Introduction

en français

Nenagh Hathaway and Brandi Lee MacDonald

The Unvarnished Truth: Exploring the Material History of Paintings was conceived by Brandi Lee MacDonald at McMaster University in 2010 as a series of conversations about the potential for nondestructive techniques to analyze works of art, and quickly evolved to become the multidisciplinary, collaborative study presented here. This project focuses on the technical analysis of nine paintings from the McMaster Museum of Art’s permanent collection. Drawing on a range of expertise, we have developed an exhibition that places equal emphasis on the scientific processes and tools used to gather information, as well as on the interpretive results of those endeavours. At the conception of the project we identified several interesting research questions for each of the works in this exhibition. Our enquiries concentrated on themes including painting technique and materials, attribution, connoisseurship, as well as issues of object condition and stability. As is the case with many research campaigns, many of our explorations into these paintings subsequently led to even more interesting questions. The results of these examinations have produced a series of unique narratives not only about the objects but also about the research process itself.

The Unvarnished Truth presents paintings as complex physical objects whose component parts tell us a story about their history. The exhibition is the result of a series of interdisciplinary workshops that bring together the contributions of a range of specialists from around the world. In displaying the results of our technical investigations, we hope to alert our audience to the valuable insights that are generated when scientific equipment is used to answer art historical questions. This approach, often called technical art history, is a relatively young field that examines artworks and their material properties by incorporating the expertise of art historians, conservators, scientists, conservation scientists, and researchers from a variety of other disciplines.

As it has become more common to study art using scientific techniques, the necessity to interpret and synthesize the expanding range of data has also grown. This type of research has been—and remains—closely connected to efforts that are focused on the preservation of artworks. Several developments in the late nineteenth century and throughout the twentieth century greatly impacted the initial formation of the discipline. The professionalization of the field of conservation, as well as the application of scientific technologies to the study of art in the 1920s and 1930s, helped establish the significance of technical research in the study of art.[i] Over the course of the nineteenth century, several scientific instruments were created that have today become standard tools in the analysis of artworks. Although X-radiography was developed in 1895 and was first applied to the study of paintings the following year, it was not until the pioneering work of Alan Burroughs at the Fogg Museum at Harvard University that the technique was used in a systematic fashion.[ii] The Fogg was a key centre for the advancement of this type of research, largely due to the efforts of Edward Forbes, who served as its director from 1909 to 1944.[iii] In Europe, Paul Coremans was a highly influential figure in the field, supervising a watershed conservation and research initiative from 1950 to 1951 that focused on the Ghent Altarpiece. One of Coremans’s younger colleagues in Brussels, the physicist J. R. J. van Asperen de Boer, invented infrared reflectography (IRR) in the late 1960s. IRR along with ultraviolet analysis, infrared photography, and X-radiography comprises some of the most important tools of technical analysis. Throughout this catalogue you will find both descriptions of these tools as well as examples of their application to the study of paintings.

Technical art history has continued to adapt as new technologies are developed and existing equipment is improved. A relatively recent example is the incorporation of the possibilities offered by the Internet and the digital age.[iv] As more sophisticated tools are created, like macro-X-ray fluorescence for example, technical art history will evolve further, encouraging more voices to join the discussion. The Unvarnished Truth is significant in that it is the product of a great range of expertise. With contributions from several institutions in Canada (McMaster University, McMaster Museum of Art, and Queen’s University) and the United States (Isabella Stewart Gardner Museum and Northern Light Studio), the nine paintings analyzed benefit from the application of a deep and varied set of skills.

Nenagh Hathaway and Brandi Lee MacDonald co-curated this exhibition, along with Ihor Holubizky. Hathaway and MacDonald also coordinated several workshops where researchers engaged in lively discussions, sharing ideas about the nine paintings now on display. Nenagh Hathaway is a PhD candidate in Art History at Queen’s University whose thesis focuses on studying the grisaille technique of fifteenth and sixteenth century Netherlandish triptychs. Hathaway completed her MLitt at the University of Glasgow in a technical art history program, and from 2013 to 2014 employed Queen’s OSIRIS infrared camera to document paintings in Europe. Her studies are concentrated on the analysis and interpretation of painting materials and techniques. Brandi Lee MacDonald has a PhD in Anthropology from McMaster University and is a Research Associate in McMaster’s Department of Medical Physics and Applied Radiation Sciences. Her theoretical interests in archaeology are related to cultural perceptions of natural places and human engagement with the mineral world, and her approach involves the use of geochemical analytical techniques to trace the acquisition, movement, and usage contexts of materials used as pigments. Her research focuses on histories of red ochre use, with a current focus on nondestructive pigment testing of pictographs located in the lower Canadian Shield.

