What Is Fire?
Water? No. Air? No. Earth? No. It’s fire. Fire is the only element that is any good at all when you want to cook yourself a hot dog. — George “Flamethrower” Nilrac
Fire making is a complex process, as you know if you’ve ever tried to start one. My mother used to smoke in bed when getting out of bed to smoke became too much trouble. Since she was always smoking, she never would have gotten any sleep otherwise. Lots easier for her just to snooze and puff at the same time.
This proves two things. One is her level of talent in not ever once falling asleep and roasting herself, anyone else, or even any of the cats. The other is how hard it can be to start a fire. If she ever really did fall asleep this way, nothing ever actually caught fire. We lived. Thanks, Mom.
Harry Houdini said “That fire could be produced through friction finally came into the knowledge of man, but the early methods entailed much labor.” Try rubbing any two random things together and you’ll see. Keep trying for several hundred thousand years until you just happen to get two nice, dry sticks that are just the right size and shape, on a day when you feel good and strong after a decent meal and have finally decided that no matter what happens, you are just, dammit, going to invent fire and get on with things.
When fire finally does happen (after the aforementioned several hundred thousand years) it’s because you got the atoms of one thing excited enough to go and fight with atoms of the other thing, and they got all mixed up together, gave each other lots of black eyes, and ended up producing lots of heat and light. And that’s what fire is.
You can start a fire by going at the old rubbing procedure nearly forever. Or, on the other hand, sometimes you just happen to walk into the room when the atoms from column A and the atoms from column B have all had a really bad day, and have all really had it with each other already, and they’re just waiting for someone like you to come along and do even one little tiny thing, just one thing, and then by golly they’ll just go at it like wildcats.
Like those days when someone has turned on the gas stove after the pilot light has blown out, and absently walked away. It’s days like this that you wish you’d stayed in bed yourself. Inside your mother maybe, in the earliest stages of pregnancy, before you were more than a few casually acquainted molecules, when it wasn’t too late to get reabsorbed and forget about all this individuality business, and being born and having responsibilities and all.
You probably will think this to yourself while running around in circles and trying to put yourself out. And if you live through it all you have to lie around in bed for a good long while, strapped up in bandages, and hurting a whole lot more than you want to. That’s the alternate way of not how to do it.
Whether you can control the resulting fire or not, you always need three things for fire to happen: oxygen, fuel and heat. Luckily for us the atmosphere is 21% oxygen, and it’s always close by and pumped up. But if you, for example, set your pants on fire, this also means that they will keep burning. You can’t get away from that crazy old oxygen. You can use your pants as fuel, of course, if you really want to, but if you’re a backpacker you generally try to avoid that, since pants are so handy for wiping your hands on. And this is why experience is such a good teacher. Do it once (or twice at the most) and you’ll learn not to do it again.
OK, that accounts for oxygen and fuel. The heat part of the equation can come from a match, a cigarette lighter, or sometimes just a simple spark, depending on the fuel.
What you want, if you’re going to make a good, hot cup of coffee, is a controlled but self-sustaining fire. You need enough heat, mixed with just enough oxygen and fuel, to start the fuel and oxygen combining in a romantic but efficient sort of way. And when they do that they produce their own heat. This gets you to what is called “ignition continuity”. That’s the feedback loop where heat from the fire cycles back into the fuel and oxygen and keeps them hot enough to continue dancing (a.k.a. fighting). It’s also called an “uninhibited chain reaction”, but a full description of that is available only in the adult version of this book.
This feedback of heat into the fire breaks down the fuel, makes it start hopping around like crazy, and sends it out looking for some oxygen to tangle with.
But a paradox! We have a paradox here! Hello! Danger! Paradox Alert!
Solid fuel doesn’t burn. Neither does liquid fuel. Only gaseous stuff does. So you need to get the solid or liquid stuff hot enough to break down and get really gassed off. Then you can have a fire, and only then. The process is called “pyrolysis”, The fuel gets pyrolized. Whee! Waking up some nice morning and finding out that you’ve been pyrolized would get you pretty hot too, and you might just burst into flame, too, pants or no pants. But it wouldn’t be that pleasant from the front row.
