Mosaics, Cosmati, and verre églomisé are important precedents for an examination of gilded glass in late medieval and early Renaissance Italian art because each of these techniques incorporates small clear glass panels backed with a sheet of gold leaf and would have been part of the visual vocabulary of artists such as Giotto,
Nicola Pisano, and Simone Martini. In the mosaic and Cosmati techniques, the piece of glass was entirely gilded, whereas in verre églomisé, or the reverse painted glass technique, only portions of the glass were treated with gold. Thus, while there are strong formal similarities among all three artistic techniques, important distinctions exist.21 What follows provides a brief history of each technique and an examination of how Nicola Pisano, Simone Martini, and Paolo di Giovanni Fei adapted gilded glass to their artistic objectives.
Gilded glass tesserae were used extensively in early Christian, Byzantine, Islamic, and medieval European mosaics. Artists from a wide range of times, loca-tions, and even religions, recognized how effectively clear glass panels backed with gold leaf could symbolize aspects of the divine. As early as Constantine the Great, the apses of Christian churches were covered with gilded tesserae, which may have functioned like symbolic messengers of divine enlightenment as they “appeared to extend the photismos imparted by Christ through baptism to the members of his church,” as Erkinger Schwarzenberg puts it.22 Eve Borsook’s study of the ways in which artists manipulated the tesserae—that is by tilting them, affixing them with their reverse side showing, and using silver in combination with gold—reveals that their irregular placement was specifically designed to “enhance the glitter.”23 Borsook finds further evidence that gilded tesserae were intentionally used to con-vey divine symbolism through their reflective surfaces in the many mosaic tituli that accompany them, which proclaimed both the spiritual and formal qualities of the mosaics they adorned.24
Mosaics with gilded tesserae also had practical, more mundane benefits.
The amplifying effects of the reflective tesserae would have illuminated the dark, mostly enclosed, interior spaces they decorated, providing greater visibility. And as Borsook explains, from at least the fourteenth century onwards, their role as a durable form of decoration was increasingly valued. Simultaneously, there was also growing interest in their costly nature and therefore a subsequent association with luxury and status.25
This is not to say that material value was not of interest during the earlier medieval period. After all, in the Byzantine tradition, gold was considered the most precious material in terms of both intrinsic and spiritual value.26 Even tes-serae without gold were highly valued because they were either made of some other precious material or they were fashioned using a high level of skilled crafts-manship. In fact, tesserae were so prized that they were treated as sought-after spoils. In one instance Charlemagne received tesserae which had been removed from churches in Ravenna, and in another, Venice was the beneficiary of a “ship-load” worth of the precious pieces after the 1204 conquest of Constantinople.27
Interestingly, the shift away from an interest in divine symbolism to more mundane motivations observed in mosaic imagery coincides with the increasing application of individual gold-backed glass panels in Italian sculptures and paint-ings. Thus, it is worth considering that the use of gilded glass in works such as the pulpit, tomb, and paintings under discussion here was both a continuation of the mosaic tradition and a new application of the medium, one which carried on gilded glass’s association with divine illumination, and one that suited the unique visuality of duecento and trecento Italy.
Although not as ubiquitous or well studied as mosaics, the cosmatesque technique—a variation of the ancient art of opus sectile, or cut work—was also a rich potential source of inspiration for artists using gilded glass, espe-cially those artists who had spent time in Rome. Cosmatesque, or Cosmati work, derived its name from the Cosmati family of Roman artists. The tech-nique involved assembling small pieces of stone, glass, or other materials into elaborate geometric patterns. Unlike mosaics, however, Cosmati typically does not feature figurative imagery or involve setting the tesserae at irregular angles;
rather, the pieces are set flat against a solid surface, and the designs they create are dominated by repeating geometric shapes and abstract patterns. Also unlike mosaic, the pieces of gilded glass used in Cosmati are more often standard-size tiles with smooth edges, flat faces, and consistent, geometric shapes, not irregu-lar shapes or surface textures.
This labor-intensive technique was most commonly used to decorate floors, tab-ernacles, altars, and tombs from the eleventh through the thirteenth century. Some of the most famous monuments decorated with Cosmati include the tomb of Hadrian V from ca. 1276 by Arnolfo di Cambio at San Francesco in Viterbo; the same artist’s ciborium at San Paolo fuori le Mura from ca. 1285; the tomb of Honorius IV from the 1280s in Santa Maria in Aracoeli; the tomb of Clement IV from 1271–74 at San Francesco in Viterbo; the high altar of the Upper Church in San Francesco, Assisi, from 1253; and the floor of Westminster Abbey.28 As this list indicates, although the technique is most commonly associated with Rome, monuments featuring Cosmati with gilded glass can be found throughout Italy and even farther abroad.
In addition to actual, physical, artworks with Cosmati, depictions of Cosmati can also attest to the medium’s captivating qualities. Two of the most famous panel paintings to feature Cosmati include works by Duccio and Giotto. As men-tioned in Chapter 2, Duccio’s Maestà altarpiece for the cathedral of Siena shows the Virgin’s throne covered in elaborate Cosmati with gilded glass as does the throne of Saint Peter in Giotto’s Stefaneschi Altarpiece, along with many other depictions of furniture in trecento art.
Orcagna’s Tabernacle in Orsanmichele, Florence, is another example of the long-lasting influence of the Cosmati technique. Though it now houses a paint-ing of the Virgin Mary by Bernardo Daddi, the monument was associated with a lineage of paintings depicting the Madonna that were credited with miraculous healing powers. To imbue the marble structure with a sense of holiness worthy of these miraculous images, Orcagna’s Cosmati included extensive use of glass panels throughout the spiral columns (Figure 3.2), in the reliefs, and especially in the depiction of the Assumption of the Virgin on the back of the tabernacle where reflective panels fill the sky and frame the scene. The style of Cosmati closely reflects the medieval Roman examples, which Orcagna may have seen firsthand on a 1350 trip to Rome to celebrate the Jubilee. As this monument was made midway through the fourteenth century, it will be discussed in more detail later in this chapter after an examination of the works by Nicola Pisano and Simone Martini, which predate it by several decades.