Identification of collagen-based materials that are supports of cultural and historical objects

The TG, DTG, DTA methods were used for investigation of the thermal degradation in static air atmosphere of some collagen-based materials (some sorts of collagen, recent manufactured parchments and tanned leathers, patrimonial (historical) leathers). At the progressive heating, all investigated materials exhibit two main successive processes, associated with the dehydration and thermo-oxidative degradation. The patrimonial leathers were divided in two groups, namely: a group containing the majority of the analyzed materials, for which the rates of the thermo-oxidation process are substantially lower than those corresponding to the recent manufactured leathers, and a group for which the rates of thermo-oxidation process are closed to those corresponding to the recent manufactured leathers. Consequently, if by the thermal analysis in air atmosphere of a leather sample, a value of the rate of the thermo-oxidation process smaller than that corresponding to the recent manufactured leathers is obtained, then the analyzed leather is a patrimonial one. The reciprocal statement of this qualitative criterion for distinction between recent manufactured leather and patrimonial leather is not valid. The DSC analyses of collagen-based materials were performed in air (DSC(air)) and in water (DSC(water)). The denaturation process takes place at lower temperatures in water than in air. Unlike recent manufactured leathers and parchments, each patrimonial leather exhibits on DSC(water) plot 2-4 peaks. Consequently, the number of peaks from DSC(water) curve could be another qualitative criterion for distinction between a recently manufactured leather and a patrimonial leather.