Wood Warping After Resawing

[Len Rosenberg]

I've been saving a gorgeous piece of 4/4 AAAA quilted maple to use for a foyer table top. It's been acclimating in my heated shop for 2 or 3 years. Finally built the table and started on the top.
First jointed it so it was dead flat. Resawed it down the middle, one half came out fine, the other went "sproing" and bowed over 1/8" in the middle (on a piece only 44" long).
If I joint it flat it will be too thin to use for the top.
Is there any way to prevent this? Other than buying 5/4 or 6/4 (if you can find it) and be prepared to joint it once again after resawing? I have enough of the original board left to make a second top, but expect the same problem to occur.

Thanks for any suggestions.

Len

[Jason Beam]

First and foremost: Wait.

I mean it - give it a few days and see what it does. After a week or two, I'll bet it changes - better or worse, i dunno - but the first thing is to wait it out.

Second: How thick is the piece? If it's thin and going to be captured in a frame of some kind, I wouldn't worry about it.

But in the end - wait it out, give it some time to settle - no matter what, it's likely to end up different than it is right now - which means whatever you do now may not be the best course of action. It may flatten itself back out pretty well - it may curl into a tube - chances are, it will change from what it is now, though.

[Andrew Hughes]

Len the only thing I can think of is to rip the piece down the middle,then resaw a shorter board.That will hopefully take some of the tension.Leave them long so you can match the figure back.Figuerd maple can be sometimes difficult to edge join back together,So get you plane your jointer sharp and ready to work.Dont wait after resawing to get your boards back together.

[Len Rosenberg]

Thanks Jason, I'll wait and see what happens. Although, I've never seen a piece of wood un-warp. After resawing, each piece is about 5/8" thick. Will not be in a frame, will be a solid top.

Andrew, this piece was only 7 inches wide, resawed down the middle to make two pieces, which when joined would be a book-matched 12" wide by 42" long.

Len

[Lee Schierer]

First and foremost: Wait.

I mean it - give it a few days and see what it does. After a week or two, I'll bet it changes - better or worse, i dunno - but the first thing is to wait it out.

Second: How thick is the piece? If it's thin and going to be captured in a frame of some kind, I wouldn't worry about it.

But in the end - wait it out, give it some time to settle - no matter what, it's likely to end up different than it is right now - which means whatever you do now may not be the best course of action. It may flatten itself back out pretty well - it may curl into a tube - chances are, it will change from what it is now, though.

I agree, but put both pieces on stickers and place a weight on top of them while you wait.

[Len Rosenberg]

Thanks Lee, I will try that.

Len

[Andrew Hughes]

Oh i see now, that's a bummer and tough one.Maple is such a unpredictable wood.Good luck

[Phil Thien]

Maple is one of the most reactive woods I've resawn.

I've vote for waiting, I've had pieces improve to the point of being usable.

But these days I purchase my lumber as close to final thickness as possible, or at least make sure I have enough to handle warping.

[Len Rosenberg]

Thanks Phil. I will wait to see what happens, put a 25 pound weight on the board. It barely budged.

For my second attempt with the remainder of the original board, I dropped it on the floor several times (there was a Fine Wood Working article by a guy who said that would relieve some of the internal stresses), and will use a blade with a thinner kerf to give a touch more room to joint/plane if it bows. Other than that, this is an expensive lesson....

Len

[Chris Padilla]

Wood: a fickle medium!

You can wait and hope for the best but I doubt it'll get better seeing how it has dried for a few years. You simply released internal tension...it happens.

I've never heard of the drop method to release internal stress. It makes zero sense to me that it would work. The internal stresses are built into the fibers of the wood as it was growing or perhaps as it was dried or both. No amount of banging it going to change that. Cutting through it, you betcha. :) Imagine the wood is built of several thin wires under tension and you cut through them...bang...tension released.

