The Art and Science of Illuminated Manuscripts
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colour – the art and science of illuminated manuscripts 118 section seven: masters’ secrets Masters’ Secrets 7 Stella Panayotova and Paola Ricciardi he rich hue, delicate texture and palpable volume of the bishop’s blue robe Tin the Metz Pontifical (Cat. 6, ill. 7.1) produce a luminous, three-dimensional effect. How many pigments did the artist use? Did he mix them or apply them in separate layers? Were the same materials used for the blues in the initial and border? Were they painted at the same stage, by the same hand? What do the pigments reveal about the artist’s skill or the patron’s taste and purse? Are they typical or unusual for the time and place of production? Scientific analysis may not answer all of these questions, but it divulges many a master’s secret. The basic palette and painting methods of illuminators are well known from recipe collections, artists’ manuals and meticulous observations (see Essays 2, 5). What we may glean under the microscope or from historic sources can be corroborated, amended and expanded by scientific analyses. Cutting-edge technologies allow us to penetrate beneath the painted surface without touching it. The identifications of illuminators’ materials and techniques that extend beyond the common ones reveal surprising levels of sophistication, ingenuity and experimentation. Technical analyses, long established as scholarly and conservation tools in other artistic media, constitute a more recent, rapidly developing branch of research in the field of manuscript studies.1 As their precision, specificity and pace of development increase, they can advance our knowledge about medieval and Renaissance painting in general – for three main reasons. Firstly, the sheer number of surviving manuscripts – some with hundreds of images within their covers – offers the richest resource for the identification of artists’ materials and techniques; no other types of painted artefacts survive in comparable quantities from the Middle Ages and early Renaissance. Secondly, less exposed to the elements, social upheavals and unsympathetic restoration than panel paintings, frescoes, polychrome sculpture or stained glass, most manuscripts preserve their original pigments in a superior condition. Finally, some illuminators were documented as working in other media, notably easel or wall painting, mosaics, glass or metal. Identifying the materials and techniques of their illuminations offers insights into the transfer of technological expertise across media. Analytical protocol The variety of painting materials employed by illuminators requires the use of multiple, complementary analytical methods in order to clarify their identity. The wish to characterize painting techniques calls for an even larger set of analytical tools. For a comprehensive interpretation of the methods of production, the technical data need to be considered alongside evidence gathered within the fields of manuscript studies and social, political, intellectual and art history. ill. 7.1 Fitzwilliam Museum, MS 298, Since 2012, the MINIARE project has examined fifty-six volumes and an equal number of fol. 73r illuminated fragments – a total of almost four hundred illuminations. Our integrated, cross- 119 colour – the art and science of illuminated manuscripts Near-infrared imaging Summary of pigments and paint binders identified 120 section seven: masters’ secrets Site-specific spectroscopic methods (FORS and XRF) Additional methods such as Optical Raman spectroscopy and MA-XRF scanning microscopy ill. 7.2 Analytical protocol used by the MINIARE project for the non-invasive analysis of illuminated manuscripts 121 colour – the art and science of illuminated manuscripts disciplinary study of the manuscripts begins with codicological, textual, palaeographical and art-historical examination of structures, contents, scripts, iconography and style, with identifications of liturgical uses and heraldic devices when relevant. Historical investigation sometimes reveals the specific circumstances of communities and individuals involved in the manuscripts’ creation or early use. This cumulative evidence about places and dates of production provides the broad framework for the technical analyses, while art history and codicology formulate specific questions about artists’ materials, techniques and division of labour. Our technical analyses employ only non-invasive analytical methods – no samples are taken and the instruments approach the painted surfaces without touching them. Sampling is the quickest and most reliable method for the identification of artists’ materials. Commonly used in the investigation of polychrome sculpture, panel and wall paintings, its suitability for manuscripts is debatable