[HN Gopher] Air-dried vs. Kiln-dried Wood
___________________________________________________________________
Air-dried vs. Kiln-dried Wood
Author : crescit_eundo
Score : 140 points
Date : 2025-06-08 15:45 UTC (3 days ago)
(HTM) web link (christopherschwarz.substack.com)
(TXT) w3m dump (christopherschwarz.substack.com)
| HPsquared wrote:
| 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 wrote:
| 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_pag...
| ofalkaed wrote:
| 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 wrote:
| 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 wrote:
| 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.
| arturocamembert wrote:
| I can only speak to my own experience of doing this
| professionally in northern climes without power tools for
| ~5 years, but both of your suggestions are foreign to me. I
| take this as a nice reminder that there is lots of regional
| variation to this craft around the world, which isn't
| surprising.
|
| Even then, building a barn with dried pine or hemlock is
| _much_ more tedious and incurs many more trips to the
| sharpening wheel. It is in no way easier.
| ofalkaed wrote:
| The joints used in dried are dictated by the operations
| which are easier to do in dry wood and are not influenced
| by what the wood will do as it dries. Dried you get to
| use a saw with considerably less kerf and a thinner
| plate, augers can be more aggressive and take better
| advantage of lead screw and spurs. Chisel work will be a
| bit slower when chopping across the grain but not harder
| and if it incurs many more trips to the sharpening stone
| you are most likely trying to chop that mortise as you
| would in green wood.
| exDM69 wrote:
| Green woodworking is an entire field of its own. Not very
| common in industrial scale but it was a common method a few
| centuries ago.
|
| Examples of things where green woodworking is common: spoon
| carving, bowl turning, chair making, etc.
|
| The idea is that wood is worked while green to make 80%
| finished blanks, which are dried slowly for some months or
| years before finishing the rest of it. This gives less
| distortion to the shape as it dries. And the drying times are
| faster because it's all small pieces at that point. The time
| from tree to product is shorter.
|
| It is an almost extinct craft but it is a lot of fun for
| woodworkers not under schedule pressure.
| ne8il wrote:
| I just finished a green wood post-and-rung chairmaking
| class last week. The posts are split out and steam-bent,
| while the rungs are dried in a makeshift kiln (a box with a
| heat lamp). The posts are then above ambient humidity,
| while the rungs are dried below it. As the entire chair
| equals out, the posts will dry out and compress onto the
| tenons of the rungs, which will swell up a bit and lock in
| place. We did use glue but you don't really need to. Neat
| stuff.
| exDM69 wrote:
| Cool. I've also built a bar stool with green wood but
| it's a fairly crude shop stool rather than a fine chair.
|
| A green wood specialty in my neck of the woods is sauna
| ladles (used for throwing water). You can buy wooden ones
| but they are made from seasoned lumber with CNC machines
| and don't survive more than a year before they crack. The
| one I made from green wood is still going strong after 7
| years in extreme humidity and temperature environment.
| rollulus wrote:
| 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 wrote:
| 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
|
| 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 wrote:
| 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 wrote:
| 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.
| DannyBee wrote:
| "Initial shrinkage is larger when drying from green wood"
|
| ?
|
| It's not - it's exactly the same as anything else. The
| wood doesn't know it's green.
|
| The calculator you gave is shortcutting it, and has an
| entire article in how they shortcut it the same way as
| anyone else, based on the swelling coefficients/etc, but
| assuming thickness is small enough to not matter.
|
| If your projects are outdoors, you will be affected by
| more than just humidity - UV will also have a significant
| effect on the properties of your projects :)
|
| The moisture transport is also not as simple as you are
| making it out to be, and has a not insignificant effect.
|
| See:
|
| https://gupea.ub.gu.se/handle/2077/54179
|
| https://www.mdpi.com/2076-3263/8/10/378
|
| https://www.sciencedirect.com/science/article/abs/pii/S12
| 962...
