LED illumination-induced fading of traditional Korean pigments

Light is an important factor in the conservation of museum collections because of its strong electromagnetic characteristic that can degrade artifacts. To investigate the effects of illumination on paintings, particularly in museums equipped with popular light emitting diode (LED) lamp systems, we investigated the fading process of traditional Korean pigments. We used four illumination conditions: a combination of high and low color rendering index (CRI) at two light temperatures of T-cold = 5600 K and T-warm = 3200 K. Among all samples tested, realgar, also known as Wunghwang in Korea, showed the most marked change in color. UV spectrometric analyses after 100 h of exposure at 11 000 and at 5500 lux showed high color differences exceeding the color change threshold under all illumination conditions. When the illumination intensity was reduced to 300 lux, T-cold lamps showed a faster fading process than T-warm lamps did, suggesting that appropriate illuminating conditions can reduce the adverse effects of museum lighting systems. A further experiment using narrow-band, single-color, LED lamps showed how specific wavelength bands could influence the fading of artifacts In particular, we newly confirmed that discoloration of Wunghwang could be induced by the illumination of green light, in addition to blue light generally known to induce discoloration. These results demonstrate that the fading of a specific pigment of the artifacts in museum collections can be minimized by tuning the intensities of the wavelengths of light emitted by the museums' lighting systems. (C) 2018 Elsevier Masson SAS. All rights reserved.