Note 253 — Chapter XV · (XXIX.)

It has been noticed at some places, as at Torcello, that before the cubes were laid in the soft cement the whole design was washed in in colour on the surface of the cement. This facilitated correct setting and avoided any appearance of white cement squeezed up in the interstices between the cubes. On this particular feature of the mosaic technique Berger has founded an ingenious theory of the origin of painting in fresco. It is his thesis, in his Beiträge zur Entwicklungs-Geschichte der Maltechnik, I, München, 1904, that the ancients did not employ the fresco process, but that this was evolved in early mediaeval days out of the mosaic technique as seen, e.g., at Torcello. The stucco, that Vasari describes, must be put on portion by portion, for it only keeps soft two or three days, and can only be used for setting the cubes while in a moist state. Now, Berger contends, if the design for the mosaic be painted in colours on the wet stucco, and the whole allowed to dry, without any use of the mosaic cubes, we should have a painting in fresco, and he imagines that fresco painting began in this way. Unfortunately for the theory, (1), the testimony of Vitruvius and Pliny is absolutely decisive in favour of the knowledge in antiquity of the fresco technique, and, (2), the use of the coloured painting on the stucco as a guide for the setting of the cubes was not normal, and can never have been used so freely as to give rise to a new technique of painting. As a fact, this colouring of the stucco is objected to by the best modern workers on aesthetic grounds, for they point out that the lines of grey cement between the coloured cubes answer to the lead lines in the stained glass window, and should be reckoned with by the designer as part of his artistic effect. No doubt the older mosaicists, like the workers in stained glass, instinctively apprehended this, and had no desire for the coloured cement.