Gary,
I am building a kitchen table top (40″ wide x 72″ long). The top is glued up with 5 pieces of maple, each one about 8″ wide. The process has taken me a couple of months, but as I prepared each piece (planing and squaring the edges), I took care to sticker them to keep them from cupping or bowing. I have finally glued them up a couple of weekends ago into a nice flat piece. I put the top on my bench but forgot to sticker it underneath, and when I went to work on it yesterday, it has cupped a fair amount (I’d guess about 3/8″ from the edge to the center). I suspect that it’s because of the large humidity change (my shop is air-conditioned when I work, but not otherwise).
Do you think the cupping is because of the humidity change? I have since put stickers between my bench and the table top; will the top flatten itself given enough time for the moisture to equilibrate? If not, what can I do to flatten it before I put breadboards on the end.
Thanks for your advice in advance.
Replies
Well yeah I think the top cupped because of the humidity change. Try this: clamp your top to your bench, on stickers. Wet down the concave side with a damp cloth oh I'd say four or five times an hour. Some folks do this out on the lawn with a hose and bricks. But if your top moved in a night, I'd be careful about using too much water. Wet it down, let it adjust, see if cups back to shape. It may take overnight with the surface being left damp. Or it may take just a few hours. Hard to say.
I once wet down one surface of a 20" square, 1/2" thick piece of laminated maple. I was raising the grain of the top. Dang thick cupped on me in a hurry. Without too much panic, I flipped the thing over and wet down the other side and it went back to straight. All this in the space of 15 minutes.
But it sounds like if you're patient and get moisture to the cupped side it will straighten out. Good luck with this.
Gary
Gary,
Thanks for the reassurance that it will eventually flatten out. I have stickered it and put weight on top. It looks like it has slowly un-cupped itself, hopefully by the time I get to it this weekend it will be flat. If not, I will try wetting down the concave side.
Thanks!
Don't wet down the concave side. I'll show you why. Take a piece of paper and wet it down. It cups. And the concave side is the side that didn't get any water. So keep the concave side dry and wet down the convex side if you want to try to get this panel flat. Gary
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