Wood dries from the end? Or sides? Or BOTH?

[BlueRidgeMark]

Back in another thread, someone asked if he could speed the drying of logs by making 4 cuts in the bark along the length of the log.

I said he'd be wasting his time, as wood dries mostly from the end grain.

Someone disagreed, and stated that "very little drying occurs at the end of the grain", and he could find the citations to prove it.

Rather than hijack that thread, I thought I'd start a new one.

Of course, I don't think anybody believes that wood dries ONLY from the ends, and of course, wood that is split will dry faster than bucked logs, which will dry faster than UNbucked logs. It's all about exposing surface area.

That said, my contention is that wood dries mostly from the end grain, rather than from the sides. Because sawing wood exposes more end grain than splitting, sawn wood will dry faster than split wood of a similar size.

In support of this, I offer the following:

Wood dries along the grain up to 15 times faster than
across the grain.

Source. This source is talking about milling operations, so discusses drying boards, which dry mostly from their sides, due to the exposed end grain and the relative dimensions. Boards are obviously much thinner than firewood chunks.

This end grain absorbs (or releases) water much more quickly than the other wood surfaces...

Source.

Two important characteristics of the longitudinal direction are that water moves up to 50 times faster in this direction (i.e., end grain dries much faster than side grain) and wood shrinks very little in this direction.

Source.


I could go on posting citations, but they would all say the same thing. Wood dries mostly from the end grain. Some drying from the sides does occur. Split wood dries faster than unsplit wood because it exposes more surface area, thus allowing for evaporation from the sides as well. Sawing wood exposes even more end grain than splitting, thus it dries even faster for a piece of similar dimensions.


So there you have it. Reliable sources saying that wood dries from the end grain anywhere from 15 to 50 times faster than from the sides.

 

[sly13]

opcorn:

 

[BlueRidgeMark]

I think your logic is fine Mark but don't overlook the fact that when a large round is split up into firewood.........that the side exposure increases by an order of magnitude or so while the end grain exposure does not increase at all.

Oh, Dan, I think you're right! Why didn't I think of that? :bang:

Split wood dries faster than unsplit wood because it exposes more surface area, thus allowing for evaporation from the sides as well.

 

[12vdzl]

I mainly posted sawing slots into the bark so it then dries faster and falls off faster, equating to the logs giving up moisture quicker to sun and wind. I would think after the logs have lost it's bark it will dry completly. Drying time wouldn't matter much if scrounging is good.

Mark thanks for posting, hopefully this thread will remain positive and all of us gain in knowledge.

 

[Streblerm]

I don't have any supporting information, but my observations of the wood that I have split and stacked leads me to believe that wood dries better when split than in rounds, and better when cut into rounds than in log length

I have been working with some large (30"+ diameter) rounds. They have been cut for a year and spent several years before that cut into log lengths. When I split them, water was squirting out. They measured approx. 40% moisture with my cheap moisture meter.

That wood has been split and stacked for about 60 days measures about 30% moisture in the center of a fresh split. You can clearly see a line about 1-2" around all the edges where it is more dry than in the center.

So, I think wood dries through any "disturbed" surface, whether that be the ends or the sides. The smaller the split, the faster the dry.

 

[Wood Doctor]

End grain dries faster on unsplit wood (rounds). However, exposed side grain dries the total mass of the wood (all logs from the round added together) when the rounds are split because more surface is exposed to air and sun.

Also, when the round is split, the bark sometimes falls off the outside of the split logs, and that dries the total mass even faster. Bark holds in moisture. That's what helped the tree live. Without bark attached, the air and sun dry the wood far more quickly. Eventually, the bark dries also and makes good tinder.

 

[SSG Medic]

There are some common sense ways that can help make sense on how wood dries. It essentially goes down to the molecular and cellular makeup and cellular layout. It goes back to high school biology(I do realize that was several years ago for some :biggrinbounce2

The cells in a tree are similar to a drinking straw. They are long hollow tubes that are used to carry water and nutrients from the soil to the upper part of the tree and to the leaves. Since it is easier for water to travel up and down these straw like cells it leads water loss at the ends.

explaining how water can leave the sides is a little more difficult. Since water does not pass through the cell walls very easily it has to go around the cells. This can end up causing the moistrure to pass around the cells like the disk going around the pegs in plinko on the price is right.

On top of being able to get around the cells the moisture needs to escape from the cells. The cell will start to dry which cause the cell wall to crack and allow moisture to pass through the crack.


