Replies

1. 
   Oilstone | Mar 09, 2009 03:38pm | #1

   That's a big slab.  You could try steaming the concave side - put moderately damp towels on it and iron with an iron.  If it does flatten out you have to be able to put the board into its place in the project immediately.  This works great on smaller boards, I'm not terribly hopeful for the one you mentioned. 

   
   

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   Edited 3/9/2009 8:41 am ET by Oilstone

2. 
   joinerswork | Mar 09, 2009 03:44pm | #2

   chuck,

   Your best bet would be to rip the board into two or three pieces , thickness them, and re-join.  The glue lines will be inconspicuous, and thicknessing the narrow boards will allow for greater finished thickness.

   Ray

1. 
   chuck3 | Mar 09, 2009 04:49pm | #3

   Ray, I wonder if I could try a variation on your suggestion.  What if I used my circular saw to cut a series of grooves along the length of the board, almost it's full thickness.  With the cupping force relieved, I could clamp the board to a flat surface and fill the grooves with epoxy, or perhaps thin wood strips and yellow glue.  This should permanently relieve the board's tendency to cup, no?  I wonder if it creates an issue with wood movement causing the top surface to crack over time?

1. 
   joinerswork | Mar 10, 2009 01:47am | #9

   chuck,

   I have tried kerfing and filling the underside of a tabletop.  My experience was mixed on this technique.  I was able to flatten the top, but some of the kerfs "telegraphed" their presence thru to the top surface as a series of lines, and left the top looking sort of like it was made of a bunch of cupped strips.  There is always a risk of the top cracking along one of the kerfs when you press it flat, and the filled kerfs will need to be concealed on the ends somehow.  Filling them with wood is a finicky job, as you want them tightly filled, but not so tightly wedged that they split the fragile top surface.  I'd only consider this technique on an antique that's worth the extra effort.

   Ray

3. 
   ctsjr | Mar 09, 2009 05:14pm | #4

   How long ago was it milled and dried, and how long ago did it cup? If this is a recent development, then it should be able to be reversed, or at least till you can get it on the base to hold it flat. Tom

   "Notice that at no time do my fingers leave my hand"
4. 
   JeffHeath | Mar 09, 2009 05:51pm | #5

   The idea of kerfing the board to allow it to be bent back into place parallel with the grain of the wood is a bad idea.  It will almost certainly crack along one or more of the kerfed cuts.

   It is cupping for one of a few possibilities. 

   1. It isn't dry, and hasn't reached equilibrium with your shop environment.  If that's the case, you will continue to have problems with it until it is.  Check it with a moisture meter to see if it is around 10% to 12%.
   2. It has warped during the drying process, which can sometimes be corrected by steaming with a wet towel and a hot iron.  This can definately be corrected by the advice Ray (joinerswork) gave you, which is to cut it in 2 or 3 sections, flatten, and re-glue just like a table top.  If you choose wisely where you rip the boards, the joint lines will be nearly invisible.  This option is probably your best bet.
   3. You might have reaction wood, which is quite common in crotchwood.  If this is the case, you have expensive firewood, as each time you mill it, it will continue to cup, warp, and twist.  Just turn on some Buddy Holly music, and watch the dance.  And, if this is the case, BE CAREFUL!  Reaction wood and table saws do not go well together.

   Jeff

5. 
   Jfrostjr | Mar 09, 2009 05:55pm | #6

   Has the board been stored so that air able to access both sides equally?

   If not, do so and wait. It may surprise you by resuming its flat shape in a couple of weeks..

   Frosty

   "I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922

6. 
   Oilstone | Mar 09, 2009 06:47pm | #7

   I absolutely would wet and/or steam the concave side before you start ripping and all that stuff. You won't hurt anything and it might work.

7. 
   jimmy | Mar 09, 2009 11:03pm | #8

   Do what Ray said....

8. 
   forestgirl | Mar 10, 2009 04:33am | #10

   Frosty asked a very important question!!  Before you apply any treatment (steaming), be sure it has had equal air exposure all the way around and that the cup is not a reaction to uneven drying.

   I've used the steaming method (with sun and grass, or towels and a heat lamp) with good success on smaller boards, have no idea how it might work with a big board like yours.  Sometimes it has taken two or three treatments to get a solid result (when 3 are required, I go ever so slightly past flat).  The other important thing has been to get some kind of finish on the board (both sides) fairly soon.

