Understanding Ring Shake and Bacterial Action

      The Wood Doctor explains the bacterial causes of ring shake. September 5, 2011

I cut a fair bit of red oak, and the butt logs often tend to split around the circumference of an entire growth ring. There must be a name for this phenomenon, but more importantly, is there a way to avoid this and what is it caused by? I'm not talking about the normal end checking that happens with all logs that aren't end coated.

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
Cracks that follow the rings are called shake. Some folks might call it ring shake and others, wind shake. In any case, the failure is caused because the wood has been weakened in the tree by bacteria. The bacteria also create a foul odor, and increase the wood's green MC. In some species, the MC is so high that the logs do not float (called sinkers). In drying, because of the weakening, the wood is likely to check and honeycomb even under normal drying conditions. Also, in drying, because of the high MC and reduced flow of water, the wood tends to develop wet pockets (water pockets) or wetwood.

The bacteria enter the tree through the roots (they are "no air" bacteria, so they like wet soil) and move up the tree about 1" per year. That is why you only find them in the butt end of the bottom log. They exist in pockets within the log, so not all the lumber in a log is infected; oftentimes, it is just the bottom two feet of a few pieces from the butt log.

From contributor B:
Is that just in oak, or in most/all woods? Also, is that the reason (or likely to be) I sometimes see logs for sale that are listed as "not the butt end of the log"?

From Gene Wengert, forum technical advisor:
This is in all species, but in some it seems worse. Oak, cottonwood, and hemlock are some really bad ones for sure.

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