Anyway, one method I've used (on a much shorter board) was to soak it in water (I used a wallpaper 'tub'...fit perfect) for a couple of days and then bring it out and clamp it to oppose the bend. Don't clamp it flat...you have to clamp it slightly over-bending it the opposite way. Ignore it for several days and see what you get. Maybe I was lucky...I unbowed a piece of maple this way.

315988

And just to be clear, it did 'bow' as show in the above pic, right? I want to make sure it didn't cup on you.

[Len Rosenberg]

Thanks Chris. I'm skeptical about the drop method but nothing to lose. And yes, it did bow. Meanwhile, anyone know of a good source for 6/4 premium quilted maple?

Len

[Peter Quinn]

It happens. 4/4 is pretty thin to split for a top, I'd generally start with thicker stock if possible. I'd be very surprised if it flattened itself at this point. If the moisture content were different between core and surface perhaps it might equalize and move towards flat...I wouldn't count on it. A this point I'd consider ripping the cupped piece down the middle or along the apex of the cup on the bandsaw to minimize the kerf, joint and reglue. This wont make it flat but it may lessen the severity of the problem to the point the wood is again usable, and with minimal visual impact. Then you can glue the two halfs and pull it down when attaching the top to the table.

[Phil Thien]

Anyway, one method I've used (on a much shorter board) was to soak it in water (I used a wallpaper 'tub'...fit perfect) for a couple of days and then bring it out and clamp it to oppose the bend. Don't clamp it flat...you have to clamp it slightly over-bending it the opposite way. Ignore it for several days and see what you get. Maybe I was lucky...I unbowed a piece of maple this way.

I did this once with some zebrawood, both halves bowed pretty bad. I applied water (via spray bottle) to one side only (the side that needed to be longer). I did this repeatedly, maybe a couple of dozen times over a two week period. I got them pretty flat and thought for sure I had just added too much water but I let them sit for a year and in the end I'd say I reduced the bow by 75%.

Doesn't help if you need the wood immediately but I was able to use the wood for a different project.

[Matt Day]

The math isn't working for me. You said you started with 4/4 and ended up with 2 - 5/8" pieces after resawing? Based on your last post I think you started with 6/4 right?

I've had similar problems with maple where it reacts to milling. Solution - buy more than you need!

[Phil Thien]

The math isn't working for me. You said you started with 4/4 and ended up with 2 - 5/8" pieces after resawing? Based on your last post I think you started with 6/4 right?

I've had similar problems with maple where it reacts to milling. Solution - buy more than you need!

This last weekend I did some resawing, a little maple, and a little walnut. The maple bowed (I still was able to get the 1/2" I needed, it was oversized enough to allow for some bow).

The walnut was really perfectly straight.

Why is maple so prone to this?

[Len Rosenberg]

The math isn't working for me. You said you started with 4/4 and ended up with 2 - 5/8" pieces after resawing? Based on your last post I think you started with 6/4 right?

Matt you are correct, the actual dimension was 1 1/4", which is 5/4, and the resawn wood is 9/16, not 10/16 (5/8). If I had started with 6/4 the 1/8" bow could be jointed away.

Thanks,

Len

[Brian W Smith]

A very slight tangent.....

Most will agree on a "balanced' approach to finishing.You can apply that to resawing as well.Test it for yourself,take a resaw,leave one side jointed or planed....and leave the other side with the kerf marks from BS.See which way it "bows".To a lessor degree,the same is true for your sanded finishes,one side vs other(the more drastic the diff,the more it shows up).Good luck with your table,BW

[Kent A Bathurst]

Thanks Chris. I'm skeptical about the drop method but nothing to lose. And yes, it did bow. Meanwhile, anyone know of a good source for 6/4 premium quilted maple?

Len

Have you considered plain-sawn maple, with 1/8" veneers cut from the piece you have?

[Myk Rian]

A very slight tangent.....

Most will agree on a "balanced' approach to finishing.You can apply that to resawing as well.Test it for yourself,take a resaw,leave one side jointed or planed....and leave the other side with the kerf marks from BS.See which way it "bows".To a lessor degree,the same is true for your sanded finishes,one side vs other(the more drastic the diff,the more it shows up).Good luck with your table,BW
I don't get it. What is that supposed to tell you?

