Thread: Smoke control
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Old 11-20-2010, 10:26 PM   #8
bigabyte
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Join Date: 05-10-06
Location: Overland Fark, KS
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The reason you had such a big change between chunks and logs is really air.

A wood fire is the result of a chemical reaction from wood being heated in the presence of air (oxygen specifically). As the wood heats up, it begins to break down into mostly gases and some solids. These gases (and the finer solid particles) escape from the wood, and if there is enough heat and air present, then most of these gases will ignite producing flame, and are thus burned up. If there is either not enough heat or air present, then these gases and solids will simply float away from the fire and are visible as a thick smoke. The compounds contained in that thick smoke that were not burned up contain lots of nasty stuff, one of which is creosote, which will stick to the walls of your cooker, and also stick to your food, giving it a bitter, nasty taste, and in really bad cases will even make your lips/tongue feel numb and give you a real bad case of the chits.

Alternatively, a good clean burning fire will have the wood burning clean, which means it has all of the air it wants to burn clean and hot. A small clean burning fire will give you thin blue smoke, the sign your fire is burning clean.

A common mistake people make is overloading their cooker with too much fuel. This makes a situation where the amount of fuel can not get hot enough to burn clean without making the cooker too hot. So the operator closes down the air intakes to keep the temps down, but this causes the wood to not have enough air to burn cleanly, and it will pour out a thick smoke.

For any offset cooker, the trick is to have a small clean burning fire that will put your cooker at the temp it wants to run at. One way to make sure you can't screw that up is to leave your intakes open wide, this forces you to control your cooker temps solely by the amount of fuel burning in the firebox. You don't have to run it this way all the time, but it is a good way to learn about how to run your cooker and what size fire you whould run in it.

For a vertical cooker, like a UDS, WSM, Backwoods, etc, your fuel will be basically charcoal. The smoke will come from just a few (not many at all really) chunks dispersed throughout the charcoal, and using the Minion method to burn. The intakes will be dialed in to the temp you want to run the cooker at, and the fire will smolder thoughout the charcoal, occasionally hitting a piece of wood. Now, granted, this piece of wood is not necessarily burning as efficiently as it can, but it is a small amount of wood, thus there is plenty of heat and air around to take care of what comes off of it, and any nasty stuff remaining will be in such a small amount you won't notice it on your food, and your cooker walls will take several cooks before you see a build up of creosote, if at all. If you add too many chunks in one of these kinds of cookers, you will start to see a thicker smoke coming out, and the food will taste worse for it.

Hope that helps. Remember, let the fire get as much air as it needs to let the wood in your cooker burn clean. Use more charcoal and less wood if necessary. I'm going to guess your cooker is not big enough to burn split logs efficiently without it running too hot, either that or you put too many split logs in. either way, same result, too much fuel and not enough air.
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