Honeycombing and Fresh Checking in a Newly Turned Newel Post
A woodworker's report of a honeycombing and checking problem leads to a good discussion of wood drying defects and how they manifest themselves. March 3, 2009
Question
I have recently turned a few large red oak stair newels only to find severe honey comb in one and overnight de-lamination in the other two. I don't want this to happen again obviously. Is there something I can look for up front to avoid this condition? I assume this is due to faulty kiln process. Does anyone have the skinny on this?
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Forum Responses
(Architectural Woodworking Forum)
From contributor K:
The images don't do justice to this.
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From Gene Wengert, forum technical advisor:
The pieces are too wet for the environment that they are in. It is likely that the cracks are pre-existing cracks and not new cracks, but the drying is making them worse. To verify this, you need to know the RH around the pieces or the MC of them, although since they have dried, shrunk and cracked, the MC now is lower than it was previously when you started.
From the original questioner:
I picked these 8/4 pieces from a stack that had some of this honey comb on the ends (not like checking) but the ends were showing voids or pockets and so I discarded these and carefully picked out the best I could find. However when I turned the newels the voids showed up in these as well. The surfaces looked very nice but the inner wood had these pockets or voids. The next day the de lamination began. I did not check for moisture content.
From contributor H:
The honey combing is from incorrect kiln drying - overdry. On 8/4 stock I have seen it as deep as 1/3 of the way through.
From Gene Wengert, forum technical advisor:
We can have surface checks (caused by drying too quickly above 50% MC) and end checks (caused because the ends are drying too quickly above 50% MC). The checks initially are very small. Either of them can go deeper, forming internal checks (also called honeycomb), if drying continues to be too rapid. In fact, 99.9% of all internal checks are an end check or surface check that got worse. (The cure is to prevent the initial checking. If prevented, then it cannot get worse).
It is common to find that on the surface or end of the rough stock, the checks are closed so tightly at the end of drying that they are undetectable. If the lumber is cut shorter, is re-sawn, is planed or routed heavily, or is turned, then the open internal checks will be exposed. That is what we have here. (In picture #1 you can see the check is associated with discolored wood, which can be wood that is weaker than normal - maybe bacterial infected).
From Gene Wengert, forum technical advisor:
In picture #2 we have the de-lamination at the glue joint. This occurred overnight, so it is 100% certain that the wood was too wet for its environment, shrank, and the glue joint (being the wettest link) broke. In fact, the glue joint was probably weak because prior to gluing it began to shrink a bit and so when glued there was a gap (as a result of the shrinkage) greater than 0.006" creating a weak glue joint. Of course, shrinkage only occurs because the MC is dropping, which means you had wood that was too wet. It was not over-dried.
In summary, the wood was improperly dried - dried too fast initially (above 50% MC), creating checks, dried too fast as drying continued (30-40% MC range), and then not dried to the correct final MC.
From the original questioner:
My hardwood supplier suggested that the oak was dried too quickly as well. Someone told me once that kiln drying oak involves some steaming and that the steam process, if done incorrectly, can cause this. Regardless this should all be less of an issue with 6/4 wouldn't you agree?
From Gene Wengert, forum technical advisor:
Steam is not required to dry oak. Thinner stock is easier to dry, but oak is not easy to dry without knowledge and proper procedures.
From the original questioner:
Thanks to you both for your response. Is there anything to look for to avoid this in the future since, at least in this case, it was hidden from the surface.
From Gene Wengert, forum technical advisor:
The de-lamination should be 100% covered by the person who glued the wood. The person who glued the wood should have checked the MC before processing. The honeycomb is virtually impossible to detect in dry lumber without processing it. Again, the supplier should stand behind the product 100%.
In the future, you need to stop processing when you encounter such defects in more than one or two pieces and immediately return the wood for full credit. The wood supplied to you was obliviously not suited for its intended use. Then find a new and better supplier. It does not make sense that you should suffer because of other people's errors.
From the original questioner:
I did get credit from my hardwood supplier. As for the de-lamination, the wood was pulling away after it was turned. In other words you could feel over the faulty glue line and feel that the wood was raised on one side of the glue line - not swelling but pulling away.
From contributor R:
Gene is correct, this sort of defect is hard to detect in rough lumber. The only thing I have noticed on occasion is the rough stock tends to have a bit more cup on average in a pack when this defect is present. If you see this defect on a couple of boards in a unit avoid the entire pack or better yet seek another supplier and make the supplier take back the product, even if it has been partially processed. This type of defect infuriates me, it is a well known issue regarding drying oak and preventable not to mention a sickening waste of good wood. When discovered as in the above examples, it can cost the end user many times over the value of the wood itself.
From Gene Wengert, forum technical advisor:
Contributor R is correct except that a few times there can be defective wood (such as bacterially infected) in which honeycomb is impossible to prevent. That is why in picture #1 the discoloration in the honeycombed area may indicate bad wood in the tree. Indeed, the shrinkage discussed will seem like it has pulled away. A good glue joint will always be stronger than the wood itself.
From contributor J:
Just curious, is what you're describing also called case hardening? I read something a while ago about it and it sounds very similar.
From Gene Wengert, forum technical advisor:
Casehardening is a stress condition that causes immediate warp when machining. The case is not harder than the core. Casehardening, also called drying stress and tension set, develops very early in drying.
From the original questioner:
I wondered about this as well since 8/4 red oak on another job (same supplier) seemed to warp slightly right off the jointer.
From Gene Wengert, forum technical advisor:
It is difficult to remove casehardening stress from lumber that is a bit too wet. So, it does indeed sound like your supplier has some drying issues that need to be corrected.
From contributor C:
The wood is not ruined. A little epoxy fill will take care of it aesthetically and the wood is more than likely structurally sound. I do not see why people think a little check "ruins" a piece of wood. Like it or not, wood is a volatile material and will occasionally check even if dried carefully.
From the original questioner:
I have used a fill on occasion. In two other cases though I have had oak newels crack severely. When the customer contacted me about checking I thought they were being picky. When I saw the pictures of the pieces I couldn't believe what I was seeing.
From Gene Wengert, forum technical advisor:
A round piece is probably the most sensitive shape to moisture changes. If you think about it, the outside fibers are a bit too wet for the environment, so they dry and shrink. But their circumference cannot change because of all the wood underneath. That is, the circumference is fixed unless the diameter can decrease. In some case we actually drill a large hole in a piece to allow it to shrink a bit in diameter, which will change the circumference. Perhaps the best example of this is a wine barrel.
In any case, if the MC never changes (the piece was dried to the same MC that it will have in manufacturing and in use), then it will not crack. In practice, we can tolerate about a 2% MC change before we create a crack. A good finish allows and changes to occur more slowly.
The problem is that oftentimes wood is not dried to a low enough MC, so the finished piece will shrink in use. Many houses are at about 30% RH (6.0% MC), and many pieces of wood are above 8% MC. Companies with experience, will make sure that the wood is no wetter than 7.5% MC, and no drier than 6.0% MC. Many kiln operations have 5,000 pieces of wood in a kiln chamber and they sample only 10 pieces and that is the basis for saying that they are done drying. No wonder wet lumber (or too dry sometimes) is all too common. Of course, once dry, if stored at a wetter condition than it was dried to, the wood will gain moisture. Bad storage can screw up proper drying.
