Résumé
Boxwood (Buxus sempervirens L. and sometimes also B. balearica Lam.) is an important material in the making of many woodwinds for early music and/or traditional music (including oboes, bagpipes, clarinets, recorders…), where its aptitude to turnery, precise edges and beautiful polish are much appreciated. Boxwood is also an emblematic material in several other traditional woodcrafts. Surprisingly enough, there are virtually no scientific publications about its physical-mechanical properties. The main scientific data available indicate that this hardwood does not produce tension wood, but instead compression wood like softwoods. The presented project originated from interviews with French makers of woodwinds for whom boxwood is essential, who were facing many problems of dimensional stability at all steps from felling the tree/shrub, to seasoning the wood, to turning the instrument, and finally playing it. On the one hand, variability of wood used by makers was sampled (>100 specimens). On the other hand, a wide experimental plan (approx.150 specimens) started from biomechanical measurements on a living “archetypal” tree of 110 years, that restored verticality in a steep mountain slope. Lab-measurements were made of its internal profile of residual growth strains, and on hygrothermal recovery, followed by assessment of green wood properties, then drying behaviour is assessed stepwise. Air-dry mechanical properties are measured on both samplings (variability of makers’ material, and “from standing tree to making conditions”). Measured physical-mechanical properties include isotherms of sorption and associated shrinkage/swelling, ultrasonic velocities in the 3 principal directions, and dynamic Young’s modulus and damping at audio-frequencies. First results highlight boxwood as a peculiar wood material, and show that the atypical compression wood formed in this hardwood does show strong mechanical similarities with those of softwoods. Work currently in progress aims at relating the material properties to hygro-mechanical behaviour of wooden tubes machined from the same sampling, to assess the deformation of resulting woodwinds instruments.