In a museum where one should not touch the objects it's a bit weird to see people sitting on the mosaics. I asked what they were doing, and they explained they treated the mosaic with some substance that made their colours more intense. A bit like the bucket of water that one sometimes wants to throw over a dull mosaic. The effect seems to diminish so after a year or so a new treatment is necessary. The effect is startling, I hope the substance does not turn out to be degrading the tesserae.