Monday, October 29, 2012

Fire

History

The Story of Prometheus1

Prometheus, who had saved [Deukalin and Pyrrha], looked upon the men and women of the Earth with compassion. Their labor was hard, and they wrought, much to gain little. They were chilled at night in their houses, and the winds that blew in the daytime made the old men and women bend double like a wheel. Prometheus thought to himself that if men and women had the element that only the Gods knew of -- the element of fire -- they could make for themselves implements for labor, and they could build houses that would keep out the chilling winds, and they could warm themselves at the blaze.

But the Gods had not willed that men should have fire, and to go against the will of the Gods would be impious. Prometheus went against the will of the Gods. He stole fire from the altar of Zeus, and he hid it in a hollow fennel stalk, and he brought it to men.

Men, possessing fire, were then able to hammer iron into tools; they were able to cut down forests with axes, and sow grain where the forests had been. They were able to make houses that the storms could not overthrow, and they were able to warm themselves at the hearth-fires. They had rest from their labor at times. They built cities; they became beings who no longer had their heads and backs bent, but were able to raise their faces even to the Gods.

Zeus spared the men who had now the sacred element of fire. But Prometheus he did not spare. He knew that Prometheus had stolen the fire even from his own altar. And he thought on how he might punish the great Titan for his impiety.

Background

The history of fire goes back before recorded time. We see it in the oldest cave drawings found. We see it in the camps discovered in archaeological digs. Fire has always existed and man put it to use as one of his first tools.

Nobody really knows when humans started to use fire, but we do know some of the things they used fire for. They cooked with it. They used it to heat treat wood. The used it to help clear land. They used it for light and comfort.

Fire really is the oldest tool and it is something we should have with us at all times in some form or another.

What is Fire

Fire is a tool. It has been used by humans for thousands of years. It is used to heat our shelters, cook our food, make our water safe, create tools, make shelter, keep us safe at night, boost our spirits, signal from afar and tell us that all will be well with the world.

If you look at the Rule of Threes, fire has its place in each of the levels. Fire is used in a first aid capacity. It's used to help create shelter. It is one of the best tools for purifying water. It allows us to cook our food. It gives us hope and turns a camp site or tent into "home."

Most people think of fire in terms of the cozy campfire. A circle of rocks to keep the fire in bounds, cheery flames leaping and dancing, hot dogs and marshmallow on sticks, good friends talking about ghosts and goblins, all to the sound of crickets... A safe happy place.

Fire is also hidden in the depths of your car engine, or in the breech of a gun, expanding gases to cause the bullet to fire. Fire is in your furnace adding heat to your home. Fire is in the forge of the blacksmith, turning raw metal into tools and weapons. Fire turns rocks of ore into the metal of industry. Fire makes metal soft enough to bend or hard enough to hold an edge.

Fire is our friend, our compatriot, our partner in life. We need to tame it and hold it true to our needs. We must learn to create it, feed it, respect it, and in the end kill it.

Fire is an exothermic reaction which results from the combination of a fuel source, heat and oxygen. It can be as fast as black powder burning or as slow as a lazy campfire. Regardless of where it is and how it was created, fire is a simple process of heat being combined with oxygen and fuel which creates more heat than it consumes.

The process

Warning!! Minor science ahead -- but you should still read this.

While we think of wood burning, that isn't exactly what is happening. Instead, heat is causing the wood to "out-gas." Wood is made up of C (carbon), H (hydrogen) and O (oxygen) with a chemical formula of C10H15O7. When it is heated it gives off a gas which is flammable, CH2O. When this gas is combined with O2 it reacts to form H2O (water), CO2 (Carbon dioxide) and CO (carbon monoxide). 2CO will then combine with O2 to create still more CO2. There is a bit more going on but these are the primary reactions.

The reactions above are exothermic, which is to say they give off heat. They give off a LOT of heat. The amount of heat that they give off is enough to cause wood to break down and release still more gases which burn, giving off still more heat.

What this means is that we have to heat up our fuel (wood) to the point where it will out-gas, which in turn burns, which creates still more heat, which causes the reaction to continue. If the heat of the fuel/wood drops below 500°F the wood will stop creating gases which burn. If the temperature never reaches 500°F the wood will not burn at all.

Water is the enemy of fire. Why? Because turning water into steam takes vast amounts of heat. The heat that goes into turning water into steam can't be used to heat the wood to the point where it will out-gas. Water turns to steam at 212°F which means that most, if not all, of the water must be driven from your wood before it will burn.

If the wood is not dry then even if it is burning, much of the heat that should go to useful work is instead going into driving out the water in the wood near the flames, preparing that wood to burn.

