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# The Science of Campfires

This experiment comes from my neighbors at the Malibu Creek State Park campground. While taking my morning walk, I heard a lady bragging to her husband that she started the campfire with only one match. That made me think of the fellow that I watched the night before as he poured two bottles of charcoal lighter fluid onto a pile of wood and still failed to get the fire going. He would pour on the liquid and get a huge blaze, which quickly died. How could the heat of one match work better than a gallon of blazing lighter fluid?

To find out, you will need:

• an adult (Any time you are working with fire, you should have another adult with you, even if you are an adult yourself.)
• a wooden pencil or a stick about the same size
• a wooden toothpick
• a candle
• a bowl of water

Place the candle on a flat surface or in a holder, so it will stay upright. Instead of using matches, we will use the candle as an easier and safer heat source. Next we will need some wood for our campfire. Lets begin with the pencil. Look carefully to be sure that it is really made of wood. Recently, I found some that were plastic. That would not work well at all for our experiment. Holding the end with the eraser, put the other end into the candle flame. Watch to see how long it takes for the pencil to catch fire so that it will burn on its own, without the candle flame. Once it is burning, dip the end in the bowl of water to put it out.

Next lets try the same procedure using the toothpick. Once it is burning, drop it into the bowl of water. Did you notice a difference? The pointed end of the toothpick should have caught fire much faster. Why?

First, it is smaller, so it takes less heat energy to raise its temperature to the point where it will burn. The lady that started her fire with only one match knew to begin with small pieces of wood. Once they are burning, you can use their heat energy to heat larger pieces of wood. By going in steps from small to large, you can soon have a large log burning on your fire.

Second, for our fire to burn, we need to get plenty of oxygen to the wood. If there is not enough oxygen, then the wood will not burn, even if it is very hot. With a large piece of wood, the oxygen is on the outside, but there is a lot of wood on the inside that the oxygen can't get to. With a bundle of small sticks, oxygen and heat can get to the pieces on the inside, letting the bundle of small sticks burn much faster than a large log. The better air can flow through your campfire, the better it will burn.

Does that mean that you should not put large pieces of wood on your campfire? No. Once it is going, you want it to last for a while. That is where the log comes in. The same things that make it hard to get the log burning will make sure that it burns slowly, making your fire last long enough to cook your supper and still have plenty of heat for toasting marshmallows later.

But what about the fellow with the lighter fluid? Why didn't all of that flame start his fire? Take a close look at the burning candle. Watch the wick carefully. Is it burning? At first, it would seem that the answer is yes, but as you watch, you will see that even though the candle burns, the wick is lasting a very long time. What you are actually burning is the wax from the candle. The heat melts the wax, which then soaks into the wick. This liquid wax climbs up the wick in the same way that water climbs up a paper towel when you are cleaning up a spill. As the liquid wax gets closer to the flame, it is heated enough to break down into gases which will burn. As long as there is plenty of wax, the wick does not burn at all. When the wax melts down enough, the liquid wax will not be able to climb all the way to the top of the wick. Then the end of the wick burns away.

The lighter fluid was doing the same thing as the liquid wax. It made nice flames, but as long as there was plenty of lighter fluid, the wood did not burn. The majority of the heat was moving upwards, away from the wood. Because he was using large pieces of wood, the last bit of heat as the fluid ran out was not enough to set the wood on fire. He could have fixed this by placing small pieces of wood on top of his fire, so that the heat of the big flame would get them hot enough to burn. Then he could have used that heat to start larger pieces of wood. It would have been much easier and safer for him to skip the lighter fluid and build his fire correctly. Besides, toasted marshmallows taste much better without the kerosene taste of the lighter fluid.

Have a wonder filled week.

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