Introduction:
This effort may not hit its mark; but, the target audience for this thread is Firecraft Newbies. The purpose is to assist those with little fire experience to build their understanding of fire and to grow their firecraft skills.
As the thread progresses, I hope to add posts (with photos and/or videos) about the basics of: making char cloth; TJ’s PJs; reflective and refractive means to focus solar radiation; beginner’s guide to bow drill fire making; etc. My hope is that experienced forum members will add to this effort to help our newer, less experienced members develop this skill so important to the idea of “wilderness survival.”
Part One, Basic Concepts:
When most people think of FIRE they think of words like “burning” or “combustion,” and clearly they visualize FLAMES as a major attribute of the fire. Within this frame of reference – burning with a visible flame -- WOOD DOES NOT BURN.
Try this: light a wooden match and hold it up in front of your face. You will see that the wood is not “flaming.” Rather, the flame is above the wooden match, not on it. If you watch for a while, you will see the gradually wood turning black, while the fire’s flame is dancing in the air well above the wood.
A few key definitions…
Burning (or combustion): This is a self-perpetuating reaction between oxygen and other gasses or vapors that will rapidly react with the oxygen, giving off heat and light as a result.
Ignition: The process of starting the combustion reaction.
Ignition Temperature: The minimum temperature a fuel (such as wood) must reach before ignition is achieved and the exothermic, oxidation reaction begins.
Here’s how the ignition process works…
We’ve all heard of the “fire triangle:” Fuel (wood), Heat (ignition source), and Air (oxygen).
As heat is applied to the wood, the temperature of the wood rises.
As the temperature of the wood rises, volatile oils and tars that are trapped in the cells of the wood begin to evaporate and rise above the wood, mixing with the air.
When the temperature of the wood and the escaping gasses reach the ignition temperature, the gasses suddenly begin reacting with the oxygen in the air, giving rise to a visible flame (above the wood), giving off heat and light.
As the volatiles leave the wood, pure carbon is left behind. Thus the wood turns black.
Wood, minus all of its oils and tars, equals charcoal -- carbon!
Important, related concepts…
Convection: Convection is a heat-driven movement of fluids. In a fire, the heated gasses become less dense than the surrounding air. Gravity pulls dense fresh air down into the base of the fire, pushing the less dense gasses upward. As more burning gasses are pushed up, additional dense, fresh air is pulled into the fire to replace it. This is what makes the fire a self perpetuating process. IF PROPERLY BUILT, the fire will continually supply itself with fresh oxygen. Construct you fire lay to enhance the natural convection process!
Latent Heat of Vaporization: We’ve all boiled water. It’s a simple process; but, there is something about it that many people are not aware of – the latent heat phenomenon. Start with one pound of water at 60 degrees F (about one pint). Add 10 BTUs of heat and the temperature will go up to 70 degrees. Add another 30 BTUs of heat and the temperature will go up to 100 degrees. Add another 50 BTUs of heat and the temperature will go up to 150 degrees. Add another 62 BTUs of heat and the temperature will go up to 212 degrees. NOW, add another 100 BTUs, and NOW the temperature stays at 212 degrees. Add 300 more BTUS…the temperature is STILL 212 degrees. Add 500 more BTUs and the temperature still stays at 212 degrees! WHY? Because the added heat is absorbed by the process of turning liquid water into steam. WHY IS THIS IMPORTANT TO FIRE MAKING? Because you will NOT have fire until the wood reaches its ignition temperature, near in excess of 550 degrees F. It’s critical to use dry wood! Otherwise, the heat you are adding to achieve ignition will be wasted on evaporating the water inside the wet wood.
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