Science here: You will often read the term "work". "The wood does work", "the gun powder burns doing work". "Work" is a technical term in this case and it means "Force applied over distance". In the case of the gunpowder, the powder burning causes a gas to form and expand (greatly). This causes an increase of pressure behind the bullet. This pressure applies a force to the bullet and causes the bullet to move down the barrel. This is work. This is "mechanical work" (there is also "electrical work" and "thermodynamic work").

Dry wood works much, much better, giving off a lot more heat than wet/green wood does.

Making Fire "Hotter"

A fire is made hotter by increasing the rate at which the fire burns. The more the wood/fuel out-gases and the faster those gases burn, the hotter the fire.

The means that we need to make sure the fire has all it needs in order to continue the combustion process. As we noted in the science section above, the process requires heat to cause the out-gassing, fuel to provide the gases which will burn, and oxygen to react with the gases.

If any part of those three requirements is missing or is in low supply, the fire will go out or at the very least react (burn) more slowly.

We increase the fuel by adding more. It is that simple. If the fuel is dry then so much the better, but if it is not dry we are lowering the heat of the fire. The more fuel in a given volume, the higher the temperature will be.

But even if we have a large fuel supply with plenty of heat, if there is not enough oxygen getting to the fire, the reaction will slow down and some of the gases will escape without burning. So the question becomes, "how do we add more oxygen to the fire?"

Simple: blow on it.

Normal air at sea level contains about 20% oxygen. The air we exhale contains about 16% oxygen. Therefore we take about 20% of the oxygen out of the air when we breath it in. When we blow on a flame we actually increase the total amount of oxygen that the fire gets as long as we provide more than 20% more "air".

A bellows does the same thing as blowing but with 20% oxygen instead of 16% oxygen. This makes a bellows better than blowing. A fan or other blower can do the same. As long as the amount of heat taken from the reaction does not cause the fire to die, the addition of air to the fire will cause it to burn hotter.

When I would start a fire in the wood stove in my work shop I would catch a spark in a bed of wood chips. Once the flame was partially established, I used my air compressor to provide air which gently blew into the fire via a blow gun attachment. This extra air was enough to quickly heat the fire to the point where the logs would start to burn. Once that happened there was no more need for the compressed gas. It made starting the wood stove so much faster and easier. You did have to make sure it was clean, though, so you didn't get a lot of ashes back in your face.

Another way to increase the air flow is to take advantage of the fact that heat rises. As heat rises it pulls air upwards. This creates a low pressure area near the fire. Putting a chimney above a fire increases this up draft and air flow. The better the chimney draws, the more air it pulls into the burn chamber.

If you create a system where the primary place where air enters the system is at the bottom or base of the fire, or even under the actual flames, this will increase the area in which combustion takes place as well as increasing the amount of air being pulled into the system.

If you look at most wood stoves there is a grate that the wood sits on. The fire burns just above the wood. The grate and design of the wood stove allows air to enter from under the wood and then flow upwards through the combustion zone, supplying more oxygen and increasing the speed of reaction.

A hobo stove or rocket stove is designed around this principle. A hobo stove has a series of holes around the bottom of the can. This is where air enters the stove. The fuel fills the bottom third of the stove (mostly twigs and such) and burns very hot. The can acts as a chimney to increase draft. As long as the chimney is not blocked, a hobo stove will burn very efficiently.

A rocket stove is similar to a hobo stove in that air enters through the bottom but it has one other advantage. Fuel is also added at the bottom. The thing that makes a rocket stove a rocket stove is that there are two openings at the base of the stove. A low opening which provides the air supply and a second opening just above which is where fuel is fed in. With the addition of a chimney to increase draw, you again have a very efficient fire.

Steps To Creating Fire

For we simple folk, creating a fire consists of a couple of steps: creating the original spark or ember, getting the spark to ignite the tinder, feeding the tinder into kindling to established a fire, building the fire until it is well established, and using the fire.

Most people will never have to just create the spark. Instead they'll flick a Bic or light a match or push a button for "electric ignition". All of these are the "sparks of life" for fire, even if they don't actually create a spark.

A Bic lighter works by having a liquid fuel under pressure. When a valve is opened the gas on top of the liquid (butane) flows out. Butane is a highly flammable gas. When a spark reaches this fuel, the fuel will ignite. As the gas is flowing out of the lighter, sparks from the flint and wheel flow into the gas stream causing that ignition.

A safety match consists of a temperature sensitive compound on the head of a stick of wood or paper. As the compound is moved across the strike surface the friction causes the strike surface to heat up, releasing red phosphorus which turns to white phosphorus which ignites. This ignition causes the compound of sulfur on the tip of the match to ignite. This in turn causes the match stick to ignite.2

A light-anywhere match just needs a bit of friction in order to create the heat required to ignite the compound on the head. In order to strike a safety match with out a strike surface try sliding it across a piece of glass.

