8 ms·

Air-dried vs. Kiln-dried Wood

159 points by crescit_eundo 1y ago

HPsquared 1y ago
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.
- arturocamembert 1y ago
  Small addendum: some traditional wooden joinery is deliberately prepared to account for the varying rates and effects of drying across the timber. This is particularly relevant in timberframing, where you want to work with the wood when it is as green as possible. Green pine, though heavier to lug around, is significantly more receptive to a chisel than drier lumber. In a classic mortise and tenon joint [0], it's common to leave the outer edge of the shoulder slightly raised from the inner edge to account for the natural warping as the exterior of the beam dries more aggressively. Although it's more outside my area of experience, I believe fine carpentry also has a few techniques that see a higher frequency of use in areas that enjoy seasonal swings in humidity. The split-tenon is the only one that comes to mind, but, now that I think of it, I realize my mental model isn't great. More surface area to account for seasonal swelling / shrinkage? Maybe someone else can chime with a better explanation of this one. [0] https://www.barnyard.com/sites/default/files/styles/full_page/public/uploads/2021-02/mortise-tenon-0.jpg?itok=9IFdY9sN https://www.barnyard.com/sites/default/files/styles/full_pag...
  - ofalkaed 1y ago
    Timber framing uses dry wood as well, slightly different techniques but in the softwoods and some of the hardwoods its is not all that harder to work dry than green and in some ways easier. It depends on the tradition and location as to the exact process and technique, some preferred dry timbers, some green, some something between. In US farm country it was common to fell the trees in late fall/early winter after the harvest was all taken care of and then leave the trees where they dropped until the ground froze. After the ground froze you haul them to the build site, much easier to drag logs on hard frozen ground than on soft wet ground. Then you would forget about them until after the spring planting is taken care of and build in the summer. Those big timbers would be far from dry but they will have lost a fair amount of weight and will be more stable which makes everything easier.
    - HeyLaughingBoy 1y ago
      I read a biography of the earthmoving equipment maker R.G. Le Tourneau, and it was really eye-opening how much this was a thing before mechanized equipment was readily available. A lot of moving was put off until winter because it was so much easier to drag logs, boulders, buildings, etc. over ice than over thawed ground.
      - potato3732842 1y ago
        Or waiting for things to freeze real good so you can dig the kind of hole or trench that would make HN clutch its pearls or simplify de-watering problems.
        lazide 1y ago
        I’ve never tried to dig in frozen ground - isn’t that going to require blasting equipment or techniques closer to mining? (Heavy pneumatic jackhammers)
        HeyLaughingBoy 1y ago
- rollulus 1y ago
  I’ve been taught that in the length it can expand/contract at most 1%, but in the width at most 10%. This is also why properly designed tabletops are attached to the frame with a “floating” construction that can handle those changes.
  - exDM69 1y ago
    This is correct but the numbers are off by an order of magnitude. The annual movement of wood is maybe 2% width wise and almost negligible lengthwise. This is for wood that is dried and stabilized, the shrinking is a bit more from green wood to seasoned lumber (but not an order of magnitude more). You can use online calculators such as this one for estimates based on the species of wood and your location: https://kmtools.com/pages/wood-movement-calculator https://kmtools.com/pages/wood-movement-calculator The numbers here match my experience, a 600mm wide spruce table top shrunk and expanded by about 12mm during a year of being outdoors but under a roof at temperatures from -25C to +30C. The structure had sliding dovetails to allow growth but keep it flat.
    - DannyBee 1y ago
      See my other comment - they are closer than you think in some sense, but there are too many missing variables to say anyone is right or wrong. The annual movement of wood depends (basically) on the local RH swing, thickness, absorption/diffusion rates, and swelling coefficients. So giving any percents here without more data is just incomplete. This is assuming bare wood too, with no coatings/etc. A lot of the bare percents you see are making assumptions of various sorts. Usually they ignore the diffusion rates/etc and shoot for EMC at some parameters (the calculator you linked does) because doing it for real require more complex math. The calculator you linked is better than most for sure, but it is still a simplification of reality where it may be off by orders of magnitude depending on thickness. It will be much closer to reality for thinner pieces than thicker ones.