| exDM69 wrote:
| Yeah, the coefficients are the same but the initial
| moisture content in green wood is much higher than the
| wood will ever get to after seasoning, it won't suck that
| much moisture from the air (unless you're in a swamp or
| something). So the annual absolute change in millimeters
| is lower than from green to seasoned.
|
| I have my woodworking projects in temperatures ranging
| from -25C to +100C (sauna) and extreme humidity changes
| from near zero to 100% RH. It is a form of art to make
| wooden things survive that, and I don't always succeed.
| kurthr wrote:
| Ummm, most wood starts at a much higher moisture content
| (50%-200% noting that this is as a percentage of fully
| dried so it can easily be over 1) than it will ever have
| after drying (typically 5-15%).
|
| Frankly, the idea that a piece of wood after initial
| drying was moving even an in/ft (eg "only" 8%) would be
| pretty shocking. Even good joinery won't deal with much
| more than a quarter of that ~2%.
| DannyBee wrote:
| You missed my point, which is that initial drying is
| absolutely 100% not different than any other time. Wood,
| especially outdoor projects like the person is making,
| will definitely see states where the moisture content is
| as high, if not higher, than when the wood was originally
| dried.
|
| Also, most green hardwood starts at about 30%.
|
| No reputable lumber supplier is kiln drying hardwood that
| is 200% moisture content. That's crazy town.
|
| Even if they dried it super slowly, it would end up as
| mostly checked/warped garbage that they couldn't sell.
|
| Beyond that, wood is moving a lot, sorry you don't
| believe it, but its still gonna do it.
|
| Rather than say it's "pretty shocking", and dismiss it,
| care to present any studies that back up your assertion?
|
| I sent plenty, both in here and other comments. I'm not
| aware of any sourced, actual scientific research that
| says anything other than what i did, since I was careful
| to use cited figures from actual research studies, and
| not random pages on the internet about "wood movement"
|
| I think you are also assuming a lot about how it moves
| and what 8% radial swelling/shrinkage really means that
| isn't necessarily true.
|
| Also your point about joinery doesn't seem to make a lot
| of sense. While it's true that most joinery can't handle
| lots of flex, if everything expanded or contracted
| uniformly, it wouldn't be a problem.
|
| You seem to be assuming the opening will not expand the
| same as the thing going into the opening. It will. That
| is why you try not to mix conflicting grain directions in
| joints, and why you see so many joints that go out of
| their way to do that (IE 90 degree mated dovetail boards
| are not made by two conflicting grain directions, the
| pins and tails are made of the same grain direction that
| happens to mate at an angle)
|
| https://cad.onshape.com/documents/3e489410fcf65e1f0f82663
| d/w...
|
| I made two tabs for you, one with a 25% transform and one
| without.
|
| Notice the opening gets larger when scaled. So would the
| mate. They would still fit fine. The same is true if you
| made a dovetailed box. It would just become a
| bigger/smaller box.
|
| I didn't bother to scale it differently for tangential vs
| radial but it wouldn't matter as long as the same scaling
| factors apply equally to the mate, and the mate is made
| the same way. As is true of most woodworking joints, on
| purpose.
|
| So the only issue is if (assuming 2% was the limit) the
| non-uniformness lead to >2% difference somewhere that
| mattered.
|
| All of this is also why wood glue has such
| expansion/contraction characteristics. if wood was only
| changing 0.1%, it wouldn't matter.
|
| So far i've seen a lot of doubt but nobody else actually
| seems to be bringing any real scientific rigor to that
| doubt, or saying some silly things.
|
| Please feel more than free, i'd love to see papers with
| real measurements that suggest something else.
| kurthr wrote:
| Sorry, it's not true that "initial drying is absolutely
| 100% not different than any other time".
|
| https://extension.oregonstate.edu/catalog/pub/em-8600-woo
| d-m...
|
| Fiber saturation is a thing and it rarely exceeds 30% for
| usable lumber.
