warped panel fix?

[Tamara White]

I have some resawn panels of walnut that are about 13" wide and around 1/2" thick. They cupped pretty badly, and fairly immediately when resawing. I've wetted the concave side and they will flatten out. Great right?! but once they are flat and I put them up on stickers and weigh them down, they keep going back to their cupped state within a day or so. I've repeated the process multiple times now and things don't seem to be improving much. What am I missing? Is there something else I need to be doing after they go flat to help them STAY flat? I hate to just trash the whole bunch of panels but right now there's no way they will stay flat in their frames.

[Lee Schierer]

Sometimes you just can't fix them. It would have been best if they had been stickered, stacked and weighted right after they were cut and left that way for several weeks to several months. A moisture meter is a good tool to have to let you know whether to proceed or wait a bit longer.

For your boards, I would suggest a thorough wetting the concave side and immediately stacking them with stickers and weighting or clamping the stack so that all the boards are flat. Give them several weeks or more to stabilize. Keep them stacked and stickered until they are processed into a project.

[Michael Burnside]

Sounds like you've done things pretty much right. The only suggestion I have is try to dimension them within 1/2" of their final dimension and do as Lee suggests. You'll need to give it several weeks and make sure they're stickered like you did before so the wood can dry out evenly over time

[Tamara White]

Sometimes you just can't fix them. It would have been best if they had been stickered, stacked and weighted right after they were cut and left that way for several weeks to several months. A moisture meter is a good tool to have to let you know whether to proceed or wait a bit longer.

For your boards, I would suggest a thorough wetting the concave side and immediately stacking them with stickers and weighting or clamping the stack so that all the boards are flat. Give them several weeks or more to stabilize. Keep them stacked and stickered until they are processed into a project.

Unfortunately they cupped like this immediately after cutting, and we actually did sticker and weight them at that time but they cupped anyways. I hope they aren't a total loss

[Mel Fulks]

It’s the convex side that gets the water. Cells get smushed making them less fat. So, when they dry ,they are skinnier.

[Brian Tymchak]

Unfortunately they cupped like this immediately after cutting, and we actually did sticker and weight them at that time but they cupped anyways. I hope they aren't a total loss

When you resawed the boards, did you also plane the opposing sides so that you had relatively equivalent moisture levels exposed to air when you stickered? If you left the opposing sides untouched, then the drying was uneven side to side, with much more moisture being drawn off the cut side, leading to the cupping.

It could be that they were improperly kiln dried too. If that's the case, there's not much you can do and you end up with a bunch of firewood.... :( or material for small parts like childrens building blocks, etc.

[Kevin Jenness]

If they are to be held in a frame and not seen on the back you could kerf them before wetting, stickering with weights and redrying. Resawing wide panels can be troublesome. If the wood is worth the effort more predictable results may be had by resawing to <1/8" and laying up on a stable substrate.

[Lee Schierer]

It’s the convex side that gets the water. Cells get smushed making them less fat. So, when they dry ,they are skinnier.

Mel, are you sure?
494268

[Mel Fulks]

Yep, look up “ compression ring-set”.

[Andrew Hughes]

I don’t think there’s any fix. A better approach would have been to rip the thicker board into 4+ pieces slightly over 1/2 inch then face joint and glue then back into a 13 inch panel.
Walnut pretty friendly. I once tried resawing a 10 inch board of hard maple in half it nearly exploded 2 inches from the end.

Good Luck

[Mel Fulks]

The method I posted is used on really old fine furniture. Often museum stuff. Obviously some owners will decide to not fix. Even just the
head of a moose hanging on a den wall sends a “moose message “ to visitors of : “BiG MOOSE” , and is moosic to their eyes.

[Lee Schierer]

Yep, look up “ compression ring-set”.

Please provide a source link.

[Kevin Jenness]

Yep, look up “ compression ring-set”.

Here's an explanation of this counter-intuitive process https://www.conservation-wiki.com/wiki/Warped_Wood

Compression Set
Deformation of wood by compression set very effectively makes use of the dimensional change of wood in relation to moisture content. The underlying concept of the method is that the convex side is wider than the concave side and that the panel will be flat if both sides are equally wide. In order to make the convex side smaller, it is first moistened or steamed, causing it to swell. The panel tries to curve even more, but this is prevented by clamping it on a flat surface. The swelling cells are crushed in this process, making this side smaller and the panel straighter after drying. Crushing of the cells is an irreversible process. The technique makes use of the same mechanism that has been explained briefly in the causes of warping. The treatment can be executed in several stages for better control of the effect. Since only the convex side is moistened, tensions can arise in the concave side of the panel.

[Tamara White]

When you resawed the boards, did you also plane the opposing sides so that you had relatively equivalent moisture levels exposed to air when you stickered? If you left the opposing sides untouched, then the drying was uneven side to side, with much more moisture being drawn off the cut side, leading to the cupping.

It could be that they were improperly kiln dried too. If that's the case, there's not much you can do and you end up with a bunch of firewood.... :( or material for small parts like childrens building blocks, etc.

Thanks for the note about the planing but there really wasn't an opportunity to do that before they cupped. literally came out the other end of the blade SUPER cupped. There was a ton of tension in these boards.