Louis Menand has a meditation on Harvard’s Rothko murals and their light-powered restoration:

Rothko’s work is pretty much all about the color, so the murals, in their faded condition, seemed to be dead. Because of the methods and materials Rothko used (a long and interesting story), it was impossible to restore them by conventional means. So a solution was borrowed from a technique known as “compensating illumination,” which was pioneered by the art conservator Raymond Lafontaine. Five digital projectors have been programmed to light the canvases so that the original colors reappear. At four o’clock every day, the projectors are turned off one by one, and the colors revert to (mostly) muddy blacks and grays. You can still see the bones of the murals, the formal architecture—Rothko’s floating blocks, made to resemble portals in these pieces—but the glow is gone. As one observer put it, when the lights go off, comedy turns into tragedy.

It’s interesting that this is so interesting. When the museum staged events with discussions of the virtually restored murals, hundreds of people turned up. The “back from the dead” aspect of the phenomenon is captivating: you are seeing, or you feel that you are seeing, something that once was believed to have vanished forever. You also (this is why people come to watch the projectors turned off) get to see the Rothkos both as they were and, almost simultaneously, as they are. You experience a transformation that took many years in a few seconds.

Watching Them Turn Off the Rothkos  (The New Yorker)