[David Ragan]

Thanks Phil. I will wait to see what happens, put a 25 pound weight on the board. It barely budged.

For my second attempt with the remainder of the original board, I dropped it on the floor several times (there was a Fine Wood Working article by a guy who said that would relieve some of the internal stresses), and will use a blade with a thinner kerf to give a touch more room to joint/plane if it bows. Other than that, this is an expensive lesson....

Len
have any idea what issue this is in?

[ian maybury]

I'd need a bit of convincing on the dropping deal - it'd presumably have to shock the wood hard enough to cause problem/highly stressed fibres to fail or stretch for it to work.

There's to my mind two naturally occurring causes of warping in the wood - moisture induced stress, and locked in stress.

With moisture imbalance one face of your resawn board is wetter than the other when cut free. So it as a result promptly warps as it dries out.

It's possble in this situation (presuming poor kilning) that uneven moisture content may also have pulled a bow into/put stress into the plank before the mill sawed it straight - so that what looked like a straight piece before resawing was in fact relying on this moisture induced uneven internal stress to hold it (temporarily) straight.

The other possibility is that there's as a result of the growth pattern (e.g. from uneven loading of the tree) or case hardening during kiln drying stress built into the timber independently of anything to do with moisture. Which was held in balance in the plank as received, but is made unbalanced once the board was resawn free. So it immediately warped.

Since your wood was very well dried/fully equilibriated before it was resawn Len, perhaps the latter is the greater possibility? (poor kilning seems to be a major issue these days)

If a board was straight after resawing, but got damp on one side afterwards and warped then it'd seem likely that it might straighten again as it dried (presuming it's held straight as it does so). i.e. the 'resting'/relaxed/unstressed state of the wood is basically straight. This is different to the situation in either of the above cases where the resting state of the wood is warped.

Changing this later requires the wood to stress relieve in some manner.

Steaming (which isn't all that controllable, and which may have other undesirable side effects) is one treatment that definitely causes stress relieving. Another is kilning. I'm not sure its applicable to already machined wood (it'd require a great deal of precision - it may be more applicable prior to milling), but here's a discussion on using kilning processes to stress relieve wood: http://www.woodweb.com/knowledge_base/Conditioning_Relieving_those_stresses.html Wonder if it's the heat, or the moisture or both that do the business here? Wonder if anybody has ever made a proper investigation of the use of heat and/or moisture to straighten wood after it's been machined?

One useful point made in the piece is that if the problem is down to built in stress (rather than moisture), then the board will warp immediately when it's sawn free. If on the other hand it's down to moisture imbalance then it'll likely take some time (maybe a few hours) for the water distribution to change and for the warping to kick in...

[Charles Taylor]

I'd need a bit of convincing on the dropping deal...

I think the trick is to drop it enough times so that in addition to still being bowed, it's dented and dinged enough to require another trip through the jointer and planer to shave away the mess. After that it will be straight and flat.

[scott vroom]

Will not be in a frame, will be a solid top.

Len, when Jason asked if the top would be in a frame I'm guessing he meant attached to an apron. Exactly how will the top be attached to the table structure? An apron with figure 8's would easily flatten the top.

[Mike Cutler]

A very slight tangent.....

Most will agree on a "balanced' approach to finishing.You can apply that to resawing as well.Test it for yourself,take a resaw,leave one side jointed or planed....and leave the other side with the kerf marks from BS.See which way it "bows".To a lessor degree,the same is true for your sanded finishes,one side vs other(the more drastic the diff,the more it shows up).Good luck with your table,BW

Len

My experience has echoed Brian's summation.

