Chapter XV (Xxix.)
Of Glass Mosaic and how it is recognized as good and praiseworthy.
§ 94 Glass Mosaics
We have spoken sufficiently above, in the sixth chapter on Architecture, of the nature of mosaic and how it is made, and, adding here just so much as really refers to pictures, let us say that very great mastery is needed to arrange the pieces so harmoniously that the mosaic appears at a distance a genuine and beautiful picture, seeing that this kind of work demands great experience and judgement and a profound knowledge of the art of design. For if any one in his designs obscure the mosaic with too great wealth and abundance of figures in the groups, and with multiplying over-much the pieces, he will bring it all into confusion. Therefore the design of the cartoons made for mosaic must be open, broad, easy, clear, and carried out with excellence and in admirable style.243 The artist who understands the force of shadows in the design and of giving few lights and many darks, leaving in these certain vacant spaces or fields, he above all others will make his mosaic beautiful and well arranged. Mosaic to be praised must have clearness in itself, with a certain harmonious obscurity towards the shadows, and must be executed far from the eye with the greatest discretion that it may be esteemed painting and not inlaid work.244 Therefore the mosaics that have these qualities, are good and will be praised by everyone; and it is certain that mosaic is the most durable picture that exists. Other painting fades through time, but mosaic continually brightens with age; other painting fails and wastes away, while mosaic on account of its long life may almost be called eternal.245 For this reason we perceive in it not only the perfection of the old masters, but also of the ancients246—by means of those examples from their epoch that we recognize as such to-day, as in the Temple of Bacchus at Sant’ Agnese outside of Rome, where all that is there executed is exceedingly well done.247 At Ravenna also there is some very beautiful old mosaic in many places, and at Venice in San Marco, at Pisa in the Duomo, and at Florence in the tribune of San Giovanni,248 but the most beautiful of all is that of Giotto in the main aisle of the porch at St. Peter’s at Rome249—truly a miraculous thing in that kind of work—and among the moderns there is that of Domenico Ghirlandaio above the door outside Santa Maria del Fiore that leads to the Annunziata.250