THE IDENTIFICATION OF BLUE PIGMENTS IN EARLY SIENESE PAINTINGS BY COLOR INFRARED PHOTOGRAPHY
3 EXPERIMENTAL FINDINGS
IN THE mid-13th century, an extravagant use of ultramarine can be found in a number of large and seemingly prestigious commissions by Guido da Siena and his circle. Ultramarine blue is thickly applied for the mantle of the Virgin in the Madonna and Child Enthroned of 1262 by the San Bernardino Master (Torriti 1980, 23, color plate). This panel, now greatly cut down, must originally have been a huge, important work in the tradition of Coppo di Marcovaldo's Madonna del Bordone (Sta. Maria dei Servi, Siena) of 1261 and Guido da Siena's Palazzo Pubblico Maest� of ca. 1270 (Eglinski 1963, 205–12).
Extensive use of ultramarine is also found for draperies in two important dossals in the Siena Pinacoteca from the shop of Guido da Siena. In Dossal No. 7, attributed to Guido da Siena and datable ca. 1271–79, a thick coat of dark ultramarine was used for the mantle of the Virgin, and a lighter ultramarine, perhaps of a lower grade, was employed for the gown of St. John the Evangelist, the cloth sash of the Christ Child, and the inner portion of the Virgin's headdress (Torriti 1980, 26, color plate). The relative transparency of this lighter ultramarine in the painting and the weakness of its red translation in the color infrared photograph suggest that a lower grade ultramarine is present rather than a mixture of high-grade ultramarine and the opaque white lead pigment. For Dossal No. 6, ascribed to a close follower of Guido and dated ca. 1280, high-grade, dark ultramarine is again found for the Virgin's mantle, whereas a lighter ultramarine was employed for the gowns of St. Paul and St. John the Evangelist (Torriti 1980, 32, color plate). These dossals have both been cut down at either end; they each most likely had two extra figures of saints. In reconstructed form they would constitute the largest polyptychs to survive from the 13th century (Eglinski 1963, 125, 135–43). They represent two of the major commissions remaining from the period, and, as their materials indicate, they were very expensive to produce.
In contrast, the small Madonna and Child Enthroned (Pinacoteca, Siena), is a much more minor product from the workshop of Guido da Siena (Torriti 1980, 31, color plate). Predictably azurite was chosen for the Virgin's mantle. This miniature shop-replica of Guido's magnificent Palazzo Pubblico Maest� was clearly not a prestigious commission, as the small size, together with the inferior quality of workmanship and materials, suggests.
In general, a less extravagant use of ultramarine is found in paintings by Duccio and his workshop. Ultramarine is extensively used only in certain of the most important commissions, most notably Duccio's Maest� of 1308–11, which was adorned in the expensive fashion appropriate for the high altar of the Duomo in Siena. Ultramarine was identified in many locations on the Maest� when the work was examined and restored at the Istituto Centrale del Restauro in Rome, and no other blue pigments were found (Brandi 1959, 197). In addition, the predella panel of the Transfiguration from the Maest� was tested by scientists at the National Gallery in London, and Christ's robe was found to be ultramarine (Plesters 1966, 75). Ultramarine has also been identified in the mantle of the Virgin in Duccio's small, exquisite Triptych (National Gallery, London), indicating that some investment of materials was put into this high-quality work (Plesters 1966).
Nevertheless, for many of the altarpieces produced by Duccio and his workshop azurite was used, even for the Virgin's mantle. Beginning with an early work, the blue of the Virgin's mantle in the huge and magnificent Rucellai Madonna, commissioned for a chapel in the Florentine church of Sta. Maria Novella in 1285, has been identified during the recent cleaning as azurite (Del Serra 1990). The now-dark mantle of the Virgin in the Madonna and Child (Galleria Nazionale, Perugia)—formerly part of a polyptych most probably designed for the high altar of San Domenico in Perugia sometime after 1304 (Teuffel 1979)—is azurite, blackened by a layer of discolored varnish caught in the matrix of azurite particles. Given the importance of these two commissions the choice of azurite is quite surprising.
