Straightening a board with a Shower????

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Forum topic by TheWeiss posted 08-25-2015 06:46 PM 2166 views 0 times favorited 10 replies Add to Favorites Watch
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53 posts in 2248 days

08-25-2015 06:46 PM

Topic tags/keywords: door frame bow bowing stream bend straighten white oak oak tip shower boiling water iron

Something went weird with the original post. Let me try this again…

I have built some doors for a small (4ft tall) bookcase. They will have frames, faux muntins and a single piece of glass in each door, when complete. The wood used to make the door frames (frame around the glass in the doors not the frame into which the door will go) is white oak that I re-sawed from thicker stock down to around half an inch thick and 2.5 inches wide.

I thought that I had waited long enough between my re-sawing and the assembly of the doors to minimize wood distortion but apparently not. The door frames are bowing significantly but this bow didn’t show up until after I have completed the door frame (glue and biscuit joints). Now I have 4 foot tall 14 inch wide frames with serious bows in both doors. I like the grain pattern in the wood and I don’t want to disassemble the door work that I’ve done so far sooooo…... do you have any ideas for how I might straighten these door frames out while keeping them intact? I definitely don’t want to build a giant steam box because that will involve more work than making new doors, so proper steam bending seems unrealistic.

This problem happened about two weeks ago. In the interim I clamped the frames to some straight sturdy wood and put the whole thing in my bathroom. The goal was to get it near some humidity while I came up with a real solution. I know that the stream generated is highly unlikely to have a real effect but I thought I would include it in this write up for comments.

I have also tossed around the idea of using boiling water or perhaps an iron to see if they might be able to help things along but haven’t experimented with either yet.

Any comments or advice are welcome. Thanks!

10 replies so far

View AlaskaGuy's profile


6409 posts in 3322 days

#1 posted 08-25-2015 06:57 PM

Did you have a question?

-- Alaskan's for Global warming!

View MT_Stringer's profile


3183 posts in 4244 days

#2 posted 08-25-2015 07:16 PM

Would you care to start over? I can’t tell if you are asking us or telling us. :-(

-- Handcrafted by Mike Henderson - Channelview, Texas

View TheWeiss's profile


53 posts in 2248 days

#3 posted 08-25-2015 08:29 PM

Sorry guys, something went wrong with the original post. I edited it to what it was supposed to say.

View Robert's profile


4451 posts in 2493 days

#4 posted 08-25-2015 09:18 PM

I believe his question was how can he straighten out the doors.

I doubt keeping them in a moist environment will do it.
You need a differential to bring it back (and it probably won’t work).
For example, put a light or fan on the convex surface and/or moisten the concave surface.

Here’s another suggestion that should work:

Cut a groove lengthwise mid-edge about 2 1/4” deep.
(Ideally you want the groove on the inside but that’s not an option for you.)
Make a 2 1/4+” wide spline and plane to fit snugly in the groove.
Glue in the spine, clamp the doors down to something flat, and let dry overnight.
Use TBIII or an other really hard drying glue.
Yes, you will see the spline, but you could choose a darker wood and turn a problem into a design feature ;-)
Good Luck.

-- Everything is a prototype thats why its one of a kind!!

View DrDirt's profile


4615 posts in 4755 days

#5 posted 08-25-2015 10:11 PM

not sure if you can straighten it, or if it will just go back to the bowed (stress relieved state) again over time.

perhaps some kind of cross bracing at the back… such that the glue line makes the door more like a lamination and becomes “locked flat”

a door that big, you have to really really watch the grain. Flat sawn might work on small panels, but won’t stay flat over 4 feet.

Are you on/close to quartersawn for the rails and stiles? I am presuming so – - since that is usually the goal to see the ray fleck of the Quartersawn white oak but??? a pic would help.

How bad is the bow? If you lay the door on a flat surface how much gap is in the middle to the surface?

