Chiral characteristics of thin wood sections

In common with most natural materials, wood displays chirality (handedness) at several length scales. At the wood cell wall level, the most important expression of chirality is the right-handed helical winding of the S2 layer. This chiral structure has been invoked previously to explain the tendency of individual fibres and thin paper strips to twist in a given direction with changes in moisture content. Some evidence for a corresponding macroscopic chiral deformation of wood is presented here. Thin sections of neverdried wood from juvenile red spruce (Picea rubens Sag.), red pine (Pinus resinosa Air.) and balsam fir (Abies balsamea L.) twist to give right-handed helical strips when viewed along the grain. This tendency was observed with neverdried sections, before and after drying, and even with some sections cut from kiln-dried lumber. The results suggest that a chiral internal stress is present in many wood specimens.