In particular - the section on drying - air drying would have been too rapid/harmful to the wood - so they put it into a purpose-built dehumidifying kiln for 9 months.
Wood expands and contracts with moisture content. More moisture makes the fibers "fatten up".
The interesting thing is that this is anisotropic: the expansion/contraction occurs across the grain, NOT along the grain. The rate of expansion also depends on the local characteristics of the grain itself (hence the effects of warping due to uneven expansion) ... Also there's a big difference between the direction "across the growth rings" (i.e. radially when it was still a tree) and tangentially to the growth rings. And these surfaces are curved, of course. But one thing we can always say is: the wood doesn't significantly change size along the grain.
Design and construction methods can make wooden artifacts more or less susceptible to cracking and distortion from this. For example dovetail joints can be pretty good as all the wood expands/contacts together the same way. Especially if the pieces are joined together from the same piece of wood. Stuff like that. Or at the other extreme, metal fixings like nails don't move with moisture at all, which can cause problems with relative movement and stress can accumulate.
Edit: and the repeated cycling of moisture content induced stress can eventually lead to cracking, in a similar way to metal fatigue. Old wood just cracks sometimes, this is probably why.
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jimnotgym
I used to be a carpenter and joiner. I once had a batch that was badly kiln dried. We called it 'case hardening', I guess it was done too fast. If you planed a flat face on it and it instantly warped again!
If you sawed it, it would either pinch or spring apart. I made the sales rep come and see it.
lukaslalinsky
What a shame this is a paywalled article. The first part was interesting, but I'm definitely not going to subscribe. If I could pay for this one article, I would.
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pavel_lishin
> “But if you want softwoods to manufacture windows, doors, furniture and things like that, the continuous process is not the one to go with,” Avramidis says. “You have to go back to the batch process. Why? Because you cannot have stress relief in the continuous process. And, of course, hardwoods should be dried in boxes only.”
Aha, yes, of course.
(I have no idea what stress relief means here, or why hardwoods are different :/)
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cmrdporcupine
Had some poplar milled from some large trees we had to take down here. Air dried in my shop for 4 years before having it made into a table. All it took was 1 winter and it split and bent severely inside the house. I will only kiln dry from now on.
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kragen
> In 2019, near a river basin above Kalambo Falls in Zambia, archeologists discovered “two interlocking logs joined transversely by an intentionally cut notch,” according to a 2023 article in Nature. Using luminescence, the archeologists estimated this rare find was 476,000 years old.
Holy shit.
It is too bad that the post cuts off in the middle with a paywall notice. We really should ban such links. They aren't conducive to high-quality discussion.
show comments
xhkkffbf
Anyone have any experience drying the wood in a vacuum chamber?
jollyllama
Didn't read the paywalled bit but the gist of air-dried being nice to work with makes sense. But you want kiln-dried for your stove! Or so I'm told.
nemo44x
If you want to smoke food (BBQ, etc) avoid kiln dried wood. It's too dry. You want dry wood but you generally want some level of moisture (15%-20% is often good, more in some other styles) in most of your wood.
For some reason this reminds me of :
https://www.thefenlandblackoakproject.co.uk/our-story
In particular - the section on drying - air drying would have been too rapid/harmful to the wood - so they put it into a purpose-built dehumidifying kiln for 9 months.
(It was briefly discussed here a few years ago: https://news.ycombinator.com/item?id=36912861 )
Wood expands and contracts with moisture content. More moisture makes the fibers "fatten up".
The interesting thing is that this is anisotropic: the expansion/contraction occurs across the grain, NOT along the grain. The rate of expansion also depends on the local characteristics of the grain itself (hence the effects of warping due to uneven expansion) ... Also there's a big difference between the direction "across the growth rings" (i.e. radially when it was still a tree) and tangentially to the growth rings. And these surfaces are curved, of course. But one thing we can always say is: the wood doesn't significantly change size along the grain.
Design and construction methods can make wooden artifacts more or less susceptible to cracking and distortion from this. For example dovetail joints can be pretty good as all the wood expands/contacts together the same way. Especially if the pieces are joined together from the same piece of wood. Stuff like that. Or at the other extreme, metal fixings like nails don't move with moisture at all, which can cause problems with relative movement and stress can accumulate.
Edit: and the repeated cycling of moisture content induced stress can eventually lead to cracking, in a similar way to metal fatigue. Old wood just cracks sometimes, this is probably why.
I used to be a carpenter and joiner. I once had a batch that was badly kiln dried. We called it 'case hardening', I guess it was done too fast. If you planed a flat face on it and it instantly warped again!
If you sawed it, it would either pinch or spring apart. I made the sales rep come and see it.
What a shame this is a paywalled article. The first part was interesting, but I'm definitely not going to subscribe. If I could pay for this one article, I would.
> “But if you want softwoods to manufacture windows, doors, furniture and things like that, the continuous process is not the one to go with,” Avramidis says. “You have to go back to the batch process. Why? Because you cannot have stress relief in the continuous process. And, of course, hardwoods should be dried in boxes only.”
Aha, yes, of course.
(I have no idea what stress relief means here, or why hardwoods are different :/)
Had some poplar milled from some large trees we had to take down here. Air dried in my shop for 4 years before having it made into a table. All it took was 1 winter and it split and bent severely inside the house. I will only kiln dry from now on.
> In 2019, near a river basin above Kalambo Falls in Zambia, archeologists discovered “two interlocking logs joined transversely by an intentionally cut notch,” according to a 2023 article in Nature. Using luminescence, the archeologists estimated this rare find was 476,000 years old.
Holy shit.
It is too bad that the post cuts off in the middle with a paywall notice. We really should ban such links. They aren't conducive to high-quality discussion.
Anyone have any experience drying the wood in a vacuum chamber?
Didn't read the paywalled bit but the gist of air-dried being nice to work with makes sense. But you want kiln-dried for your stove! Or so I'm told.
If you want to smoke food (BBQ, etc) avoid kiln dried wood. It's too dry. You want dry wood but you generally want some level of moisture (15%-20% is often good, more in some other styles) in most of your wood.