JOURNAL OF RAMAN SPECTROSCOPY J. Raman Spectrosc. 2006; 37: 1160–1170 Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/jrs.1604 Evidence for the degradation of an alloy pigment on an ancient Italian manuscript Maurizio Aceto, 1*,† Angelo Agostino, 2‡ E. Boccaleri, 3† F. Crivello 4 and A. Cerutti Garlanda 5 1 Department of Environmental and Life Sciences, University of Eastern Piedmont, via Bellini, 25/G – 15100 Alessandria, Italy 2 Department of General and Applied Organic Chemistry, University of Turin, C.so M. d’Azeglio, 48 – 10125 Turin, Italy 3 Department of Sciences and Advanced Technologies, University of Eastern Piedmont, Spalto Marengo, 33 – 15100 Alessandria, Italy 4 Department of Artistic, Musical and Performance Disciplines, University of Turin, Via S. Ottavio, 20 – 10124 Turin, Italy 5 Archive and Chapter Library of Vercelli, P.zza Angennes, 5-13100 Vercelli, Italy Received 2 September 2005; Accepted 7 May 2006 An unusual metallic pigment was identified on an ancient Italian manuscript containing the Homilies on the Gospels of Gregory the Great, belonging to the Archive and Chapter Library of Vercelli (Italy) and datable to the IX century. Green uncial text and part of decoration on this manuscript were described as ‘being of golden fashion’ in a book written at the beginning of XX century. Investigations carried out with portable XRF and Raman instruments revealed that the green colouration is actually the result of a marked degradation process that has altered the original composition of the pigment, an alloy of copper, lead and zinc. Probably because of the conditions of storage of the manuscript, the pigment tarnished owing a chemical process that could resemble the infamous ‘bronze disease’: that is, the conversion of metallic copper into inorganic salts. Measurements were performed both in situ, i.e. directly on the manuscript, and on small fragments of ink collected from the page gutters. Copyright  2006 John Wiley & Sons, Ltd. KEYWORDS: degradation; Italian manuscript; XRF; alloy pigment INTRODUCTION A major contribution of analytical chemistry to studies of the history of art is the identification of degradation processes on coloured artworks. Changes in colour have been known since the Middle Ages. In a letter to a friend, Pieter Paul Rubens stated ‘I am afraid that the fresh painting, after remaining so long packed in a case, may suffer a little in the colours, particularly in the flesh tones, and the whites may become somewhat yellowish’. The causes of these phenomena were of course not entirely known to ancient artists. Nevertheless, artists were soon able to select pigments and dyes according to their characteristics, choosing those that were more durable and lightfast and avoiding those known to alter after some time. What ancient artists could not foresee were the effects of modern pollution on their L Correspondence to: Maurizio Aceto, Department of Environmental and Life Sciences, University of Eastern Piedmont, via Bellini, 25/G – 15100 Alessandria, Italy. E-mail: maurizio.aceto@unipmn.it † Centro Interdisciplinare per lo Studio e la Conservazione dei Beni Culturali (CenISCo), University of Eastern Piedmont, via Manzoni, 8 – 13100 Vercelli, Italy. ‡ Istituto Nazionale Fisica della Materia (INFM), via Perrone, 3 – 13100 Genua, Italy. artworks due to increasing concentrations of chemicals such as H 2 S, SO 3 and NO x in the environment. At present we are able to explain which physicochemical reactions occur: light can induce structural changes in light-sensitive pigments and pollutants can react with either pigments or binders and cause chromatic alterations. All this information comes from the application of powerful analytical techniques to artworks. Analytical investigations on degraded coloured artworks are therefore important to identify the decomposition products, to try to explain the degradation process and to suggest a proper restoration intervention to conservators. Among the several techniques available at present, Raman spectrometry is particularly effective in terms of spatial resolution, sensitivity and, most importantly, the possibility of in situ application. Some works have been published that used this technique to spread light on degradation phenomena in artworks such as paintings 1 or frescoes. 2 As far as illuminated manuscripts are concerned, most of the published works have been devoted to the degradation of parchment or paper, but relatively few have focused on chromatic changes. Clark and collaborators 3–5 identified an alteration process occurring on the pigment lead white (2PbCO 3 ÐPb(OH) 2 ) that changes to black PbS, probably due Copyright  2006 John Wiley & Sons, Ltd.