|
| I'm mostly going on what I've read though I went outside
| to measure a 30" fir just now and it's 100% (REED
| Pinless). The 100 yr old apple trees were over 80%, but
| that's not peer reviewed (nor is it pay walled). Maybe
| people can cut down trees and toss them straight into an
| Alaskan for exactly this reason? Firewood sitting covered
| outside is <10%.
|
| As for pretty shocking. Yes it would be, if the 36" door
| (flat sawn book matched) to my house didn't open, because
| it was an inch too big (it accommodates <1/4"/ft). It's
| about a hundred years old, and I'm pretty sure that's
| never happened.
| DannyBee wrote:
| Again - Nothing in any of this says anything about the
| equations being different for green wood.
|
| I don't even know what you are arguing and why - it seems
| to change with every post.
|
| So I give up - you still haven't actually shown me a
| study that says it's wrong, and now your argument is "my
| door would be too big".
|
| This is a silly discussion.
|
| Since you still haven't given me a single scientific
| study suggesting the movement doesn't actually occur, I
| guess i'll offer you this and then walk away:
|
| Is your door surrounded by brick or something rigid? Or
| is it surrounded by wood and blocking, like most doors?
| What species is it? What are the radial/tangential
| shrinkage rates? Is it painted or otherwise sealed in a
| way that would affect rate of absorption, like most
| doors?
|
| As an aside, did you know that basically no door company
| will warranty unpainted doors because of exactly the
| issue you say doesn't happen? Just about every single one
| will say something on the order of "this door must be
| painted or stained within x days or the warranty is
| void", where x is usually <7, and will unequivocally
| state that unpainted and unstained doors will warp.
| Because they do! Like potato chips, a lot of the time.
|
| There are some _made_ to be bare unpainted wood, but it
| 's not common and it requires different construction
| techniques. Most of them are not solid wood either, they
| are 1/4" or 1/2" veneer pretending to be solid wood.
| Otherwise, doors left exposed to the elements often
| totally fall apart in years. All the time. I can show you
| one that fell apart due to movement in <5 years.
|
| Beyond that -
|
| Doors surrounded by brick or rigid things _frequently_
| become too large to open /close at various times.
|
| My home was built in 1929, and the doors are painted, but
| the jamb is surrounded by limestone or brick on all
| sides. Not a facade. The jam is up against well-set brick
| or limestone. This is actually a super-bad construction
| technique, since in most cases, the brick/limestone is a
| facade to avoid this issue. I can send you videos if you
| want to see what happens.
|
| In the winter, it is about 1/2-3/4 inch smaller than it
| is now overall. I've measured it. It does in fact, become
| unopenable in the summer. It actually is right now. I
| plane it until it can be opened again. It will show a
| very large gap in the winter.
|
| This is on a painted door, so not even one that is
| totally exposed to the elements.
|
| This is uncommon, again, because most doors are not
| surrounded by highly rigid materials. If they are, it's a
| facade instead of structural. Those doors that are
| structurally unable to move, will in fact, break apart.
| This is one of many reasons totally solid wood doors are
| uncommon (besides weight and cost)
|
| Since you seem big on anecdote, and your door is your
| baseline, there's a door for you.
|
| Most people with historic homes would laugh at what you
| are saying. Since you say your door is >100 years old,
| i'm sort of shocked at your view.
|
| For example, my wife's _interior_ office door, is wildly
| out of square and plumb. By about 2 inches. The concrete
| foundation and tile is _exactly_ in the same place, and
| perfectly level and square. No tiles have broken or
| cracked, and they are original to the home. Only the
| things made of wood are no longer where they should be.
| The two exterior doors in her office on opposite sides
| were built identically ~100 years ago. They don 't even
| close to line up any more, and are easily 1" off. Again,
| foundation is exactly where it should be. only the wood
| has moved.
|
| But still, i'm out since we aren't actually having a
| useful discussion that involves more than vibes about
| doors.
| ComputerGuru wrote:
| Yeah, the Midwest is cursed for this reason. Humid
| summers with incredibly high RH for being inland while
| temperatures push 100deg F followed by bone-chillingly
| dry winters with temperatures falling to -20deg F (and
| relatively little relative/absolute moisture). But all
| our homes are built of wood and the consequences are
| pretty drastic.
