L'invenzione della nuvola

The ground colour in early Christian mosaics shifts from blue to gold. This story was told many times but the origin and meaning of the blue was never really studied. Considering this element on the long run it’s clear that the blue is not the naturalistic colour of the sky, but – at least since the Hellenistic period – connotes the genre of the image as official, public, “monumental”, classic, versus lighter colours, which are usually more apt for narrative and “Hellenistic” scenes. When in the early Christian period there is the need to place the scene of the fresco or of the mosaic in the sky, they need to add a new element: the cloud or the stars. The stars have a longer tradition in ancient classical art, but the cloud is completely new: it is used both on the blue and the gold ground to connote a “theological”, heavenly sky as an echo of the biblical symbol of the cloud alluding to the presence of God.