Check out this website.

http://timber.ce.wsu.edu/Supplements/Moisture/moisture page2.htm

Hopefully the pictures below will help visualize what I am talking about.

 

[BlueRidgeMark]

Some of the 'straws' must also get torn or broken. I believe it would be a mistake to assume that they all still ended at the ends of the piece of split firewood.

Yep, that's especially true of sawn wood, but still true of split wood.

 

[SSG Medic]

Some of the 'straws' must also get torn or broken. I believe it would be a mistake to assume that they all still ended at the ends of the piece of split firewood.

that is true. There are still other variables that are involved.

Also the inside layer of bark is also very good at holding water which can add to the slow drying from the sides of unsplit wood.

I think it goes without saying but cut and split wood will dry faster. One reason for this is you are lowering the distance and resistance that the water has to travel to get out of the wood.


I understand that there are several more factors that can effect the drying time. I am sure someone with a Phd has Written a lengthy paper or book on the subject.

 

[howellhandmade]

When valuable logs are milled, the ends of the lumber are sealed with wax or paint to slow drying from the ends and reduce checking. Thus the board or billet dries more evenly instead of more rapidly at the ends and more slowly in the center. In this case even drying is desired at the expense of time, while for firewood we want rapid drying and don't care how much it cracks. I don't think anyone would argue with the assertion that moisture escapes more rapidly from the end grain than from the split sides, but I think I read the assertion that it didn't matter if rounds were split for speed of drying because virtually all of the drying occurs from the end grain. This is counter to my experience, which is that splits dry faster than rounds, and smaller splits dry faster than large ones. To check the seasoning of wood I'll often split pieces to check internal moisture. If a stack is not quite ready, smaller splits will be dry on the inside while larger ones will still be damp. If all the drying occurred from the end grain, all the pieces would be equally dry for the same length regardless of width.

Jack

 

[Nosmo]

Bark is Waterproof

I know the bark of a tree is waterproof. If a piece of bark is sliced off a live tree sap will ooze out.

When camping in the woods and it rains before trying to start a fire cut the wet bark off some of the kindling and that wood is dry.

Nosmo

 

[BlueRidgeMark]

When valuable logs are milled, the ends of the lumber are sealed with wax or paint to slow drying from the ends and reduce checking. Thus the board or billet dries more evenly instead of more rapidly at the ends and more slowly in the center. In this case even drying is desired at the expense of time, while for firewood we want rapid drying and don't care how much it cracks.

Excellent point.

I don't think anyone would argue with the assertion that moisture escapes more rapidly from the end grain than from the split sides

On the contrary. That's exactly what the person who disagreed with me said.

Here's the quote:

I think I called you on this before;it is simply not true.Very little drying occurs at the end of the grain.It is the reason that we split our wood to speed drying and limit rot.I will be happy to provide any citations that you require.

(Emphasis added.)

but I think I read the assertion that it didn't matter if rounds were split for speed of drying

Really? I didn't see that anywhere.

 

[Wood Doctor]

When is a Dead Tree Dead Dry?

Mark, I think all of this implies something very important. Don't just check the end grain of any log with a moisture meter. Check it in several spots and only after splitting. Case in point:

I recently cut and split up a pile of elm logs from a huge American elm than had been dead for 5 years with all the bark gone. I cut them to length in June and split them last month. The larger pieces near the trunk were dry on the ends but still wet after splitting--water started oozing out when the wedge made it about two inches in. Inside, the long grain was still damp.

I told the lady who owned the property about it and she was in disbelief. Remember, this tree had been standing "dead" for 5 years. However, the roots were still feeding the cellulose. Gasp!

 

[Lugnutz]

small split wood dries faster than large split wood which dries faster than non split wood that is cut which dries faster than logs which dries much faster than the tree itself before it is cut down...I think I got it! :jawdrop:

 

[Lugnutz]

I agree that standing dead trees don't season very much but I'm quite sure the roots are not still drawing water up into the tree. The process that causes that stops when the tree dies.....is my understanding!

could it be a wicking action taking place? like holding a small strip of paper towel above a glass of water so that just the end touches the water?
The paper towel will wick the water up its length a good ways.

 

[howellhandmade]

I agree that standing dead trees don't season very much but I'm quite sure the roots are not still drawing water up into the tree. The process that causes that stops when the tree dies.....is my understanding!

So long as the capillary tubes remain open, capillary action will take place. This isn't a process that depends on the tree being alive, it's the result of surface tension, a molecular property of water. I think when the tree dies and starts to shrink the capillaries start to collapse.