| bee_rider wrote:
| Are there designs that exploit this effect? I want a
| house with walls that intentionally become more permeable
| in the summer, less in the winter, haha.
| roberthahn wrote:
| I think you're off by an order of magnitude. With those
| numbers, a 12" board would expand and contract 1.2", and an
| 8' long board would vary by almost an inch.
|
| Much more reasonable would be 1% across the grain and 0.1%
| along it. You can confirm this in some of the wood movement
| calculators found online.
|
| To those learning about wood movement, these ratios are
| decent but approximate; if you end up caring about these
| things you'll want to check the species of the lumber you
| plan to work with.
| DannyBee wrote:
| Serious woodworker here:
|
| They aren't off by that much. You are further off if you
| assume some standard parameter ranges :)
|
| But in the end, it depends on factors i didn't see listed.
|
| Overall, the percents are usually calculated by swelling
| coefficient. Swelling coefficient is percent change in
| radial/tangential for each 1 percent of moisture change.
| There are well-known sources for these that calculated them
| in sane ways. The US forest service is one of them, and
| they publish their methodologies/etc for how they determine
| them. See, e.g., https://wfs.swst.org/index.php/wfs/article
| /download/1004/100...
|
| Take standard flat sawn red oak. The swelling coefficient
| is 0.001-0.002 for radial (0.1% per 1%), and 0.004-0.005
| for tangential (0.4% per 1%).
|
| So in initial drying, which is usually 30%->15%, it will
| move 1.5-3% radial and 6-7% tangential.
|
| Without humidity control, houses swing from 30%<->60%.
| Sometimes per day, sometimes per month, sometimes per
| season. So even more than initial drying. But because the
| swing varies, depending on thickness/etc, how much moisture
| change you get in the wood, and how fast, will vary a lot.
|
| If you assume it causes a 10% change in moisture content
| over the year, throughout the wood, we get 1-2% radial
| movement, and 4-5% tangential movement for red oak. But
| that is both swelling and shrinking, not solely one or the
| other.
|
| So the GP would be off by a factor of 2 in one, but not off
| in the other.
|
| It's obviously trickier in practice to calculate the actual
| rates because the moisture is going to diffuse through the
| wood at some rate, and as long as the RH is changing faster
| than the diffusion rate, the wood will not really have a
| consistent moisture content all the way through. To be
| accurate, you'd have to slice it into enough pieces to
| capture the different moisture levels in the wood, apply
| the coefficients to each slice, and, etc. Worse, because
| boards are rarely square, and instead often much wider than
| they are thick (IE 12"x1") , you'd have to slice and
| calculate it one way to deal with this for radial, and
| slice and calculate it the other way to deal with
| tangential.
|
| I'm too lazy to calculate how coarse/fine of a slice you'd
| need to get within say 5% of the "real" number.
|
| I'm also assuming you are trying to do it by hand, since
| this is obviously an integral of some sort that you could
| also just directly solve. I'm sure it's in a paper
| somewhere.
|
| This is all for bare wood too, with no topcoats. The
| topcoat would seriously affect absorption rates, etc, even
| assuming you applied it to all sides.
|
| Nobody does any of this calculation in practice, we just
| accept large error bars and build floating tables :)
| HPsquared wrote:
| Given limited absorption rates, does that mean varnish
| etc helps keep the internal moisture content more steady
| over time (and therefore less variation across the wood
| internally as well)?
| DannyBee wrote:
| It depends on how vapor permeable they are. Some of them
| are good at resisting liquid water but not vapor, and
| some are good at resisting both.
|
| But all things being equal, yes, they generally can only
| help keep moisture content more steady over time.
| aaronax wrote:
| 30-60% RH range in a house surely must not be this
| strongly related to moisture content of wood? ("10%
| change in moisture content over the year")
|
| https://www.wagnermeters.com/moisture-meters/wood-
| info/how-r...