What I have done is take the face that was jointed and flip the two new board so that the jointed faces are against each other. I have then clamped them immediately coming off the bandsaw. Sometimes they stay that way for weeks.
If it helps to alleviate you beating yourself up, this same reaction could have occurred on either board later on in the project. As material is removed from the sides of the board, the internal stresses are able to relieve themselves. Sometimes even removing material equally from each side doesn't help, and the wood just does what it's going to do. If there was one sure fired way to "read a board", we all would know how to do it. You try your best.
If it doesn't straighten itself out, you might consider re-sawing the piece that didn't move for book match, and glue to a Qsawn piece of "plain" maple, or baltic birch ply, and then finish to thickness.

[ian maybury]

More from Gene Wengert here about stress relieving wood: http://www.woodweb.com/knowledge_base/Techniques_for_Equalizing_and_Conditioning_Lumber. html

How a billard cue maker stress relieves maple to minimse warping: http://www.cuecomponents.com/strema.html

It's very possible that doing XYZ on occasion solves a problem, but the chances are that there's no reliable answer at the level of sawing procedure. Because the situation in the wood can vary so widely. Juddging by this lot there's some possibility that a one size fits all stress relieving process (before working on it) can leave most (but not all) timber in a relatively stable condition...

[Wayne Jolly]

I had a 20"x10"piece of 4/4 QSWO I re-sawed a while back. When the two halves came out the other end of the bandsaw there was at least a 1/2" gap between the two halves in the middle. It might have even been 3/4", but in any case the two pieces were completely unusable.

What I finally did was take them out into my back yard and throw them into my swimming pool. A half hour later I put them into my oven at 300 degrees for an hour, then as fast as I could took them out into my garage (that is where my shop is), supported the edges with some wood strips, and put about 40lbs of weight on the center. Since the pieces were only a little more than 1/4" thick I expected them to just crack right down the middle, but they didn't. Amazing stuff that QSWO.

After a couple of hours I took all the weight off and they looked to be aaaaaalmost flat. After a couple of passes through my drum sander, they were in a usable condition. I didn't really expect them to maintain that flatness so I left them in the garage for a couple of weeks. During that time we had some warm days and some cold rainy days, but they held their shape. Then I put them in the house for a week or so and they still held it.

If they ever do decide they want to warp again, they are going to damage a really nice dart board cabinet. It was a present for my son to put in his new shop which for now is simply a 30x50 steel building. I would guess that the summer temps in there hit at least 130 in the summer but at least it's a dry heat. :-) In the winter it gets cold and humid but no problems yet.

The bottom line of all this is that maybe you could try steaming the pieces.

Wayne

P.S. For those of you in the north I know that Cold is relative and here it rarely freezes. And for those of you in the south (Like Baja for example) hot is relative too, but we have had a few 110+ days.

[Allan Speers]

With moisture imbalance one face of your resawn board is wetter than the other when cut free. So it as a result promptly warps as it dries out.

That's an interesting idea. I wonder if, with a "complex" piece of wood, it would be wise to wet the outsides before resawing?

[Allan Speers]

...... it may be more applicable prior to milling), but here's a discussion on using kilning processes to stress relieve wood: http://www.woodweb.com/knowledge_base/Conditioning_Relieving_those_stresses.html Wonder if it's the heat, or the moisture or both that do the business here?

IMO, it's primarily the heat, with steam / moisture only aiding to distribute the heat deeply into the cells.

I say this based on one simple fact: violin bowmakers set the curve of their bows with nothing but heat, and that curve remains, under a bit of stress, for decades & even centuries.

I have always assumed that the heat softens the lignin in the cells, allowing them to become pliable. - Just like heat softens any glue. Then the lignin cools, hardens, and Bob's your bent lamination.

[Chris Padilla]

That's an interesting idea. I wonder if, with a "complex" piece of wood, it would be wise to wet the outsides before resawing?

It is hard to say. It might appear to work or maybe it would have been fine had you not wet the wood. I say in this case with a piece of wood acclimated and probably dried to an acceptable 6-8% moisture content, that that would not have helped. The stress was built into the wood.

[Mel Fulks]

My guess is case hardening and wood on thin side to start with. I'm skeptical about methods to straighten. I would try light jointer facing on CONVEX side ,that will often make both sides straighter at once. Use a straightedge to check progress on concave side. Try it. And as mentioned before you can resort to making it a thick veneer or facing.

