Disposable Indicators for Monitoring Lighting Conditions in Museums

The photo-induced alterations of light-sensitive artifacts represent one of the main problems that conservators and curators have to face for the environmental control in museums and galleries. Therefore, an increasing attention has been recently devoted to develop strategies of indoor light-monitoring, especially aimed at minimizing the cumulated light exposure for the objects on exhibit. In this work a prototype of a light dosimeter, constituted by a photo-sensitive dyes/polymer mixture applied on a paper substrate, is presented. This indicator, especially designed for a preventive assessment of the risk of damage for highly light-sensitive objects, undergoes a progressive color variation as its exposure to the light increases. Different, easily distinguishable color-steps are exhibited depending on the light-dose received, so that the dosimeter can be straightforwardly used to have a first, instrumentation-free, estimation of the total light exposure. A reflectance spectroscopy study carried out on sets of artificially light-aged samples was performed in the 350-860nm range, in order to investigate the response of the dosimeter to the light and study the fading mechanism. Two different approaches were evaluated for the calibration of the prototype: colorimetry and principal component analysis of the reflectance spectra. The usefulness of the two methods in providing a quantitative indication of the light-dose received was evaluated.