|
| This table shows up to a 4% moisture content seasonal
| difference in a climate controlled house (20-50% RH).
| DannyBee wrote:
| I can't tell where their data comes from, and they don't
| cite it.
|
| The 10% number was not meant to be real, i just was
| giving an example :)
|
| Real is much harder.
|
| 4% is not a horrible guess from as best i can calculate
| (but see below because this page has some crazy claims).
| Studies suggest that wood RH tracks RH pretty closely,
| slowing down with depth. Transport also appears to
| depends on temperature, independent of humidity itself.
| But if you assume it's going to track RH closely and
| throw out the rest, you can just assume the wood will
| always fall within the EMC range for the RH range.
|
| If you look at
|
| https://www.fpl.fs.usda.gov/documnts/fplgtr/fplgtr282/cha
| pte...
|
| You can see that between 30-60% RH, you really don't get
| more than like a 7% span (i'm eyeballing it) of EMC that
| the wood could vary around at any temperatures likely to
| exist in your house.
|
| So 4% is probably not a horrible guess.
|
| However,the site you link to says some very wrong things,
| interestingly:
|
| "Temperature Has No Significant Effect on Wood MC"
|
| This is 100% wrong, in more ways than one.
|
| First actually even wrong if you ignore humidity
| entirely, because studies suggest wood moisture transport
| changes at high/low temperatures, even ignoring humidity.
| The exact mechanisms are not pinpointed (AFAICT from
| skimming), but that's what _real_ data says.
|
| Second, the temperature affects the EMC (and relative
| humidity).
|
| It's very weird for them to go on and on about how
| humidity affects would but then say temperature doesn't
| matter at at all.
|
| You can't actually separate these things, and say
| humidity level matters but temperature doesn't, because
| they are linked.
|
| If you want real data/simulations to try to figure out
| more, here's some references - i didn't read all of them,
| busy morning, but i did at least look at most of them.
|
| https://www.sciencedirect.com/science/article/abs/pii/S12
| 962...
|
| https://gupea.ub.gu.se/handle/2077/54179
|
| https://www.mdpi.com/2076-3263/8/10/378
|
| https://pmc.ncbi.nlm.nih.gov/articles/PMC8320951/
| exDM69 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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-basi...
| lukaslalinsky wrote:
| 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 wrote:
| 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 wrote:
| I could read the full article without problems. Using
| MacOS/Firefox. Maybe just clear your cookies.
| hn8726 wrote:
| And the non-paywalled part doesn't even get into the
| differences between air-dried and kiln-dried wood.
| cmrdporcupine wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 4 years is actually not that much for a passive air drying
| process.
| exDM69 wrote:
| 4 years is more than enough time for drying. Rule of thumb is
| year per inch of thickness.
|
| I'm just speculating here but probably the support structure
| didn't allow for wood movement. You need something to keep the
| table top flat while allowing it to move. Screwing it to a
| stiff frame (steel or cross grain wodo) is certain to crack
| when the wood moves.
|
| Breadboard ends, sliding dovetails or steel support with
| elongated holes (going to a threaded insert and bolt) are good
| ways to support a table top.
|
| The wood was probably stabilized to your shop atmosphere but
| indoors in the dry winter, maybe with air conditioning or a
| fire place, and there's going to be movement.
|
| Kiln drying does not stop seasonal wood movement.
|
| If you share a picture we can take an educated guess what
| caused the table to warp and crack.
| gorgoiler wrote:
| Breadboard ends were always confusing to me because they are
| trotted out as a solution for movement yet they solve two
| quite different problems.
|
| On flush, jointed boards, they are a permanent jig to hold
| the ends in vertical alignment. Imagine taping your fingers
| together to keep your fingers flat. Lateral movement is
| impossible because the boards are glued tightly together.
|
| If you're concerned about lateral movement then the more
| important concern is to have gaps between the boards. The
| bread board end is now a rail in which your boards can slide
| like wobbly carriages on a train track: aligned in one
| direction (up/down for a table) but with the ability to move
| independently in another (across the width of the table.)
