Which wood burns the longest?

[distaff1776]

I have completed my experiment and I am analyzing my data. I test burned birch, pine, oak, poplar, and maple. My hypothesis was that the oak would burn the longest, and it was not supported by the experiment. The oak and poplar were very close, but the poplar burned the longest. I have had trouble finding research information, which tells me why one wood burned longer than another. Can you give me some suggestions or tell my why?

[ChrisG]

Hi. Congrats on finishing your data collection. The question of 'how long' a particular wood will burn can be very difficult to answer, because there are many factors that affect the rate of oxidation (burning).

Usually, woods are rated by the amount of energy released per mass or volume of wood oxidized. You might have seen charts like this:
http://chimneysweeponline.com/howood.htm
Here is another chart that has similar info for oak and poplar
http://www.hiteshewtimberplus.com/firewood.php
Because Oak releases more energy per mass burned than poplar, it makes sense that oak would burn longer if the rate of oxidation were the same. In your experiment, the poplar likely oxidized at a lower rate, which could result from the inherent properties of the wood, environmental factors such as air circulation and moisture content of the wood, and experimental factors such as the dimensions of the samples and the apparatus used.

If you give some more details about your experiment & the woods you used, we might be able to tell you more about the possible factors affecting your results.

Chris

[Craig_Bridge]

Oak tends to grow more slowly with narrower growth rings than Poplar. This means that a freshly cut section of oak trunk has more heart wood (the dark wood in the center of the trunk) which in oak is much drier than the new wood. Poplar heart wood tends to be dark purple to green and still holds a lot of moisture compared to the wetter yet new wood which is white/gray. This dark purple/green heart wood is not desirable for wood working applicaitons that will be stained so most lumber applications will use younger poplar trees which will also mean a higher moisture content. In order to burn, you have to boil out any remaining sap/water content. Did you notice any difference in bubbling action at the end grain of your samples as they burned?