How to flatten warped wood

[OCtoolguy]

I read about this subject on Steve Good's blog and he said to tune in the next day to see how it worked out. Except that he never addressed it again. What brings this up is, a couple of months ago, I bought some wood for a project but didn't get to it fast enough. It is 1/4" poplar about 8 inches wide and 48" long. It has become cupped the full length of the board. So, according to Steve, I should be able to apply damp paper towels to the cupped side and turn it face down on my work bench with weight on top of it for about 24 hours. But, since he never did the follow up, I don't know if it worked or not. Have any of you ever tried to "uncup" warped wood? Did it work? I sure hope so. I hate to see good wood go bad. I'll be awaiting your knowledgeable answers.

 

[jollyred]

Dampening the cupped side will cause that side to expand, which will flatten the board.  However, it will re-warp when it dries out.  You need the weights on the wood to hold it in place while drying.  This does work, just be sure to allow plenty of time for the wood to re-dry.

[kmmcrafts]

I've never tried to un-cup wood like this.. i have in the past just flipped it over so the wood would breath from the opposite side and put some weight on it and it straightened out but not completely... Something i have learned about is.. certain wood types are way more prone to this than others.. especially thinner boards that are quite wide..  Something else I've learned is.. tight grained wood is less prone to cupping than loose grain wood.... Rarely ever see quarter sawn wood cup like this. and I look specifically for quarter sawn when buying Oak because of this issue as I don't saw a lot of Oak so the boards sit around for quite a while..  Hard to pick your own lumber for those that have to mail order it.. but if you have the option to sort out your own lumber.. always get tight grained boards where the grain lines are close to one another..   

[JTTHECLOCKMAN]

Ray yes wetting the cupped side can but not always take some of the warpness out. The thing is to wet the cupped side but let it sit for about 15 minutes or so. Do not put weight on it right away or it will crack. After the water has soaked in then either clamp it flat or add weight so that it sits on something flat. Let it thoroughly dry before using. Now this wood will have a tendency to cup again depending what you are doing with it. If you are cutting fret work from it will help release the inner tension because of the holes. It would be worth the effort to mount on a solid backboard. 

[OCtoolguy]

I was also thinking that I could rip it into strips and flip and glue them back together. I know that it works with thicker wood. Not sure it would work with something this thin.

[Roberta Moreton]

Wetting the cup well, waiting a bit, adding weight has worked for me   

[Bill WIlson]

It may work and it may not.  It's just the nature of wood.  Worth a try.  I'd give it a shot before I would rip the board and re-glue it.  To me, ripping and re-glueing just gives you a board that looks like it was all chopped up.  Sometimes it's necessary, but takes a lot of extra work to get it back together and smooth again.  Do that as a last resort or get another flat piece and use the cupped one for something else.

[OCtoolguy]

Thanks to you all. I will give the wetting a try. I have gone back and re-read Steve's explanation several times. So, now it's time to give it a try. Unfortunately, the only place I have that is flat and that long is my workbench so it will be unusable for a day or two. I have some projects that will keep me busy. I will be installing my new Pegas clamps. I look forward to using them. 

 

[Roberta Moreton]

I have found a spot on the floor that was flat and large enough before. 

[OCtoolguy]

1 hour ago, Roberta Moreton said:

I have found a spot on the floor that was flat and large enough before. 

Now, why didn't I think of that?

 

[stoney]

Ray your issue with poplar reminded me of a problem our family had with it years ago.   As I have said before I was born and raised on a sawmill.   We had a contract with a window company that made aluminum storm windows to provide crating material.   We provided them with green 1x6 and 1x3 poplar boards for making their crates.   When we got an order cut we would set the bunk of wood outside to be delivered.   If we didn't weight the top of the bunk down we would end up with most of the upper most boards ends curling upwards.   In all my years working around the mill poplar was the worst wood we ever worked with for cupping and bowing.   Ray I might suggest if you have a paved driveway or sidewalk wet the wood down and then weight it down good the full length for a few days.   Then I would suggest storing it with weight on it until you are ready to use it.     

[OCtoolguy]

1 hour ago, stoney said:

Ray your issue with poplar reminded me of a problem our family had with it years ago.   As I have said before I was born and raised on a sawmill.   We had a contract with a window company that made aluminum storm windows to provide crating material.   We provided them with green 1x6 and 1x3 poplar boards for making their crates.   When we got an order cut we would set the bunk of wood outside to be delivered.   If we didn't weight the top of the bunk down we would end up with most of the upper most boards ends curling upwards.   In all my years working around the mill poplar was the worst wood we ever worked with for cupping and bowing.   Ray I might suggest if you have a paved driveway or sidewalk wet the wood down and then weight it down good the full length for a few days.   Then I would suggest storing it with weight on it until you are ready to use it.     

Thanks Stoney. I'll have to do something like that. It's about 4 ft. long by 8 inches wide. It's not cupped too bad so I think I might be able to save it. I should have known to weight it down while storing it. But I am short of space so I just stood it up in the corner. Live and learn.

 

[dgman]

Here’s my two cents. I haven’t had much luck flattening cupped boards, but I have had luck keeping them from cupping in the first place. You need to keep equal air circulation around your board, especially thin boards. Stacking and stickering  is the best way if you have multiple boards. Don’t lay them flat on the floor or table. This only allows air circulation around the top of the board not allowing air on the bottom of the board. 

If you mill your own lumber, you have to take equal amounts off both sides. I always lean my freshly planed board so it receives equal air circulation around the board. 

[OCtoolguy]

37 minutes ago, dgman said:

Here’s my two cents. I haven’t had much luck flattening cupped boards, but I have had luck keeping them from cupping in the first place. You need to keep equal air circulation around your board, especially thin boards. Stacking and stickering  is the best way if you have multiple boards. Don’t lay them flat on the floor or table. This only allows air circulation around the top of the board not allowing air on the bottom of the board. 

If you mill your own lumber, you have to take equal amounts off both sides. I always lean my freshly planed board so it receives equal air circulation around the board. 

Oh how wonderful it would be to have more room than I need. I'd love to have the room to "sticker" my wood. I should not have ordered the wood so far in advance of working with it.