Study of materials and techniques in painted ceiling panels from a palace in Cremona (Italy, 15thcentury)
© Malagodi et al.; licensee Chemistry Central Ltd. 2014
Received: 23 October 2013
Accepted: 7 March 2014
Published: 17 March 2014
This study concerns the analysis of four painted wooden panels from the second half of the 15th century which embellish the ceiling of a palace situated in Cremona (Northern Italy). This type of painting was generally used to decorate the top of the walls and the ceilings of the rooms in aristocratic palaces and they usually portray the owner’s ancestors, family members or important visitors. The paintings are of historical importance since they enable us to study the clothing and hair styles which were in fashionable in Italy during the Renaissance. These panels were heavily damaged and required a lot of restoration including the cleaning of the paint layers. This enabled us to carry out a thorough examination of the materials and techniques used for creating these paintings.
Various micro-samples were taken in order to distinguish the materials and, in particular: (i) to analyze the ground layer and study its function; (ii) to typify the organic binders and the pigments of the polychrome films. The stratigraphic sequence of micro-samples was analyzed using optical microscopy, the elemental composition was determined by means of the SEM-EDX technique while the organic binders were analyzed by means of μFT-IR spectroscopy. The main component of ground layer proved to be clay. The organic binder was probably composed of a protein-based material such as animal glue. This type of ground layer is similar to the traditional 15th century Flemish formula and seems to confirm the strong influence of that artistic technique in Northern Italy. Cross-section investigation showed a primer layer over the ground layer made of white lead pigment. In fact, a white primer was used to cover the ground layer of yellowish clay common in Central Europe. The importance of this research is also confirmed by the study of paint films, for which pigments such as azurite or cinnabar were used. Red lake pigment for painting the subjects’ complexions was emphasized.
The analyses provide new detailed information concerning the materials used for painting the ceiling panels, the layer sequence of the paints and Northern Italian 15th century painting techniques.
KeywordsPaint layer Ceiling panels Renaissance artworks Clay Pigments μFT-IR SEM-EDX
Aesthetic sensibility for interior furniture was of great importance from the 15th century onwards and structural elements such as walls and ceilings were also decorated in order to embellish the interior of buildings. Wooden ceilings represented an important and widespread art form in Italy . Skilled craftsmen operating in several notable “ateliers”, mainly located in northern Italy, decorated ceiling panels with subjects inspired by the artworks of famous painters, for instance Andrea Mantegna, Vincenzo Foppa or Giovan Pietro da Cemmo. Painted wooden panels were mainly produced to enhance the ceilings of aristocratic homes and churches . Today these panels represent an important source of information about 15th and 16th century customs and traditions as the subjects of the decorations were typical of the Renaissance . At that time, the wooden ceilings had a typical structure with central beams and lateral rafters with the presence of a console along the vertical faces. The surfaces of the beams were painted and decorated and small wooden panels were hung between the beams and the console . These artworks were given a ground layer which provided the base for painting. Although a lot of these paintings have been lost over the centuries, some of them can still be found in Italian museums or in the original buildings, as for example the painted ceiling panels depicting knights which adorn the ground floor of a building in Vittorio Veneto (Treviso) dating back to 1476, or the palace of Giovanni degli Onesti in Udine . This artistic technique was commonly used in Lombardy and examples of these panels can be seen all over the region. The panels are usually square shaped and depict various subjects such as bust-length portraits of noblewomen or gentlemen, historical, mythological or allegoric episodes, as well as portraits of kings or emperors. Mantova, Brescia, Cremona and Pavia were the most important towns in Lombardy for the development of these decorations . From a technical point of view, Spruce was the main source of wood for the panels due to its ease of workability and soft color. At that time, light-colored wood was commonly treated with pigments, organic dyes, gums, natural resins or oil varnishes in order to give a transparent rosy color to the wood surfaces, conferring to wood a pleasant effect . Moreover, some of the most commonly used pigments for these kinds of paintings were azurite for bleu colors and cinnabar for red, as confirmed by historical sources . The ceiling panels analyzed in this study are part of a group of panels that probably come from a stately home in Cremona which no longer exists and belong to the “Musei Civici” in Cremona. The paintings are portraits of fashionable dames, with rich jewels and fancy headdresses, who were probably the aristocratic owners of the palace. The panels seem to be quite well preserved and no restoration has been documented in the past. Nothing is known about the binders, primer layers and pigments and it is unclear if paintings were made by the same or different workshops and/or artists of the town. A scientific evaluation performed by means of various diagnostic methods is required in order to assess the level of degradation of the painted panels and their materials. Moreover, the analyses of the paintings’ components may provide useful information about the painting techniques . The analyses performed on micro-samples taken from characteristic points of different pattern colors enabled us to study the stratigraphy of the ground layer and paint layers. The samples were studied with an optical microscope, μFT-IR micro-spectroscopy and Scanning Electron Microscopy with EDX spectrometer (SEM-EDX). The characterization of these materials represents a first step in determining the artistic techniques used to make these particular kinds of artworks during the Italian Renaissance period.
