Raised panel bow problem

[Kent E. Matthew]

I must admit I started this project a while back. I transfered the door from work to my home shop. Construction is still under way, but I have enough finished that I can start working at home. Before I could get an 18 inch raised panel put into the door it bowed on me. Way to much to run through a planer. Any ideas how I can straighten this raised panel out again? My shop is not climate controlled so did the recent heat play a part?

[Bob Feeser]

There could be a lot of reasons why it bowed. To mention a few;

Taking rough lumber and planing it, with a significant amount of wood coming off of one side, and only a little off of the other. What that does is expose the core which can, and often does have a slightly higher moisture content. The exposed surface stabilizes, and gives up more of its moisture causing shrinkage on the one side.
Leaving the workpiece laying on something with one side exposed and the other protected/trapped/flat on the table, so one side breathes, and the other doesn't. The exposed upper surface shrinks. I have seen this result after only one night of exposure. So now I stack even scrap pieces on top, so both sides are covered.
Sunlight hits one side.
The wood has an inclination to twist or cup in that direction due to the resistances with wood near a branch. That one requires a lot of talking. Read Bruce Hoadleys book, "Understanding Wood". He is one of the few who has a doctorate in wood technology.
So onto the solution. Depending on how bad it is, you can use pressure and heat to bring it back. I had an 80 plus inch door job that the customer was going to hang from the ceiling, to run on a track. What I was told when I inquired about whether it would be exposed to sunlight or not is that no it would not. Unfortunately, that was not an accurate answer. One side got a lot of sun every day. Since it was hanging from the ceiling, with no support, it twisted. So I took it back into the shop, and layed it across two large tables, and put some blocks on two catycorner corners (Did I say that right? :)) then used heavy weights to force the other corners down close to the table. So I overstretched it in the opposite direction. Then I took a kerosene salamander blast heater, and let it run. I monitored the temperature so that it would get hot enough to bother my hand if I let it sit on it too long, but not hot enough to blister the finish. I did this across the entire door. Then I let it cool down. Sure enough the next morning, I came into the shop, let off the weight, and the door was straight again. It stayed that way too. I told the customer that she needed to close the drape in her bedroom during the day when she left for work, because sunshine beating on one side probably would make the twist reoccur.
So heat and pressure. That presents a challenge with an 18 inch piece, but on the other hand it makes it such a small surface that even a heat gun used carefully will get the job done.

[David DeCristoforo]

Assuming that the wood is unfinished, take a "spray bottle" and lightly mist the concave side of the panel. This should cause the wood fibers on that side to swell, resulting in the panel flattening out. Then (this time assuming that the panel actually did flatten out), get the panel into the frame pronto. The moisture will cause some grain raising that will have to be sanded or scraped out but I would do this after the panel is in the frame so as to run as little risk as possible that the panel will cup again.

[Lee Schierer]

I just completed a wall placque that bowed on me. In the initial design stages I was going to make the edges like a raised panel so I needed the wood to be perfectly flat. The board was 9.25" wide and the cupping was about 1/8" at the center of the width. I wet down the concave side with a wet rag for about 10 minutes and then laid the board on my shop floor with the damp side down over night without any weights. The next day the board was flat. However, it cupped slightly a second time so I repeated the process with a bit more wetting time. After the overnight with the wet side on the floor, again without any weights. After the second treatment the board stayed flat and is now completely finished on both sides and has stayed flat for over two weeks so far.

[Matt Hutchinson]

I have used a similar method to undo bowing in a panel. Instead of applying moisture to the panel, I set it concave-face down on the lawn. In the direct sun the bow comes out rather quickly, and you run the risk of it bowing in the opposite direction. But with frequent monitering I think you could meet with success. This method worked great for me, but I don't have a bead on its permanance.

I think I heard about this trick in a book or magazine.

Hutch

[Kent E. Matthew]

I am please to report that the lawn trick really worked. I put the panel out when I got home from work. I was out there for about an hour and a half. Most of the bow came out. I'll check it tomorrow and set it out for a while longer. Thanks.

[Matt Hutchinson]

Glad to hear that' it's moving in the right direction. Also, once you get the panel virtually flat, you may want to let it set a few days to see if it will try to move back. As I mentioned, I really dont' know how permanent this is, and the last thing you need is to insert a raised panel that will soon try to bend again. But hopefully it will reach an equilibrium where it's pretty much flat. Good luck!

Hutch

P.S. I recommend storing it in such a way as air can move around all sides. This is a good way to see if it's stabilized.