Lighting quantity indexes for lighting traditional Chinese paintings based on pigments protection and substrates protection in museums

In museum lighting, traditional Chinese paintings are the artworks with the highest light sensitivity. They are vulnerable to the color damage to pigments and the mechanical damage to substrates after the irradiation from light sources. As the basis of effective preventive protection, the research on the two lighting quantity indexes of illuminance and annual exposure (illuminance × time) is currently missing. In this study, the halogen lamp was used as the experimental light source to conduct a 1440 h irradiation experiment on the samples of paper and silk substrates under 4 illuminance levels, respectively, and the test of infrared spectrum was carried out on the samples every 240 h. The oxidation index of paper and crystallinity degree of silk were calculated then. Three-dimensional visual curved surface plots of mechanical damage to samples with the change of illuminance and time were established and then fitted into damage evaluation equations, which revealed and described mathematically the mechanical damage law of samples. Through the equations, the recommended values of illuminance and annual exposure for samples could be calculated. Combining the previous researches on pigments, the lighting quantity indexes of traditional Chinese paintings with different combinations of substrates and pigments were proposed.