Silk cultural relics in museum collections have high historical and artistic value, but silk materials are easy to crack and embrittle in the exhibition process. Since infrared light and ultraviolet light do not contribute to the illumination of cultural relics, the basis for effective lighting protection of silk cultural relics is to find an effective method to evaluate visible light damage to silk materials. Mechanical damage is the main photochemical damage form of silk cultural relics, which is essentially the change of its internal molecular structure. However, due to their limitations, the commonly used chromatic aberrationand Raman spectroscopy cannot effectively measure the microstructure of silk cultural. Studies have shown that infrared spectroscopy is suitable for measuring the microscopic changes of silk cultural relics, and the characteristic signals characterizing tyrosine and crystallinity in the spectrum can effectively reflect the influence of ultraviolet light on the structure and properties of silk fibroin. However, the effectiveness of the two in characterizing the damage of visible light to silk materials remains to be clarified. This study obtained the photoaged samples of silk cultural relics through irradiation experiments of ten narrow-band light sources. Two damage evaluation parameters, tyrosine index T-FTIR and crystallinity index C-FTIR > were defined based on the infrared spectral analysis of the samples. Based on using T-FTIR and C-FTIR to describe the damage law of visible light to silk samples, their performance to characterize the coupling response of silk materials to visible light wavelength A and exposure Q was further analyzed. The results of correlation analysis between Q and T-FTIR showed that, except for the 595 nm irradiation group (Sig< 0. 05), Q has no significant effect on TFTIR ( Sig > O. 05), indicating that T-FTIR is not suitable for characterizing the light responsivity of silk. The results of correlation analysis between Q and C-FTIR showed that, Q has a significant effect on C-FTIR (Sig <0. 01). They are strongly correlated ( |Pearson| > 0. 9), indicating that C-FTIR can effectively characterize the response characteristics of silk materials to Q. The results of linear regression analysis between Q and C-FTIR showed that although they are not suitable for a linear regression model (R-2<0. 8), Q is explanatory for C-FTIR (Sig<0. 05); the effect of lambda on C-FTIR is different, but there is no mutation, indicating that C-FTIR has the potential to characterize the response characteristics of silk materials to lambda. According to the above analysis conclusions, the silk light responsivity function f (lambda, Q) based on C-FTIR was constructed by polynomial fitting. The fitting evaluation parameters showed the function has good interpretability (coefficient of determination R-2 >0. 8, sum of squares due to error SSE and root mean squared error RMSE tend to 0). Finally, the lighting damage model D = integral S-780(380)(lambda) f (lambda Q) d lambda of silk cultural relics was proposed, and a typical exhibition lighting source was selected to verify it. The 380 results of paired sample T-test (Sig>0. 05) indicated that the model could accurately calculate the lighting damage of silkcultural relics. This study can provide effective help for evaluating lighting damage, determining light source damage, and formulating lighting standards of silk cultural relics in museum collections.
