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- Caracterização através de análise química da escultura portuguesa sobre madeira de produção erudita e de produção popular da época barrocaPublication . Barata, Carolina; Carballo, Jorgelina; Cruz, António João; Coroado, João; Araújo, Maria Eduarda; Mendonça, Maria HelenaMaking use of several analytical techniques, four erudite and four popular Portuguese baroque wooden sculptures were studied. The materials and techniques employed were identified and the relationship between their artistic quality and the materials used was investigated. In general, the pigments were common at the time, but one pigment discovered in the beginning of the 18th century and two rare arsenic pigments were also identified. In popular sculptures cost-saving was detected, particularly concerning the gold leaf. Regarding some technical procedures identified, recommendations found in historical documents did not seem to have been entirely followed, neither in erudite nor in popular sculptures.
- The materials and techniques of polychrome baroque wooden sculpture: three works from Baião, Portugal, studied by an integrated, complementary analytical approachPublication . Barata, Carolina; Cruz, António João; Carballo, Jorgelina; Araújo, Maria EduardaThree polychrome wooden sculptures, made between the last quarter of the 17th century and the first half of the 18th century, from a monastery in Northern Portugal, representing an episode of the Passion of Christ, were analysed with three aims: to identify the materials and techniques employed; to clarify the relationship between the three sculptures; to reveal previous restorations. Techniques such as radiography, energy dispersive X-ray spectrometry, optical and polarized light microscopy and Fourier Transform infrared spectroscopy were employed. White lead, vermillion, umber, carbon black, gypsum, anhydride and chalk were identified as pigments and fillers. These materials and the layer structure led to the conclusion that sculptures 1 and 2 were treated as a pair of sculptures and that they underwent at least two restorations: the first was probably done in the workshop where they were made. During the second restoration, the heads were replaced. Sculpture 3 is not restored and its poorer style seems to have correspondence to materials of lower quality.
- Synchrotron X-ray diffraction of bole layers from Portuguese gilded baroque retablesPublication . Barata, Carolina; Rocha, F.; Cruz, A.J.; Andrejkovičová, S.; Reguer, S.Studies based on a scientific approach to materials and techniques used in Portuguese gilded retables from the Baroque are very scarce and focus particularly on works with erudite features and on the characterization of the superficial gold leaf. The conservation and appearance of gilded surfaces, however, depended on the qualities of the clayey ground layer underneath, which is the bole. Colour and texture are closely related to its mineralogical composition. Boles were healing clays. Red to orange varieties could also be used for gilding, usually agglutinated with animal glue when the gold surface was meant to be burnished. Armenian was the name used to identify the best quality material. Microsamples collected from erudite and popular gilded retables, respectively belonging to the city of Oporto and its rural surroundings, were selected for elemental and mineralogical characterization. It was intended to shed light on the characteristics of boles used in Portuguese retables and to understand if there are any differences between materials used in works of distinct artistic quality. Elemental analysis was performed through SEM-EDS. SR-XRD was used for phase identification, performed with a six-circle diffractometer at the DIFFABS beamline of SOLEIL Synchrotron. Portuguese clay standards of identifiable composition and provenance were also analysed. The results suggest that boles are mainly kaolinitic, with variable amounts of illite and smectite. Gypsum was used as an extender. Although the proportions of the main clay minerals are similar in erudite and popular works, in Oporto homogeneity is clearly higher.