Shake in Coniferous Wood–An Anatomical Study

This study provides an excellent description of wood anatomy associated with ring shake. A separation between cells and the presence of loose fibers within the shake opening provides a basis to distinguish shakes that occur in the standing tree from tangential failures that occur during lumber manufacture. The preliminary study, in which both green and kiln-dried lumber were studied, indicated that tangentially aligned failures in wood apparently arise by either of two mechanisms–separations between the latewood cells or failure of the earlywood cell walls. The remainder of the research was on material from standing trees in order to identify the type of failure that forms before the trees are processed into lumber. In 72 of the 73 shakes observed in standing trees it was found that the cells had separated in the region of the compound middle lamella. The failure tends to occur among the last-formed cells of the growth increment, usually within ten cells of the ring boundary.

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