Revealing the photochemical damage behavior of acidified Xuan paper based on the spectroscopic investigation and principal component analysis.

In museums, there is a huge storage of Xuan paper cultural relics with profound historical and artistic significances. Exploring the photochemical damage behavior of Xuan paper that is generally in acidification, namely its damage mechanisms and laws, is crucial for the preventive lighting protection for paper cultural relics. In this study, the accelerated aging experiments in the range of visible light were conducted on Xuan paper samples with different degrees of acidification. The photochemical damage mechanisms of samples were traced, which is related with the synergistic effects of oxidation and hydrolysis reactions. It can be found that there is an effect of acidification, a long-standing material property of Xuan paper, on its damage, which further defines its preservation state in museums. On this basis, a spectral quantification method of infrared spectra combined with the principal component analysis was proposed to comprehensively analyze the photochemical damage law of Xuan paper in different preservation states. The analysis shows that the effect of acidification degree (pH values), spectra wavelength (λ), and their interaction on the damage to Xuan paper are statistically significant. Furthermore, the fitted mathematical function of pH values and λ is of great importance for evaluating photochemical damage, in order to further develop preventive lighting protection applications.