      - exDM69 1y ago
        The figures I gave are annual movement. Initial shrinkage is larger when drying from green wood. The numbers (from the calculator) match my empirical observations very closely. By the way your relative humidity figures assume constant temperature. Wood cares about absolute humidity (mass of vapor per volume of air), and temperature is the dominant factor in absolute humidity. Rainy day at +1C (100% RH) is less absolute humidity than a sunny day at +30C. This matters to me a lot because half of my woodworking projects are outdoors or not temperature controlled indoors.
- exDM69 1y ago
  A good mental model for wood is that trees are a bunch of stacked cones (growth rings) on top of each other. In the spring it fills with water and the diameter grows but the tree does not get longer because it needs to support a large mass on top and the lengthwise fibers are not able to grow and shrink (they need to be stiff to carry the weight). Because of this, the circumference of the outermost growth rings need to grow more than the inner ones. Now cut a board out of it and look at the end grain. Think what happens when the rings closer to the outside need to shrink more than the inner ones for the same humidity change. For a flat sawn board, you will always see it cup so that the concave side is on the outside. This doesn't explain why boards twist or bow but cupping is the most prevalent wood movement in typical flat sawn boards.
  - jermaustin1 1y ago
    Both are actually explained the same way because in bowing, it dries slower in the middle of the board creating the bow, and twisting is just different type of uneven drying typically due to some open grain drying faster.
- rags2riches 1y ago
  A panel door is basically designed to minimize warping as the wood expands and contracts. There is leeway for the panels to move inside the edge pieces (sorry, not sure about the terminology here) and the edge pieces have the grain along the sides of the door. Stuck doors or doors that will not close are no fun.
- cardamomo 1y ago
  One nit: there are times when you do want to use a metal nail or screw in a joint, particularly if there is some sort of cross-grain joinery going on and you want to allow for wood movement. Chris Schwarz (publisher of this article) makes the point himself: https://blog.lostartpress.com/2015/07/11/the-bare-bones-basics-of-nail-technology/ https://blog.lostartpress.com/2015/07/11/the-bare-bones-basi...
lukaslalinsky 1y ago
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.
- coldpie 1y ago
  I don't subscribe to his paid blogs personally, but Chris Schwarz is one of the best known writers in the woodworking world. I own most of his books, and I wouldn't be a woodworker today if it weren't for his writing. If you like this one article, odds are good you'll enjoy more from him, at least enough to pay for a month subscription or something. Edit: though now I see this particular article was actually written by their editor/researcher, not Chris, so uh nevermind, maybe.
- Gys 1y ago
  I could read the full article without problems. Using MacOS/Firefox. Maybe just clear your cookies.
- hn8726 1y ago
  And the non-paywalled part doesn't even get into the differences between air-dried and kiln-dried wood.
cmrdporcupine 1y ago
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.
- sarchertech 1y ago
  I’ve never dried anything that long indoors, but from what people told me when I was researching the best way to dry some red oak I had milled there are issues drying indoors doors. Wind does most of the drying outside. Did you use a moisture meter?
  - trey-jones 1y ago
    Worse, I've been told that attempting to dry indoors would result in rot (given not enough air flow, which might not be the case in all indoor environments), and consequently have never tried it. I've exclusively air dried pine, oak, poplar, pecan, cedar, all under open walled structures and not had too many problems over the last 20 years (and my dad was doing it for another 30 before that).
- zitsarethecure 1y ago
  Four years of air drying may not have been enough, depending on the thickness of the boards and the moisture level in the air. Also the issues of wood movement and grain direction must be considered during the design and manufacturing of furniture with that wood. Home sawn wood will often have knots, randomly curved grain, etc, so it can be more difficult to get predictable results.
- CallMeJim 1y ago