Mark, I remember the comment you quoted about very little drying occurring from the end grain, and I think it's a question of where you want to put emphasis. If you have a long log,it can be said that very little drying will occur from the ends. If you have a cookie, almost all of the drying occurs from the ends. Firewood, stands to reason, is somewhere in between.

I'm basing my opinion of what happens on how firewood behaves at various stages. When I re-split a large split, it may have a damp spot in the center, but there will be dry wood all around the outside, both on the sides and the ends. It hasn't occurred to me to try to quantify how much it dries in which direction, but my impression is that the moisture will be further from the ends than it is from the sides, and further from a split surface than from adhering bark. Which is good enough for me; I'll stick by the advice that for faster drying wood should be split.

Jack

 

[oxbow]

Great thread

This is a great thread!
Wisdom from hands-on experience and observation, mixed with textbook facts about the technical and scientific properties of wood.

Mark: Here is a source which supports drying faster from end grain:

“Understanding Wood”, R. Bruce Hoadley, the Taunton Press, 1980, eighth printing, August 1992, (page 84)

“Uneven drying … perhaps the most universal problem is end-checking. Water moves longitudinally through wood 10 to 15 times faster than it moves perpendicularly to the grain. Therefore, endgrain surfaces rapidly lose their moisture and will be first to drop below fiber saturation point (FSP) and begin to shrink. If the shrinkage exceeds about 1.5%, tension failures in the form of end-checking may occur.”

Hoadley has a PhD in wood technology from Yale, and researches and teaches at University of Mass, Amherst.

 

[coog]

This is a great thread!
Wisdom from hands-on experience and observation, mixed with textbook facts about the technical and scientific properties of wood.

Mark: Here is a source which supports drying faster from end grain:

“Understanding Wood”, R. Bruce Hoadley, the Taunton Press, 1980, eighth printing, August 1992, (page 84)

“Uneven drying … perhaps the most universal problem is end-checking. Water moves longitudinally through wood 10 to 15 times faster than it moves perpendicularly to the grain. Therefore, endgrain surfaces rapidly lose their moisture and will be first to drop below fiber saturation point (FSP) and begin to shrink. If the shrinkage exceeds about 1.5%, tension failures in the form of end-checking may occur.”

Hoadley has a PhD in wood technology from Yale, and researches and teaches at University of Mass, Amherst.

Wow.Miss a day and look what happens! Mark, we may or not agree on this, but I believe your original statement, certainly applied to the logs in the original thread, is mis-leading at best.If you are talking about a 12'-20' log, the fact that it dries out "most" or "fastest" through the end grain is meaningless and suggests that bucking, and more importantly, splitting are only means to get it top fit the stove.The fact is, as we all agree, that wood will rot without exposing it to more air.Oxbow to continue with Hoadley:

Wood dries along the grain up to 15 times faster than across the grain. Therefore, a board will dry at a faster rate from its ends. However, because a board is usually many times longer than it is thick, most of the moisture loss occurs across the grain and out the surfaces of the piece. In other words, the moisture travels across the grain at a slower rate, but it has to cross a much shorter distance and, except near the ends of the board, it dries more through the surfaces.

The rate at which lumber dries is controlled both by the rate of evaporation from the surface and by the rate of movement of the water within the piece. As long as the moisture can move from the interior to the surface at a fast enough rate to keep the surface moist, the drying rate will be increased if the surface evaporation rate is increased


So if you started this new topic to avoid a hijack, do remember how you applied your original statement.We had a guy who wanted to know if a pile of old logs was worth $500.The consensus was no, many would be rotted.Your statement would leave the novice to think otherwise.

 

[loadthestove]

small split wood dries faster than large split wood which dries faster than non split wood that is cut which dries faster than logs which dries much faster than the tree itself before it is cut down...I think I got it! :jawdrop:

WOW,,My thoughts exactly LOL

 

[Wood Doctor]

The Roots of Trees Linger

I agree that standing dead trees don't season very much but I'm quite sure the roots are not still drawing water up into the tree. The process that causes that stops when the tree dies.....is my understanding!

Dan, as already reported by others on this thread, the "death" of a tree does not mean the top alone. The roots continue to feed it water if they are still alive. Even after all of the bark and leaves are all gone, many roots are alive and well beneath the ground, pumping water from the ground into the trunk as best as they can.

It's a pointless effort by the roots, but they do not know any better. So, wood from a "dead' tree can still not be ready to burn in a stove or fireplace, even if split, stacked, and dried in the air for a couple of months.