Gilded wood from the organ of the Church of Santa Cruz (Coimbra)

Abstract

A talha dourada é uma parte importante do patrimônio cultural português. Aproveitando uma intervenção no órgão da Igreja de Santa Cruz (Coimbra) procedeu-se à caracterização da talha dourada da sua decoração. Fontes históricas indicam que o órgão data dos séculos XV-XVI, tendo posteriormente sofrido várias intervenções. As amostras foram recolhidas em diferentes locais da parte central do órgão e foram caracterizadas por microscopia óptica e eletrônica de varredura, microanálise, difração de raios-X e espectroscopia de infravermelho com transformada de Fourier. A sequência estratigráfica e as análises química e mineralógica permitiram elucidar as técnicas de douramento usadas. A técnica que os artistas portugueses trouxeram da China, introduzindo caulim na composição do bolus, foi identificada em todas as amostras. O uso de gesso (gesso mate e gesso grosso) na camada de preparação está evidente em algumas amostras, indicando o uso da técnica desenvolvida na Itália e em Flandres no século XIV e largamente usada no século XVII.Gilded wood is an important part of Portuguese cultural heritage. We profit an intervention in the organ of the Church of Santa Cruz (Coimbra) to make a study on its gilded wood decoration. Historical sources indicate that the organ dates from the XV-XVI centuries, although it has suffered several restoration works over the centuries. Samples were collected from different places of the central part of the organ. Scanning electron microscopy combined with energy dispersive X-ray spectroscopy, optical microscopy, X-ray diffraction and Fourier transform infrared spectroscopy were the techniques used in this work to analyze the samples. Stratigraphical sequence and global chemical and mineralogical analysis data allowed the identification of the gilding techniques. All the samples exhibit the typical technique brought by Portuguese artists from China, with kaolin in the bolus composition. Some samples present a typical Italian and Flemish technique developed in the XIV century, and used in the XVII century, with gypsum (gesso mate and gesso grosso) in the preparation layer.

Ancient ‘gilded’ art objects from European cultural heritage: a review on different scales of characterization

“…Studies in the field of archaeology, technical art history and conservation, report analytical data about the identification of provenance/origin, composition and manufacturing techniques of gold objects (coins, sculptures, paintings) and its alloys used for decorating surfaces 2, 4, 12, 18, 20–99…”

“…Although many research studies were dedicated to archaeological metal artifacts coated with gilding layers,5–10, 13–16, 20–21, 27–30, 32–35, 86–89 some interest was showed to other typologies of gilded art objects, mainly wooden sculptures, retables and altarpieces, leather and parchment‐based objects (such as illuminated manuscripts or gilt leather decorations on wall) and wall paintings from the European cultural heritage 12, 19, 26, 31, 36–85, 91–99…”

“…The major part of these studies report data about the typologies, material composition, degradation and deterioration processes, and also the restoration treatments undertaken on important local artifacts with some connections to the international Gothic, Renaissance or Baroque heritage 41–85, 91–99…”

“…According to the literature review and international surveys in this field, extensive and comparative researches were done in Spain, Portugal, Greece, Italy, France and Albany not only for better understanding the materials and characteristics of the decorative gilding layers in ancient polychrome artifacts, but also for authenticating them 12, 16–20, 43–83, 94. Nevertheless, in many cases these researches focus on historical, typological, religious and technical aspects related to treatises and other documents from the manufacturing periods, but not enough scientific and instrumental studies were performed and published.…”

“…A wide range of imaging and spectroscopy‐based techniques is nowadays available for analysis of gilded art objects (Table 2): from optical microscopy (OM, PLM), infrared reflectography, thermography, to scanning/transmission/environmental electron microscopy (SEM/TEM/E‐SEM), confocal microscopy coupled with laser profilometry, atomic force microscopy (AFM), FTIR and Raman microscopy (micro‐FTIR, micro‐Raman), X‐ray spectrometry (WDXRF/EDXRF/TXRF, XPS), ion beam analyses (PIXE/PIGE, RBS, SR), etc 1–2, 5, 12, 18, 20–34, 38, 41–42, 49–99…”