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Shakes are cracks in timber. Arising in cut timber they generally cause a reduction in strength. When found in a log they can result in a significant amount of waste, when a log is converted to lumber. Apart from heart shakes, often found in trees felled past their best, shakes in a log have no effect on the strength of shake free lumber obtained therefrom.[1]
They are often seen in oak-framed buildings, which are constructed of oak which has not been dried and thus cracks while drying. Due to the immense strength of the oak beams, they are not a cause for concern in a properly engineered building, and are considered part of the charm of the style.
In the majority of cases of shake, the underlying cause is a weakening of the wood due to action by anaerobic bacteria which have entered the tree stem through the root system. researchers have isolated anaerobic and facultative anaerobic bacteria from shake surfaces, in particular the anaerobes "Clostridiu".[2]
Research suggests that shakes develop due to natural stresses in wood which has been weakened by bacterial degradation of the middle-lamella between cells.[3]
- ^ Practical Home Woodworking. Odhams. 1952. pp. 62–3.
- ^ Ward, J.C., Kuntz, J.E., McCoy, E.M. (1969). Bacteria associated with 'shake' in broadleaf trees. Abstr. in Phytopathol. 59 (8), 1056. from Paper to 61st Ann Meeting of the American Phytopath, Soc., Spokane, Washington.
- ^ McGinnes, E.A. Jr., Phelps, J.E., Ward, J.C. (1974). Ultrastructure observations of tangential shake formations in hardwoods. Wood Science 6 (3), 206-211