Colour identification, degradation processes and findings in a fifteenth-century Book of Hours: the case study of Cofre n.º 31 from Mafra National Palace

Abstract

This paper presents the work done as part of a master dissertation on Conservation and Restoration at the Faculty of Sciences and Technology, Nova University of Lisbon. The "Cofre n.º 31" is a French fifteenth century Book of Hours from the Library of the National Palace of Mafra, Portugal. This prayer book, composed by illuminations and devotional texts, was in bad condition due mainly to the rebinding done between eighteenth and nineteenth centuries. According to the assessment of the state of conservation, the main damages observed in the text block and binding were: volume distortion, loose and deformed gatherings, distortion and cockling of folios, and damages in the illuminations. The pigments palette was identified by µ-EDXRF, FORS, µ-Raman and µ-FTIR, which is consistent with the materials used in the fifteenth century. Nevertheless, some particular application techniques such as mixtures and overlays were found, namely in the red colours and specifically in the metallic leaves. Some of these colours also show specific degradation: darkening of the mixture of minium and vermillion; silver tarnishing with strong migration into the parchment support, especially when associated with minium; detachment of azurite, lead white and its mixtures, such as flesh tones and light colours. The main deterioration processes associated to silver and pigments can be assigned to their reactions with humidity and air pollutants, to the grain size of the pigments and to mechanical factors related to the book binding and its use. The presence of different pigments application techniques in different groups of folios lead us to conclude for the existence of a pigments palette with variations, and finally, three different illuminators and two different techniques, confirming the proposals of art history studies.

Quantitative Analysis of Minium and Vermilion Mixtures Using Low-Frequency Vibrational Spectroscopy

“…In heritage science, there is demand for noninvasive and nondestructive techniques for determination of chemically specific data regarding composition and condition of cultural and historical artifacts . Proper characterization and identification of pure and mixed colorants in these artifacts are crucial steps in determining provenance and designing appropriate protocols for conservation and restoration efforts. − Various approaches for pigment identification are currently employed and include X-ray fluorescence spectroscopy and secondary-ion mass spectrometry, as well as near-infrared (near-IR), mid-IR, and Raman spectroscopies. − However, low-frequency vibrational spectroscopies that access ≤200 cm –1 (≤6 THz) vibrational motions in solid samples have attracted great attention in recent years. − Terahertz time-domain spectroscopy (THz-TDS) and low-frequency Raman spectroscopy (LFRS) are appealing methods for in situ studies of artifacts because of their specificities, acquisition times, and nondestructive approaches. − The utilization of these emerging techniques has been driven largely by improvements in instrumentation capabilities and costs, , and advances in the quantum mechanical solid-state simulations used to assign and interpret the spectral data. , …”

“…In this work, the focus is on the ancient pigments minium (Pb 3 O 4 ) and vermilion (HgS) because of their frequent use together in artists’ palettes and their visual similarity (see Figure ) necessitating analytical evaluation for quantification. ,,,− Previous terahertz ,− and Raman studies have reported the spectra of pure minium and vermilion, while mixtures of the two have been studied using other techniques including midrange Raman spectroscopy and first-derivative reflectance visible spectroscopy . Here, these inorganic crystalline pigments were investigated using a combination of THz-TDS, LFRS, and ss-DFT to fully characterize their sub-200 cm –1 vibrations.…”

The Book of Uí Mhaine: An Interdisciplinary Analysis of the Materiality of the Gaelic Manuscript Tradition

“…The overall lighter hue contribution could be associated with the presence of lead white, which was added to cinnabar to obtain the lighter red hue observed. Finally, the XRF of the purple/gray area (s18, Figure 8e) showed a prominent presence of Pb-based pigment(s), known to be prone to degradation towards brown and black colorations (galena, PbS) [42][43][44].…”

Pigments—Lead-based whites, reds, yellows and oranges and their alteration phases

“…)-century polychrome sculptures in the porch of the main and south portals of Ferrara cathedral (Pinna et al 2020); & 14 t h -century wood ceilings of the Hall of the Abencerrages and the Hall of the Two Sisters in the Alhambra at Granada (Arjonilla et al 2019a); & 14 th -century (third quarter) wall paintings of the Dominican Monastery at Ptuj in Slovenia (Gutman et al 2014) & 15 th (also 16 th ? )-century manuscripts on parchment (for the 15 th century, see, e.g., Chaplin et al 2005;Duran et al 2014;Bonizzoni et al 2016;Carvalho et al 2018; for a 15 th /16 th -century parchment see Vanmeert et al 2018); & 15 th -to 17 th -century panel paintings on wood or walnut (for the 15 th century, see, e.g., Duval 1990, 1998;Dunkerton and Roy, 1996;Hradil et al 2007;Bersani et al 2008;Ricci et al 2004;Sodo et al 2019;Gutman Rieppi et al 2020; for the 16 th century, see, e.g., Penny et al 1996;Higgitt et al 2003;Roy et al 2004;Mottin and Laval 2004;Plazzotta et al 2006 (doubtful); Borgia et al 2007;Hradil et al 2007;Dunkerton and Howard 2009;Amadori et al 2016;Želinska et al 2018; for the 17 th century, see, e.g., Roy 1999; Olszewska-Świetlik et al 2013); & 14 th -to 17 th -century wall paintings (for the 14 th and 15 th centuries, see, e.g., Perardi et al 2003;Gutman et al 2014;Arjonilla et al 2019a;Levstik et al 2019;Pinna et al 2020; for the 17 th century, see, e.g., Vlachou-Mogire et al 2020); & 17 th -and 18 th -century oil paintings on canvas (Feller 1973;Hradil et al 2007;…”