Hello! I need some helps! My live edge table top cupped.
I searched everywhere for the answers but all the post has posted the problems often because they let the top sit flat on the surface or cover it with something. But mine is different.
I just built my first live edge table with steel legs.
I read all the warning and tips and tricks how to work with solid wood, slabs and how to keep the top stay flat.
I ordered the bookmatched slabs online, get them jointed and glued up, planed both faces before shipped to my home, the slabs arrived to my garage completely flat.
I put it on the sawhorses to expose both faces to the air.
After almost a week, I didn’t see any movement in the slabs, still flat and the MC is around 8-9%
I started working on it, i cut the slabs to length, epoxy filling any voids, cracks…sanded and finished both sides of the slabs evenly with wipe on poly.
Always keep the slabs on the sawhorses to exposes both faces.
waited for 3 days after final coat completed.
Then i moved the table into my house my dining room, let it sit there on the table base for three days before we can start using it. I planned to attach the top the legs right before we can start use it to make sure nothing wrong with the top.
But after three days, it cupped, almost 1/2”, the concave side is on the top, i don’t know what cause it, been kept both faces exposed all the time.
Anyone know could help me explain why?
Replies
I would say you allowed the slab to acclimate to your shop and then brought it into your house where the humidity was significantly different?
Slabs are pretty notorious for misbehaving. They really ought to sit for years, not days or weeks, before doing something with them. Even then, they are apt to move. You've got heartwood, maybe even pith (or closer to the pith), sapwood, maybe even bark. You've got a huge chunk of the tree taken off of one face, and very little off the other. You have tangential shrinkage fighting with radial shrinkage. Moisture exchanges rapidly near the ends, and very slowly in the middle.
Slab's gonna do what a slab's gonna do. Waiting is about all you can do.
Unfortunately yes
Checking the moisture content on the outside of the plank can give an unreliable reading. Moisture escapes through the outer edges, faster from the end grain, but still some from the flat part of the board. Moisture in the center of the board migrates slowly to the outside. The outside can be "dry" but there can be much more moisture in the center. A better way to measure MC is to cut a piece off several inches from the end or and inch or so from the edge. Then measure MC in the middle of the fresh cut. I had some 2" walnut boards that I found out, after cutting them, had been milled recently. The exterior of the board measured 12% MC or so, the interior of the board was over 20%. You take boards inside to an average humidity of 50% or less and they will dry out and the competing stresses will work and the boards move. You might need to let them settle for a couple years, then cut the table top along the joint line, flatten both halves and re-glue it. Your resulting table top will be only slightly smaller, but hopefully will stay flat. Also, you never said what species you used. Mesquite moves very little as it dries, beech moves a tremendous amount. Most other woods are somewhere in between.
This is one reason why it is important to fix tops to bottoms of tables - it can help to prevent warping. You can see this with wet treated timber on farm fences. A 2 x 6 board has to be installed in situ wet and nailed down otherwise it will warp badly.
A very interesting article on a competing site gave some useful tips that are not directly relevant to your case, but still helpful in general. https://www.popularwoodworking.com/article/finish_both_sides_not_necessary/
The issue is how to fix the problem. First turn the top over on the frame in the house. You did finish both sides! Wait to see if the board eases or warps the other way.If not,time for radical fix.Cut slots with a skil saw but stay 6 inches from each end,Cut the slots 2 inches apart about half way through the back.Torn the table over,Lightly attach to the base and tighten uhe clips a bit each week till it is flat
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