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Archeometry

Hidden paintings

Diagnosis brings to light hidden details of paintings and works of art

ELIZABETH KAJIYA-IF/USPThe female portrait above appears on the back of the Marinha painting by Italian, Virgilio Guidi (top of the page), which forms part of the MAC collectionELIZABETH KAJIYA-IF/USP

Nothing can substitute the eye of a specialist when it comes to assessing the particular characteristics of a painting. But the use in important museums and cultural institutions in the country of a series of physical and chemical analyses has become an additional tool for understanding the style and creative process of certain painters, giving parameters for conservation and restoration work and bringing to light hidden facets of some paintings. In this sense the history of the painting, Marinha, an oil on wood, probably produced at the beginning of the 1940s by Italian painter, Virgilio Guidi (1891-1984), is fairly illustrative. In the catalogue of the Museum of Contemporary Art at the University of São Paulo (MAC-USP), where it is kept, this canvas officially houses just one painting: a view of the Grand Canal of Venice, prominence being given to the Church of San Giorgio Maggiore. However, one only has to turn the picture around to see a portrait of a woman on the back with the naked eye. Infrared images of this B side of the canvas revealed a third picture hidden under the paint that was used to portray the woman: another maritime scene of the Italian city.

Discovery of the work hidden on the back of the Marinha painting was obtained by using a non-destructive optical technique called infrared reflectography, which enables one to see through the layers of paint and therefore identify drawings hidden by the more superficial painting. “We thought we were going to study two paintings by Guidi, the one on the front and the one on the back, but we ended up discovering a third,” says Márcia Rizzutto, from the Institute of Physics at USP, a specialist in archeometry, a discipline that uses scientific methods for analyzing works of art and archeological objects. The physicist had access to the Italian painting through collaboration with art historian, Ana Gonçalves Magalhães, from MAC, who in a project funded by FAPESP, is reassessing and updating the university’s museum catalogue. “Scientific information is today indispensable for studying and conserving works of art,” says Ana.

Infrared reflectography is a technique based on the reflection and absorption capacity that some chemical elements have when subjected to electromagnetic waves. Infrared images are captured on a high-resolution digital camera, fitted with a light filter for this wavelength. Incidental electromagnetic radiation oases through the external layers of paint until it is absorbed and reflected back into the camera by some material. The effect of the method is to make surface pigments, which form the image that is visible to the naked eye, more transparent and increase the contrast of possible drawings in the background. Each compound reflects in a different way in infrared. Carbon-based pigments, often used by artists to make their preliminary versions or sketches of paintings that are subsequently covered by other paints, reflect well in infrared light. According to the lengths of the waves used for the analyses, the thickness of the layers of surface paints and the type of pigments present in the work, the resulting transparency and contrast equation may favor the discovery of surprises, like the version of the Grand Canal of Venice, which the Italian Guidi preferred to cover over with the portrait of a woman.

The Marinha canvas forms part of the Francisco Matarazzo Sobrinho Collection, comprising 429 works by Brazilian and foreign artists, which belonged to the former Museum of Modern Art in São Paulo and in 1963 was transferred to the MAC collection. In her cataloguing work of the paintings from the São Paulo museum, Ana prioritized a batch of 70 canvases produced by Italian painters in the first half of the last century that were bought by Ciccillo Matarazzo, as the rich Italian-Brazilian industrialist was better known, right after the Second World War. Within this subset of canvases, five paintings attracted the historian’s attention. They exhibited paintings on both the front and the back.

The works that were on the front are those that Ciccillo officially bought. There is information about them in the museum’s registers. Those that are on the back, even when visible to the naked eye, have no documentation or have incomplete registers. “In these cases, Ciccillo bought one work and ended up getting two, the one in front and the one at the back,” says Ana. The Guidi canvas is an extreme case, in which there are three paintings in the same frame, one of which is invisible to the naked eye. As a matter of fact, thanks to the work of cataloguing the historian discovered that the female form portrayed on the back was the wife of the Italian artist.

Finishing touches
Another interesting case is that of the painting Nu inacabado [Unfinished Nude], an oil on canvas from 1943 by Italian artist, Felice Casorati (1883-1963), which was also in the Francisco Matarazzo Sobrinho Collection. The painting, duly catalogued at MAC, shows a naked woman sitting in a chair. On the back of the painting there is a second work, also visible to the naked eye, about which there was no information: the portrait was of a little boy. Márcia Rizzutto took pictures of the two paintings using different methods, like infrared reflectography and also ultraviolet light fluorescence. “This second technique enables surface information of the picture layer to be visualized and dirt, fungus, tears, cracks and retouched areas to be detected,” explains the physicist from USP. When exposed to ultraviolet radiation some materials used in the paintings, like the different types of varnish, become fluorescent. Retouched areas, in which the original varnish was removed and recovered by another pigment, appear as dark stains when seen using this technique.

