Replies

1. 
   flairwoodworks | Dec 10, 2008 04:52am | #1

   Jack,

   One trick that may work is to moisten the concave side to make it warp the other way, then fasten it down or attach battens while it is flat to keep it that way. (Thanks to David Keller for passing that tip on to me).

   Chris @ www.flairwoodwork.spaces.live.com
   (soon to be www.flairwoodworks.com)

    - Success is not the key to happines.  Happiness is the key to success.  If you love what you are doing, you will be successful. - Albert Schweitzer

1. 
   SteveSchoene | Dec 10, 2008 05:40am | #2

   But, in the case of this card table, you can't do that since the folding leaf is not attached except by a couple of hinges. 

   You do need to diagnose why the cup is occurring.  Was the wood not in moisture equilibrium when it was planed flat?  Has it been moved into a drier or wetter atmosphere.  If the two leafs are folded onto each other, the top of the top leaf gains or loses moisture more rapidly than the bottom, possibly leading to warping, particularly if you haven't finished it yet.  (Has it been finished?) 

   I would certainly place the table in a way where both sides of the top leaf can get equal air circulation and see what happens before I would do anything drastic.  You may find that it flattens itself out. 

2. 
   forestgirl | Dec 10, 2008 07:47am | #3

   "Now when folded up the upper half has a 1/2 separation at the end, where the other half meets."  Not sure that I follow this as "cupping" but if, indeed, that's what it is, Steve's questions are important.  Is the table finished?  Is the finish equal on both sides (top and bottom) of the wood? 

   If the wood cupped because the finish was thinner or non-existant on one side of the boards, then the technique of wetting one side might work.  I've used it on a handful of old, cupped, tables.  If the wood is cupping because of internal stresses or uneven moisture content at time of build, not so optimistic.

   The common approach is to lay the board or top on grass -- concave side down (I put a sheet of newsprint underneath), a little sun helps -- and leave it there while the concave side absorbs moisture and the convex side dries a bit.  An indoor arrangement can be made with barely damp towels and a heat lamp (careful!)   When it flattens out, put it up on stickers in your workshop for a day and see if it stays flat.  If not, repeat the procedure.  If the 2nd try doesn't work, you can try one more time, but let the boards go ever so slightly past perfectly flat -- cup in the other direction -- then sticker for a half-day.

   If you think you've got it where you want it, get finish on it right away.

   Good luck!

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

   
   

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   Edited 12/9/2008 11:50 pm by forestgirl

3. 
   KeithNewton | Dec 10, 2008 05:51pm | #4

   Sparky, I don't think much of the suggestion of wetting the wood, especially when there was likely to have been too much moisture in the wood to begin with.

   My suggestion is to take the top leaf off, and find a heat source, like your fire-place where there is radiant heat that can warm the convex side only. If you warm the large side more than the cupped side, it will give up moisture faster on that side, and pull back the other way.

   If you look at the annual rings on the end of the boards which you used, and some of them have a small arc, as in cut from near the heart of the tree, then this may make it a bit harder to control with the above suggestion.