Giotto in Florence: Shedding New Light on the Peruzzi Chapel
Cecilia Frosinini, Opificio delle Pietre Dure e Laboratori di Restauro, Florence
Edmond J. Safra Visiting Professor, spring 2013
During my 2012 fellowship at CASVA I began to elaborate my study of the technical analyses carried out on the mural paintings by Giotto di Bondone in the Bardi and Peruzzi chapels in the basilica of Santa Croce in Florence. After enduring a long history of abuse, including damage accrued from whitewashing, in 1958–1961 both chapels were the focus of a restoration campaign conducted by Leonetto Tintori under the direction of Ugo Procacci. At the time, few forms of scientific analysis were available for fresco paintings, and in the intervening decades little attention was paid to the chapels from a technical point of view. Seeking a more precise understanding of Giotto’s artistic technique in the late phase of his career, in 2009–2012 the Opificio delle Pietre Dure and its scientific partners carried out an investigation with the support of the Getty Foundation. The results of this campaign are being published as a book, currently under editorial revision in Italy.
Much of my attention this year has been devoted to studying the results collected in the Peruzzi Chapel by means of ultraviolet fluorescence photography. The observation of works of art under long-wave UV light, which makes visible specific characteristics of painted surfaces otherwise invisible to the naked eye, is one of the most commonly used noninvasive means of analysis for paintings. Depending on their chemical composition, certain materials, especially organic ones, produce differently colored fluorescence under UV light. The distinctive luminosities emitted under such conditions can differentiate or make evident the presence of substances that are not clearly distinguishable in visible light. Aged varnishes also emit different-colored fluorescence depending on their chemical makeup.
Examination of the paintings of the Peruzzi Chapel under UV light revealed extraordinary details. The causes for this unusual UV fluorescence are unknown, but many hypotheses are viable. The intonaco layer may have an unusual composition, causing the anomalous UV scattering, or the artist may have employed unconventional painting materials. Other factors may be related to aspects of the murals’ conservation history, such as the removal of whitewash (which could have initiated a process of saponification) or the effects of past preservation treatments (probable albeit undocumented). Such treatments could have employed high-retention solvents or solvents that reacted strongly with organic materials in the paint layers. The presence of additional organic materials from previous treatments employing fixatives and consolidants or interaction between later restoration materials and the original materials may also be partially responsible.
Unusual fluorescence may also be due to the interaction of pigments and binders over time. The painting technique of the Peruzzi Chapel is generally considered to be a secco. Even if a more thorough analysis shows notable differences in technique from one part to another, it is most probable that the unusual results obtained by UV fluorescence are due to the use of the a secco technique and, in particular, the interaction between the binding medium that Giotto utilized and specific pigments. (It must be underlined that the analysis has shown the presence of numerous pigments incompatible with the technique of buon fresco, such as cinnabar, minium, malachite, verdigris, and orpiment.)
The current condition of the Peruzzi Chapel murals and the material contamination brought about through previous restoration campaigns has made definitive scientific analysis of the artist’s technique difficult. The chemical analyses that were conducted on several areas of the painted decoration during our diagnostic campaign revealed the presence of lipids, but only in some parts. In general, a proteinaceous binder was detected, probably egg. It is possible, therefore, that the application of whitewash to the murals in the eighteenth century could have saponified superficial fatty substances, making them more difficult to detect.
Notwithstanding these difficulties, the UV photos we gathered provide compelling physical evidence of the enormous importance of the Peruzzi murals for Giotto’s contemporaries and ensuing generations of Florentine artists. In these photographs the damaged figures become three-dimensional again. We can see all the chiaroscuro effects, the construction of bodies under garments, and the architectural rendering of the buildings. Many details that were no longer visible resurface, such as the folds of the garments and the expressions of the faces. The UV fluorescence photographic campaign is worthy of a full monographic study in itself. It will further allow us to propose new hypotheses regarding the chronology of the cycle and its influence on the contemporary and later Florentine school of painting. If it was difficult to imagine how the wall paintings would have appeared when just completed, now we have some better insights.
All the photographic materials will be made available online after the publication of a book on the UV images and the speculations we may make from them regarding the original appearance of the Peruzzi Chapel murals.