Vitor Serrão

Characterization of glue sizing under calcium carbonate ground layers in Flemish and Luso-Flemish painting – analysis by SEM-EDS, μ-XRD and μ-Raman spectroscopy

This work regards the study of painting techniques in Portuguese workshops of the 15th and early 16th centuries, specifically addressing the methodology used on the preparation of ground layers. The influence of Flemish painting in Portugal is evident in stylistic and iconographic themes of that period. As regards the painting materials, we confirmed that this influence also extended to the ground layer technique. The use of a sizing layer with calcium sulphate or garlic to isolate the support from the calcium carbonate layer was verified by SEM-EDS but not confirmed by μ-XRD or μ-Raman spectroscopy. This work is part of a larger project, “The invisible ground layer and its influence in Portuguese paintings from the 15th and 16th centuries: a question to be settled”.

Characterization of Glue Sizing Layers in Portuguese Wood Paintings from the 15th and 16th Centuries by SEM Secondary Electron Images and μ-FTIR

According to treatises on 15th and 16th century paintings, artists dedicated particular attention to the sizing layer-consisting mainly of animal glue applied onto the wood support before further application of the ground layer. The stability of a painting mainly depends on the presence of a very cohesive sizing layer. However, the study of these layers has not received special attention from researchers. In this article we present a methodology for characterization of the sizing layer both chemically, by IR spectroscopy (Fourier transform infrared spectroscopy), and morphologically, by scanning electron microscopy (SEM). Secondary electron images obtained by SEM allow precise characterization of such layers. Painting reconstructions were used as references in development of the method to study the sizing layer in real painting samples. Presented herein are examples of this study on 15th and 16th century Portuguese paintings, particularly on the Triptych of S. Simão, from the Aveiro Museum, and S. Pedro, belonging to the Mercy of Tavira.

GREGÓRIO LOPES painting workshop: characterization by X-ray based techniques. Analysis by EDXRF, μ-XRD and SEM-EDS

Gregorio Lopes is one of the most famous Portuguese painters of the 15th–16th centuries. This work is a contribution to the study of his painting technique, specifically addressing the methodology used in the preparation of ground layers, which has never been carried out previously with this multianalytical method. For this purpose characterization of the ground layers of a selection of his paintings was carried out by micro-Energy Dispersive X-ray Fluorescence spectroscopy (μ-EDXRF), micro-X-ray Diffraction (μ-XRD), Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM-EDS) and complemented by micro-Raman spectroscopy. This work presents the results obtained on two altarpieces (c.1544) produced at the same period by this Portuguese artist. Ground layers are composed mainly of calcium sulfate — anhydrite and gypsum — and other compounds such as dolomite. Reference samples were prepared to obtain diffraction pattern of different percentage of gypsum and anhydrite and compared with the results from historical samples.

A multidisciplinary approach to the study of the brightening effects of white chalk ground layers in 15th and 16thcentury paintings

This paper employs various techniques to analyze the mixture of chalk and binder materials used, by Portuguese and Flemish painters in the 15th and 16th centuries, to enhance the reflection of light in paintings. The cases studied show evidence of the search by painters for light effects created when combining specific fillers and binders to obtain absorbent or non-absorbent ground layers in order to reflect superficial or deep light in paintings. These brightening effects are largely provided by microscopic coccoliths and calcispheres – the main constituents of chalk. The composition, size and slightly concave-convex shield-like shape of calcareous nannofossils (micrometrical dimensions) also facilitate application, thereby increasing the speed of handling. These calcareous nannofossils are crucial proof that chalk was used in the ground layers of Portuguese paintings. They have proved to be important in defining the various stages of Portuguese painting workshops, such as the Viseu Workshop (1501–1569), which used powdered chalk in the first phase and powdered limestone in the second phase in the production of a ground layer. A two-layer structure has been verified in some Flemish paintings of the period, but the use of different binders to provide different levels of light absorption and reflection in these artworks had not been previously identified. The results showing this two-layer ground structure are significant in making the connection between Flemish and Portuguese art in the context of a specific painting technique. The use of calcium carbonate ground layers was verified by SEM-EDS and confirmed by μ-XRD, and μ-Raman, while binders were analyzed by μ-FTIR and optical microscopy, using staining tests.

Deus está nos detalhes. Ouro, prata e policromia

he visible polychromy of a wooden sculpture representing St. John the Evangelist, from Museu Nacional de Arte Antiga, Lisbon (Portugal) presents several techniques that comple-ment each other on the creation of a sumptuous estofado. This case-study allowed the survey on gilding, silvering and polychromy practices, and observations on their execution are briefly reported and documented with results from a multi-analytical approach. Examina-tion included digital photomicrography and the observation of micro-samples cross-sections, while material identification resorted to several analytical methods that included scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD).