# Authentication of a Stradivarius \"Petite Violin\" Type from 1723
## 3 Results and Discussions
### Micro-FTIR Analysis  
From the data of \(\mu\)-FTIR spectra (Figure 10), based on the two groups of vibrations (deformation and valence), it is possible to identify the structural groups belonging to cellulose (1318, 1172, 1043 and 895 cm\({}^{-1}\)), lignin (1602, 1513, 1463, 1431, 1377 and 1234 cm\({}^{-1}\)), calcium sulfate (1121, 1089 and 676 cm\({}^{-1}\)), alum (617 cm\({}^{-1}\)) and borax (1653 cm\({}^{-1}\)) [2; 30; 31; 32]. The peaks in the range 2906-2744 cm\({}^{-1}\) represent the deformation vibrations of the symmetric C-H bonds in cellulose and hemicellulose [23]. The variations of the FTIR spectra around the value of 2906 cm\({}^{-1}\) show that these absorption peaks increase with aging, the mechanism of which is based on the degradation process by oxidation and acid-base hydrolysis [33]. Instead, the increase in the intensity of the 1653 cm\({}^{-1}\) band can be attributed to the CO group and the COO group at 1602 cm\({}^{-1}\), respectively. Both demonstrate evolutionary oxidative and hydrolytic processes [34]. The peak at 1513 cm\({}^{-1}\) is a marker for lignin. Figure 8: EDX spectrum for the varnish sample, zone 3. Figure 9: EDX spectrum for the varnish sample, zone 4. Over time, the FTIR signals at 1653 and 1602 cm\({}^{-1}\) are the most affected due to the aging processes. Furthermore, the group of absorption bands in the region 1400-1200 cm\({}^{-1}\) corresponds to the crystalline component of cellulose [35]. Peaks with frequencies at 1431, 1377 and 1318 cm\({}^{-1}\) are very sensitive to the degradation process of crystalline cellulose [36]. The peak at 895 cm\({}^{-1}\) represents amorphous cellulose [36, 37]. Of interest is the peak at 813 cm\({}^{-1}\), which can vary in shape from the appearance of a shoulder to a small peak. This may be due to the presence of a substituted aromatic ring, an aliphatic C=C group or a furan group. Lignin and hemicellulose show this peak when they are aged [37]. The crystallinity index of the cellulose from the analyzed samples can be determined by calculating the ratio between the intensity of the absorbances corresponding to the bands which are characteristic of the crystalline and amorphous domains of cellulose (1377 cm\({}^{-1}\) (C-H band), 1431 cm\({}^{-1}\) and 895 cm\({}^{-1}\) and 2906 cm\({}^{-1}\)). Thus, the ratio between the absorbance of the band at 1377 cm\({}^{-1}\) and that at 2906 cm\({}^{-1}\) corresponds to the crystallinity index, and the ratio between the absorbance of the band at 1431 cm\({}^{-1}\) and that at 895 cm\({}^{-1}\) can be attributed to the strength of the bonds of hydrogen [38, 39]. The cellulose crystallinity index from the FTIR spectra is calculated according to the following relationship [40]: \(\chi\) = A1377/A2906, where \(\chi\) is the cellulose crystallinity index, and A1377 and A2906 are the characteristic absorbances of the bands from 1377 and 2906 cm\({}^{-1}\). The degradation rate of cellulose fibers was determined by calculating _the crystallinity index_ (IC), _the degree of lateral ordering_ (GOL) and the _intensity of hydrogen bonds_ (IlegH). Table 1 shows the values of the crystallinity indices, the degree of ordering, the intensity of hydrogen bonds and the energy of hydrogen bonds calculated from the IR spectra for the spruce wood sample taken in the study. The high values of the index are correlated with the higher amount of type I cellulose. According to the data in the table, it can be concluded that the crystallinity index of the sample justifies the degree of degradation due to both hydrolytic cleavage and oxidation processes of glycosidic groups. \begin{table}
\begin{tabular}{c c c} \hline
**Crystallinity Index** & **Degree of Lateral Ordering** & **Intensity of Hydrogen Bonds** \\ (**IC**) & (**GOL**) & (**IlegH**) \\ \hline A\({}_{1377}\)/A\({}_{2906}\) = 1.17 & A\({}_{1431}\)/A\({}_{896}\) = 1.12 & A\({}_{3420}\)/A\({}_{1318}\) = 0.94 \\ \hline \end{tabular}
\end{table}