The project could not have happened without the enthusiastic support of our supervisors, Fiona McNeill and Ron Spronk. Dr. McNeill is a Professor in the Department of Medical Physics and Applied Radiation Sciences and an Associate Vice-President of Research at McMaster University. For this project, she provided expertise in the areas of X-radiography and X-ray fluorescence. It is thanks to Dr. McNeill and the generous support of McMaster University that this exhibition has been able to access the necessary facilities to pursue important research questions. This project is deeply indebted to such consistent support. Dr. Spronk specializes in the technical investigation of paintings. He is a Professor of Art History at Queen’s University and Radboud University Nijmegen, the Netherlands. Since his initial involvement with the McMaster exhibition, Spronk has encouraged the participation of staff and students from Queen’s, acting as a major driving force behind the project and enriching its interdisciplinary nature. At Queen’s, Spronk is setting up a mobile laboratory for technical art history (QU-MoLTAH). He is currently closely involved with three major international projects: the conservation/restoration treatment of Jan and Hubert van Eyck’s Ghent Altarpiece, the Bosch Research and Conservation Project, and the research cum exhibition project on Pieter Bruegel the Elder in Vienna.

Staff at the McMaster Museum of Art have provided essential support and expertise. Carol Podedworny holds an MA (Art History) from York University, an MMSt from the University of Toronto, and a BA (Art History) from the University of Guelph. She has worked in the arts community as a curator and director since 1982. She has taught at York University, Queen’s University, the University of Waterloo, and McMaster University. Her research interests include museum and curatorial practice and contemporary First Nations art. She is currently a member of the Board of Directors of the Ontario Association of Art Galleries, and the Director and Chief Curator of the McMaster Museum of Art. Ihor Holubizky did his undergraduate degree in History and Political Science at the University of Toronto, and a PhD in Art History at the University of Queensland (Australia), examining transnational cultural traffic in the modern age. He has held curatorial positions across Canada and in Australia, and is currently Senior Curator at the McMaster Museum of Art. Julie Bronson received her BA, Honours (Classics and Art History) from McMaster University. She is currently the Collections Administrator at the McMaster Museum of Art, overseeing its permanent collection, loans, and exhibitions. Her organization of materials and archival research has contributed significantly to the logistical success of this project.

Specialists from McMaster University have also made significant contributions to this project. Mike Noseworthy is an Assistant Professor of Electrical and Computer Engineering in the Department of Medical Physics and Applied Radiation Sciences. He is also Co-Director of the McMaster School of Biomedical Engineering, and Director of Imaging Physics and Engineering at the Imaging Research Centre, St. Joseph’s Hospital, Hamilton. He and his doctoral student, Evan McNabb (biomedical engineering), contributed their expertise in image co-registration, which provided an invaluable tool for the comparative analysis of the imaging formats presented here.

Two other members of the project team come from Queen’s University. Alison Murray is an Associate Professor in their Art Conservation program. With degrees from McGill University and Johns Hopkins University, Murray brings expertise in materials science, engineering, and conservation science to the group. Her current research interests include the characterization and conservation of modern materials. Professor Stephanie Dickey holds a Bader Chair in Northern Baroque Art and teaches courses on seventeenth century Dutch and Flemish art. She has worked on exhibitions at the National Gallery of Art in Washington, DC, and the Metropolitan Museum of Art in New York City.

Experts working in the United States form an essential part of this exhibition. We have been fortunate enough to have involved Gianfranco Pocobene, Head of Conservation and Paintings Conservator at the Isabella Stewart Gardner Museum in Boston, Massachusetts, in our initiative. Pocobene trained at Queen’s University in conservation, and his years of experience in the field have been of great value to the group. When he worked at the Harvard Art Museums, he co-edited a publication on John Singer Sargent’s mural cycle Triumph of Religion, which was published in 2010. Not only was Pocobene responsible for creating the condition reports from which many of our initial insights about paintings developed, he also offered the equipment and training necessary to conduct the reflectance transformation imaging analysis. Pocobene has been an integral member of our team.

