A Hidden Portrait by Edgar Degas

2016

A historical self-portrait painted by Sir Arthur Streeton (1867−1943) has been studied with fast-scanning X-ray fluorescence microscopy using synchrotron radiation. One of the technique's unique strengths is the ability to reveal metal distributions in the pigments of underlying brushstrokes, thus providing information critical to the interpretation of a painting. We have applied the nondestructive technique with the event-mode Maia X-ray detector, which has the capability to record elemental maps at megapixels per hour with the full X-ray fluorescence spectrum collected per pixel. The painting poses a difficult challenge to conventional X-ray analysis, because it was completely obscured with heavy brushstrokes of highly X-ray absorptive lead white paint (2PbCO 3 •Pb(OH) 2) by the artist, making it an excellent candidate for the application of the synchrotron-based technique. The 25 megapixel elemental maps were successfully observed through the lead white paint across the 200 × 300 mm 2 scan area. The sweeping brushstrokes of the lead white overpaint contributed significant detrimental structure to the elemental maps. A corrective procedure was devised to enhance the visualization of the elemental maps by using the elastic X-ray scatter as a proxy for the lead white overpaint. We foresee the technique applied to the most demanding of culturally significant artworks where conventional analytical methods are inadequate.

Analytical Chemistry, 2008

5) Vergeest, A. In The Paintings of Vincent van Gogh in the Collection of the Kröller-Müller Museum, Van Kooten, T.; Rijnders, M., Eds.; Kröller-Müller Museum: Otterlo, The Netherlands, 2003; pp 78-81. (6) Vekemans, B.; Janssens, K.; Vincze, L.; Adams, F.; Van Espen, P. X-ray Spectrom. 1994, 23, 278-285.

The preservation and understanding of cultural heritage depends increasingly on in-depth chemical studies. Rapid technological advances are forging connections between scientists and arts communities, enabling revolutionary new techniques for non-invasive technical study of culturally significant, highly prized artworks. We have applied a non-invasive, rapid, high definition X-ray fluorescence (XRF) elemental mapping technique to a French Impressionist painting using a synchrotron radiation source, and show how this technology can advance scholarly art interpretation and preservation. We have obtained detailed technical understanding of a painting which could not be resolved by conventional techniques. Here we show 31.6 megapixel scanning XRF derived elemental maps and report a novel image processing methodology utilising these maps to produce a false colour representation of a " hidden " portrait by Edgar Degas. This work provides a cohesive methodology for both imaging and understanding the chemical composition of artworks, and enables scholarly understandings of cultural heritage, many of which have eluded conventional technologies. We anticipate that the outcome from this work will encourage the reassessment of some of the world's great art treasures. Preserving and interpreting the world's material cultural heritage requires increasingly sophisticated under-standings of chemical composition, environmental history, and deterioration mechanisms 1. Knowledge and understanding of historic materials has conventionally required the removal of samples which are subjected to analytical techniques, and the process frequently alters or destroys the specimen. Even sub-millimetre sampling " damage " to works of substantial cultural heritage can be unacceptable for highly valued objects. In art examination it is highly desirable that materials can be identified without sampling, and without change to the material being studied. Conventional analytical techniques have given inconclusive outcomes, in particular where the area of interest is obscured by an upper layer 2,3. Concealed paintings, early compositions that have been hidden by subsequent work, are important insights into artworks and artists. They can reveal the evolution of an artist's technique and can prove invaluable to the attribution of a work 4,5. Conventional X-radiography of paintings has been undertaken since 1896, and has been heavily relied upon in the understanding of paintings 6. X-ray absorption is mainly provided by the heavy metal components of pigments used, and the technique provides minimal quantitative or specific elemental identification information. The interpretation of X-radiography images is a highly subjective process. In recent years considerable effort has been expended into developing large-area non-invasive examination techniques of artworks and archaeometric study of objects to fulfil a growing need to accurately understand the elemental and molecular composition of artworks 7–16. This new analytical information has become critical in attribution and degradation studies and art historical assessments and is used to direct the practices of art conservators as they seek to implement new preservation strategies. It has been demonstrated with the X-ray fluorescence (XRF) technique that metallic elements from pigments in an underpainting can be detected and resolved with sufficient sensitivity to enable reconstruction of concealed paint layers 2,4,5,7,10,17. The first major synchrotron study, which revealed a woman's head under the Van Gogh painting Patch of Grass required extended examination time (~2 days, 2 second per pixel dwell time), and produced modest resolution 0.5 mm over an area of only 175 × 175 mm 2 2. This showed the power of scanning XRF, but also highlighted what had been the traditional limitation of slow pixel acquisition rates, which often resulted in compromises to the overall scan size and/or spatial resolution. In recent years the development of rapid scanning XRF methods 8,19,20 with millisecond analysis times have dramatically improved data collection

Lasers in the Conservation of Artworks XIII, 2023

In recent years, a range of spatially resolved imaging techniques to examine paintings has become integrated into the arsenal of analytical methods used in many museum laboratories worldwide. An example is scanning X-ray fluorescence (XRF), a non-invasive method that provides distribution maps of a wide range of elements in materials used for paintings. Scanning XRF has recently been used together with conventional methods for technical study to investigate paintings from the Courtauld Gallery, including Christ and the Woman taken in Adultery, dated to 1565, one of the three surviving grisaille paintings by Pieter Bruegel the Elder, a large-scale Portrait of Don Francisco de Saveedra, painted by Francisco de Goya in 1798, and Le Déjeuner sur l'herbe by Édouard Manet, a smaller an undated version of the large work of the same title painted by the artist in 1863 and on display at the Musée d'Orsay in Paris.

