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 )
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.
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.
Yeah, 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.
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.
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.
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.
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...
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.
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.
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.
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.
"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/S12962...
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.
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%.
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/3e489410fcf65e1f0f82663d/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.
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-wood-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.
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.
I don't know what you're saying either, because not only is it completely at odds with the measured data presented in a lumber university textbook, but you seem to be unclear on how moisture is even measured.
Please reread the section about fsp and measured MC, because it explains clearly why wood does not expand beyond it's fsp ~30%. Then look at the simplified MC% vs RH% table and read data for shrinkage vs MC for various wood types. No pay walled university papers required, it's not that complicated.
If your wife's door is 2" out of square you probably have a house framing issue not door expansion due to indoor humidity.
I've sawn enough timber and built enough decks out of them that I know wood moves.
Yeah, the Midwest is cursed for this reason. Humid summers with incredibly high RH for being inland while temperatures push 100° F followed by bone-chillingly dry winters with temperatures falling to -20° F (and relatively little relative/absolute moisture). But all our homes are built of wood and the consequences are pretty drastic.
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.
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.
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 :)
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).
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/chapte...
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/S12962...
https://gupea.ub.gu.se/handle/2077/54179
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)?
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.
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.
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...
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.
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.
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.
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.
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.
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)
Well, in the era we're discussing, there wouldn't be jackhammers. Mainly a bunch of guys with pickaxes.
Generally you just build a fire on the ground you want to dig up, possibly throw in some good sized stones to hold the heat longer. If the frost is deep might turn it all over once the flames have died down and bury those coals and stones so their heat is more contained and not just going up into the air, or have a second fire after you have dug out the thawed soil.
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.
It's absolutely routine for hobby and artisan turners and carvers, though. In between the first turn and the second turn, you can air dry, kiln dry, and other techniques. With air drying, you actually want to slow the drying so that it happens more evenly. Otherwise, the outside of a vessel dries faster than the inside, which splits the wood. In general, packing a vessel inside and out with wood shavings helps even the process.
I've also had great results using silica gel on smaller items, although it can be hard to scale it to larger vessels. Much faster drying than air alone, with greatly reduced distortion and cracking.
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.
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.
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.
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.
I could read the full article without problems. Using MacOS/Firefox. Maybe just clear your cookies.
And the non-paywalled part doesn't even get into the differences between air-dried and kiln-dried wood.
> “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 :/)
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.
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.
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.
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.)
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.
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.
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.
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?
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).
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!
What was the moisture % at the end, and what was the joinery of the end product?
> 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.
Here [1] is the Nature article in question, if you want to dig in.
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 archæological dating method before, but Wikipedia comes through as usual: https://en.wikipedia.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.science/insu-03418831/file/MurrayEtAl-2021-... looks potentially relevant.
Yeah it's hard to believe this was done intentionally before the existence of stone tools... did they bite the notches?
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
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!
I wonder how they could differentiate the age of the wood from the age of the construction
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.
But somehow the wood is still intact 500k years later?
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.
It was probably buried under anoxic conditions, which would weaken it and make it less suitable for new construction.
"Intact enough to be recognized" is a lower standard than "intact enough to be useful as a building material".
From the Nature article posted by unwind, it sounds like they dated the sand surrounding the wood, not the wood itself.
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.
Many folks soak the chips in bowls of water
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.
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.
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.
