史特拉底瓦里小提琴木材性質的化學研究

三個世紀以來，史特拉底瓦里 (Stradivari) 小提琴，因其非凡音色而聞名於世。至今許多理論試圖闡述其獨特音色成因，其中之一是認為史特拉底瓦里使用的製琴木材與現代製琴木材，在材料本質上有所不同。為了證實這個理論，本研究中，使用了核磁共振光譜儀（nuclear magnetic resonance, NMR），X光繞射法（X-ray diffraction, XRD），差示掃描量熱儀（differential scanning calorimetry, DSC），熱重分析儀（thermogravimetric analysis, TGA）和電感耦合等離子體質譜儀（inductively coupled plasma-mass spectrometry, ICP- MS），分析從四個史特拉底瓦里和一個瓜奈里 (Guarneri) 提琴背板上，取得的楓木木屑樣本。藉由核磁共振光譜，發現史特拉底瓦里提琴木材，其化學主成分有所改變，約三分之一半纖維素含量分解和輕微地木質素氧化。而結晶性纖維素，透過X光繞射法，量測其晶體尺寸，發現三百年來並沒有明顯改變，仍保持結構上的穩定。由於半纖維素含量減少，史特拉底瓦里提琴木材，於熱重分析表現出較低程度的平衡含水量。而另一熱分析，差示掃描量熱法，則驚訝地觀察到，史特拉底瓦里小提琴木材有獨特地放熱曲線，但史特拉底瓦里大提琴和現代製琴楓木卻沒有。因此我們推測，這種獨特的放熱模式，可能與小提琴木材，經歷長期高頻振動有關。此外，為了確認斯特拉迪瓦里楓木是否經過化學處理，採用電感耦合等離子體質譜儀，測定木材樣品的元素含量。史特拉底瓦里的楓木相比於現代製琴楓木，富含高濃度的元素含量，如B，Al，Ca，Cu，Na，K和Zn。其中，鋁離子會與木材纖維分子產生交聯，鋁離子以三種類型的配位鍵結（四、五和六配位）存在於小提琴木材中，但大提琴和現代楓木卻只含有六配位模式。史特拉底瓦里小提琴的分析結果，闡明化學處理，自然老化和長期高頻振動的綜合作用，會賦予木材獨特的化學特性。現代小提琴製琴師，可以根據本研究的發現，嘗試以各種化學或物理方式處理現代製琴木材，或許能再現史特拉底瓦里小提琴的非凡音色。

關鍵字

史特拉底瓦里；克雷莫納；弦樂器；木材處理；木材老化；意大利小提琴

並列摘要

Stradivari violins were renowned for their extraordinary tone over three centuries. There are many hypotheses to explain the unique tone, one of which is that the wood used by Stradivari is different from modern tonewood. In this study, we used a combination of five analytical methods including nuclear magnetic resonance (NMR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and inductively coupled plasma-mass spectrometry (ICP-MS) to analyze maple specimens removed from four Stradivari and Guarneri instrument. By NMR, we observed around one-third of the hemicellulose undergoing decomposition and slight lignin oxidation in Stradivari instruments. In Stradivari’s maple, the crystalline cellulose remained stable to provide structural support, without obvious alteration in crystalline domain sizes measured by synchrotron XRD. By TGA measurement, Stradivari maple showed lower equilibrium moisture content due to the reduction of hemicellulose. Surprisingly, in DSC measurement, there were unique exothermic profiles observed only in Stradivari violins, but not in his cellos and natural maples. We speculated that the distinctive pattern may be due to long-term high-frequency vibration in violins. In addition, to confirm whether Stradivari’s maples were subjected to chemical treatment, the elemental content of maple specimens were measured by ICP-MS. The unnatural elemental abundance in Stradivari’s maples compared to natural maples demonstrated complex mineral treatments containing B, Al, Ca, Cu, Na, K, and Zn. Among these, the boron and aluminum in the violins were confirmed to crosslink with the wood fiber molecules. For aluminum, there were three types of coordination sites in violins (4-,5- and 6-coordination), but only one type in the cellos and modern maples (6-coordination). It seemed that the wood used by Stradivari was subjected to the combination of chemical treatments, natural aging, and long-term vibrations, and hence exhibited distinctive chemical properties compared with modern tonewood. Therefore, modern violinmakers may experiment with various chemical and physical treatments of tonewood based on our findings and try to reproduce the extraordinary sound of the Stradivarius.