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I cut some Maple and Walnut from two billets.
This is for an electric build, and each sawed piece is 3/4" thick.
After sawing, the Walnut pieces formed a terrible bow and cup, the Maple too, but not quite so bad.
I clamped the pieces together, sawed side out, hoping by some miracle they will retain straightness after sitting for a while.
I assume these billets were dried, but I don't have a way to check.
Any advice is very much appreciated.
Thanks,
Dan

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Any wood can have built-in stress. Eventually much of this will work itself out, but it can take a long time. I have some spruce that I was told is between 200 and 400 years old, and it bowed a little when I re-sawed it. It took several days to show up. It's in reaction wood, and normally that would be evident immediately.

I'm working on an acoustic bass guitar, with a walnut top, and the quartered walnut cupped badly when I re-sawed it. Eventually I used Super Soft 2 on it, and it helped a lot. I drenched the wood and wrapped it in plastic over night to allow it to penetrate. Then I used the go-bar deck to impose an opposite curve on it. That had limited success until I got out the heat gun and warmed it up. The top is stil not dead flat, but it's usable, and should be fine once it's thicknessed and braced.

You likely have wood that is case hardened. This usually is the result of a poor job of kiln drying, where the surface of the boards is dried too fast. The surface takes a set before the center dries out enough to shrink to size. When the center does finally dry, tension is set up in the board and when it is resawed it allows that tension to be relieved and what was the inside, now one face of your resawn piece, can finally shrink, cupping your pieces.

Very difficult to fix, especially in the thicker pieces like you have. Sometimes soaking or steaming the wood and clamping flat helps, sometimes, not much. Obviously thinner cut slices are easier to fix than thicker. Do an internet search on "case hardened wood"...you might find more suggestions.

Good luck,

Grant

It can also happen when the middle of the board has a much higher moisture content than the outside of the board. Once you make the cut, there is a large imbalance in MC, and you get the cupping.
You can try wetting the dry side, and leave it face down on a bench so that the moisture doesn't evaporate to fast.
If it seems release the cupping a bit, repeat until it gets flatter. If it doesn't work, then it is likely that it is case hardened, as Grant suggested. Sometimes figured wood acts a little squirrelly, just because it feels like it, as well. Good luck, Dan. That wood is too pretty, and pricey, to not get used!

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

You could resaw the wood thinner for laminated tops. You could get more mileage out of the figured wood that way. An old method of removing cup from the board was to lay it cup side down on the earth, and let it reabsorb moisture. That doesn't seem like it would be permanent, but might take the cup out for resawing.

Are the dims ions close to final?



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The pieces have an extra 1/4" thinckness, knowing that I would have to plane or sand them after sawing. The maple is useable, I'll have to figure out what to do about the walnut.
Thanks,
Dan

After overnight clamping, I unclampled. The bow has gone away, and the cupping is minimal and can be planed away.
I'll let the pieces sit unclamped to see what they do. This lumber was air dried, so maybe the pieces will be OK.
Dan

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"After overnight clamping, I unclampled. The bow has gone away, and the cupping is minimal and can be planed away. "

That's common when the humidity is changing: the inside of the piece is at a different moisture content than the outside, so it cups or bows. Once things even out it's OK.

geee...let's see...was nice and wintery cool the beginning of last week with nice dry/cool sleeping weather..then came the humid and warm climate just before Christmas...now a cold front just blew through and things are wet yet nice and cold...

as others have noted you can apply a bit of moisture to the cupped side and it will stretch out (swell) in reaction...

You got that right Mike!
Summer on Saturday, winter on Sunday.
Dan

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After a week of acclimation, the top and back ended up nice and straight.

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I'm glad you got that straightened out, Dan! That's some pretty wood. Who gets the SG?

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Thanks Alex!
This one is for me!
Dan

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Once upon a time - I sawed up some wood which twisted and warped very badly. I let it sit to acclimate for a while to no avail. Not even clamping had any effect. Finally - I was completely disgusted with it and pitched it out back into the snow. 3 months later the snow was gone and it was sitting on the end of the deck in the rain. A couple months later I stumbled over it and it was straight as an arrow.

I brought it back in and put it up for a while to see if it would go crazy on me again. It stayed good and straight - so I used it and it was stable ever since.

Sometimes, you have to use advanced persuasion methods on wood.

Thanks

If thickness allows in situations like this I'll usually joint the cupped side on my jointer then plane the opposite in the planer after letting the wood sit for a while to make sure it's done moving. Glad things worked out for you. That would have been a waste of nice wood.

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It is called "seasoning". It is how most lutherie wood was stored in the past. Sometimes in an attic where it froze in the winter and cooked in the summer. Sometimes in an unheated shed "out back", or in a pile covered with a tarp. And the moisture content cycled with the seasons. Over the course of a few decades, much of the stress in the wood was "worked out". Some wood did crack, split, or warp worse, so it was culled out before any effort was wasted attempting to make it into an instrument. That is why you used to hear about lutherie wood needing to be seasoned for 25 years or more.

We no longer do this. Now we coddle our wood in controlled environments....it never gets "seasoned", even if it does sit for decades. And when the humidity control goes south in our shops, wood starts cracking, and warping, and we go into panic. We no longer have seasoned wood to work with.

I do season my wood as best I can. When I had some huge cocobolo logs sawn into cants in 2004, they then spent the next 3 years outside under a tarp...covered with snow in the winter and filtered sun on them in the summer. Most of my un-sawn wood is stored in an unheated metal shed, and right now, it is freezing in there.

Alas, I guess most of us are stuck in this cycle because the wood we have access to never starts out being treated correctly, so we have to go with what we are served up with. But where the opportunity presents itself "DON'T CODDLE THE DAM WOOD"

There, I got that off my chest

Grant

Great point, Grant. I know some builders "bake" their tops in an effort to achieve some of the same effects. I've wondered if putting tops (and backs and sides?) through a similar cycle in the a freezer might offer some benefit. Maybe a bake/freeze/bake/freeze routine. I'm sure it wouldn't be as effective as the seasoning you described but might offer similar benefits on a smaller scale and in a shorter period of time???

Well, shortcuts are usually just that...shortcuts, and frequently in results as well as time. The "seasoning" of wood, as done in the past, I think requires time and many "cycles" to actually be effective. The example of baking tops, may alter some properties of the wood, but does not "season" it, IMO. The more recent processes of "torrefaction" or "thermal modification" cause major physical changes in the wood, but they don't make new wood "old", in spite of what some claim.

Hopes of actually obtaining 25 or so year seasoned wood is probably just a phantasy because I doubt if there is any amount in the pipeline. The important point, I think, is to understand the principles and, in whatever small ways we can, work in concert with them.

Grant

Is there documentation, rather in the form of pictures, out there showing the results of these processes compared to new/old wood?
Would be interesting to see some pictures under high magnification.

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Wake up and smell the rosewood!

I started amassing guitar wood over 30 years ago. That includes red spruce as early as 1985, and Brazilian rosewood from the early-1980's through to the CITES ban in 1992.
I season the hardwoods in a building without humidity or temperature control, so they go through cycles which tend to eliminate internal stresses. After several years of this, I have found that it seldom cups or bows during resawing.
Though I have sold the older wood in the past, it does become more precious to me as the years roll on.
IMHO, nothing beats the old wood for stability and sound.

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John