Inside Drying Wood

Cross-section of poplar wood as it dries.

Wood must dry before it can be used in most applications, but with its complex internal structure exactly how wood dries out has been unclear. New experiments combining MRI and x-ray imaging reveal a process quite different than expected.

Inside hardwoods like poplar — the species studied here — wood contains both solid structures and pores where water can gather. The pores do not form a fully interconnected network, so capillary action alone is unable to carry water through the pores and out to a surface where it can evaporate.

Instead, researchers found that water evaporating at the surface came from so-called “bound water” in the wood’s solid structures. As the bound water evaporated, it caused water in the wood pores to diffuse into the solid walls, becoming bound and continuing to feed the evaporation. (Image and research credit: H. Penvern et al.; via APS Physics)

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