due to their smaller painted surfaces and thinner layers of pigments. Sampling is sometimes used, ranging from the rubbing of pigments with a cotton swab or testing of damaged areas, offsets on the facing page and debris in the gutter to the removal of microscopic paint cross-sections.2 These methods are justified by the reliability of the results, the minimal handling of the original and the small samples that leave lacunae almost invisible to the naked eye.3 However, even the tiniest loss of material – visible or not – compromises the integrity of the manuscript, weakens the delicately painted area and could result in further loss of pigment over time. In monumental painting sampling is sometimes required by conservators to inform conservation treatments. Such samples are taken in existing areas of damage that are usually restored. By contrast, damages in manuscripts are not normally repaired, as most manuscript conservators do not infill paint losses (see Essay 8). Even when the conservation of manuscripts involves consolidation of pigments, their identification is welcome as an explanation of the damage observed, but rarely required for the treatment. The choice of the consolidant is determined by the support (parchment or paper) and it is applied to actively deteriorating pigments regardless of their chemical composition. While non-invasive, in-situ techniques involve more handling than the removal of samples, with careful planning and proper support, the scientists’ use of a manuscript is no different from that of manuscript scholars or conservators. Moreover, a sample or two could never build the comprehensive picture offered by non-invasive analyses of the entire painted surface. Finally, the increasingly sensitive non-invasive techniques, especially when used in combination, can identify most inorganic materials as reliably as sampling. The identification of organic colourants and binders as well as complex mixtures still presents challenges, but our intellectual curiosity could exercise patience and spare the illuminations until suitable non-invasive methods are developed. To answer the questions formulated on the basis of the combined evidence, we developed a multi-step non-invasive analytical protocol involving the following methods (ill. 7.2; see Appendix): 1. Near-infrared (NIR) imaging, to investigate the presence and appearance of underdrawing, pentimenti and retouched or inhomogeneous areas; 2. Spectroscopic analysis by fiber-optic reflectance spectroscopy (FORS) in the ultraviolet-visible-near-infrared range (UV-vis-NIR) and by X-ray fluorescence (XRF) spectroscopy to identify pigments and paint binders; 3. Optical microscopy, aimed at supporting and clarifying the spectroscopic results, assessing the conditions of the paint layers, documenting damage, and suggesting the presence of pigment mixtures, layers, glazes and alteration compounds; 122 section seven: masters’ secrets 4. Additional methods including Raman spectroscopy, X-ray diffraction (XRD), Optical Coherence Tomography (OCT), Macro-XRF (MA-XRF) scanning, Fourier-Transform Infrared (FT-IR) spectroscopy, all carried out in collaboration with colleagues from multiple institutions in the UK, Europe and the United States (see Appendix). Apart from offering answers to pre-formulated questions, the technical analyses can yield unexpected results and raise new questions for manuscript experts and conservators.4 Secrets revealed The technical analyses undertaken by the MINIARE project since 2012 not only confirmed the wide-spread use of common materials and techniques across medieval and Renaissance Europe (see Essay 2), but also revealed shifting preferences for some colourants and increasingly sophisticated use of others over time. Furthermore, they identified a wider range of pigments and binders than previously found or suspected in illuminated manuscripts. Some of these newly detected materials suggest links between illumination and other media, and point to specific artistic centres. For instance, the three blues favoured throughout the Middle Ages and the Renaissance – ultramarine, azurite and indigo/woad – varied in availability and popularity in different periods and regions. They were sometimes used in combination to achieve stunning effects, such as the exquisite gradation of blues in the Metz Pontifical where all three pigments were employed (Cat. 6, ill. 7.1). Indigo provided a cool, blue-grey ground for the raised gold leaf in the initial’s inner background and the miniature’s frame. The initial’s outer background and the border ornament were painted with azurite. The miniature’s blue frame has a light blue base layer of azurite over which darker blue details were painted in ultramarine accompanied by lead white motifs. The bishop’s robe was painted with ultramarine and highlighted