Qualitative detection of type of fat used to make a leather bottle attributed to Seljuk period by ATR-FTIR spectroscopy

Leather artifacts having degradable organic structures can rarely survive through the passage of time. Study and conservation of these artifacts has a great importance to better understanding of leather making process during the time. Some leather relics have been discovered in the excavation (2006) of Ghalee Kooh-i Ghaen related to Seljuk period. The relics were discovered from buried environment and were required to appropriate structural assessment. Type and content of free fats in leather have great information about leather making procedure and fats source. Also, the information helps to technologic study of Seljuk period. Characterization of fat source of fat source is one of the main problems in leather making process. In this approach, one of discovered leather bottles has been investigated to characterization of applied fats. Firstly, free fats of leather samples were extracted by dichloromethane (DCM) or methylene chloride solvent in Soxhlet extractor apparatus. Extracted fats were analyzed by a Fourier transform infrared spectrometer (FTIR) equipped with attenuated total reflectance (ATR) accessory with ZnSe crystal plate. The spectra were evaluated with explanation of main absorbance regions and comparison with documented spectra of fats and oils. Results indicated to 4.285% fat in the leather sample. It is a high content regarding to dry environment during the time. The high content of fatty acids in the leather sample shows the application of fats for waterproofing of leather bottle. ATR-FTIR results and comparison of spectra showed that animal fat (sheep or cow tallow) has been used for lubrication of leather.