Animal skin,as a natural polymer material with abundant sources,was used to make various leather items in early human society.Ancient books,archives,and other cultural relics made from them carry profound cultural value.Studying the internal structure of them can provide good theoretical support for the protection and inheritance of cultural relics^[1].For example,artifacts such as parchment and Chinese shadow puppets that have not been tanned with tanning agents are called untanned hide artifacts.This system combined traditional production methods and modern processing techniques to study the performance changes of untanned hide during the production process.

The research method for untanned hide referred to IDAP(Improved Damage Assesment of Parchment)^[2],and quantitative and qualitative measurement methods such as SEM and FTIR^[3] were used to measure the effects of different pretreatment methods and chemical reagents on material properties.

The treatment methods for the samples in this study include saponification or emulsification reactions for defatting the raw skin,and adding different depilatory reagents, including alkaline reagents such as sodium sulfide or gastric protease,to the pretreated samples.

The analysis of infrared spectra in the study can reveal the effects of different chemical reagents on the peak shift of untanned Pete's characteristic,and SEM scanning can observe the changes in its intrinsic fiber configuration.The wet heat shrinkage temperature and stress-strain curve reflect the changes in its mechanical properties.