[ian maybury]

Hi Allan. Length warning - only for those interested in the topic. Reading some of the Gene Wengert and USDAFPL material it seems as though the position is pretty clear- and the causes of stress/case hardening in wood are well understood. Going back at least to the 60s, and probably much further. This is another long one - it's an attempt to briefly summarise what's going on. Important to go to the original documents if working in this area - no guarantees here.

The problem in a nutshell seems to be that either due to operating error, or cutting corners/skimping kiln operators don't always properly equalize or condition wood - with the result that it can end up highly stressed.

Wood ends up stressed after kilning because of the moisture gradient that develops during the drying process. As in the outer skin of the wood dries first and tries to shrink, but is prevented from doing so by the still wet and swollen core. This causes the outer shell to 'take a set' in the 'stretched' condition. The core subsequently dries and forces the stretched outer shell to contract around it. Which causes the stresses that cause our problem. (known as case hardening) They can act lengthwise, or crosswise, and produce differing symptoms.

The material below describes fairly simple tests for both types of stress. It involves cutting out a sample of wood to form a forked shape, and observing what direction it distorts in if any. i.e. properly equalized and conditioned wood should be stable. The trick is perhaps to use these tests before working the wood - because it's still possible to stress relieve (condition) it at this stage.

The equalization step is very important, because unless all the wood in the kiln is very close to the correct moisture content the conditioning/stress relieving step won't work consistently. Equalising entails holding the kiln conditions very close to the required equilibrium moisture content (it's necessary to have moisture content numbers for the wettest and driest wood in the kiln to calculate this - the result is a very slow drying step compared to previously when the kiln was hauling ass to get the moisture out quickly), and waiting the time needed for all of the wood in the load to reach the correct moisture content. (the cost of this time is why it gets skimped)

Once the wood is equalized its conditioned/stress relieved by raising the temperature, injecting steam and holding the wood in this condition for a period. Not all kilns or kiln types have this capability - another reason apart from the time why it gets omitted. This conditioning cycle reverses what happened during the main drying cycle - the outer shell ends up wet and hot, while the core is largely unaffected. The result is that the shell now relaxes from it's previously stressed condition, and assumes a state very similar to that of the core.

Short paper describing the issues:
https://www.extension.purdue.edu/extmedia/FNR/FNR-132.pdf

Gene Wengerts summary on Woodweb:
http://www.woodweb.com/knowledge_base/Drying_Oak_Lumber_Step_6C_Equalizing_and_Condition .html

The USDAFDL drying kiln manual which contains the information on cycles etc:
http://www.esf.edu/scme/wus/documents/DryKilnOperatorsManual.pdf

The processes involved are decribed in the paper, the conditioning and equalizing process is fully described in the manual. (it sets out the kiln cycles and procedures) The temperatures are not that high - 160 - 180 deg F Going much higher seemingly can stablise the wood, but it reduces its strength by degrading the lignin - and causes colour changes.

It's worth noting that the problem (presuming the wood is properly dried and has ended up with equal moisture content throughout) seems very much a consequence of fast/aggressive/commercial kiln drying - the steep moisture content gradient that causes the problem wouldn't otherwise arise. Air drying it seems largely avoids the issue - because it's a slow process, and because high night and morning humidity (not to mention wet weather) have a natural conditioning effect. (they wet the surface of the wood, and prevent in from becoming dry enough in advance of the core to stop stressing/case hardening from arising.

Projecting tentatively from what the professionals have to say, it seems that most woods (but they vary a good bit in the time required) become quite plastic when heated. The steam/moisture seems to be used primarily as a means of applying the forces required to cause the wood to de-stress. Hard to know if it would work, but if wood has already been resawn and checks out as being of uniform moisture content and is very thin it might be worth trying heating it (for the time in the equalising schedule), maybe (?) wetting the concave sides and closely sticking it flat under pressure to get the stresses out.