So let’s review here. You need oxygen which you’ve got plenty of, then fuel, and some kind of energy to kickstart things. Then the burning will begin, and it will throw off enough heat to keep itself going. And it will keep going until it runs out of (all together now) fuel, or oxygen, or heat. You need all three.
That’s why you can put out a fire by throwing water or sand on it (cuts off oxygen and cools it) or by pulling sticks out of the fire or scraping the ground bare (removes the fuel). Or by taking your pants off.
A typical flame has some structure to it as well. If you’ve ever gone to the hobby shop and bought a “Visible Flame”™ model kit to assemble at home you know after close inspection that a flame has three basic parts.
Lacking a properly assembled “Visible Flame”™ kit, you can also carefully look at a candle flame. (Be careful about the eyebrows, though – yours.) There’s an inner part of the flame just next to the wick where the wax and the wick are starting to get all hot and vaporized. That’s where they mix with air. This part of the flame doesn’t look like much, which may be why you fell asleep trying this in high school chemistry class.
OK, it gets better though. The next layer is hotter. This layer is above the first one and kind of surrounds it, and in this layer there’s some actual burning going on. Way more exciting for us science buffs. WooHoo! The flame here is usually bluish, grading to yellow toward the outside. Carbon, hydrogen and oxygen combine here to produce carbon dioxide, carbon monoxide, water and a few noxious substances with terribly complicated names and generally bad reputations. And heat, too. Don’t forget our friend, Mr. Heat.
The outermost layer, at the top of the flame, is yellowish or whitish. That means it’s hot. Really hot. Amazingly hot. Which is why you shouldn’t stick your finger into it, let alone your eyebrows. And watch the tip of your nose, too. The burning finishes in this region of the flame. It’s where the last bits of carbon hang out, getting incandescent and making the flame bright with their glow, just before they enter into a permanent relationship with oxygen.
Stick something relatively cold like a cooking pot into this top part of the flame (remember now, no fingers!) and you’ll cool down the flame. Carbon will condense out of the flame and collect on the pot instead of burning, and you’ll get a bunch of soot. (Science fact: soot is raw, unburned carbon!) This also proves that chemistry is real, and that it can hurt a lot if you didn’t listen and stuck your finger in there anyway.
And I believe we’ve proved our point about the three essentials needed for fire. When you stick a cold cooking pot into the flame you suck up heat, and by doing that you deprive the carbon of its chance to glow and burn. Instead it gets all limp and wussy and falls out of the flame and sticks to the bottom of your pot.
Right here is about the point I dropped out of the Boy Scouts. Nothing much had any interest for me after I got permission to start fires, burn things, and make soot. The rest of it seemed so impractical, so lame, so organized. Basically I’ve hung onto an immature fascination with fires and cooking things outdoors and left it at that, which is where my interest in backpacking really came from.
If after all this you still don’t think that fire can be fascinating, then look up George Goble, a Purdue University engineer who received the 1996 Ig Nobel Prize in chemistry for starting a barbecue fire in three seconds.
Mr. Goble used 60 pounds of charcoal briquettes, 10 gallons of liquid oxygen (LOX), and a match. And destroyed the grill. But got nice, hot coals. “Warning” he says, “If charcoal is PRESOAKED in LOX first, an explosion will result. One briquette presoaked in LOX is approx equiv to 1 stick of dynamite.”
In the words of Terry Pratchett, “Build a man a fire and he’ll be warm for the night. Set a man on fire and he’ll be warm for the rest of his life.”
See? Fire really IS fun!
Exercises
- Locate two sticks and bond with them.
- Get a tattoo in the shape of a large flame, with this text:
When I’m burning,
When I shout, and
Scream out loud –
Please put me out. - Befriend an oxygen molecule.
- Look up the story of George Goble and reassure yourself that it’s true.
- Extra credit: If you look up the story of George Goble and feel reassured, then please stay away from me.