The images of both sides of the painting obtained with these two different techniques, provided evidence that the style of the paintings was different. Casorati drew the scene of the nude with some carbon-based paint before adding color to it. The painter of the little boy on the other hand had a more Impressionist style. There is no drawing in charcoal and the artist painted making small smudges with the paint. This information, allied to historical research into the life of Casorati, led Ana to a discovery: the figure of the little boy was painted by Daphne Maugham Casorati (1897-1982), Casorati’s wife and mother to the boy.

ELIZABETH KAJIYA-IF/USPImages in visible and infrared light (right) of the canvas, “A adivinha”, by Achille Funi: details of the background of the canvas are improved by archeometry techniquesELIZABETH KAJIYA-IF/USP

Sometimes the marriage between the various archemotry techniques and artistic analysis of the paintings does not produce such apparently spectacular results, as in the studies of the works of Guidi and Casorati. Even so unsuspected traces of a painting may come to the surface when science throws light on a painting. In the canvas, A adivinha, by Italian Achille Funi (1890-1972), another oil on wood in the Ciccillo Matarazzo collection, Márcia and Ana noticed that part of the background scenery on the right side of the work, where there was a wall and an arched doorway, was covered by a dark paint. For some reason Funi changed his mind and hid this part of the background. “We discover changes that painters make and do not incorporate into the final work by analyzing the various types of image we can obtain from a painting,” says Ana. As a matter of fact this painting, although it has no picture hidden or visible on the back, is unheard of in international historiography and is not mentioned in the general catalogue of the work of Funi in Italy.

Routine of the museum
In large museums in Europe and the United Sates, like the Louvre in Paris, the National Gallery in London and the Metropolitan in New York, archeometric analyses have already been incorporated into the routine of these institutions for decades. The establishments themselves have the apparatus and the qualified personnel for carrying out the studies. In some cases it is not even necessary to resort to partnerships with university researchers. Here, the museums began to open up to this type of collaboration just a few years ago. In the Pinacoteca museum of the State of São Paulo, for example, every item that today enters the collection is obliged to undergo five examinations: an organoleptic analysis (carried out by an art specialist) and obtaining pictures in infrared, ultraviolet, oblique light (to detect surface irregularities and cracks in the painting) and transversal light.

Most of the examinations are carried out in the museum itself. In some cases, the paintings have to be taken to the Institute of Physics at USP, where studies are carried out of the pigments or radiographies taken. “These analyses were incorporated into the documentation of the works,” says Valeria de Mendonça, coordinator of the center for conservation and restoration at the Pinacoteca. “They will be used for possible restorations in the future and for research into the style of the artists.” Valeria calculates that some 100 works at the Pinacoteca have already been the target of archeometric examinations by Márcia’s team. Currently there is a major study ongoing, in a partnership with USP, into the stylistic characteristics and types of pigment used by Brazilian painter, Oscar Pereira da Silva (1867-1939). The Pinacoteca has a dozen of the artist’s paintings, which are good material for analysis.

Some archeometric techniques allow for the pigments originally used by an artist to be detected and the paints that were subsequently used in restoring the work to be differentiated. Chemist Cristiane Calza, from the Laboratory of Nuclear Instrumentation of the Federal University of Rio de Janeiro (Coppe/UFRJ), has a portable, X-ray fluorescence system that has produced interesting results when its beam is pointed at canvases and sculptures. Recently, with the help of the apparatus, the researcher identified 10 different layers of paint on the old statue of St. Sebastian in the Capuchinhos Church in Rio de Janeiro.

The original layer, which goes back to the 16th century when the work was brought from Portugal by Estácio de Sá, comprised white lead mixed with a little vermillion (mercury sulfate based). “The idea behind this pigment was to give a pink tinge to the skin,” says Cristiane. The composition of the second to the fifth layers was the same as the first, with a greater or smaller addition of vermillion to the white lead. In the sixth and seventh layers appear pigments that began to be used in the 19th century: lithopone (white obtained from a mixture of barium sulfate and zinc sulfate) and red ochre. In the eighth layer the white lead reappears, now mixed with the ochre and vermillion. In the ninth layer there is zinc white and ochre. The final and current layer, the legacy of a restoration carried out in the 20th century, was characterized by the use of zinc white, titanium white and ochre. “With this information it is possible to think about restoring the statue to try and preserve the original characteristics of the work,” says Cristiane.

The projects
1. Critical reassessment ad updating of the catalogue of the collection of the MAC-USP – no. 2009/01041-7
2. External beam of ions for the non-destructive characterization of archeological objects and works of art from the cultural heritage – no. 2007/08721-8
Modality
Regular Line of Research Project Awards
Coordinators
1. Ana Gonçalves Magalhães – MAC-USP
2. Márcia Rizzutto – IF-USP
Investment
1. R$ 18,400.00 (FAPESP)
2. US$ 38,000.00 and R$ 34,500.00 (FAPESP)

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