Mineral Preservatives in the Wood of Stradivari and Guarneri

Following the futile efforts of generations to reach the high standard of excellence achieved by the luthiers in Cremona, Italy, by variations of design and plate tuning, current interest is being focused on differences in material properties. The long-standing question whether the wood of Stradivari and Guarneri were treated with wood preservative materials could be answered only by the examination of wood specimens from the precious antique instruments. In a recent communication (Nature, 2006), we reported about the degradation of the wood polymers in instruments of Stradivari and Guarneri, which could be explained only by chemical manipulations, possibly by preservatives. The aim of the current work was to identify the minerals from the small samples of the maple wood which were available to us from the antique instruments. The ashes of wood from one violin and one cello by Stradivari, two violins by Guarneri, one viola by H. Jay, one violin by Gand-Bernardel were analyzed and compared with a variety of commercial tone woods. The methods of analysis were the following: back-scattered electron imaging, X-ray fluorescence maps for individual elements, wave-length dispersive spectroscopy, energy dispersive X-ray spectroscopy and quantitative microprobe analysis. All four Cremonese instruments showed the unmistakable signs of chemical treatments in the form of chemicals which are not present in natural woods, such as BaSO4, CaF2, borate, and ZrSiO4. In addition to these, there were also changes in the common wood minerals. Statistical evaluation of 12 minerals by discriminant analysis revealed: a. a difference among all four Cremona instruments, b. the difference of the Cremonese instruments from the French and English antiques, and c. only the Cremonese instruments differed from all commercial woods. These findings may provide the answer why all attempts to recreate the Stradivarius from natural wood have failed. There are many obvious implications with regard to how the green tone wood should be treated, which chould lead to changes in the practice of violin-making. This research should inspire others to analyze more antique violins for their chemical contents

Parametric Experimental Modal Analysis of a Modern Violin Based on a Guarneri del Gesù Model

Mechanical effects and dynamic behaviour of a modern violin, built on a Guarneri del Gesù model, were examined via parametric experimental modal analysis. Among the few mobile components of a violin, the soundpost has a particular relevance for the final acoustic performance, even if its dimensions are extremely small. Therefore, the aim of this first research is to understand the violin sensitivity to the soundpost position considering its influence on the overall structural-vibrational behaviour. Experimental modal analysis was performed in six different configurations, related to different positions of the soundpost inside the violin, including both the outer possible locations and optimal position, generally defined by the violinist according only to the perceived best acoustic performance. Six “Signature” modes were identified and tracked in all configurations, comparing mode shapes, damping and natural frequencies of involved modes, in order to find a correlation between mechanical vibrations and acoustic performance of the instrument. The effects of the soundpost position on the modal properties of the “Signature” mode shapes are highlighted and discussed. Finally, the potential role of soundpost as a practical engineering tool to improve the signature and sound quality is discussed