Physical and mechanical properties required for violin bow materials

Pemambuco (Guilandina echinata Spreng. syn Caesalpinia echinata Lam.), which has been used for the production of violin bows, was compared with alternative wood species from some physical and mechanical aspects and the reasons for why it is suitable for bows were discussed. A low value of loss tangent (tan delta) may be helpful for bow material, as the tan delta of pernambuco was much lower than that of the other wood species. On the other hand, the most suitable Young's modulus could not be clarified, but the lower limit of Young's modulus needed for the bow must exist. Low tan delta of pernambuco seems to be due to a high content of extractives. However, not only the quantity but also the chemical component and/or the location of extractives in the wood structure may have a different effect on the tan delta. From the result that the wood with a higher extractive content showed a lower softening temperature, it can be concluded that the extractive in pernambuco is probably influential in the thermal bending of the bow. Redness (a*) of pernambuco has a correlation with tan delta. Indentation hardness of pernambuco was somewhat higher at the same level of specific gravity than that of the other wood species, but hardness would not be an inevitable property for the bow.