  Poplar is a very wet wood. It tends to take so long to dry, and then burns so quickly, that it isn't worth processing for firewood!
- epgui 1y ago
  4 years is actually not that much for a passive air drying process.
kragen 1y ago
> 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.
- LunaSea 1y ago
  I wonder how they could differentiate the age of the wood from the age of the construction
  - infecto 1y ago
    Just an educated guess but I am assuming the age of the wood is a good enough proxy to construction. Making the assumption that wood out in nature will decompose in short order (when thinking of the stated age). Being off a few thousand years is probably ok.
    - franktankbank 1y ago
      But somehow the wood is still intact 500k years later?
      - meatmanek 1y ago
        "Intact enough to be recognized" is a lower standard than "intact enough to be useful as a building material".
      - kragen 1y ago
        It was probably buried under anoxic conditions, which would weaken it and make it less suitable for new construction.
      - infecto 1y ago
        Kind of as other said, it was buried. From what I have read archaeological finds are about piecing together good guesses. Sure some wood is rot resistant but I suspect you would be hard pressed to find wood sitting outside for 1000+ years on the ground that early civilization would find appeasing to build with. Anything is possible but I am guessing it either fell natural or was harvested by those people and they decided to build with it somewhere plus or minus a thousand years.
jollyllama 1y ago
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 1y ago
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.
- sejje 1y ago
  Many folks soak the chips in bowls of water
  - wil421 1y ago
    Use wood chucks. After thinking about it, I’ve never thought my wood chunks were too dry but I used to think that a lot about wood chips. Wood chips burn much faster so it makes sense.
    - potato3732842 1y ago
      I have a hard time not getting it to burn hot and without smoke regardless of form factor if the wood isn't somewhat wet. Can always toss in some charcoal to compensate if it's too wet. Kind of hard to do much if it's too dry.
  - BizarroLand 1y ago
    You can also put the kiln dried wood outside (but covered) for a few weeks. It will reabsorb enough moisture from the air to burn normally.
gertrunde 1y ago
For some reason this reminds me of : https://www.thefenlandblackoakproject.co.uk/our-story 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 https://news.ycombinator.com/item?id=36912861 )
- kulahan 1y ago
  I saw a thing once where a guy would make 3 large cuts at the bottom of a tree, in a particular pattern. This would kill the tree, and it would essentially air-dry over the course of a year or two. I wonder how that compares. I should note he was a homesteader doing this to provide dry wood with easy access during cold months.
  - superb_dev 1y ago
    That’s pretty clever! I’ll have to keep this in mind if ever get my dream homestead. I’m no arborist, but I’d guess the cuts sever all of the tree’s microtubules without felling it? I think 3 would be the minimum amount of cuts you’d need.
    - jaderobbins1 1y ago
      Yeah, girdling: https://en.wikipedia.org/wiki/Girdling https://en.wikipedia.org/wiki/Girdling I hadn't heard it used to get dry wood for harvesting but I recall it being useful because it actually kills the tree, so if you cut the tree down (after it's fully dead) the stump will decompose instead of trying to continue to grow.
    - tstrimple 1y ago
      Seems like it might be a good way to waste wood. Dead and dry wood tends to shatter and break apart when felled. Green wood has a LOT more flex. Depends on what you’re after I guess.
jimnotgym 1y ago
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.
pavel_lishin 1y ago
> “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 :/)
- jandrese 1y ago
  The article talks about stress relief when it went down the rabbit hole of tiny mom & pop mills who were turning their kilns off every night because they didn't have a third shift and later discovering that turning them off periodically produces better lumber because it allows the wood to relieve stress and suffer less distortion. However, the continuous process is basically just a slow moving conveyor belt where you are constantly feeding green wood in one end and dried lumber is constantly being spit out of the far end. I don't see why you couldn't incorporate ambient air chambers in strategic places on the belt to destress the lumber, at the cost of making the entire production line somewhat longer.
xhkkffbf 1y ago
Anyone have any experience drying the wood in a vacuum chamber?