Similarly in Duccio's large Polyptych No. 47 of ca. 1311–18 (Pinacoteca, Siena), which came from the Ospedale di S. Maria della Scala, an important and prestigious Sienese institution, the darkened mantles of the Virgin and St. Agnes are azurite. The colors used in Polyptych No. 28 (Siena, Pinacoteca), which is usually dated just before the Maest� of 1308–11, are particularly difficult to interpret with the naked eye because of the distorting effects of a thick layer of yellow varnish (Torriti 1980, 51, color plate). However, color infrared photography reveals that the Virgin's mantle and the robe of St. Paul are azurite but that ultramarine has been used for the inner robe of St. Peter. The robe of the angel in the pinnacle above St. Peter is also ultramarine. Blue in combination with yellow is conventional for St. Peter; still, it is interesting to discover that in this altarpiece St. Peter is given preference over the Virgin through the selective application of ultramarine. Duccio may have had a reason for giving prominence and honor to St. Peter. Yet nothing is known for certain concerning the original location of this polyptych or its patronage. Stubblebine (1979, 1:65) tentatively associates the work with a polyptych that was on the high altar of the abbey church of San Donato in Siena, whereas White cautiously suggests a location in a Dominican institution because of the inclusion of Sts. Augustine and Dominic (White 1979, 63). Duccio's reasons for singling out St. Peter must, for the moment, remain a mystery.
Another interesting distribution of ultramarine and azurite occurs later in a work associated with the circle of Simone Martini, the Casciana Alta Altarpiece (San Niccol�, Casciana Alta, Pisa; on deposit in the Museo di San Matteo, Pisa) by an artist close to Lippo Memmi and datable to the early 1320s (Cannon 1982; Bagnoli et al., 1985). Although the mantle of the Virgin in this polyptych is azurite (with ultramarine added later for quite large areas of restoration), ultramarine is used for other draperies. The shadows of the Christ Child's creamy white tunic are ultramarine, and, as might be expected, the luxurious gown of the donor figure, lined with ermine, is ultramarine. On the other hand, the choice of ultramarine for the draperies of two of the pinnacle figures—the robe of St. Paul above St. Matthew and the mantle of Isaiah above St. John the Evangelist, both relatively unimportant parts of the composition—is more puzzling. Evidently ultramarine was not reserved for the mantle of the Virgin in every case. Other figures could be honored with a robe of ultramarine, or, occasionally, in an altarpiece of some value, ultramarine might be used somewhat haphazardly throughout the composition.
In the context of late 13th- and early 14th- century uses of blue pigments, the findings for works by Simone Martini and his shop that were investigated are the most illuminating. These works were the Pisa Polyptych of 1319 (Museo di San Matteo, Pisa), the Orvieto Polyptych(figs. 1–3) and the Madonna and Child with Redeemer and Angels from the early 1320s (Museo dell'Opera del Duomo, Orvieto), the Lamentation (Gem�ldegalerie, Berlin-Dahlem), which is one panel from the Orsini Passion Polyptych probably painted ca. 1334–37, and the Return of the Young Christ from the Temple dated 1342 (Walker Art Gallery, Liverpool) (Contini and Gozzoli 1970, color plates). Ultramarine was used almost exclusively for the blue draperies in these works. Even the blue or partially blue draperies of the small figures along the predella of the Pisa Polyptych are ultramarine. The only exception is the robe of St. Paul in the Orvieto Polyptych, painted with azurite. Furthermore, the ultramarine used in these paintings seems to be consistently of a high grade. Lighter blues, because of their opacity and the pure light blue rather than gray quality of their appearance, seem to have been produced by the addition of lead white to high-grade ultramarine rather than by using ultramarines of lower quality.
Such extensive use of superior quality ultramarine is not totally unusual among Simone's predecessors in Siena. We did discover a heavy use of ultramarine in important commissions produced by the workshop of Guido da Siena and his circle in the period ca. 1260–80. Nevertheless, in the products of artists from the generation directly preceding Simone—paintings from the workshop of Duccio—ultramarine was used more sparingly, reserved for the most expensive projects.
