Wood strength and stiffness

[bstewert]

A little over my head, but pretty interesting:

http://www.fpl.fs.fed.us/documnts/pdf2001/green01d.pdf

 

[woodworkingboy]

Temperature effects on wood properties as it translates into the changes in moisture content, is generally very noticeable when working with the material. Perhaps only a moisture content difference of six or seven percent when you compare kiln dried to air dried, but how the wood responds to working it can be quite different. The difference in strength/resiliency is quite apparent. Pull a shaving from a hand plane apart or crush up a bunch in your hand, and the less dry wood is much springier. Unfortunately in this hurry up world that we live in, most commercial wood products get baked to death. Particularly with hardwoods, in the kilns the wood loses a lot of it's color, one of the most valuable qualities of wood for interior work. You can dry it slower in differently designed kilns and not have that loss so much, but it isn't so profitable that way. People selling the wood, mainly don't care about depriving the material of it's beauty or the subsequent loss of strength. Stability is a factor with dryer wood, but more compromise can be allowed if you want to go for the ultimate worth of the material.

Steam bending dryer or wetter material really gives clues to strength changes. What will bend easily at a higher moisture, will easily also crack when a few points lower in moisture in the wood to begin with before steaming it. Easy enough to see how that translates to hinge strength when you compare living to dead trees.