When you don't have matches or a lighter it is time for something else. The two things most commonly used to create that original spark are either a "flint and steel" or a friction created ember.

Flint and steel have come a long way since they were originally designed, and are now created with a "fire steel," which is compound that creates very large, very hot sparks. Lots of them.

Embers are created by generating heat and focusing that heat into something that will start to smolder, holding the heat for an extended period of time. Fire bows and fire sticks work this way, as does a magnifying glass.

Once you've create the "spark" you will need to carefully transfer that spark to the tinder. The tinder's job is to catch a spark and create a small flame that can then be used to ignite more fuel.

For a sparking system, the idea is to throw the sparks directly into the tinder (if the tinder is flammable enough) or to throw the sparks into something that will then smolder into an ember.

Once you have an ember, it is transfered into a tinder bundle. The O2 to the ember is increased until the heat is high enough to cause the tinder to burst into flame. Tinder is chosen for its low flash point and not for long burn times. Therefore you have a very limited amount of time once the tinder bursts into life before the tinder dies out.

Once you have the tinder going, the open flame is either inserted into (normally under) kindling or small kindling is added directly over the tinder. The latter method is used if it would be difficult to get the burning tinder under the kindling.

Kindling is small fuel pieces that will burn easily and therefore rapidly but not as fast as tinder. For example a cotton ball makes good tinder. Take one cotton ball outside and apply a burning match to it. It will light very quickly and burn out in just a few seconds.

During the time that the tinder is burning it must catch the kindling. More fires die at this stage than any other.

Once the small kindling has caught, larger kindling is added until the fire is large enough to ignite your primary fuel source. Your primary fuel source could be small branches, buffalo chips, small or large logs, split logs or a dozen other options. It could even be wood pellets or coal/charcoal.

At this point you have your fire. Unless you do something to put it out, it should continue to burn until the fuel is exhausted. If you have transferred your fire to a stove then you should be able to cook or heat via your stove.

Some Uses of Fire

The two primary uses for fire in a survival situation would be warmth and cooking. Under cooking please include boiling water to make it safe to consume.

A stove is designed to concentrate heat where it will do the most good. An open fire (like a campfire) radiates heat in all directions with most of it going upwards. All the heat that goes up is "wasted".

A good stove will extract as much heat from the fire as possible. The heat thus extract can be used to cook with or heat with. Even if you don't have a stove, a campfire can be made more efficient by building a wall of rocks behind it to reflect heat.picture of tracy's camp fire here.

Always make sure your fire has a way of venting. While smoke is very unpleasant, it is normally obvious enough that people will avoid it. CO (carbon monoxide) is a colorless, odorless gas. If the CO builds up where you are breathing it can kill you.

A fire can also be used to make bowls, cups, pitchers, arrow and spear tips. While it is possible to carve or whittle a pitcher or cup it is very difficult. The time honored method is to place a glowing coal on a piece of wood. The hot coal then chars or might even start burning the wood where it touches.

You take the coal off and place it back in the fire. You then extinguish any flame on your wood and scrape out the charred wood. Repeat as required until you have a bowl or cup or whatever you want.

The term "fire hardened" means that something has been heated in the fire and then cooled rapidly. This is normally applied to metals but it also applies to working wood. If you take a stick and char the tip you can then scrape the char off on a rock or with a knife. Repeat until you have a very nice point. The point you end up with will be harder than what you would get by just whittling.

Place fire in a container that will concentrate the heat, blow air through it and you can heat metal hot enough to work. If you make charcoal or have access to coal you can make a fire that will actually melt metal.

If you can melt metal you can cast it. If you can cast it you can then form it into other tools. While it might not be pleasant you can make a hammer of stone and then heat metal in a forge to make a hammer so that you can then make tongs so you can then make...

Summary

We have three more articles on fire coming. The first covers creating the spark of life for a fire. It will show how to use fire steel, magnifying glass and a fire bow in order to create that first ember. It will also cover creating tinder or gathering it.

The second article will cover how to build the spark into a full fire, either in a stove or in an open fire pit.

Our final article on fire is on non-electric, non-gas stoves. This will cover everything from the simple but effective hobo stove up through a Coleman style camp stoves with stops in between for wood cooks stoves.

Citations

1
PROMETHEUS, Internet Sacred Text Archive
2
How Do Safety Matches Work?

1 comment:

  1. Chris,
    I enjoyed your article. I especially liked when you have that little warning, "science included here". You break up your article so that it was interesting to read. I also like the inclusion of the Prometheus myth.
    Bridget

    ReplyDelete