Throwing a killer party? Burning some couches? This will get you from spark to ash with only minimal burns, and most of your hair intact. It may seem like just a bigger camp fire, but it comes with a whole set of dangers unique to the scale. If there is one thing the boy scouts got right, it's to be prepared. Especially when you are about to light something on fire that is at least as tall as you are. If you don't believe me, check out http://www.cnn.com/US/9911/19/students.crushed.02/ And that was before the fire was even lit!
I am an Eagle Scout, and have worked at a BSA summer camp. For reasons that shall go undisclosed, we often built bonfires which were designed to collapse on purpose (but always without hurting anyone.) Like a logger felling a tree, I learned a lot about the structure of a fire by trying to get it to collapse in a particular way at a particular time. This instructable makes up a good portion of what I learned about getting a fire to burn properly. I may save the other knowledge for another instructable.
Step 1: Basic Fire-building
Most people know how fire works. Heat meets fuel and oxygen and results in the chemical reaction of rapid oxidation called fire. Even adults who can explain this reaction in much more detail than I can show a depressing lack of ability to apply that. But you are all do-it-yourselfers, so you'll get it right. If you are absolutely confident (or plan on using a whole lot of expensive petro-chemicals) by all means move-on.
Fire needs fuel, oxygen and heat. If you hold a candle to a log, it will not light, but why? There is certainly enough fuel (see big log), and there is air all around it, and I have heat. Formula no work...Og no cook dinner. There are some people who understand this, yet still pile logs on top of each-other and stuff the whole thing to the gills with newspaper, and wonder why the newspaper just smolders and goes out.
Two keys here: surface area, and airflow. To catch a flame (and especially a spark) you need as much surface area as possible for your flame to catch (which is why newspaper works so well.) But you also need air to be able to circulate and get to where the flame is. If you need a reason, look up oxidation. In a fire, cool air has to come in from the bottom to replace the hot air escaping from the top. Keep that in mind when building any fire.
** The best tip in the whole instructable: Most people will blow on a fire that looks like it needs a little extra kick to get going really well. Do not think that this means that more blowing equals more fire. Almost everyone blows too hard and too quickly which just makes things worse. Blow at the bottom of the flames with a slow steady breath, you will hear a difference when the flames get that "turbo charge" you are looking for. You want to keep that slow stream going as long as possible, so regulate your breath. The sound is really the key here, but you'll get the hang of it. **
The fuel with the most surface area to combustible material ratio is called tinder which ranges from clumps of tiny fibers which catch quickly to sticks no thicker than a blade of grass. Next is kindling which can be about as big as your thumb. When building a bonfire, what you are really interested in is fuel. This is what really burns for a long time, gives off a lot of heat, and provides the structure for the fire. Once you have fuel going, the fire is well established; you don't have to keep feeding it, it's certainly too late to move it, and you don't want to be poking and prodding it too much lest you do more damage than good. It is often a good idea to add pockets of kindling dispersed evenly in the fuel to help ensure that everything catches together. But before we get to the big flames...
Step 2: Preparations
Once the fire is going, it's too late to move it away from the side of the barn, off of the natural gas line, or to tell the police that you just dropped your cigarette. Do some thinking about what the fire is going to be like, and how it is going to behave. You need space. Depending on the size, a comfortable standing distance around a bonfire can be 50' away! Anything within that range will be very hot for an extended period of time. The leaves on any trees overhead will die. Even if the flames do not touch them, the superheated air will kill them. Make sure the car is moved out of the way, and there is nothing flammable within that range (including plant matter.) Air is not a stationary force in your fire either. The wind can wreak havoc on a poorly made structure, and carry sparks into that gas can you thought was put away "well enough." Keep track of the wind, and if it is very windy, give up or be prepared to spend all night tracking down unwanted island fires.
Also be aware that the heat of the fire penetrates into the ground and kills all the microbes necessary for other things to grow. There will be a bald spot where the fire was for a very, very long time. To help avoid this, you can lay down a tarp and cover it with lots and lots of dirt to shield the actual ground from some heat. The bigger your fire, the wider and thicker the dirt pile should be.
Blah, blah, fire-extinguishers, blah, blah, water, blah, blah, stupid drunk people... If you need help with this part, stop reading and get the fire department to sponsor your party (they will probably be happy to, but they will drink all your beer.) Be aware that there may be restrictions on fires depending on where you live, and it is your responsibility to find that out.
Step 3: Construction: Tepee
So you know how to make a little fire. Maybe you've even practiced a time or two (or three.) Now you want to make it BIG! You have a safe spot and a semi-load of wood. Where do you start? Unless you are starting a fire with napalm (don't laugh, I've seen it done), you start with a small fire. So if you skipped ahead, go back to step 1.
