Friday, December 2, 2011

Building a Fire

Now that the weather has cooled, and the smell of woodsmoke hangs in the air from fireplaces and woodstoves (lots of people in my neighborhood heat using wood), its probably a good time to review some of the fundamentals of building fires. And, I don't mean a survival fire with flint and steel, or rubbing two sticks together. I'm talking about one in a fireplace, woodstove, fire pit, or so on, using matches and paper and dry wood from the wood pile.

I'll admit that starting a fire is an art, but there is actually a fair amount of science involved. The basic issue is raising the temperature of wood past the point of combustion so that it freely burns. Obviously, it is easier to raise the heat of a small mass of wood (i.e., kindling) than a large piece of wood. So, make sure to have some small, thin pieces of wood available for kindling. It also helps to keep a small quantity of wood inside so that the wood has a chance to heat up before you try to use it to start a fire. Otherwise, with cold wood, you simply have to add more heat before it will ignite (i.e., its harder to start).

Also, make sure your wood is dry. Water boils at a temperature that is lower than needed to ignite wood, so if there is any substantial amount of water in the wood, the water will actually regulate the temperature of the wood until the water is gone (generally through vaporization). However, if you have ever wondered why a steam burn is worse than a water burn, even if both are at the same temperature, it is because it takes considerably greater energy to turn liquid water to steam than to heat the water to the boiling point. That is extra heat and energy you must put into the water in the wood before the wood will ignite. In short, damp wood is hard to ignite. Bringing the wood indoors before hand will help allow the damp wood to dry out.

When I build a fire, I attempt to create a combustion chamber or fire box structure to contain and reflect the heat. Through experience, I have found that the best way is to take two larger pieces of wood and place them laying down in a narrow "V" shape, open only a slight amount (no more than one inch or so) on one end, and open about 3 or 4 inches on the other. How large of piece depends on the type of wood--you will need to use smaller pieces of hardwood than you will need with pine. If the wood has been split so it is triangular or squared off in a cross section, try to arrange it so it overhangs the center of the "V" rather than being open. Remember, you want to try and trap the heat in the center of the "V." Also, its easier to work with if the open end of the "V" is facing you.

Into the gap in the center of the "V", I will place a twisted piece of paper towel, a torn piece of paper-fiber egg carton, or some other fire starting material such as a cotton ball soaked in petroleum jelly (Vaseline). Don't use newspaper. Newspaper does not disintegrate as it burns, and the sheets of "ash" will smother the fire.

Over this I will put my kindling. Not too much, and make sure there is both space between the kindling and the firestarting material, and between the pieces of kindling, in order to allow air to flow to the fire. The best kindling are thin strips of pine, no more than 1/4 inch thick, and perhaps several inches long. You can shave these off larger pieces of pine using a hatchet. If using sticks or twigs, use a mixture of small pieces and two or three larger pieces no larger in diameter than your finger or thumb.

Once this is in place, use a match or lighter to light the firestarting material. Your goal at this point is simply to get the kindling to ignite.

If the kindling catches and is starting to burn strong, add one or two small pieces of wood (1/2 to 3/4 inch works well) over the original kindling (again, keeping as much as possible a small amount of space so the fire is not smothered). Your goal now is to have enough wood that it will form hot coals between the wood forming the "V". Place one or two larger pieces of wood at an angle across the "V" to form a roof that will further trap the heat in place, but still leaving gaps to allow air circulation. Essentially, it should look like an inverted "A" with one or more cross pieces. At this point, the fire will have started to ignite the faces of the wood facing the combustion chamber (both the sides and the roof), and will gather in strength.

If you are having trouble with the kindling staying lit, you need to increase the temperature of the combustion chamber. In these instances, I will add small pieces of corrugated cardboard (which works great) or paper board (which doesn't work quite as well). A few small pieces held over the flame until they ignite and dropped in a couple strategic locations will generally get things heated up.

Once the larger pieces of wood have started to burn, then its time to prop one to three larger pieces of wood around it, one end up in the air and overhanging the wood below it, to build up a bigger fire. My experience is that it is more efficient to build a large fire initially, to quickly bring your room or house up to the temperature you want, and then add one or two pieces to maintain the temperature, than to slowly heat things up with a small fire.

A ceiling fan on low, or even a small oscillating fan set on low will make your heating much more efficient by circulating the warm air.

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