# Authentication of a Stradivarius \"Petite Violin\" Type from 1723
## 3 Results and Discussions
### Age Assessment of Violin  
The age evaluation of the violin was made on the basis of the archaeometric and chemometric characteristics identified by SEM-EDX analyses for wood, varnish and thermal for spruce wood. Based on previous experiences [3; 8; 9; 19; 43; 44; 45; 46; 47; 48; 49; 50; 51] regarding the identification of some archaeometric characteristics and, thus, the evolutionary chemometric ones with archaeometric value, in the present study, the following aspects were taken into account:  
* disposition of areas of varnish contamination and superficial dirt [52; 53];
* the depth of the presence of the archaeometric characteristics (the gradient of the penetration of oxidatively encrusted dirt in the volume phase of the varnish, the crystallinity index of the cellulose, its degree of lateral ordering and the intensity of the hydrogen bonds, and, thus, the remaining concentration of the ash of the wood sample) and the chemometric ones with archaeometric value (elemental stoichiometry ratios: C/O for wood, C/S and C/O for varnish and Si/Al for the encrusted dirt on the varnish) [54];
* the morphology of the surfaces, highlighting the iridescence, texture and microtopographical structures [55];
* the shape and ordering of the structures in the wood and the old, degraded varnish, in relation to the non-degraded areas of the two structural components (elemental stoichiometry ratios: C/O in the wood, C/S and C/O in the varnish and Si/Al in the encrusted dirt superficial) [56; 57; 58]. Both the archaeometric and chemometric characteristics place the violin as having been made around 1723. The data presented above show a good correlation between the two archaeometric characteristics highlighted in the wood and varnish samples (the gradient of penetration of the oxidatively encrusted dirt in the volume phase of the varnish at a depth varying between 0.6 and 2.5 \(\upmu\)m (with a rate of 5 \(\times\) 10\({}^{-3}\)\(\upmu\)m/year), the cellulose crystallinity index (1.17), the degree of lateral ordering (1.12), the hydrogen bond intensity (0.94) and the ash concentration of the wood sample (1.21%). Among the evolutionary chemometric data, with archaeometric functions for the wood sample, the data for new hydro-stabilized wood were established within our collective (Table 2). The elemental ratios were identified as follows: C/O = 0.7127 and Al/K = 0.75 (from alum). For the varnish layer, the following were identified: C/S = 47 of the gypsum preparation under the varnish, whereas C/O = 1.08 for the varnish and Si/Al = 0.5582 for the dirt layer on the surface of the varnish. These have changed significantly, which indicates an age of about 300 years. For example, for  
Figure 12: TG and DTA curves of the wood sample from the upper cover. the newly installed wood with the same treatments, the C/O ratio decreased from 0.801 to 0.713, with a rate of about 3 \(\times\) 10\({}^{-4}\)/year. In contrast, for Al/K, it increased from 0.692 to 0.75, with a rate close to 2 \(\times\) 10\({}^{-4}\)/year. The C/S ratio decreased from 51 to 47, with a rate of 1.3 \(\times\) 10\({}^{-2}\)/year, a change attributed to oxidative fouling processes. For varnish, because over time, the surface processes have been strongly influenced by very different environmental factors throughout the use of the violin, these ratios are not subject to the same laws of variation as for wood. Archaeometric features have an easily readable evolution rate. The values vary between 10\({}^{-3}\) and 10\({}^{-4}\), as determined by SEM electron microscopy, \(\upmu\)-FTIR spectroscopy and differential thermal analysis. The rates of evolution for the four groups confirm the age of the violin as approx. 300 years. The first C/S chemometric characteristic is related to the increase in porosity following the embrittlement of the plaster preparation (the thin plaster layer under the varnish) and the penetration of CO\({}_{2}\) in the presence of hygroscopic moisture (the carbonation process), the value of which decreases by 1.085\(\times\) compared to the reference.