Cupped Panels - is there any solution?

[Drew Bru]

I do believe I've gotten myself into a little bit of a pickle. Situation is:

I'm working on some frame and panel doors for a wardrobe. I resawed some 6" wide hickory for the panels and planed it down to around 3/16". I didn't get around to gluing the 6" panels into larger (12" wide panels) and making the door frames. Over the past week, the wood has absorbed some moisture from the air in my shop and now the panels are severely cupped! The center is raised about 1/4" from the ends when the panel is laid on a flat surface. They can't be planed flat again, they're too thin.

So my question(s).
Can I salvage these boards?
Is there a way to steam bend them straight again and get the panels glued up and framed?
Do I need to start over and make new panels?
How do I make sure this doesn't happen again?
Should I be glad I didn't glue them up and risk my door being crooked?

So......any thoughts or ideas would be appreciated.

[Chris Friesen]

Take them inside and see if the different moisture levels straighten them out. Can you flatten them by hand pressure? If so, they might work inside a frame.

To minimice cupping, you can use wood selected for grain patterns that won't cup, use a more stable species, or use laminated panels.

[Drew Bru]

I'll bring it inside when I get home tonight. Hopefully it will dry out enough to bring back into a reasonably-flat state! I'm afraid to try to press it flat right now, for fear it'll split down the middle.

I wondered maybe if I should set it lengthwise on the radiator and see if that would dry it out, but I can never remember which side causes the cupping when it gets wet!

[Chip Lindley]

A panel usually cups upward when it expels excess moisture. The edges raise off a flat surface. I suppose the reverse is true if the panel absorbs excess moisture. (But I have never used wood dry enough for this to happen to me) Either way, flip the panels on a flat surface with the cup down and see if they do not equalize in a day or two.

3/16 is quite thin for door panels. If you find you must re-make the panels, make them thicker; at least 1/2". Let the panels into the stile/rail groove with a rabbet cut into the backside of the panel edges. (not unlike a reverse raised panel)

[Drew Bru]

A panel usually cups upward when it expels excess moisture. The edges raise off a flat surface. Flip the panels with the cup down and see if it does not equalize in a day or two.

3/16 is quite thin for door panels. If you find you must re-make the panels, make them thicker; at least 1/2". Let the panels into the stile/rail groove with a rabbet cut into the backside of the panel edges. (not unlike a reverse raised panel)

I was a bit worried about the 3/16" being too thin, but I'm really trying to keep the weight of the doors down as much as possible, as there's a slight "hinge" problem (which I may actually post as another topic). My doors will be around 20" wide with 2 8-ish inch panels separated by a stile. Basically, 3/16" thick X 8" wide panels.

I did notice that the bottom layer of panels didn't cup as severely as the top layer, so they may come back into shape as they dry out.

[Philip Rodriquez]

That sucks. The lessons we learn!

Next time, resaw the boards, sticker them, and let them rest for a few weeks... then mill them to final thickness.

[Steve Mellott]

Drew:

I has this happen to me several years ago. I took the panels outside to my driveway and put them in the sun. Within several hours, the panels cupped toward the sun. (This means you have to place the panels in the driveway cup side down so they straighten. You may want to try it on a cut off first to see if it works.

Steve

[David DeCristoforo]

Get a spray bottle and wet the concave side of the panels. Some people have gotten panels to flatten out by laying them on a lawn, concave side down. The idea is to equalize the moisture on both sides. It's a crap shoot and there is no guarantee that the panels will stay flat even if you get them flat again. If you do get them to flatten out, get them into a frame ASAP so there will be something to keep them flat.

[Frank Drew]

This often happens when resawing (or planing, for that matter), sometimes because the board isn't of a consistent moisture content throughout, sometimes just because wood can be a b***h!

[Chris Padilla]

Wood: a fickle medium! One can doing everything the right way and suddenly some stress in the wood jumps out and messes things up.

[Drew Bru]

I appreciate all of the responses! It's just as I thought.....there's no ONE solution! I'm thinking I'll try spraying it on the concave side as David recommends, or I'll lay one in the sun as Steve suggested.

I know there are moisture imbalances and internal stresses and whatnot, but the wood is well seasoned and has been in my shop for a couple years. Once I sliced them open, I guess that's a different story altogether.

Regardless of what works (or doesn't), in the future I might be the one to recommend a solution when someone else posts the same problem. Also, I'm glad to have the resource of the collective knowledge of the forum to bounce ideas off of.

thanks again,
Drew

[Lee Schierer]

After you planed the panels how were they stored or stacked?

It is always important to let both side breathe after thicknessing. As David mentioned, spray or wipe down the concave side with water. If the panel flattens, then stack and sticker them with a good heavy weight on top so there is air space between each piece. Leave them that way for several days to a week or more. Many times this treatment will flatten the panels. Also once they are flat get them mounted in the rails and stiles as soon as you can. Finally apply equal amounts of finish inside and out when you do the finishing.

[Drew Bru]

After you planed the panels how were they stored or stacked?

It is always important to let both side breathe after thicknessing. As David mentioned, spray or wipe down the concave side with water. If the panel flattens, then stack and sticker them with a good heavy weight on top so there is air space between each piece. Leave them that way for several days to a week or more. Many times this treatment will flatten the panels. Also once they are flat get them mounted in the rails and stiles as soon as you can. Finally apply equal amounts of finish inside and out when you do the finishing.

Good question Lee.

They were just left on my bench. 3 panels side-by-side (as though they were about to be glued up). Then the other 3 panels on top of those ones. Basically, three stacks of panels....two boards high. They weren't stickered or weighed down. My bad. The bottom boards were not as cupped as the top ones (no surprise).

I guess my course of action will be to spray them down tonight then sticker them in the morning (after they've had overnight to straighten out). And next time I'll know to sticker them and let them breath after thicknessing.

[Peter Quinn]

Try all the spraying, pressing, hoping, bending. Park the car on them. Some or none of this may work. As was noted resawing gets to the center of the tootsie roll, so to speak, and things my be drier or wetter there. Don't rule out the wood stove as the best alternative for these panels. hickory is not one of those species known for laying down and playing nice.

Do you have the capacity to make and press veneer? perhaps making your own 1/4" panels using 1/8" ply with a 1/16" veneer would let you make use of the hickory you have, you would just need a backer?

I made some cherry panels last year from some nice 6/4 cherry, 11" wide, resawed for a book match on an end panel. Acclimated it, sawed it, stacked it with stickers, kept it in HVAC environment. The material was sawn on a Friday, looked good coming off the BS, by Monday it was a twisted mess I couldn't flatten to 3/8" over 30". It happens. Wood stove and start over for me.

[Cameron Reddy]

Some guys in the luthier biz take pull out a hot iron and a spray bottle of distilled water... and have at it. If you can bend it you can probably straighten it.

When you've paid several hundred to a thousand bucks (or more!) for virtually extinct Brazilian Rosewood or some such...