Materials and methods
Area of sampling
Complexion color of the neck
Absence of a ground layer; presence of a thin colored layer on wood
Red color of a woman headdress
Evidence of a thick red paint and ground layer
μFT-IR SEM-EDX Optical Microscopy
Ground layer visible on the edge of the portrait
Homogeneous and thick material; yellowish color
Green background behind the neck of the woman portrait
Evidence of a dark-green paint layer with not homogeneous surface; presence of a small blue area on the edge of the paint layer
μFT-IR SEM-EDX Optical Microscopy
Fourier Transform Infrared (μFT-IR) micro-spectroscopy analyses were performed with a Nicolet iN10 Thermo Fischer μFT-IR spectroscope, in Attenuated Total Reflectance (ATR) mode with germanium crystal and in reflection-absorption mode on gold foil following the treatment of some micro-fragments with H2O used as solvent to solubilize the binding media from the pigments. The spectral range was 4000-700 cm-1 with a resolution of 4 cm-1. A small amount of various micro-samples was embedded in epoxy resin and cut using a diamond blade. The cross-sections were first abraded with carbon papers (800-500 mesh) and then polished using diamond pastes (6, 3, 1, 0.25 μm). The cross sections were observed under a Leitz Laborlux polarizing microscope (VIS and UV lamps) and then sputtered with an Au coating, using a Cressington 208HR sputter. Scanning Electron Microscopy (SEM) images and energy-dispersive X-ray spectra (EDX) were collected by using a Tescan FE-SEM instrument (MIRA XMU series) equipped with EDAX spectrometer. The microanalyses were performed maintaining the current electron beam at 20 kV, with counts of 100 s per analysis. The semi-quantitative data were obtained by processing the measurements with the EDAX Genesis software.
Results and discussion
In general the study of the cross sections shows several superimposed paint layers illustrating a complex painting technique. The paintings often contained an intermediate layer between the ground and the paint layers called “imprimitura” (priming layer) which was made of oils and/or resins or proteinaceous binders and fillers. Their function is to ensure adhesion between the paint layers, to protect the underlying paint layer, and, in the case of the imprimitura, to fix the underdrawn and reduce the absorbency of the ground layer .
Further information about the composition of the panels ground layer, come from the μFT-IR analysis performed on the T4 sample: the main absorption bands are due to silicates (1029 cm-1), sulphates (1114 cm-1, with a weak shoulder at 1085 cm-1), and carbonates (1406 cm-1). Moreover, the peak at 1650 cm-1 can be due to the N-H stretching absorption which is a characteristic of proteinaceous binders such as animal glue (Figure 3B), possibly used as organic binder of this layer and in accordance with the fluorescent image observed in the UV cross section examination.
These compositional results are very important because in Italy it was not a common practice to use clay as the main material of the ground layer. One of the most famous manuals concerning painting techniques and materials is the early renaissance work by Cennino Cennini, first published in 1437, in which all the main formulas were described. Ground layers applied to wood panel surfaces were already very common at that time and they were usually made of gypsum mixed with proteinaceous glue binder (mestica). This ancient recipe was particularly widespread in Italy, because of the bright white color and the low level of shrinkage of the ground layer. The use of a clay-based ground layer in these panels could be due to the influence of Northern European artistic techniques  and it is strictly related to the great increase in trading between northern Europe and Lombardy. Following Gothic times, Flemish artworks reached the most outlying regions and Flemish artists travelled to almost every southern European country, either as students or as workmen, as they were sometimes more skilled than the natives . Clay minerals, at times mixed with chalk grounds, were present in the grey layer that was observed in 14th century Central-European wooden panel paintings and sculptures . The similar composition of the ground layer and relative amounts of the elements observed in the three samples could suggest a univocal origin of the panels.
These results, together with information given by optical microscopy and SEM investigations, seem to confirm the presence of azurite mineral as the main pigment for the paint, although the presence of traces of copper oxalate cannot be ruled out. The green color in the background of the fourth panel could be due to a partial alteration of the azurite pigment . The blue background made of azurite has often been seen to turn into green malachite, e.g. in the blue robe of the Virgin Mary in many oil paintings which have frequently become greenish. As a compositional material, azurite [Cu(CO3)·2 Cu(OH)2] has a relatively rare carbonate of copper base, which is formed chiefly by the action of carbonated waters on other copper minerals in the upper oxidized zone of the deposits . Similarly to azurite, malachite [Cu(CO3)·Cu(OH)2] has a carbonate of copper base and a secondary mineral found in copper deposits, although it is more common than azurite. The main interest in these minerals stems from their use in art works. In fact, azurite may have been employed as a paint pigment as early as the Fourth Dynasty in Egypt and was the most important blue pigment in European painting from the Middle Ages [26, 27].
The results of this research provide new information concerning the artistic techniques used on ceiling panels during the Renaissance in Italy. The analyses were performed on micro-samples in order to characterize the pigments of the colored painted films, the composition of the ground layers and to make some hypotheses concerning the nature of the organic binders. The analysis of the stratigraphic sections enabled us to recognize clay minerals mixed with gypsum as ground layer, possibly held together by a proteinaceous material, e.g. animal glue which is an unusual mixture for Italian artistic traditions. This choice is probably due to the strong influence of the Flemish culture in Northern Italy, also for the paint ceiling panels of stately homes, blending artistic techniques and materials. Moreover, μFT-IR and SEM-EDX techniques have enabled us to determine the same ground layer composition of three panels. Results suggest that the artworks share a common origin, i.e. they come from the same palace in Cremona, or that the panels were made by the same artistic workshop. The presence of a thin primer layer made of white lead covering the ground layer confirms the Flemish influence and indicates a high technological standard of making. The study of the layers of the paintings has emphasized the use of high quality and expensive pigments such as cinnabar and azurite, proving the importance of this kind of artwork at that time. Moreover, the presence of a red lake applied directly onto the wood for the complexion tone of a woman’s portrait appears to be very interesting: the artistic aim of this technique was probably related to the transparent effect of the varnish obtained on the panel surface.
Scanning electron microscopy-energy dispersive x-ray microanalysis
Micro fourier transform-infrared spectroscopy
Attenuated total reflectance.
We would like to thank Dr. Elisabetta Arrighetti and Dr. Roberto Bonomi from the Restoration School of Botticino, Italy, for their cooperation during sampling and results discussion and Dr. Mario Marubbi, Conservator of Musei Civici “Ala Ponzone”, Cremona, Italy, for his valuable advice.
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