Rusticated Masonry
[See § 20, Rusticated Masonry and the Tuscan Order, ante, p. 65.]
In masonry of this kind the sides of the stones, where they come into contact with each other, are dressed smooth, but the face of each stone is left to project beyond the plane of the wall. The projections may be rough and irregular, in which case the appearance is that of natural stones, and a rugged rock-like aspect is given to the wall-face. The projections may however be wrought into bosses of regular form, or into the diamonds and facets of which Vasari goes on to speak, and of which a notable example is the so-called ‘Palazzo de’ Diamanti’ at Ferrara.
This method of treating stones, at least when they are left rough and irregular, saves time and labour, and hence it has been in use among many ancient peoples, but almost always for substructures and parts not meant to be seen. The Romans made a more extensive employment of it, and we find it not only on sustaining walls, such as those of the Hadrianic platform of the Olympeion at Athens, but on monumental wall-faces, as on the enclosing wall of the Forum of Augustus near the Arco dei Pantani at Rome, one of the finest extant specimens of Roman masonry but still utilitarian in character. The deliberate use of rustication, as an element of artistic effect, on the façade of a public building, is another matter, and it is doubtful if any instance of this occurs before the Italian Renaissance. There is a piece of Roman rusticated masonry behind the ancient theatre at Fiesole, the classical Faesolae, and Professor Durm thought at one time that the Florentine builders might have derived from this their idea of using the device as a means of expression in stonework. It may be questioned however whether this was visible at all in the fifteenth century, and it is much more likely that Renaissance rustication was a natural development from the treatment of the wall in many mediaeval Tuscan buildings, in which the surface of the stones is left to project in an irregular undesigned fashion. The Palazzo Vecchio and the Gothic Palazzo Alessandri at Florence are examples. In any case, in the hands of the architects of the Renaissance rustication became an important element in the architectural style of the period, and is one of the special contributions of this style to architecture at large.
Rustication has two artistic advantages. In the first place, it emphasizes the separate stones in an assemblage, and when these are of great size and boldly hewn, as at the Pitti Palace at Florence, the work gains in dignity through this individualizing of the distinct units of the structure. The bossed surface of some of the blocks at the Pitti stands out as much as three feet from the wall, and one of the stones is twenty eight feet in length. In the second place, this rustic treatment gives a look of rugged strength that is very effective, especially on the lower stages of monumental buildings, where indeed the treatment is most in place. The façade of Michelozzo’s Riccardi Palace, which Vasari refers to under its older name the ‘Casa Medici’ is epoch-making in its fine handling of rustication in degrees according to the stages of the elevation.
It needs hardly to be said that the elaborately cut facets which Vasari finds so beautiful, and of which we have seen an example in Fig. 4, ante, p. 69, are too artificial to be reckoned in good architectural style. It was a common practice, when the stones themselves were not all of the same size, to cut these diamonds and other geometrical forms in independence of the joints of the masonry, so that a facet might be half on one stone and half on another. As this ignores the individuality of the blocks, which the simpler rustication so effectually emphasizes, it is by no means to be commended. Vasari’s last sentences in § 20, about this treatment of stonework in general, are excellent. The rustication on the Fortezza, shown in Fig. 4 is sincere, in that the jointing corresponds with the design.