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 
   
1. 
   ctsjr | Mar 10, 2009 05:11pm | #11

   This thread has struck a cord with me because of a project I'm working on. I'm in the midst of building a 'down and dirty' bookcase for the office. Cheap red oak, 3/4" sides and shelves. I cut the dados in the case sides, cut the shelves to rough length, and set it aside as I ran out of time. A cold front came through, and the combination of dry air (Orange, TX is VERY humid most of the time) and the milling caused the sides to cup (the boards were all laying on the bench). As the weather turned humid again, the boards flattened out again. We've had a stretch of dry weather and air, and the boards again cupped, but in the last three days it's been getting progressively warmer and more humid, and voila! Today the boards are flat again. I'm going to get it glued together today and the shelves and glue should hold it flat. Tom"Notice that at no time do my fingers leave my hand"

1. 
   forestgirl | Mar 10, 2009 07:01pm | #12

   Wow, that's enough to drive you batty!  Best get some finish on that piece quickly if your weather going to continue cycling like that.

   We're having a cold front too, snow and ice crystal falling from the sky!  Crazy stuff for us.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

1. 
   chuck3 | Mar 10, 2009 07:27pm | #13

   To all who have taken the time to address my question, many thanks!

   To answer some of your questions:  I received the board from a friend, who tells me it was cut from a tree that fell on his farm about 10 years ago.  After rough milling, it's been in his garage rafters all that time, stacked with other boards.  I removed it in December, and placed it standing upright in my garage.  It was cupped at this point.

   About three weeks ago, I took the time to rough sand both sides of the board.  It was ony then I was able to tell it was walnut, and saw the beautiful crotch figure.  While sanding, it seemed that one side of the board (the convex side) had some sort of finish on it (varnish, shellac?).  My friend couldn't remember anything about this.

   Since then, I've had the board standing upright in my garage, air on both sides, with clamps pulling it flat.  It sounds like I should try warm moisture on the concave side next.

   Again, many thatns for your advice.

1. 
   zolton | Mar 11, 2009 05:09am | #14

   Chuck,

    Ditto on the advice you were given by several posters to forget about the kerfing idea. I've done that a few times and the board almost inevitably cracks at some point. A kerf cut deep enough to weaken the board sufficiently to de-warp it is a split waiting to happen.

   I'm not sure about the steaming idea either. I know it works temporarily, as does laying a cupped board on damp grass. But after the wood reaches equilibrium moisture content again it's likely to re-warp to the way it was. Throwing a finish on it after steaming is risky, as the wood would be moist. And the finish would probably only slow down the moisture transfer, not stop it. In other words, the board would probably warp again at some point. And if you'd already made it into the tabletop the results would be even more frustrating.

   Cutting it into smaller pieces might work, but any time you cut into a piece of wood like this you relieve some stresses and set up others. So the smaller pieces might warp or bow too, leaving you with less stock to work with than what you started out with.

   Have you considered just flipping the board over and planing down the hump in the middle? That would leave you with a board that was thinner in the middle, but at the orginal thickness on the edges. Because the thinned section wouldn't be visible, this might be something to look into..

   Zolton

    If you see a possum running around in here, kill it. It's not a pet. - Jackie Moon

2. 
   forestgirl | Mar 11, 2009 05:57am | #15

   Zolton, the boards I've done the grass/sun thing with have, for the most part, been warped furniture tops (end-tables and such).  It's worked well.  I've also done it with some thinnish cedar boards.  Pretty good luck there. 

   I was hoping that our OP had laid the slab on the floor or somethin' -- no such luck!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

3. 
   Sawdust4real | Oct 19, 2009 02:02am | #17

   what is the dimension of the board in the rough ? , you can probably joint it and then reduce the thickness  somewhat and let it dry, obviously the problem is the amount of moisture in the board , cutting it into small pieces will be of no help if it's a thick piece of wood and worse yet it will change the figure .

   Venio.

4. 
   forestgirl | Oct 19, 2009 06:34am | #18

   I think you meant your reply for Chuck3, but the original post is from way back in March, so I suspect it's all a moot point by now, LOL.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

5. 
   philip | Oct 17, 2009 11:10pm | #16

   Chuck,
   After reading your last message I would not waste any further time: rip it into three or more pieces, machine or hand joint, and re-join.You will lose minimal material this way and it will look fine-especially as it is curly grained as the glue lines will be harder to see.Philip Marcou