The problem with overdoing the wetting or steaming is that it may raise the moisture content of the wood high enough to become a problem. Against that maybe if it's sticked in warm and dry enough conditions (at the correct EMC) it might not take too long for it to dry again….

[David Ragan]

have any idea what issue this is in?

The FWW article that has the much-quoted article is #232, April 2013; Title "Doors That Stay Flat".
page 29.

There is a picture of Steve Latta (who is going to debate him?) dropping some large pieces of wood on the floor to relieve the internal stresses.

So there.

I leave further discussion to the experts.

(Ian, et al, I will have to read your most excellent stuff a little later-and I certainly will).

[Allan Speers]

Hi Allan. Length warning - only for those interested in the topic. .


the problem with all this, Ian, (although it is indeed fascinating) is that it's only describing how stresses can get inadvertently added to wood during the drying process. It doesn't help in any way with fixing a problem after resawing.

I'm talking about the latter, which doesn't even involve internal stresses, once you've reached this point.

[Scott T Smith]

I have successfully removed bow from boards by placing them bow-side down on a thick grassy yard on a sunny day. The face that is laying against the grass will absorb some moisture, while the other face in the sun dries out a bit. Leave them there until they have bowed slightly the other way, and then take them into a climate controlled environment and stack/sticker/weight them and allow them to acclimate and redry for a week or two.

The only time that I have seen a board that was case hardened on only one face of the board was when it was placed at the top of the kiln stack during the drying process.

[ian maybury]

Yes and no Allan. The suggestion is that there's two potential causes - either issues with moisture content (probably uneven/wetted or not properly dried) or internal stresses.

There's potential as at the start for reaction wood/stresses built in during growth - but the hypothesis is that many of the stress problems we experience originate in the drying process.

Either way it seems to be the territory that offers some pointers to processing methods that may help resolve the issue...

[Mark Rakestraw]

Len, when Jason asked if the top would be in a frame I'm guessing he meant attached to an apron. Exactly how will the top be attached to the table structure? An apron with figure 8's would easily flatten the top.

I agree with Scott here. It will take very little force to pull 1/8 bow out of 5/8" stock over 40" long -- most any attachment method would hold the top reliably flat

[Len Rosenberg]

Thanks all for the informative replies. Since a 25 pound weight is not entirely taking the bow out of the board, it looks like I'm dealing with some significant internal stress. This makes it very difficult to glue the two boards together. I may go the veneer route as some have suggested, but likely will just start over with a new board, that will be at least 6/4 before re-sawing; or given the highly figured nature of the wood, just forget about book matching and avoid re-sawing altogether. It's great being part of Sawmill Creek.

Len

[Chris Padilla]

Your next 4/4 board may resaw perfectly. I've resawed plenty of wood...think, thick. Most of it turned out just fine but there is always some wood here or there that rolled up on me something fierce. It is a natural product and not always easy to deal with.

Like I said:

Wood: a fickle medium! :)

If you have a drum sander, sand both boards down until they are nice and flat and you'll have some thickish veneers to use elsewhere. Or glue them to some plainsawn maple for your top. There are lots of ways to skin this cat. Good Luck!! :)

[David Ragan]

I read most every word of the post explaining the case hardening, etc phenomena. Did not read the references you were kind enough to post.

I always thought (in ignorance) that the twisting of the wood was on account of the weird ways the upright tree had to support limbs, prevailing winds, ground slopes, etc. Is there a scientific basis for that point of view?

[Jim Dwight]

I think it bowed due to internal stress. Maybe steaming would straighten it. Figure in boards can be due to where it came from in the tree. Crotches have figure. Stumps have figure. Maple sometimes has figure in a straight trunk but often the figure is essentially a sign of internal stress.

I made some jewelry chests of figured maple 10 years or so ago for Christmas presents. I used a 3/4 board which I sawed to the necessary 1/2 thickness on my table saw leaving a scrap about 1/8 thick. I hated to waste that so I laminated it to some plain maple and made two more jewelry boxes for the two grandmothers. I could tell the difference between the solid boxes and the laminated ones but they couldn't.