Significantly, the lavish use of ultramarine found in Simone Martini's paintings also stands apart in relation to the use of blues by his contemporaries in Siena, the Lorenzetti and their circle. Color infrared photography indicates that Pietro Lorenzetti used high-quality ultramarine for the Virgin's mantle in the large and elaborate Carmine Altarpiece of 1329 (Pinacoteca, Siena) (Torriti 1980, 97, color plate). But in the somewhat later and more ordinary Polyptych of San Giusto (Pinacoteca, Siena), probably by a close follower of Pietro, the Virgin's mantle and the light blue robes of Sts. Peter and Paul are predominantly azurite (Torriti 1980, 105, color plate). In this case, the slightly purplish appearance of the robes of Sts. Peter and Paul on the color infrared photographs suggests that a small amount of ultramarine blue may have been layered over the azurite. This technique may represent an economy measure: the thickness and intensity of the blue was ensured with less expenditure of ultramarine. The technique has been identified by Plesters in a number of later Venetian Renaissance paintings and according to van Os is “a common technique in early Flemish painting” (Plesters 1966, 64; Os et al., 1978, 16).
It is perhaps surprising to discover that the mantle of the Virgin in Ambrogio Lorenzetti's Annunciation of 1344 (Pinacoteca, Siena) is an intense, high-grade ultramarine, as this panel seems to have been commissioned for the Office of the Biccherna in Siena, a relatively unprestigious location (Torriti 1980, 125, color plate). Other findings for works from the shop of Ambrogio Lorenzetti are less puzzling. Azurite was chosen for the Virgin's mantle in two medium-sized and moderate commissions, the Sta. Petronilla Altarpiece datable ca. 1340 (Pinacoteca, Siena) and the Serre di Rapolano Madonna and Child also of ca. 1340 (Pinacoteca, Siena) (Torriti 1980, 110, 120, color plates).
As regards the later 14th-century Sienese painters, the most interesting feature discovered is their creative use of the full range of grades of ultramarine. In Bartolomeo Bulgarini's St. Peter Enthroned with Sts. Paul and John the Evangelist of ca. 1340 (Pinacoteca, Siena), where a substantial amount of fine-quality ultramarine is used for the blue and purple robes of St. Paul and the blue lining of St. Peter's mantle, low-grade ultramarine ash appears for the grayish lining of St. John the Evangelist's mantle (Torriti 1980, 134, color plate). Similarly, in Luca di Tomm�'s St. Anne Altarpiece, dated 1367 (Pinacoteca, Siena), a dark, high-grade ultramarine is employed for the mantle of the Virgin, and a lighter, medium-grade is found for the robe of St. Agnes. A third color variation is produced by using gray ultramarine ash with the addition of a small amount of red lake for the mantle of St. Anne in the altarpiece (Torriti 1980, 157, color plate). A technical quotation provides another interesting example: Pietro Lorenzetti's use of ultramarine ash for two figures in his Birth of the Virgin of 1342 (Museo dell'Opera del Duomo, Siena) painted for the major altar dedicated to St. Savinus in the Siena Cathedral, was imitated by Paolo di Giovanni Fei in his later painting of the same subject (Pinacoteca, Siena) datable ca. 1380–90 (Torriti 1980, 180, color plate). In addition, several other instances of the use of a variety of grades of ultramarine have been detected, most notably in the Polyptych No. 51 (Pinacoteca, Siena), a joint work by Niccol� di Ser Sozzo Tegliaci and Luca di Tomm�, where high-grade ultramarine is found for the Virgin's mantle and lower-grade for the mantle of St. Thomas, and in Jacopo di Mino Pellicciaio's Polyptych no. 58 (Siena, Pinacoteca), where dark, fine-quality ultramarine is used for the mantle of the Virgin and a poorer quality, lighter variety for the mantle of St. John the Baptist and the inner robe of St. Augustine (Torriti 1980, 151, 145, color plates).