ambush ?) to survive the flaming and rush out heroically and do something PETA would probably complain about.
That kind of stuff.
It depends on how hot the dragon's flame is, and how long it lasts. If the dragon is capable of just a brief burst of flame, it will probably work, depending on just how thick the mud layer is.
OTOH, if the dragon is capable of a prolonged flame of even moderate intensity, then you will have created a succulent new dragon delicacy, knight baked in clay. See e.g. this recipe for trout: http://innatthecrossroads.files.wordpress.com/2011/06/dsc_0407.jpg?resize=584%2C388 "The clay acts as kind of a dutch oven for the food, keeping the moisture inside the fish. When the first clay fish finally cracked, we were surprised and delighted to find the flesh perfectly cooked and flaking off the bones. It was creamy and tender, with a wonderful, clean taste."
Water is good at protecting from heat as long as it can evaporate and thus subtract heat. I think this is the idea behind the mud armor and incidentally also behind our natural sweating mechanism.
The problem we don't face when sweating is that once you have the cloud of hot vapor it will condensate on colder surfaces, such as a body, transferring back the heat.
And of course once the mud has been cooked it will absorb much less water.
All in all, I think the only way for this to work is that your hero keeps moving under the flames, so that he can leaves as much steam as possible behind, and that he has chances to completely renew the mud armor after each "roasting session".
- short contact with the flames, not a "dive through them to aim at the mouth"
- reasonable time to be hidden, naked and spreading mud on the body
No, the hero is going to die a horrifying death.
Not by the mechanisms demonstrated so far in other answers (although they are going to be pretty horrible anyway) but because you have made no provision to protect the lungs. The hero is going to be exposed to the heat of a large industrial kiln or molten glass tank in a glassblowing studio. Unless he can hold his breath for the duration of the fight, he is going to breath in fire and destroy his lungs.
Modern stuntmen are often filmed being set on fire, and special precautions must be taken to do the stunt, including slathering all exposed skin in fireproof gel, wearing Nomex or similar fireproof undergarments and not breathing in the flames.
Scenes in which someone is actually set on fire are among the most dangerous ever filmed. The stuntman wears several layers of protective clothing, including fire-resistant materials like asbestos. Special gloves and a hood cover the hands and head. In most burn scenes, the hood is clearly evident, though its appearance can be minimized by good editing. Inside the hood is a small breathing apparatus connected to a small oxygen tank. The performer is then coated in a specially prepared flammable gel. They are not simply doused in gasoline -- that would be suicidal. Before the burn is lit, multiple extinguishers and paramedics must be at the scene. The burn itself is carefully timed.
Firemen and industrial workers exposed to these sorts of conditions are similarly protected by multiple layers of fireproof clothing, ventilation or breathing systems and so on.
Based off the comments, I don't think mud will be particularly effective. If your protagonist is instead near water and has a shield, you could have him use the water as protection and the shield to ward of any direct flames when they are away from the water or luring the dragon to the water.
The mud could probably help your protagonist in warding of some minor burns as the heat is deflected off the shield and can be constantly be reapplied if your protagonist uses the shoreline and keeps moving into the water and out of it, basically covering themselves in mud as they fight.
Or you can have the dragon land in the mud or crash into it, and slowly be bogged down by it, giving your protagonist a better chance of reaching the dragon and hitting it.
TL;DR Give him a thin layer of non-circulating air under the mud. Air is an excellent insulator.
First, the science on insulation. The principle proposed is the same one used for thermal window panes.
A possible way to work it into the plot is that the hero discovers the mud from a certain river is magnetic (maybe from high iron content) when it "clings" to pan that he was washing. He previously learned a legend or bit of ancient lore that the only way to withstand the fire of a dragon was with the protection of the Gods of Earth and Air and that the stream he chose to wash his pan in was, in fact, sacred to them (uh oh!).
Once it's time to face the dragon, the elders insist that the hero engage in the traditional ceremony prior to facing a potent enemy. The warrior tradition is to be painted in protective runes from head to toe from the Gods of Air. The hero realizes ceremonial paint is also magnetic and, if he's lucky, will repel the mud. This would give him a thin layer of stationary air between the mud and his skin, acting as an insulator, fulfilling the legend.
So painted in runes prior to facing the dragon, he wallows in the river mud, forming a protective, insulating layer of air under the wet mud.
- He has a limited supply of air while in this state. He either has to finish quickly or devise a way to get air.
- He has to be able to see or otherwise sense the dragon. His entire body will be covered in mud.
- The mud isn't going to just "hover" in place over his skin, so maybe there's an attraction of the mud to the iron in his blood to keep his "shell" intact.
- The insulation will not protect against physical dragon strikes. One swipe of the claw and it's lights out.
To quote Mr. Miyagi -- "Best defense... no be there."
Going up against a huge, fire-breathing beast with only a sword, shield and some mud sounds like a perfect mix for a funeral pyre honoring your intrepid warrior.
I would suggest an alternative of the warrior somehow outsmarting the dragon so that it can be defeated without directly engaging and succumbing to the flames. Perhaps fighting somewhere that the dragon cannot use its abilities or is hindered somehow. OR -- something that gives the warrior a huge advantage in the engagement (traps or the like.)
I keep thinking of Schwartzenegger going up against the Predator. Direct confrontation is borderline suicidal. Outwitting the beast to whittle it down and eventually finish it is probably a better, more likely, finish.
Just my 2 cents.