You don't want to be rushing to build the structure around a small fire after it is already lit. Know which type you are building first and get everything set up. If done right, one match in the right place does the trick and then you can stand back and watch the destruction. Stability during the whole burn is key. If one key log burns quicker than the others it can be fun to watch but painful to clean up. Think about not only size, but density, dampness, and proximity to the flames.
Tepee fires can be very impressive and give off huge amounts of heat and light. They are also notoriously unstable. Generally there is a tripod of strong, thick logs which provide the structure around which the other fuel is arranged. They must be stable themselves, and be locked together well at the top. If one goes down, everything goes with it. When stacking wood around it, try to keep an even distribution of weight and combustibility all around. A perfect tepee fire will burn up evenly and collapse in on itself. Leave at least one opening somewhere big enough to fit both your arms inside it to add more wood and for when you need to light it.
Inside this shell, add kindling and smaller fuel. The more wood you add inside, the bigger and hotter the fire, but remember to leave room for air. In the very center, stuff a big wad of tinder, and a pile of kindling around it. You want the middle to catch quickly and light all around the outer structure. Once you light it, there is no going back so make sure that it is going to stay up before you take the match out of the box. Even after it is burning, more fuel can be added to a side to keep it burning longer, or to help stabilize (assuming you can get close enough to carefully place something on the fire.)
Step 4: Construction: Pyramid
The pyramid fire is a personal favorite. It uses fuel in a very efficient way by burning from the top down. This means it takes a little longer before you get the full effect, and it does not give off quite as much heat and light, but these structures are much more stable and can be build up very tall with enough wood. The idea here is that heat and coals from the fire on the layer above trickle down to ignite the next layer below. You need to have a nice gradient of log sizes to get this to work, but you can have a fire last for hours without touching it once.
A couple of large logs are set on the bottom for stability and to give some room off the ground for air to circulate. On these are stacked successively smaller and smaller rows of logs perpendicular to the previous row. Do not fit the logs tight against one another, but give some room for air to come through. For extra stability, logs can be split in half and laid flat side down.
To start the pile, I will often build a lean-to fire or a hunters fire on top. A lean-to, as its name implies, is a bunch of kindling leaning against a log and full of tinder underneath. The difference in a hunters fire is the addition of another log parallel to the first so that they form walls, and the kindling lays across the top as a flat roof and has lots of tinder (with room to breathe of course) underneath.
Step 5: Construction: Log Cabin
The log cabin is a synthesis of the pyramid and the tepee which is a variation with its own pros and cons. Picture a square, hollow pyramid. If you only use two logs on each level, you can stack it up higher, and there is a huge column of air which can move quickly up the middle to burn from the inside out. Inside of this, set a tepee fire with an opening to light it parallel to the to large logs on bottom supporting the pyramid. The tepee will light first and catch the bigger log cabin structure. The more stable log cabin can also help to catch a log that falls out of the tepee, but be aware that if one log in the pyramid gets knocked out, burns through, or rolls out, everything above it comes rolling off onto your foot!
Step 6: Ignition
Spark the match, give yourself a pat on the back, grab a beer, and watch the show. If you did it right, your bonfire will go without incident and will require no attention to keep it going. This is my first instructable, so any constructive criticism is welcome. For some more tips check out:
>Army Rangers - pros/cons of starting methods, and funny pictures:
>WikiHow - more pictures of fire lays, and some general tips
>Campfiredude - silly name but good descriptions if you learn better by reading
>A Scruffy BSA Scoutmaster - video of a scoutmaster building a fire
Last thoughts and tips:
-Gasoline: While gasoline can get something burning quickly, the way most people use it sacrifices a lot of control in how the fire burns. With a single ignition point and carefully placed wood, you can get a fire to burn exactly how you want it to. Pouring gasoline over the whole thing only leaves you with one option: a flash in the pan and something possibly left smoldering afterwards. However, gasoline can be very useful if all you have is very wet fuel. Give it a wick of some sort: a can filled with dirt, a roll of TP in a container, something so that it burns slowly. These can make good impromptu tiki torches as well.
-Tinder: there are lots of great tinder sources out there, including cedar, lint, certain kinds of fungus. There is a good instructable for charcloth if you want to start from a spark or an ember (rock out with your bowdrill out) as well: https://www.instructables.com/id/Make-Char-Cloth/ People who build a lot of fires this way often have a particular favorite that they will carry with them (and can be very protective of.) I tried to outline the basic characteristics of good tinder, but if you have a favorite and want to share it, please do.