克里蒙納名琴木材的化學處理

Abstract

史特拉底瓦里和瓜奈里所製造的樂器普遍被認為具有超凡的音色及品質，因此過去三個世紀，許多學者和製琴師投入了大量的精力來找出克里蒙納名琴的秘密及關鍵，其中一個假說是克里蒙納製琴師所使用的木材性質與現代的木材有所不同。因此我們針對了現代木材、歐洲古建築和克里蒙納提琴中的楓木和雲杉樣品進行了分析，並發現了克里蒙納樂器具備獨特的特徵：經由衰減全反射-傅立葉變換紅外光譜（attenuated total reflection-Fourier-transform infrared，ATR-FTIR），我們觀察到在名琴中發生了半纖維素的脫乙醯化和木質素特殊的氧化，後者增加了名琴樣品的羰基含量，並且在13C多重交叉極化核磁共振光譜（13C multiple cross-polarization nuclear magnetic resonance spectroscopy，multiCP NMR）也觀察到相同的結果；另外藉由電感耦合電漿體質譜法（inductively coupled plasma-mass spectrometry，ICP-MS），我們觀察到史特拉底瓦里和瓜奈里提琴中的一些元素含量異常增加，尤其是具有大量的Na、Cl、K、Ca和Al，其中這些元素並非來自於木材生長的自然環境、也不是來自於人為的污染而極有可能來自於製琴師在木材處理上施加了各自的化學配方；為了確認Al在克里蒙納名琴中的功能而測量了27Al核磁共振光譜（27Al magic angle spinning NMR，27Al MAS NMR），其中在名琴樣品中發現了六配位和四配位的Al，而現代木材中僅有六配位的Al；另外以同步輻射X-射線繞射分析（X-ray diffraction，XRD）觀察到纖維素的結晶度在名琴中保持完整，結晶狀的區域大小沒有明顯的改變。綜合以上結果，克里蒙納的製琴師們很可能將木材泡入礦物質的溶液使木材吸收礦物質，並藉此改變了木材的性質，化學處理搭配上自然老化以及長時間振動可能是重現克里蒙納名琴超群聲音的關鍵。

So far, the violins made by Antonio Stradivari and Giuseppe Guarneri were generally considered as having extraordinary quality over three centuries. Therefore, lots of scholars and luthiers invested their lives to figure out the secrets in Cremonese violins, and one of the hypotheses is that the wood properties used by Cremonese luthiers are different from modern tonewood. Analyses of maple and spruce samples removed from modern tonewood, old buildings and Cremonese instruments were implemented, and the unique characteristics in Cremonese instruments were revealed. By attenuated total reflection-Fourier-transform infrared (ATR-FTIR), we observed the deacetylation in hemicellulose and unusual oxidation in lignin which increased carbonyl in Cremonese samples. The similar result was also observed by 13C multiple cross-polarization nuclear magnetic resonance (multiCP NMR) spectroscopy. By inductively coupled plasma-mass spectrometry (ICP-MS), we observed unusual elemental profiles in Stradivari and Guarneri violins, especially the increases of Na, Cl, K, Ca and Al, which cannot be explained by natural variations or human contamination, and may have come from the chemical recipe for wood treatment. To find out the function of Al inside the Cremonese instruments, 27Al magic angle spinning (MAS) NMR spectra were measured, and six- and four-coordinate Al were confirmed, while only six-coordinate Al was observed in modern tonewood. The crystallinity of cellulose remains intact and without obvious alteration in the domain sizes measured by synchrotron X-ray diffraction (XRD). From the combined results of these analytical methods, the Cremonese luthiers were likely to have soaked the wood into the mineral solution to make the wood absorb the minerals, thereby changing the properties of wood. It seemed that the combination of chemical treatments, natural aging, and long-tern vibration could be the key to reproduce the extraordinary sound of the Cremonese violins.