Illumination of light-sensitive exhibits

When displaying light-sensitive exhibits, no lighting level can be considered harmless. The energy contained in light triggers a photochemical decomposition leading to the fading of colours. The less light falling on an exhibit, the less damage is caused. Important in such cases is not the absolute lighting level but the exposure (lxh), i.e. the product of illuminance (lx) and duration of illumination (h). From a conservation point of view the specification of lux hours with exhibits documents a just acceptable level of damage by light, but not the ideal lighting for presenting sensitive art.