Science reveals the secrets of art

Science reveals the secrets of art

Infrared, x-ray radiographs or exposure to ultraviolet light are essential techniques for historians and restorers to decipher the true story after the works

   In a precise intersection between science and the arts, in the Department of Technical Studies of the Prado Museum, researchers apply the methods of the first to the second. They try to extract from the works all the possible empirical information to put it in the hands of conservators and restorers. In recent years, technical reports have helped them to discover, for example, the copy of La Gioconda made in the study of Leonardo da Vinci himself. His analysis included infrared reflectography, X-ray scanning, ultraviolet fluorescence induction, stratigraphic analysis and solubility tests.

"Normally I do two infrared of each frame, one before and one after the restoration. In La Gioconda I made five, but of course, they are special paintings that demand another way of acting, "explains Ana González Mozo, doctor in Fine Arts and researcher at the Technical Documentation Office of the Madrid museum.

  When González Mozo went to work at the Prado, almost 18 years ago, the museum had just acquired a new digital infrared system "and they needed someone who was a little familiar". Each of the three members of the cabinet is dedicated to an area or a specific collection, "because the more you specialize, the more you understand and the more you can help the people who work in the tables," says the researcher. Although she no longer works as such, her training as a restorer has helped her, she says, "to understand the subject. How the paintings are made ».

The great museums of the whole world use this type of technologies to investigate the secrets of their collections, or to analyze the state of the works during the restoration processes. "The systems we use are based on the response of materials at different energy wavelengths. From the ultraviolet which is the most energetic, to the X-rays that have a greater power of penetration, to the infrared that represent an intermediate level. The materials absorb and reflect energy, and that response is collected in different media, "explains González Mozo. However, it is not as easy as it sounds. At each level you see layers that are mixing, never a single layer. There are different levels of information that must be interpreted a posteriori.

Innovation in the museum

These institutions tend to be conservative when it comes to adopting new technologies, but innovation is present, above all, when it comes to improving the systems they already have. "The tendency is always to have better resolution, greater penetration or to be able to work on different layers," says the Prado researcher.

They are currently testing new infrared light sources. "Lighting is a very important issue, we are very interested in having rich sources of tungsten in order to extract more information from pigments," says González Mozo, "we are also investigating multispectral systems, or with other types of filters".

One of the problems of infrared spectrography when studying a preparatory drawing is that blue or yellow colors are not visible. One of its challenges is to find wavelengths that can give that information to the restorers. "If there is a drawing done in blue or done in red, I do not see it, and many times I know it is because it shows on the surface. We try to find the source of light that gives me information about that pigment. It's what we're trying to work on now. "

At the Louvre in Paris they have researched about it and this researcher, specialized in the Italian painting collection of the Prado, will move there to check the progress and share techniques. It is another of the peculiarities of these art scientists. They work with each other and practically all the great museums of the world have the same technical equipment, "because more or less we have the same needs, we tend to use the same equipment so that the information is comparable. For example with the Louvre or the National Gallery. More or less we are acquiring the same equipment so that then the processes are not different, "says González Mozo.

The Prado was, however, a pioneer institution in the use of digital image applied to research. "We were the first to open this field by starting to use high-resolution images to investigate the paintings. In 1997 or 1998, very soon, "recalls González Mozo. Just a decade before, in 1989, the latest X-ray medical equipment was retired in the museum and they began to acquire specific equipment for art, which gives an idea of ​​the youth of the discipline.

In the bunker

These technical studies are carried out in a double room, with high ceilings, known as "the bunker" and located in the basement of the new building of the Prado, next to the warehouses of the funds. Next to the white door is a warning sign with a radioactive clover.

Inside, another member of the technical cabinet takes infrared images of La caza del tabladillo, an oil painting by Juan Bautista Martínez del Mazo, disciple and son-in-law of Velázquez, painted around 1640. This camera, which frames the court of Felipe IV hunting deers in Aranjuez, although digital, it remembers in its design a bellows. "It is a very compact camera, developed in England and first used by the National Gallery. It has a little less penetration than other industrial prototypes. And these are the new focuses that we are testing now, richer in infrared and capable of offering more resolution, "says González Mozo.

The structure that holds the camera and that locates millimetrically in front of the precise point of the frames is developed by a Spanish engineering company. "Sometimes it takes me more time to prepare the frame with the machine than the infrared itself. I can spend hours with the light, the focus is a slow process because each shot is ten minutes. A picture of this size measures 249 centimeters wide and 187 centimeters high can take a couple of days, "adds the researcher.

In another of the walls there is a negatoscope like those used by doctors to illuminate radiographs in their offices, only several meters high and wide. They turn it on and the negative appears in a work by El Greco, who is commemorating this year the fourth centenary of his death. "It allows you to make the size of the whole picture, throughout," says González Mozo. "Now we also have an X-ray scanner and from there we extract a lot of resolution, but even so, I prefer the plate."

   In recent years, the digitalization of its infrared system has represented a leap of comfort for these researchers. Before they were forced to photograph the screen where the infrared image was shown, and then join the photos. However, the advances from analog to digital have not always been so beneficial. For example, In digital photography of the paintings, González Mozo confesses that "a lot of quality has been lost, not so much because of the resolution, which is good, but above all in terms of details and textures, where digital does not arrive where analog photography arrived. In this camp we are doing a lot of research on how to get what we had. "

As often happens, when they began to develop these techniques, traditional historians distrusted. Then it imposed itself as fashion, technique by technique. For González Mozo, both positions have managed to redirect the situation. "The technique itself does not make sense if you do not put it in relation to the history of art, painting and the materials used." And he concludes: "It does not make sense to show this radiography if it does not help you explain how El Greco worked, or how the painting is."