The European Physical Journal Plus

Historical paintings with important iconographical changes represent an analytical challenge. Considering the case study of a fifteenth-century French painting studied during its restoration, the efficiency of a combined noninvasive approach of two-dimensional scanning macro-X-ray fluorescence imaging (MA-XRF) and a laboratory-based depth-resolved confocal micro-X-ray fluorescence (CXRF) is discussed. Large chemical maps of several elements were obtained by MA-XRF, enabling the identification of zones of interest representing changes in the painting composition. In these areas, depth profiles were measured with CXRF, allowing to evidence overlaying paint layers. The advantages of this technique are that it can give direct information on the stratigraphy of paint layers in a nondestructive way and can reduce the sampling needed, as well as increase the locations analyzed (in our study twenty-two depth-resolved scans). These results complement information obtained by scanning electron...

Journal of Analytical Atomic Spectrometry, 2013

Scanning macro-X-ray fluorescence analysis (MA-XRF) is rapidly being established as a technique for the investigation of historical paintings. The elemental distribution images acquired by this method allow for the visualization of hidden paint layers and thus provide insight into the artist's creative process and the painting's conservation history. Due to the lack of a dedicated, commercially available instrument the application of the technique was limited to a few groups that constructed their own instruments.

Signal Processing, 2013

This paper describes our methods for repairing and restoring images of hidden paintings (paintings that have been painted over and are now covered by a new surface painting) that have been obtained via noninvasive X-ray fluorescence imaging of their canvases. This recently developed imaging technique measures the concentrations of various chemical elements at each two-dimensional spatial location across the canvas. These concentrations in turn result from pigments present both in the surface painting and in the hidden painting beneath. These X-ray fluorescence images provide the best available data from which to noninvasively study a hidden painting. However, they are typically marred by artifacts of the imaging process, features of the surface painting, and areas of information loss. Repairing and restoring these images thus consists of three stages: (1) repairing acquisition artifacts in the dataset, (2) removal of features in the images that result from the surface painting rather than the hidden painting, and (3) identification and repair of areas of information loss. We describe methods we have developed to address each of these stages: a total-variation minimization approach to artifact correction, a novel method for underdetermined blind source separation with multimodal side information to address surface feature removal, and two applicationspecific new methods for automatically identifying particularly thick or X-ray absorbent surface features in the painting. Finally, we demonstrate the results of our methods on a hidden painting by the artist Vincent van Gogh.

Annual review of analytical chemistry (Palo Alto, Calif.), 2013

We review methods and recent studies in which macroscopic to (sub)microscopic X-ray beams were used for nondestructive analysis and characterization of pigments, paint microsamples, and/or entire paintings. We discuss the use of portable laboratory-and synchrotron-based instrumentation and describe several variants of X-ray fluorescence (XRF) analysis used for elemental analysis and imaging and combined with X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Macroscopic and microscopic (μ-)XRF variants of this method are suitable for visualizing the elemental distribution of key elements in paint multilayers. Technical innovations such as multielement, large-area XRF detectors have enabled such developments. The use of methods limited to elemental analysis or imaging usually is not sufficient to elucidate the chemical transformations that take place during natural pigment alteration processes. However, synchrotronbased combinations of μ-XRF, μ-XAS, and μ-XRD are suitable for such studies.

Journal of Analytical Atomic Spectrometry, 2011

It is generally known that radiographic inspection of 15-17th century paintings can easily be done with a polychromatic X-ray source using a voltage between 20 kV and 40 kV in combination with classic X-ray films. Unfortunately, the spatial structure of numerous 19 th and early 20 th century paintings cannot be visualized with conventional radiography due to several reasons such as the use of lead white grounds or low absorbing pigments. Radiographic images are blurred or worse, they do not contain the picture of the painting. During the last decades, many technological innovations have been introduced in the field of radiography but their possibilities in cultural heritage have not been explored in full detail. In our investigation we used phosphor imaging plates, energy dispersive detectors and CCDcameras in combination with synchrotron radiation and conventional X-ray tubes in order to improve the quality of radiographic images. Several promising techniques that could improve the quality of radiographs of paintings were identified.

Analytical Chemistry for the Study of Paintings and the Detection of Forgeries

This essay traces the evolution of connoisseurship in the Netherlands from the early twentieth century to current and future challenges. In the twentieth century, the attitude of art historians towards chemistry varied from extreme distrust to extreme optimism about the possibilities of the discipline to provide conclusive evidence in authentication matters. While the chemical methods and technical means to research paintings have developed at an unprecedented pace in the twenty-first century, some of the key questions crucial to classifying works of art remain largely the same (e.g. how much consistency to expect in an artist’s brushwork, painting technique and choice of materials?). However, other questions are new (e.g. how to interpret vast amounts of new data?) and call for a fundamentally different approach: for a cross-pollination of (technical) art history, chemistry and data science. While surveying recent developments, this essay discusses the merits and drawbacks of sever...