Phoebe Weil, Co-Director of Northern Light Studio in St. Louis, Missouri, has also been an integral part of our research. Both Pocobene and Weil bring to the group a deep understanding of the materials and techniques of painting. Don H. Johnson, J. S. Abercrombie Professor Emeritus of Electrical and Computer Engineering at Rice University, also performed thread count analysis on the Van Gogh. Our understanding of the paintings included in this exhibition is greatly enriched by the contributions of these individuals.

There are a number of other individuals from Canadian institutions who have contributed their time, skills, and facilities. Joanne O’Meara (Department of Physics, University of Guelph), offered X-ray fluorescence technology for the elemental analysis of pigments. Ajesh Singh and Sandra Charbonneau (both of the Health Sciences program at Mohawk College) provided technical expertise in X-radiography of the paintings. Joshua Vandersteldt (Nray Services Inc., Hamilton) was instrumental in both X-radiography and neutron radiography at the McMaster Nuclear Reactor. Jim Britten and Victoria Jarvis of the McMaster XRD Lab assisted with molecular analysis of pigment samples. Elstan Desouza (Department of Medical Physics and Applied Radiation Sciences, McMaster University) established the technology and protocol for 2-D XRF elemental scanning. This project has truly been supported by a broad foundation of technical and analytical expertise, and without these individuals this project could not have been possible.

We are also indebted to research conducted by those outside of North America. Dr. Peter Klein, a wood biologist and retired professor from the University of Hamburg, performed dendrochronology on two paintings to determine the wood species and to clarify their dating. The Unvarnished Truth is, and has been since its inception, a highly co-operative and interdisciplinary initiative.

It is our hope that this exhibition stimulates an interest in looking more closely at paintings. When we study an object on many levels, including not only its surface but also those layers that are usually hidden to the human eye, we can begin to understand the story of the object. Paintings can be examined from many angles, as demonstrated by the contributions in this volume. We can interpret their meanings based on a variety of information including data gathered from technical analysis. We hope that this exhibition will add a new dimension to the way our audience thinks about paintings, and that it inspires other Canadian collections to pursue technical investigations and exhibit their findings to the public.


[i] Erma Hermens, “Technical Art History: The Synergy of Art, Conservation and Science,” in Art History and Visual Studies in Europe: Transnational Discourses and National Frameworks, ed. Matthew Rampley et al. (Leiden, The Netherlands; Boston: Brill, 2012), 151.

[ii] Ron Spronk, “Standing on the Shoulders of Giants: The Early Years of Conservation and Technical Examination of Netherlandish Paintings at the Fogg Art Museum,” in Recent Developments in the Technical Examination of Early Netherlandish Painting: Methodology, Limitations & Perspectives, ed. Molly Faries and Ron Spronk (Turnhout, Belgium: Brepols Publishers, 2003), 45.

[iii] Spronk, “Standing On the Shoulders of Giants,” 40–45; see also Francesca G. Bewer, A Laboratory for Art. Harvard’s Fogg Museum and the Emergence of Conservation in America, 1900–1950 (Cambridge, MA: Yale University Press, 2010).

[iv] An excellent example of the way in which the Internet has generated access to the results of technical study is the website “Closer to Van Eyck,” http://closertovaneyck.kikirpa.be; n.d.

The Art of Connoisseurship

en français

Stephanie S. Dickey

“Hello. It’s me.” You hear the voice on the telephone, and with just four syllables you recognize the caller immediately. If asked to explain how or why, you might mention qualities such as pitch, cadence, or accent, but ultimately, the distinctively personal character of the voice may be hard to define. That flash of recognition happens before you have even realized it, a product of intimate familiarity with the speaker.