159 points by crescit_eundo 1y ago

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.

arturocamembert 1y ago
Small addendum: some traditional wooden joinery is deliberately prepared to account for the varying rates and effects of drying across the timber. This is particularly relevant in timberframing, where you want to work with the wood when it is as green as possible. Green pine, though heavier to lug around, is significantly more receptive to a chisel than drier lumber. In a classic mortise and tenon joint [0], it's common to leave the outer edge of the shoulder slightly raised from the inner edge to account for the natural warping as the exterior of the beam dries more aggressively. Although it's more outside my area of experience, I believe fine carpentry also has a few techniques that see a higher frequency of use in areas that enjoy seasonal swings in humidity. The split-tenon is the only one that comes to mind, but, now that I think of it, I realize my mental model isn't great. More surface area to account for seasonal swelling / shrinkage? Maybe someone else can chime with a better explanation of this one. [0] https://www.barnyard.com/sites/default/files/styles/full_page/public/uploads/2021-02/mortise-tenon-0.jpg?itok=9IFdY9sN https://www.barnyard.com/sites/default/files/styles/full_pag...
- ofalkaed 1y ago
  Timber framing uses dry wood as well, slightly different techniques but in the softwoods and some of the hardwoods its is not all that harder to work dry than green and in some ways easier. It depends on the tradition and location as to the exact process and technique, some preferred dry timbers, some green, some something between. In US farm country it was common to fell the trees in late fall/early winter after the harvest was all taken care of and then leave the trees where they dropped until the ground froze. After the ground froze you haul them to the build site, much easier to drag logs on hard frozen ground than on soft wet ground. Then you would forget about them until after the spring planting is taken care of and build in the summer. Those big timbers would be far from dry but they will have lost a fair amount of weight and will be more stable which makes everything easier.
  - HeyLaughingBoy 1y ago
    I read a biography of the earthmoving equipment maker R.G. Le Tourneau, and it was really eye-opening how much this was a thing before mechanized equipment was readily available. A lot of moving was put off until winter because it was so much easier to drag logs, boulders, buildings, etc. over ice than over thawed ground.
    - potato3732842 1y ago
      Or waiting for things to freeze real good so you can dig the kind of hole or trench that would make HN clutch its pearls or simplify de-watering problems.
      - lazide 1y ago
        I’ve never tried to dig in frozen ground - isn’t that going to require blasting equipment or techniques closer to mining? (Heavy pneumatic jackhammers)
        HeyLaughingBoy 1y ago
rollulus 1y ago
I’ve been taught that in the length it can expand/contract at most 1%, but in the width at most 10%. This is also why properly designed tabletops are attached to the frame with a “floating” construction that can handle those changes.
- exDM69 1y ago
  This is correct but the numbers are off by an order of magnitude. The annual movement of wood is maybe 2% width wise and almost negligible lengthwise. This is for wood that is dried and stabilized, the shrinking is a bit more from green wood to seasoned lumber (but not an order of magnitude more). You can use online calculators such as this one for estimates based on the species of wood and your location: https://kmtools.com/pages/wood-movement-calculator https://kmtools.com/pages/wood-movement-calculator The numbers here match my experience, a 600mm wide spruce table top shrunk and expanded by about 12mm during a year of being outdoors but under a roof at temperatures from -25C to +30C. The structure had sliding dovetails to allow growth but keep it flat.
  - DannyBee 1y ago
    See my other comment - they are closer than you think in some sense, but there are too many missing variables to say anyone is right or wrong. The annual movement of wood depends (basically) on the local RH swing, thickness, absorption/diffusion rates, and swelling coefficients. So giving any percents here without more data is just incomplete. This is assuming bare wood too, with no coatings/etc. A lot of the bare percents you see are making assumptions of various sorts. Usually they ignore the diffusion rates/etc and shoot for EMC at some parameters (the calculator you linked does) because doing it for real require more complex math. The calculator you linked is better than most for sure, but it is still a simplification of reality where it may be off by orders of magnitude depending on thickness. It will be much closer to reality for thinner pieces than thicker ones.
    - exDM69 1y ago
      The figures I gave are annual movement. Initial shrinkage is larger when drying from green wood. The numbers (from the calculator) match my empirical observations very closely. By the way your relative humidity figures assume constant temperature. Wood cares about absolute humidity (mass of vapor per volume of air), and temperature is the dominant factor in absolute humidity. Rainy day at +1C (100% RH) is less absolute humidity than a sunny day at +30C. This matters to me a lot because half of my woodworking projects are outdoors or not temperature controlled indoors.
exDM69 1y ago
A good mental model for wood is that trees are a bunch of stacked cones (growth rings) on top of each other. In the spring it fills with water and the diameter grows but the tree does not get longer because it needs to support a large mass on top and the lengthwise fibers are not able to grow and shrink (they need to be stiff to carry the weight). Because of this, the circumference of the outermost growth rings need to grow more than the inner ones. Now cut a board out of it and look at the end grain. Think what happens when the rings closer to the outside need to shrink more than the inner ones for the same humidity change. For a flat sawn board, you will always see it cup so that the concave side is on the outside. This doesn't explain why boards twist or bow but cupping is the most prevalent wood movement in typical flat sawn boards.
- jermaustin1 1y ago
  Both are actually explained the same way because in bowing, it dries slower in the middle of the board creating the bow, and twisting is just different type of uneven drying typically due to some open grain drying faster.
rags2riches 1y ago
A panel door is basically designed to minimize warping as the wood expands and contracts. There is leeway for the panels to move inside the edge pieces (sorry, not sure about the terminology here) and the edge pieces have the grain along the sides of the door. Stuck doors or doors that will not close are no fun.
cardamomo 1y ago
One nit: there are times when you do want to use a metal nail or screw in a joint, particularly if there is some sort of cross-grain joinery going on and you want to allow for wood movement. Chris Schwarz (publisher of this article) makes the point himself: https://blog.lostartpress.com/2015/07/11/the-bare-bones-basics-of-nail-technology/ https://blog.lostartpress.com/2015/07/11/the-bare-bones-basi...

