Contributor
Looks like white oak to me, too. White oak doesn't play nice when it dries, especially plain sawn, and air drying makes it an even greater challenge to end up with good wood. It's very easy to get checks and stresses, especially if it was cut in the Summer and got exposed to direct sun and a stiff breeze during the first few days/weeks of drying. I ruined several hundred BF of white oak by letting that happen. From your account of the situation, I think you have a pile of firewood.
John
Moderator
All this being said, I don't know that checking is a big deal. You may be able to re-flatten the top somewhat and keep it in decent shape with a well-designed base. Tops aren't structural, so as long as any warp can be gently kept in check and is not so noticeable to the eye (I used the does-a-pencil-roll-off-by-itself) test, then I don't think you or the client will really care long term...
I have and have made several slab/burl tops. Some movement or checking is not always out of sync with the aesthetic - especially when the primary motivation for the piece is posterity.
Member
I've heard of WO "case hardening" when drying. Don't know much about it, but that might be something to look into. I seem to recall hearing that it can be reversed. Google it, maybe.
Contributor
My understanding is that case hardening happens when too much heat is used at the wrong times during kiln drying and this was air dried.Originally Posted by Jacob Reverb
Member
I agree. Although it's _nice_ for the wood to be flat and free from checks etc., it doesn't _have_ to be, you can always work around it. You are trying to convince the wood to be something that it is not.
Member
From what I've read, it also happens (though less) with air drying. I think the main problems are the high degree of shrinkage from green to dry in WO, and the tyloses that run perpendicular to the main direction of shrinkage...sounds like a recipe for lots of internal stresses.
See:
https://www.finewoodworking.com/foru...comment-275502
Last edited by Jacob Reverb; 01-30-2020 at 2:53 PM.
Moderator
Tyloses are bubble-like structures within the pores of some wood, stopping or slowing water and moisture movement in the pores. They are present in woods like white oak and osage orange. You can see their "sparkle" with a microscope or 10x hand lens.
Compare the hollow pores in red oak to pores plugged with tyloses in white oak.
red_oak.jpg white_oak_larger.jpg
Member
I guess I meant "medullary rays." I get them fouled up. Thanks.
Last edited by Jacob Reverb; 01-30-2020 at 7:52 PM.
Member
Bryan, that IS white oak, and it appears to be stressed/reaction wood milled from either a leaning tree or limbs. In the photo showing the table top, it appears that one edge of the boards is significantly closer to the cathedral grain than the opposite edge. Unless you ripped several inches off of one edge of the board and little from the other side, this is an indicator of stress wood that is present in the lumber.
Plus, your description of the movement is classic stress wood description. There is nothing that you can do to resolve this. The wood never should have been milled to begin with.
the internal checking visible in the end grain usually results from the lumber being dried too quickly from green. Thick White oak is problematic in this regard.
Scott
Moderator
From Bryan's post:
The end grain cracks formed parallel to the rays and perpendicular to the tangential direction. I've seen this 100 times on air-drying wood of various species. If I cut through a piece of incompletely dried wood and fail to seal the newly exposed faces the cracks will often develop overnight as Bryan reported, or in a few days. The report that the cracks formed after cutting some off the ends indicates to me there may still be a moisture gradient through the board. If more is cut off the end of the board the cracks can likely be cut away but will form again if there is still a moisture gradient through the board. Even air dried 2-1/2 years outdoors may not have been enough for white oak depending on local conditions. When I encounter end grain cracks I cut back the wood until they are gone then seal the end grain. Then wait.It checks massively when I cut the ends off....
The the next day these checks developed on the end grain
Attachment 424715
It sure would be nice to know the actual moisture of a sample cut from the inside. And while at it, the actual moisture of a sample cut from the surface. Besides the oven method, checking various places on the end grain of a fresh cut with a pin-type moisture meter could show this. Another way to check for moisture in wood is to cut off a chunk away from the end of the board, weigh carefully, then reweigh over the next few weeks or months. If the weight decreases over time, it was not dry enough for the current environment. I use a scale that gives the weight in grams. I mostly dry woodturning blanks so I'm usually tracking the weight on dozens of representitive pieces.
drying_tracking.jpg
JKJ
Contributor
The first picture shows very few checks in the end grain, stored without sealing. My guess is that it was cut in winter when it was relatively dry to start with and then the drying was very gentle. Good for the wood but slow. Probably still a long way to go.
You have included a lot of 'active grain' in that top. Looks like knots and burl. It seems that this tree was low and wide with no clear trunk, or the good wood didn't come to you.
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