All Replies on Flattening a Warped/Warping Slab Table

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View jbdc's profile

Flattening a Warped/Warping Slab Table

by jbdc
posted 02-01-2018 02:28 PM

10 replies so far

View Aj2's profile


3340 posts in 2650 days

#1 posted 02-01-2018 02:45 PM

Sounds like a train wreck. I’ve never worked with Elm but my rule with any woods that don’t behave stand them up in the corner of my shop till they settle down. I had some Beautiful Douglas fir that sat for years till it stopped weeping sap and cupping.
Good luck

-- Aj

View Robert's profile


3946 posts in 2332 days

#2 posted 02-01-2018 04:38 PM

How long ago was it cut? You’re never gonna get it equilibrated doing what you’re doing.

As you’ve already found, the cup will never come completely out &/or will reappear after you think you’ve solved it. This is because unequal stresses develop in wood that is dried unevenly (this is my theory anyway).

My suggestion is store the slab on stickers in your house for at least 1-2 years. Then build a router sled and flatten it.

-- Everything is a prototype thats why its one of a kind!!

View johnstoneb's profile


3154 posts in 3024 days

#3 posted 02-01-2018 04:45 PM

All the sealer will do is slow the wood movement. You need to remove all the finish, rip the table top into narrower pieces, let them dry and until the wood and moisture content stabilize. Then square up the stock and start over.

-- Bruce, Boise, ID

View Loren's profile


10594 posts in 4500 days

#4 posted 02-01-2018 04:47 PM

Is the base slotted to allow the table to
move in width?

I agree with Bruce. I would consider ripping it
down the joint and regluing it. Perhaps once
cut in half the two sides can be rejoined to
form a relatively flat plane. If the two sides
are themselves cupped severely, either they
will need to be flattened and thicknessed or
ripped into narrow boards as Bruce suggests.

View Carloz's profile


1147 posts in 1443 days

#5 posted 02-01-2018 04:57 PM

All the sealer will do is slow the wood movement. You need to remove all the finish, rip the table top into narrower pieces, let them dry and until the wood and moisture content stabilize. Then square up the stock and start over.

- johnstoneb

I am curious why ? Do narrower pieces ( not as narrow a half inch or so ) dry any noticeably faster than one whole piece ? If you talked about thinner pieces with the following lamination that could be a different story.

View Woodknack's profile


13474 posts in 3232 days

#6 posted 02-01-2018 05:33 PM

Wood movement is hydraulic so its almost impossible to force a slab to stay flat. I would try your plan of flattening the slab again and sealing the bottom, might work, might not. But it’s easy to try. General rule with panels is that what you do to one side, you do to the other. If that doesn’t work then you’ll need to take more drastic action. But I would try the easiest thing first.

-- Rick M,

View OSU55's profile


2658 posts in 2841 days

#7 posted 02-01-2018 10:56 PM

Are there any fundamental flaws with my plan? Unfortunately it is severely flawed. Until the wood dries out, it will move any which way. Trying to restrict it will result in something breaking, bowing, cupping, who knows. Get the top off and replace it with a piece of plywood or something, strip the finish, and let it sit around for a year or 2.

Are the inserts I plan on using the correct type? Possibly, but probably not. Even after the wood is dry, it will move with moisture change. The top has to be attached allowing it to move.

Is my planned sealant appropriate, or are there better options I’m unaware of? No, those sealer products will rub off on clothes. Once the wood has dried, been reworked to flat and the panel glued again, finish both top and bottom.

Would Titebond wood glue work just as well as AnchorSeal? Actually better since it wont rub off, but don’t do it until the wood is dry.

Other thoughts or ideas? Not until the wood dries. You will just be chasing your tail in circles until then. It’s just not worth fighting it. You could build a “tent” and use your dehumidifier to dry the wood faster. The existing finish needs to be removed. Too fast and you could create large cracks etc.

View jbdc's profile


5 posts in 967 days

#8 posted 02-02-2018 09:44 PM

Thanks all for the feedback; in the interval I got some additional information: The sealant is water-based Varathane; So, not nearly as bad in terms of VOCs etc. as epoxy or oil-based sealants. I may simply send wife and baby away for the day when it gets warm enough outside for me to put a box fan blowing out the window, then seal the underside with the same number of coats applied to the top (maybe a few more since the top could do with a few more layers too).

I have no expectation that the inserts will prevent the table from warping entirely; the hope is that they’ll provide an extra bit of stability as the sealant helps slow and even-out the diffusion of water out of the wood over a longer period. (Like using low-power settings on the microwave to avoid pockets of ice and lava in a burrito.) I understand that without sufficient drying (and even then), the wood will continue to move. The existing anchor holes in the base are already oblong (whether that was by design or a fudge, I don’t know); and the anchors will only be lightly tightened.

Further, I know I may be on a fool’s errand, but I’m trying to make the best out of an unfortunate situation with what little resources and time I’ve got: There are countless little projects as we transition our century home from 3 apartments to a more conventional home + basement suite.

That said, I’ll try to keep all your helpful advice in mind as I put this plan into action to ensure that I don’t prevent myself from being able to take some of the more comprehensive measures you guys have suggested in the future.

I’ll post some process photos soonish, and I’ll follow-up with updates in the longer term.

Again, thanks to everyone who’s contributed thus far!

View Gene Howe's profile

Gene Howe

12241 posts in 4280 days

#9 posted 02-02-2018 10:52 PM

I’ve seen 8/4 elm, dried to 6% , cup. And it was coated on both sides with epoxy. Elm is just plain ornery.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View rustfever's profile


797 posts in 4162 days

#10 posted 02-03-2018 12:15 AM

Throwing good money after bad!
Do it right or forget it.
Rip into smaller boards, sticker, air dry for as long as it take to get equilibrium.
Glue up and Watch the Grain.
Plane true and then a good finish on ALL edges.
Or just keep fighting a loosing cause.

-- Rustfever, Central California

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