lukaslalinsky 1y ago

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.

coldpie 1y ago
I don't subscribe to his paid blogs personally, but Chris Schwarz is one of the best known writers in the woodworking world. I own most of his books, and I wouldn't be a woodworker today if it weren't for his writing. If you like this one article, odds are good you'll enjoy more from him, at least enough to pay for a month subscription or something. Edit: though now I see this particular article was actually written by their editor/researcher, not Chris, so uh nevermind, maybe.
Gys 1y ago
I could read the full article without problems. Using MacOS/Firefox. Maybe just clear your cookies.
hn8726 1y ago
And the non-paywalled part doesn't even get into the differences between air-dried and kiln-dried wood.

cmrdporcupine 1y ago

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.

sarchertech 1y ago
I’ve never dried anything that long indoors, but from what people told me when I was researching the best way to dry some red oak I had milled there are issues drying indoors doors. Wind does most of the drying outside. Did you use a moisture meter?
- trey-jones 1y ago
  Worse, I've been told that attempting to dry indoors would result in rot (given not enough air flow, which might not be the case in all indoor environments), and consequently have never tried it. I've exclusively air dried pine, oak, poplar, pecan, cedar, all under open walled structures and not had too many problems over the last 20 years (and my dad was doing it for another 30 before that).
zitsarethecure 1y ago
Four years of air drying may not have been enough, depending on the thickness of the boards and the moisture level in the air. Also the issues of wood movement and grain direction must be considered during the design and manufacturing of furniture with that wood. Home sawn wood will often have knots, randomly curved grain, etc, so it can be more difficult to get predictable results.
CallMeJim 1y ago
Poplar is a very wet wood. It tends to take so long to dry, and then burns so quickly, that it isn't worth processing for firewood!
epgui 1y ago
4 years is actually not that much for a passive air drying process.

kragen 1y ago

> 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.

