As professionals, my colleagues and I have had the experience of walking through the galleries after hours when the lights are off, a truly magical and privileged moment. The familiar paintings and sculptures are there like silent beings in the night, asleep but physically present. Shut down my video installations for the night, however, and nothing remains. Not only is there no movement or sound, there are also no images on the walls–only empty, cold rooms. No works of art are present, even in trace amounts. These pieces are not sleeping; they are dead. So the question becomes: Where did they go?

Bill Viola, “Permanent Impermanence,” Mortality, Immortality.  The Legacy of 20th Century Art. Miguel Angel Corzo, editor.  The Getty Conservation Institute, Los Angeles, 1999. (via thinkingconservator)