Woodworking in America: The Shakes

No, not withdrawal from the overdose of the Woodworking in America conference. This is another kind of shakes.

During his session on understanding wood for chairmaking, Brian Boggs explained the concepts of wind shake and fell shake. Think of growth rings as layers (because they are). One of the things that holds the layers together is the wood fibers of the medullary rays. Wind shake, which is most common in cherry in my experience, is an internal separation between growth rings. The term "wind shake" is a bit of a misnomer, since the separation is not caused by wind moving and twisting the tree -- at least not directly. Wind shake occurs when a fungus enters the tree and attacks the growth rings. The fibers connecting the growth rings are compromised by the fungal attack. With these interstitial fibers weakened, movement from wind can be the culprit that separates the damaged growth rings. Wind shake manifests itself as checks (or cracks) inside a board. It should be avoided because it lacks structural integrity (sometimes, so do I). I'll post a picture later of some shakey cherry that I keep around just to have as an example.

Fell shake can occur when a tree is felled. The tree may crash against another tree or a log or fencepost or something that causes it to crack internally. It may also crack when it is felled because of its own weight or because it crashes onto pavement or frozen ground. Insect and/or fungal attacks can play a role in the integrity of a tree and can therefore contribute to the likelihood of fell shake.

It's important to note that these kinds of checking are different than the checks you almost always see at the ends of boards. These are caused by the fibers separating as the wood dries.

PS As always, I'm writing this, first, to learn about it myself and, second, to share what I've learned with anyone who's interested. If I'm off my rocker or write something that is just plain incorrect, please email me or comment. The last thing I want to do is misinform.

PSS Alternate title ideas for this post included Do you want some fries with that shake?, Shake me baby all night long, Shake it like a Polaroid picture, Shake it up (the Cars) and All Shook Up.