LunaSea 1y ago
I wonder how they could differentiate the age of the wood from the age of the construction
- infecto 1y ago
  Just an educated guess but I am assuming the age of the wood is a good enough proxy to construction. Making the assumption that wood out in nature will decompose in short order (when thinking of the stated age). Being off a few thousand years is probably ok.
  - franktankbank 1y ago
    But somehow the wood is still intact 500k years later?
    - meatmanek 1y ago
      "Intact enough to be recognized" is a lower standard than "intact enough to be useful as a building material".
    - kragen 1y ago
      It was probably buried under anoxic conditions, which would weaken it and make it less suitable for new construction.
    - infecto 1y ago
      Kind of as other said, it was buried. From what I have read archaeological finds are about piecing together good guesses. Sure some wood is rot resistant but I suspect you would be hard pressed to find wood sitting outside for 1000+ years on the ground that early civilization would find appeasing to build with. Anything is possible but I am guessing it either fell natural or was harvested by those people and they decided to build with it somewhere plus or minus a thousand years.

jollyllama 1y ago

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 1y ago

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.

sejje 1y ago
Many folks soak the chips in bowls of water
- wil421 1y ago
  Use wood chucks. After thinking about it, I’ve never thought my wood chunks were too dry but I used to think that a lot about wood chips. Wood chips burn much faster so it makes sense.
  - potato3732842 1y ago
    I have a hard time not getting it to burn hot and without smoke regardless of form factor if the wood isn't somewhat wet. Can always toss in some charcoal to compensate if it's too wet. Kind of hard to do much if it's too dry.
- BizarroLand 1y ago
  You can also put the kiln dried wood outside (but covered) for a few weeks. It will reabsorb enough moisture from the air to burn normally.

gertrunde 1y ago

For some reason this reminds me of : https://www.thefenlandblackoakproject.co.uk/our-story 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 https://news.ycombinator.com/item?id=36912861 )

kulahan 1y ago
I saw a thing once where a guy would make 3 large cuts at the bottom of a tree, in a particular pattern. This would kill the tree, and it would essentially air-dry over the course of a year or two. I wonder how that compares. I should note he was a homesteader doing this to provide dry wood with easy access during cold months.
- superb_dev 1y ago
  That’s pretty clever! I’ll have to keep this in mind if ever get my dream homestead. I’m no arborist, but I’d guess the cuts sever all of the tree’s microtubules without felling it? I think 3 would be the minimum amount of cuts you’d need.
  - jaderobbins1 1y ago
    Yeah, girdling: https://en.wikipedia.org/wiki/Girdling https://en.wikipedia.org/wiki/Girdling I hadn't heard it used to get dry wood for harvesting but I recall it being useful because it actually kills the tree, so if you cut the tree down (after it's fully dead) the stump will decompose instead of trying to continue to grow.
  - tstrimple 1y ago
    Seems like it might be a good way to waste wood. Dead and dry wood tends to shatter and break apart when felled. Green wood has a LOT more flex. Depends on what you’re after I guess.

jimnotgym 1y ago

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.

pavel_lishin 1y ago

> “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 :/)

jandrese 1y ago
The article talks about stress relief when it went down the rabbit hole of tiny mom & pop mills who were turning their kilns off every night because they didn't have a third shift and later discovering that turning them off periodically produces better lumber because it allows the wood to relieve stress and suffer less distortion. However, the continuous process is basically just a slow moving conveyor belt where you are constantly feeding green wood in one end and dried lumber is constantly being spit out of the far end. I don't see why you couldn't incorporate ambient air chambers in strategic places on the belt to destress the lumber, at the cost of making the entire production line somewhat longer.

xhkkffbf 1y ago

Anyone have any experience drying the wood in a vacuum chamber?