What makes for better coaling of firewood when two types of wood are very close in BTU's? Is it do to the wood fibers or something else, for example Mulberry is close to Oak in btus but I have never thought it coaled as well, another is white ash in the same area as btus but does not coal as well as oak or have some of you found different results? I am sure there is many other examples for us to ponder.
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Dont think so I have all types of Oak at 17% or less, wet wood would be obvious when yu burn it. Been burning oak for 30 years great stuff.Wood Duck said:
oldspark said:
I don't really think so either. They say that all wood fibers have about the same BTUs and weight regardless of tree species, so the only difference between woods is the density of the wood (how closely fibers are packed together). if two woods have similar BTUs, then I guess the fibers and the number of fibers per volume are similar. Perhaps the differences in coaling are not due to fibers, but due to the pores. Maybe oak pores allow air in at a slower rate, or don't allow air as far into the wood as the pores of other woods do, so oak burns more slowly. Just a guess.
oldspark said:
Generally speaking, if both types of wood has the same moisture content, then the harder of the two should give more coals and that is mainly why oak is one of the better woods for btu. But one has to always keep in mind that you appear to get more coaling from wetter wood. That is one reason we get so many posts on here about folks having problems burning down the coals. It gets so bad that we have many actually scooping out their coals daily, like ashes and throwing them outside because they can't get them burned down. Terrible thing to do....
Oldspark, I also tend to think that oaks in different parts of the country will have different moisture and some will be harder than others. We also have to remember, somewhere I read there are over 50 different types of oaks in the U.S.
I've wondered the same thing. Certainly the lightest wood (pine, poplar, et al) mostly gasifies (secondary burn) and leaves few coals, while the densest wood (locust, hickory) doesn't seem to gasify nearly as much but produces a ton of coals. But then you have cherry, which I find does not produce much of a secondary burn and produces a lot more coals than its density would suggest. It requires a lot more primary air than similar-density woods like red maple or ash.
I think Locust burns like coal and really coals up nicely and does not require alot of drying time like Oak. It is a heavy wood. Around here poplar seems the worst and generates a light fluffy ash. I know Leggetfa hates burning the stuff. Cherry is a nice all around wood and dry Oak is great.
That brings up another question, both locust and oak are dense woods but locust drys much quicker for what reason?GolfandWoodNut said:
oldspark said:
Locust has one of the lowest MC of all species, sitting on the stump in the woods . Ash is better, that's about it, I think. Oak has just about the highest MC when green of any hardwood. That just about says its all, I reckon.
Wood Duck said:
I think it may have something to do with the pores, but I think it might have more to do with the density of the solid parts. I have always noticed very good coaling with hickory, locust, oak and ash. Those are the only ring-porous woods I burn. The diffuse-porous woods like cherry and maple don't coal well for me at all. That's why I like to mix them in with the other stuff.
My reasoning is that since the ring-porous woods have a greater density in the non-porous late-wood bands, they outgas slower than a wood like hard maple, which has a more continuous volume of slightly less-dense wood. Ash and hard maple have almost identical densities, but the fiber and lignin is spread out more evenly in the maple, so it outgases more quickly and makes less coals.
In general, the slower the wood pyrolyzes, the more gets charred and turns to charcoal. So bigger, denser and wetter wood will makes more coals than smaller, lighter, drier wood. Anyone who was ever slick enough to load their stove up with wet oak to get an all-night burn has usually been rudely awakened by finding about 6" of unburned coals on the bottom of the stove in the morning. Then they spend all day trying to get them burned off.
Now how would I know about this?
Another thing to consider is that not all trees of the same species will have identical densities. Depending on where and how they grow, oak may surpass ash by a lot in density in some areas, not at all in others. We form our opinions based on what we find is true for us. Folks burning in an area that grows extremely dense oak? Well, that is the king of all firewoods for them. In my area, nothing comes close to shagbark hickory and black locust in density. No coincidence that I find they produce the most coals of all.
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