- Christopher Alexander, The Timeless Way of Building
Masonry: Rock Puzzles
Arctic and Maritime Safety
Messy Science: Purple Plant Potions
Memoirs: Writing your Life Legacy
We have been playing with fire for millions of years. Ironically, in this age of jet fuel and combustion engines, many people seem less familiar with fire than ever. This information is intended to help bring back that sense of familiarity, as a stepping stone to building a practical post-petroleum future.
Other critters stay well clear of fire. We tend to stick out red-handed when the planet gets in a fire-type mess.
(Other critters don't tend to read web pages, either, so I assume you're a people-type critter. You probably know something about fire? Byt maybe not as much as people(s) who play with embers before computers.)
2) It burns (causes pain and transformation).
3) We can put it out (with water, dirt, baking soda, or a fire extinguisher, for example).The "fire triangle" is fuel, air, and heat. Take one away, and no more fire.
4) Enough is enough. If it gets too big/hot, I can't blow it out anymore....
5) Flames go up. Hot air rises (through convection).
6) Firelight gives a nice glow. (Both heat and light are forms of radiation - the cosy, life-giving kind.)
7) Fire makes soot, smoke, and 'bad' gases. (Smoke and carbon monoxide are unburned fuel; complete combustion also makes water (steam) and carbon dioxide).
8) Wet wood doesn't burn well*.
1) Some fuels burn better than others. Wood fuels chart
If you ask"Is the camp firewood dry?" and they answer, "Sure - it hasn't rained for at least a week," your fire is doomed to poor fodder. Ditto if you see mushrooms growing on the logs. Firewood on the damp ground, uncovered, or mellowing under tarp with no air movement, is not fuel - it is mushroom habitat.
Hot chimneys draw up. (When people put an uninsulated chimney out the
north side of a house, instead of running it up inside the home or
insulating it, it tends to draft downward instead.)
pipe, tube, chimney, or hollow log can function as a "hot stack." The
tube gives the gases a place to go without interruptions from cold air
coming in sideways. The hotter the tube gets, the faster the gas inside
it rise, drawing more air across the fire and channeling exhaust gases
up and away. A tube or chimney acts like a "smoke vacuum," and can very
quickly turn a smouldering campfire into a rushing tower of flame.
Poorly designed fireplaces often completely fail to take advantage of this, or worse, people block the heat entirely with walls of glass.
You can direct the heat from fire with a fireback. Put a wall behind it, and some of the heat bounces back across toward you. Put it in a box (like a big square fireplace) and the heat stays near the center and goes straight up. Great for cooking, not for heating the room. You can fan out the walls and bounce heat out toward you, great for warming yourself.
If you want more light and less heat, you can arrange a log in front to bounce the fire's heat back toward the chimney.
Dome ovens focus heat inward. A ring of wildfire can light a distant tree like a magnifying lens.
When fire burns completely, it turns carbohydrate fuels (like wood/grass/paper) and hydrocarbon fuels (like oil/wax/fats) into... carbon dioxide, and water. It's just a lot of carbon and hydrogen, getting completely oxidized.
(Side rant: Yes, carbon dioxide is building up in our atmosphere. It's a product of all our combustion technologies -- smelting ores to make metals, burning gas and coal for fuel, refining limestone into lime and cement, and powering our houses and computers with the electricity produced in far-off, coal-burning plants made from cement and metal. Wood heat uses "current" carbon dioxide, assuming more wood is grown to replace the chopped fuel. Fossil fuels release 'ancient' carbon, that has not been part of the atmosphere since the time of the dinosaurs. So while a clean-burning fire produces a little carbon dioxide, a 'clean' electric heater in reality produces far more. Either is an improvement on lots of nasty smoke.
If it helps put things in perspective, methane is an even worse greenhouse gas. So stop eating beans. And dairy, and beef - cows fart too. Water is the most effective greenhouse gas of all. Yet we need it to survive.
Maybe these substances aren't "bad" as such, maybe they're even potentially "good" elements in some ways, but it's dangerous to alter the amounts in a balanced system. Burning massive amounts of fossil fuels over a short period (a few hundred years) releases trapped carbon, destabilizing the climate. As an individual, you can't put it back the way it was. But if you can provide for your needs from your own 'waste' wood, without depleting your woodlot, you know that your plants are pulling that carbon back out of the air as fast as you put it in. You can even return the mineral ashes to the same forest, along with some rich compost-type waste, to speed things up. It's not "waste" that's the problem, it's wasted waste.)
You can use the same tools to channel hot air that you use to hold and move water. Just have to turn them upside down. And upside-down bucket is an oven or hot-air balloon. An upside-down pipe is still a pipe, or a duct. An upside-down drain is a chimney. And an upside-down siphon is.... well, it's something that most people haven't really thought about using on a fire. We call it a "j-tube," or an "l-tube," or a "thermosiphon," and use it to make fire burn sideways. Ancients used them to make long, hot furnaces for heating palaces, firing ceramics, and processing ores.
6) Remember convection, conduction, radiation?
Convection is hot air rising and wind blowing. Sunlight on your face is radiation. Conduction is why having a cuddle or hot shower is a lot warmer than watching one.
The chimney facilitates convection: it convects heat straight out of your house. We can use reflective masonry to bounce some of the radiation back at us (hence the dish-like diagonal walls of elegant Rumford fireplaces). But like cats, many of us like to sit on a warm surface as well. As long as your body is between the fireplace glow and the cold chair, your seat will only get as warm as your shadow.
If we use everything we know about fire, we can get it to do amazing things, just by how we arrange its 'house'.
The basic hearth is just a non-burnable place to make fire, like flat stone, sand-pit, or bare dirt. But by adding walls, chimneys, or other features, we can create a home that encourages the aspects of fire that are most useful or delightful for our own purposes.
A jug stove (photo, right) does almost the opposite - it uses dry earth to insulate and focus the heat directly beneath a chimney, which allows an African traveler to heat tea in a barren land with plenty of dry earth but little fuel.
- A masonry stove sends the exhaust from a single, batch-burned fire through a bunch of baffles on its way out, so it heats a massive masonry chimney and creates safe, warm heat for hours. Some larger examples such as the Russian stoves can combine cooking hearths, ovens, and even platform beds: a warm, raised surface owners can actually sleep on in the extreme cold of northern European winters. Others, such as German and Swedish tile stoves, offer a smaller but still efficient decorative heater for a central room.
-A rocket masonry stove combines these, plus extra features:
-A short, insulated, and therefore very hot chimney, creating powerful draw and a very hot spot at the top where the last gases re-burn in a torus of baffled energy.
Of course, in trapping all the heat in metal and masonry, we've invented a fireplace that lets off almost no light at all. On a dark night, the reflected flickering might be just enough serve as a night-light for a small child .. if they found underground flames reassuring.
But no system is perfect.
Light, and other needs like summer cooking or portable heaters, call for other solutions: less mass, different designs, and wise use of nature's gifts (our two feet, candles, and daily sunlight, among them). This Rocket Stove is an example of specialized but resourceful design to create efficient, clean, and comfortable heat with minimally-processed materials.
Other great examples are designed for quick heat, quick cooking, long baking, or other common needs.