Physical, vibro-mechanical and optical properties of pernambuco in relation to bow-making qualitative evaluation and wood diversity

Abstract

Pernambuco is the archetypal wood in modern bows of the violin-family. This species (Paubrasilia echinata) is endangered. Existing literature suggests remaining questions on how its properties’ variability relates to qualification in bow-making, and to diversity. Here 61 pernambuco specimens, with various qualitative evaluations by makers, are characterised for physical, elastic, dynamic, and optical properties. Results are compared with standard relations between-properties, and with 53 pre-selected tropical hardwoods. The tested pernambuco stands in the medium-upper range of these pre-selected species for density (ρ) and modulus of elasticity (E). It is exceptional for its very low damping coefficient (tanδ) and very intense colour (red a*, yellow b* and chroma C*). Within-species variability is high. Qualification is mostly associated to ρ, colour hue angle h° and gloss, then to elasticity – but E and E/ρ (specific modulus) overlap between groups. Qualification involves appearance (L*, h°, gloss) when freshly cut, and with anticipation of changes after ageing or finishing. The properties (damping, chroma) that make pernambuco exceptional among species, are not clearly related to the qualification within the studied sampling. Analyses help better understand the specificities of pernambuco, and highlight the multifactorial nature of wood selection at two levels: between-species preference, and within-species qualification.