shape of wood equals burn time?

[brad wilton]

took some maple 4x4 from work the other day. asked first lol it's dry wood even put it on kettle at work 850f for a couple of hours.does not burn in any way like logs very slow even burn.shape seems to make a lot of difference in burn times

 

[English BoB]

Is it the shape or the density that slows the burn?. If you filled a fire place 100% packed full there would be no room for the air to move around and the wood woodnt burn,

Bob

 

[brad wilton]

it wasn't packed put it on top of regular logs wich burnt normally the 4x4s three of them just burnt from the edges in no hissing or popping just a really slow and steady burn from sides in ?

 

[begreen]

Sounds like it may have come from an old tree. Cord wood varies in growth rate and different parts of the tree. Old growth fir with tight growth rings will burn a lot slower than new stuff with wide growth rings.

FWIW, 850F for a couple hours is not the best way to treat a stove if the goal is a long life.

 

[brad wilton]

850 was at work at the zinc bath,i haven't even reached potential of my stove yet wood not great next year just figured i could burn some 4x4 but wasn't impressed

 

[rideau]

Sounds like it may have come from an old tree. Cord wood varies in growth rate and different parts of the tree. Old growth fir with tight growth rings will burn a lot slower than new stuff with wide growth rings.

FWIW, 850F for a couple hours is not the best way to treat a stove if the goal is a long life.

I'm glad you posted this.

Some have questioned my reported low wood usage, and I have posited that it may be related to my woods growing on limestone with only an inch or so of topsoil. Very slow growth wood, dense rings. 12 inch DBH tree can be over 100 years old. I have instinctively believed the very dense wood probably has less water when green, requires less drying time, and has more BTUs per volume.

 

[rideau]

Shape of wood does effect burn time. Maximum volume with minimum surface area equals longest burn time.

 

[bholler]

Also what type of maple was it there are many different types and many different burning characteristics

 

[Oldman47]

Rideau said "Shape of wood does effect burn time. Maximum volume with minimum surface area equals longest burn time."
Fire happens at the surface of the wood where the carbon and hydrogen of the hydrocarbon can combine with oxygen. As Rideau said the larger pieces have more wood per unit surface area. It can only burn as fast as the surface is revealed to the air so larger chunks always mean slower burning. A large perfect sphere would be the slowest burning shape of all but I don't have time to create that shape and don't want to. Another shape consideration, from a purely theoretical perspective, is that fire depends on its surroundings to avoid losing so much heat that it simply cannot sustain combustion. A single huge object will lose its heat fast enough to almost extinguish itself. Think about how a large log acts with no kindling present and you will have an extreme example of this. That large perfect sphere might also go out with lots of unburned fuel. Who knows. I sure don't want to run the experiment.