Closing the Gaps

I recently acquired some 5/4, rough-cut pieces of red oak. After I surfaced planed one of the boards … about 6 feet long … I noticed that there are some “gaps” or separations (splits) in the wood along the grain. Is there any thing that can be done for that? If so, what?

Michael Dresdner: The term “kindling” comes to mind. Internal voids and cracks in wood are never a good sign. They may come from problems when the tree was standing, but more often indicate improper drying or handling after cutting. One of the more common problems in oak due to poor drying processes is called “honeycomb” and consists of internal checks and voids that often show up only after the wood is planed. Often the wood adjacent to the cracks is also weak, and such wood is not a good choice for furniture that is meant to last.

Lee Grindinger: Your gaps and separations are most likely drying defects. Your description is not enough to really identify the type of checking you have so I’ll list a few. I’ll caution you that there is no good news here.

End checking is obvious from the end of the board. The split opens from the end and runs into the length of the board to varying degrees. End checking occurs because wood loses moisture up to 15 times faster out the end grain. Since the wood got drier on the end than the center and began shrinking something had to give. End checking to some degree is common and the fix is to either cut the damaged end off or rip the board to remove the crack.

Surface checking is another problem. Surface checking will appear as a series of cracks or splits along the length of a flatsawn surface of a board; there will be many checks on the face of the board and they will not extend more than halfway into the board. These occur because the surface of the board shrunk during drying around the fat and wet center and the shrinkage caused the wood surface to fail. Surface checking is worse on the surface of the board and these checks narrow as you approach the center of the board. Your only option here is to remove as much wood as you need to get past the checking.

Honeycomb is an internal crack. You’ll frequently never know a board is honeycombed until you cut it because the outside surfaces can be largely intact. The reverse of surface checking, the splits in honeycombed lumber get wider as you approach the center of the board. Honeycomb is caused by temperatures being raised too high too early in the drying process. There is no fix for honeycombing other than incineration in a woodstove or some other suitable place.

If you paid money for this wood you are entitled to a refund. Whichever defect you have, it is a defect. If you got the lumber from a reputable dealer get your money back or exchange the wood for new lumber.

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