| franktankbank wrote:
| They aren't trotted out as a solution for movement. They
| are a solution to flatness that doesn't fuck up on the
| movement issue.
| JamesSwift wrote:
| What was the moisture % at the end, and what was the joinery of
| the end product?
| jws wrote:
| I dried three red oak trees using a dehumidifier kiln. (
| 4'x4'x16' 1" pink insulation foam box assembled with packing
| tape with a household dehumidifier and fan inside. Very low
| tech. Knock it down when not using it.)
|
| The process is mostly: measure moisture content of wood, pick a
| humidity to maintain, check wood periodically to see if it is
| drying too fast or too slow. Weigh water coming out to monitor
| process.
|
| Very low effort if you have space to allocate while in use. The
| wood came out well, no complaints.
|
| One downside is you won't kill insects with heat, so you could
| have trouble if it is buggy wood.
| kragen wrote:
| > _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 wrote:
| I wonder how they could differentiate the age of the wood from
| the age of the construction
| infecto wrote:
| 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 wrote:
| But somehow the wood is still intact 500k years later?
| meatmanek wrote:
| "Intact enough to be recognized" is a lower standard than
| "intact enough to be useful as a building material".
| kragen wrote:
| It was probably buried under anoxic conditions, which
| would weaken it and make it less suitable for new
| construction.
| infecto wrote:
| 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.
| zovirl wrote:
| From the Nature article posted by unwind, it sounds like they
| dated the sand surrounding the wood, not the wood itself.
| unwind wrote:
| Here [1] is the Nature article in question, if you want to dig
| in.
|
| [1]: https://www.nature.com/articles/s41586-023-06557-9
| peatmoss wrote:
| Not really--the topic is about wood drying, and this Nature
| article is the expanded footnote about how long humans have
| been working with wood.
|
| EDIT: Sorry, you were referring to the GP's interest in the
| historic part. However, to me it sounded like you were
| offering this Nature article as a way to go deeper on wood
| drying, not the athropological footnote. Mea culpa, I was
| reading too fast. Thank you for the link!
| kragen wrote:
| Thanks! I'm sorry I didn't include that link. They say of the
| dating method:
|
| > _Younger samples are dated using single-grain quartz
| optically stimulated luminescence (OSL) and older samples by
| postinfrared infrared stimulated luminescence (pIR IRSL) from
| potassium-rich feldspars (Methods and Supplementary
| Information Section 2). The pIR IRSL approach used
| extensively in recent years25,26 does not suffer the problems
| that can generate large uncertainties associated with
| thermally transferred OSL (TT-OSL), as seen at Site C North
| (Fig. 1b)20._
|
| I had never heard of this archaeological dating method
| before, but Wikipedia comes through as usual: https://en.wiki
| pedia.org/wiki/Optically_stimulated_luminesce...
|
| Not having read the full paper, I don't understand why they
| think the date at which the sand around the wood cooled from
| magma temperatures is relevant to when the carpenter cut the
| logs? Or maybe they're assuming the sand was exposed to the
| sun and optically bleached around the time of the carpenter,
| so any trapped charge is from after that? https://insu.hal.sc
| ience/insu-03418831/file/MurrayEtAl-2021-... looks
| potentially relevant.
| jjk7 wrote:
| Yeah it's hard to believe this was done intentionally
| before the existence of stone tools... did they bite the
| notches?
| kragen wrote:
| Stone tools predate this carpentry by 2.9 million years,
| so people had been using stone tools for six times as
| long as of that time, as the time that separates them and
| us: https://en.wikipedia.org/wiki/Stone_tool#Pre-Mode_I
| jollyllama wrote:
| 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 wrote:
| 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 wrote:
| Many folks soak the chips in bowls of water
| wil421 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 )
| kulahan wrote:
| 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.
| jimnotgym wrote:
| 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 wrote:
| > _"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 wrote:
| 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.
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