I would try hard to get veneers 1/4 to 1/8 thick from the warped board. It would make a nice top. Gluing the veneers to plain maple will also stabilize it.

[ian maybury]

I'm no expert David, and in the posts just tried to summarise what the experts have long had to say on the topic. For sure he reaction wood that gets produced when the tree has to support itself in odd situations is a cause of built in stress. As may be case hardening during kiln drying, or inconsistent moisture levels/moisture gradients inside the wood. The mechanics says that if the wood warps after cutting that some forces (=stress) have to have been present to cause it, and that these must somehow have become unbalanced as a result of the cutting..

The possibility i was trying to point to was just that judging by the linked material and some other stuff i read there's a very decent possibility that an appropriate steaming or heating and wetting process followed by re-drying while held straight may have the potential to straighten out problem wood. Most of the time anyway. This because it seems like heat and water cause the lignin to become plastic. i.e. able to take a new set.

Somebody with lots of experience of steaming might be able to offer a view on how well this might be expected to work. Springback could be an issue, there could be problems too with differing areas of the wood requiring different temperatures and moisture levels. The in kiln conditioning and equalizing processes described in the manuals for example acts locally to reverse the effects of case hardening in the zone/shell in which it occurred.

If on the other hand conditioning and equalization could effectively 'kill' a thin board (turn it uniformly plastic through it's full thickness while its hot) so that it can then be set flat it might work very well… There seems judging by published papers to have been a lot of work done on techniques for stress relieving wood for use in man made boards.

What does seem likely is that if wood has built in stresses in unpredictable locations it will be hard to get consistently accurate results by means of stuff like sawing again, wetting etc. It seems like it might work sometimes (if e.g. two boards stressed in equal and opposite ways are laminated together) - but plane away more of one than the other in that case and it'll probably warp again...

[David Ragan]

I'm no expert David,

The possibility i was trying to point to was just that judging by the linked material and some other stuff i read there's a very decent possibility that an appropriate steaming or heating and wetting process followed by re-drying while held straight may have the potential to straighten out problem wood. Most of the time anyway. This because it seems like heat and water cause the lignin to become plastic. i.e. able to take a new set.



No expert, huh? Sure........

Plasticity-that is something that had not occurred to me, and does exist in so many biological systems. When reading these posts about throwing wood into the swimming pool, then baking in the sun-well, I just wasn't sure what to think about it. But, like you say, lignin is plastic, I guess.

[Scott T Smith]

I've been saving a gorgeous piece of 4/4 AAAA quilted maple to use for a foyer table top. It's been acclimating in my heated shop for 2 or 3 years. Finally built the table and started on the top.
First jointed it so it was dead flat. Resawed it down the middle, one half came out fine, the other went "sproing" and bowed over 1/8" in the middle (on a piece only 44" long).
If I joint it flat it will be too thin to use for the top.
Is there any way to prevent this? Other than buying 5/4 or 6/4 (if you can find it) and be prepared to joint it once again after resawing? I have enough of the original board left to make a second top, but expect the same problem to occur.

Thanks for any suggestions.

Len

Len, can you post some photo's of the resawn boards? IN particular photo's showing the end grain as well as face grain photo's of each board.

It is highly unusual for one of a pair of resawn boards to stay flat while the other warps.

One other question - was the board stored flat in your shop with one face exposed and the other face flat against something?

[Robert Engel]

I'm thinking this is not moisture differential, this is internal stress relief. I've had it happen and in my (limited) experience, if this is what it is unfortunately you're never going to get this type of warping straight without remilling the wood.

I doubt it will work, but you could try wetting the concave surface and stickering with some weight or putting a light on the convex surface. Wait a couple days if nothing is happening its what I said above.

With nice wood like this, have you explored the possibility of re-milling the wood flat and face-glueing to another board to achieve desired thickeness?
I would think the glue lines on the edges would not be very visible and if they are you could do a reverse bevel on the top?