cupped tabletop

[John Carpents]

I am looking for solutions to remove the cupping from a 48" round tabletop. It is a commercially made piece (Canadel), and their stuff is pretty well made generally.

My parents bought the table this summer, and put a custom cut glass top on it to protect the wood since it is a high trafic kitchen table. I didnt check the flatness when they bought it - but it certainly was much flatter than this since the glass sat flat with only small plastic spacers. Recently the galss began to spin on a high spot.

I put a 4 foot straight edge across it and sure enough it is cupped perpendicular to the grain, about 5/8" over 48" :eek:! The cup is downward - that is to say there is a crown in the middle. It is only out about 1/8" going with the grain.

I attribute this happening since we have central forced air heat with no humidifiers (very dry). The top side is stained and laquered - but the bottom has NO FINISH. The bottom is cleary dried out and the top not as much.

I thought of steaming the piece a bit, and then coating with shellac - but I dont want to seal too much moisture in.

Any ideas on a good way to remove a good deal of the cup, and then fknow when it is safe to put shellac on the bottom?

[Chip Lindley]

Your tabletop has cupped exactly as any wide glue-up will, when finished only on one side. Simplest way to flatten would be to attach two 4/4 cleats to the bottom with 3 screws. the two outer screw holes must be slotted for expansion of the top. Maximize your chances of success by using the jointer or a hand plane to make a slight arch on the cleat surface next to the tabletop. The bow will help offset any springback.

[Ed Hazel]

Could try and wait for summer it may flatten out then seal the bottom then cleat as Chip advised or just wait and see what happens next winter.

[Lee Schierer]

You may not wan to hear this but remove the glass. It is holding moisture in the top side of the table. Those little spacers don't really allow any air movement. The top should flatten out over time. Once it is flat, apply 2-3 coats of finish to the underside. If the top stays flat after the finishing, then you can consider putting the glass top back in place.

[Adam Cavaliere]

I had this happen to a coffee table top I created. Same exact wood movement occured. To cure about 90% of the movement, I used water on a paintbrush and applied it generously to the unfinished side of the table top. It took the warp out pretty quickly (within a day or two if I remember) and then I finished it rather quickly after that.

I haven't had it cup since (**knock on wood** :D)