-- “The two most important days in your life are the day you are born and the day you find out why.” Mark Twain

View runswithscissors's profile


3128 posts in 3038 days

#6 posted 08-29-2015 03:45 AM

Are the bowed parts rails or stiles? In either case, clamp one end in a padded vice (wooden pads will do), with the bowed face towards you. Clamp the other end with a husky C clamp, again using wood pads. Using a heat gun, very carefully heat that face of the piece until it’s very hot, deeply into the wood—but be careful not to scorch it. Using the clamp as a handle, flex the wood toward you, and overbend somewhat, as there will be spring back. Remove the heat, and hold the bend in position until it’s cooled. Should only take a few minutes. This is much more effective than an iron, or any source of heat that only touches the surface. Don’t have a heat gun? HF has a cheap one that will do.

If you overbend too much, you’ll need to apply head again to straighten it out. Oh, there’s no need for any added moisture or humidity at all.

If the heat gets into your glued joints, it may spoil the gluing job, so you may have to redo that.

I do this often. I straightened out a piece of oak crown molding that looked like a ski. I got a good price on it because nobody else wanted it. It has stayed straight ever since.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View TheWeiss's profile


53 posts in 2248 days

#7 posted 08-31-2015 08:32 PM

Hey guys, thanks for the feedback. It seems like most of you have about as much confidence in the shower technique as I do. I think I’m going to give Runswithscissors’ heat gun idea a try. I’ll keep you all posted on my progress. Wish me luck and feel free to send over any other thoughts or experiences!

View BurlyBob's profile


8508 posts in 3278 days

#8 posted 08-31-2015 09:25 PM

I had a similar problem with some panels I glued up for a TV cabinet. Every single glued panel bowed on me. I spent close to a month trying to straighten them out. I’d wet one side and put a bunch of weight on the other. The next they’d be straight, left them for a couple of days to make sure they were straight. I set that piece aside and did one of the other panels. By the time it was straightened out the first had bowed again. Like I said after 3-4 weeks of this I gave and built in out of oak plywood.

I hope you get it working to your satisfaction. Honest, I know the frustration your feeling.

View runswithscissors's profile


3128 posts in 3038 days

#9 posted 08-31-2015 10:31 PM

One reason the heat gun technique works is that the heat softens the lignin, allowing the wood fibers on the inner face to distort and slide together. In an extreme bend, you can see considerable distortion. When the wood cools, that new orientation of the fibers is locked in place. If you want less bend, you have to reheat the wood so those fibers can move again.

In doing an extreme bend, I always use a steel bending strap on the outside of the bend. Wood fibers will crumple together pretty easily, but won’t spread apart without breaking the wood. The bending strap prevents this. But the slight amount of bending you are trying to do will not require a bending strap. Be sure to let the wood cool before releasing the pressure on it.

Unfortunately, plywood is not always flat, as many of us have found out. I haven’t tried this with thick stuff, but on thinner panels—1/8 to 1/4”—plywood can be bent with heat too. Bending is easiest with the face grain, rather than against it. If you bend 2 pieces to the same curve, you can laminate those (when cooled), and you get a very rigid, curved panel.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View TheWeiss's profile


53 posts in 2248 days

#10 posted 10-12-2015 07:49 PM

It took me a while to get a heat gun and to find some time to try the heat technique but….... it worked wonderfully!!!! Thanks for the advice and the details around why it would (did) work.

I clamped each of the door frames down to my workbench using a caul on either end to spread the load evenly. I also placed two pieces of half-inch-thick scrap about 1/3 and 2/3’s of the length of the frames. With a little tension now on the wood I heated it using a heat gun. I spent a good amount of time making slow passes over the wood to heat all of it as evenly as possible. I only heated it from one side of the wood (given how I clamped it down) but I kept heating it until the underside started to feel hot. I kept them clamped down until they cooled completely.

I thought that I would have to experiment with different levels of deflection by swapping the 1/2 inch stock for something thicker or thinner but it turned out to be just right. Both door frames are now straight as an arrow. I plan on keeping an eye on them over the next few days to see if they re-form back to their bowed shape. I’ll be sure to get back on at let you know if they do. Thanks again guys!

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