Characterization of Vegetable Tannins in Historical Leathers by ATR-FTIR Spectroscopy and Spot Tests (Study of a Leatherbottle Discovered in GhaleKooh-eGhaen)

Vegetable tannins are the main factor of tanning in historical leathers. The identification of tannins in vegetable tanned leathers is not only importantin determining chemical characterization, production technology and structural nature of the leather, but it is also efficient at the evaluation of new vegetable tannins for conservation purposes. Previous studies have also shown that chemical properties of tannin are the major factor in the stability of leather and its degradations. Therefore, it is necessary to identifythe type of tannin used in leather making process. Tannins can be classified as hydrolysable and condensed, each producing different properties in leather. In this study, types of tannin in a historical case were evaluated. The historical relic, discovered in GhaleKooh-eGhaen, was a leather bottle attributed to Seljuk period.This leather bottle was composed of different pieces of leather, andeight samples were obtained from the pieces. Tannin of samples was extracted and spot tests were applied to characterize tannin type and ellagitannins. Moreover, ATR-FTIR spectroscopy was applied for the assessment of chemical structure. According to the results, all samples were identified as vegetable tanned leathers. Spectra of extractions showed the presence of both hydrolysable and condensed tannins. There was a probable presence of ellagitannins and gallotannins as hydrolysable ones in some samples.