## 3 Results and Discussion
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Raman Shift (cm\({}^{-1}\))**} & \multicolumn{3}{c}{**Type of Writing Ink**} & **Solvent** & & & \\ \cline{2-9}  & **A** & **B** & **C** & **Tetraethyleneglycol** & **2-Phenoxyethanol** & **Glycerol** & **DMF** \\ \hline
483 & & & + & + & + & + & \\
570 & & + & + & + & + & \\
594 & + & & + & & & + & \\
648 & + & & & & & & + \\
680 & & & + & & & & + \\
729 & + & + & & & & & \\
747 & + & & + & & & & \\
765 & & + & & & + & & \\
780 & & & + & & + & + & \\
805 & + & + & & + & & & \\
834 & & + & + & & & & \\
915 & + & + & & & + & & \\
1008 & & + & + & & + & & \\
1053 & + & & & & + & + & \\
1087 & + & & + & + & & + & \\
1142 & + & & + & & + & & \\
1177 & & + & & & + & + & \\
1184 & + & & + & & & & \\
**1266** & + & & & + & + & & \\
1308 & & + & + & & + & + & \\
**1340** & + & & + & & & + & \\
1450 & + & + & + & & + & & + \\
1488 & & + & & + & & & \\
**1587** & & + & & & + & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of the Raman peaks of writing inks with respect to the Raman peaks of the corresponding pure solvents. Figure 7: Electronic absorption spectra of writing inks of the A-, B- and C-types. The comparison of Raman peaks of dyes as well as data on the thermal degradation of volatile components and dyes [16] show that the field of application of Raman spectroscopy can be expanded and that this technique can be used not only for analysis in forensic science (the identification of writing ink dyes and the determination of the sequence of the placing of inscriptions, drawings, and stamps on paper [1; 2; 13; 17; 18]), but also for the estimation of age of the material placed on the paper beyond the period of chromatography capabilities. Thus, within the scope of the current work, we found that the time dependencies of heating for pure dye have a linear character with a small slope angle [16]. In all cases, when a period of writing ink storage on open air exceeds 1 to 1.5 years [22; 23; 24], it can be analyzed using Raman spectroscopy without preliminary sample preparation. If this period is insignificantly smaller, the removal of volatile component traces may be implemented by controlled isothermal sample heating at 60 to 90 degrees, with heating time determined according to Table 7. According to the gas chromatography results, one can conclude that the influence of other components of a writing ink, solvents in particular, on its spectral characteristics is mainly exhibited during the initial period after drawing on paper (up to six to 12 months). Returning to [16], monotonously increasing the character or characteristic peak ratio dependency on heating time in the initial period may be explained by influence of the solvent evaporation process. For example, the presence of tetraethylene glycol in writing ink accounts for its spectral contribution to the Raman peak at 1266 cm\({}^{-1}\). If the age of inscription is significantly less (up to one year), then there is no merit in applying Raman spectroscopy since spectral contribution of volatile components is significant and time period in question is quite small. In this case, the error margin of such dating has no advantages over a chromatographic method that has extensive bibliography and application experience [22; 23; 24]. Another observation found in the results is that there is no need to simply repeat the mistakes committed by many researchers who constantly try to find one and only method, which would be absolutely perfect to study the aging of writing inks. It is apparent that, to solve such an analytical problem, several methods should be applied side by side, and, after comparing the obtained results, one should try to get the needed outcome. Also, it is quite important to properly attribute all particular analytical signals to their corresponding processes and only after that to conduct the more complex analysis.