THE IDENTIFICATION OF BLUE PIGMENTS IN EARLY SIENESE PAINTINGS BY COLOR INFRARED PHOTOGRAPHY
FROM THE findings of this study we can begin to trace patterns of the occurrence of ultramarine and azurite in early Sienese panel paintings. As the data collected indicate, the more costly blue pigment, ultramarine, was generally found in most abundance on the large, prestigious altarpieces of the period. However, the choice of ultramarine rather than azurite varied, sometimes considerably, from artist to artist and period to period. During the earliest decades under scrutiny, ca. 1260–80, ultramarine was used quite extravagantly in a number of large commissions from the shop and circle of Guido da Siena, but by the next generation, ca. 1285–1315, we see a considerable drop in use. Ultramarine is included only in the most e1ite paintings produced by Duccio's shop, and in four large and relatively important altarpieces azurite was the primary blue, chosen even for the Virgin's mantle. One possible explanation, which requires further investigation, is that the discovered drop in the use of ultramarine resulted from a rise in price due to a decline in availability of the imported pigment.
For the third generation of Sienese painting the interpretation of the evidence is more straightforward. Simone Martini stands apart from his contemporaries in his heavy and almost exclusive use of high-grade ultramarine. The high quality of his materials cannot help but reflect his success as an artist and the consequent prestige of his commissions. Simone clearly took pride in using the best that was available and was fortunate enough to be able to afford to do so.
This study has also drawn attention to the creative ways in which Sienese artists, particularly those of the generations following the Black Death, exploited the coloristic potential of the variety of grades of ultramarine blue. Artists such as Luca di Tommè in his St. Anne Altarpiece took pleasure in the decorative display of the different tones of the precious pigment across the surface of their panels.
Finally, and perhaps of most general value and interest, there is our heightened awareness of the symbolic way in which ultramarine could be employed in early Sienese images. As Michael Baxandall has pointed out in relation to 15th-century paintings, “the exotic … character of ultramarine was a means of accent that we, for whom dark blue is probably no more striking than scarlet or vermilion, are liable to miss” (Baxandall 1988, 11). Baxandall draws our attention to one particularly instructive example: in Sassetta's St. Francis Renouncing His Heritage (National Gallery, London), one panel from the Sansepolcro Altarpiece of ca. 1442, the gown that St. Francis takes off and leaves behind is a luxurious robe painted in ultramarine, and thus the gesture of discarding it is symbolic of Francis's entire renunciation of worldly goods for a spiritual life of poverty. We could add to this a similar example from another panel in this altarpiece: in The Whim of the Young St. Francis to Become a Soldier (National Gallery, London) the outer robe that Francis generously gives to a poor man is painted with ultramarine blue and glazed red lake shadow tones in order to simulate a lavish, and extremely valuable, velvet (Wyld and Plesters 1977).
In the Sienese 13th- and 14th-century altarpieces investigated in this study the expensive pigment, ultramarine, was usually reserved for the mantle of the Virgin, a traditional gesture of honor on the patron's and painter's part. And yet, as we have discovered, this was not always the case. Ultramarine might also be used to single out another significant protagonist in the composition. The figure of St. Peter in Duccio's Polytych No. 28 was accented in this way, as was the male donor in the Casciana Alta Altarpiece. Through the use of ultramarine the painters of these altarpieces, presumably on instruction from the commissioners, highlighted and drew attention to a favored saint and a donor-patron. It was a purely artistic means of paying respect.
THE AUTHOR would like to acknowledge the very generous assistance of Norman Muller, Hayden Maginnis, and Megan Holmes in the preparation of this manuscript. Furthermore, without the cooperation of the staff of several European art galleries the photographic research for this study would not have been possible. I would like to thank, in particular, the curatorial and support staff of the Pinacoteca in Siena; Monsignor Rosatelli of the Museo dell'Opera del Duomo in Orvieto; Erich Schleier and Claudia Laurenze of the Gemäldegalerie in Berlin-Dahlem, and Julian Treuherz and Xanthe Brooke of the Walker Art Gallery in Liverpool.