The practice of artistic connoisseurship can depend on a similar process of instinctive recognition, especially when it comes to attribution, the process of determining who created a given work of art. In visual terms, this instinct has often been compared to recognizing the handwriting in a letter. As with listening, it can be easier to experience such a perception than to build a rational argument in support of it. Nevertheless, this goal has long been central to the practice of art history. In keeping with our exhibition, this brief essay considers the application of connoisseurship to painting, but similar observations could apply to the appreciation of many other products of human creativity, from music to fine cuisine.[i]

The term “connoisseur,” deriving from the French verb connaître, describes a person who possesses the ability to evaluate and render critical judgments about a given cultural product. While there may be an element of natural talent, this ability is usually cultivated through a long process of study and direct experience: in this case, knowledge of art history combined with first-hand visual analysis of paintings. Within the European tradition, the self-conscious practice of connoisseurship developed during the Renaissance and was codified in art theoretical writings of the seventeenth and eighteenth centuries. Treatises by authors such as Giulio Mancini, Abraham Bosse, Roger de Piles, and Jonathan Richardson aimed to educate not only artists but also collectors wishing to make a judicious purchase in an art market that was rapidly expanding to include a new clientele: middle-class consumers.[ii] Empowered by the growth of mercantile capitalism and other economic factors, but not necessarily brought up in traditions of cultural patronage, these new art buyers sought to develop their own critical faculties while also turning increasingly to experts for advice.[iii]

When attribution adds significantly to market value, the ability to determine who created a painting is more than an intellectual exercise. In today’s market for historical paintings, where prices rise into the millions of dollars, the fame of the artist plays a key role, perhaps stronger even than intrinsic aesthetic quality. In the case of the Dutch master Rembrandt van Rijn, for instance, statistics show that a painting from his workshop can sell for as little as five percent of the price fetched by one securely attributed to Rembrandt himself.[iv] The origins of this trend can be traced in part to Rembrandt’s own milieu, seventeenth-century Amsterdam, where hundreds of artists competed in an open market of unprecedented diversity. In a treatise of 1678, his former pupil Samuel van Hoogstraten contrasted true art lovers with what he called “name buyers”: ignorant consumers who purchased a work of art not for its aesthetic appeal but simply because it carried the name of a famous artist.[v] The power of name recognition has continued to impact the art market even as a range of historical factors have conspired to complicate the assignment of extant paintings to specific masters.

Prior to the sixteenth century, much of European art was produced on commission, and elite art patrons, or their agents, often interacted directly with artists. As the art market expanded to include an increasingly broad range of products and consumers, these links grew more tenuous. Buyers began to acquire luxury goods of all kinds on the open market, through dealers, auctions, or other intermediaries. As trade developed internationally, the geographic scope of the art market broadened as well. Concurrently, easel paintings replaced more stationary works, such as frescoes and altarpieces, as the central and most prolific element of the market. As portable objects, paintings on panel or canvas could be shipped, traded, and passed from one collector to another, often without much documentation to verify authenticity.

Meanwhile, to serve the growth in demand, artists devised methods for efficient production, often generating multiple versions of the same composition or copies of works by celebrated masters. The growing taste for secular subject matter, such as landscape and still life, produced a market for subject types that were relatively uncomplicated to design and lent themselves to generic variations on a theme. For instance, Dutch landscape painters like Aert van der Neer specialized in painting the placid local terrain. While some artists became known for a particular niche within this market, such as winter or night scenes (Van der Neer’s specialties), the basic formula of land, sea, and sky was not difficult to replicate.[vi]

Then, as now, unscrupulous artists and dealers sometimes passed off copies as originals, even finding methods for making a canvas look older than it was. Yet, not all copies were intentionally deceptive. A large portion of the market for decorative luxury goods has always been happily served by well-crafted imitations. The most discerning collectors may still prefer an original work—a product of the master’s mind as well as hand—over a copy or imitation, but determining the difference can be challenging. While a signature might seem like a guarantee of authenticity, it is the easiest feature of a composition to fake. More importantly, many artists did not sign their works, while others treated a signature more like a brand, affixing their names to products that were largely the work of assistants trained to paint in their style.

Taking all these factors into account, early handbooks for connoisseurs consistently identified three requisite aspects of expertise: the connoisseur must learn how to judge quality, to identify authorship, and to separate an original from a copy. A number of early theorists were painters themselves, and although they addressed their remarks to art lovers, they asserted that only a practicing artist could truly judge the work of his peers. Others, however, maintained that amateurs could also learn the skills of connoisseurship if they were willing to dedicate themselves to intensive study—indeed, art lovers might be willing and able to devote more time and effort to this than working artists could afford.[vii] In this way, connoisseurship contributed to the professionalization of art dealing and to the rise of art history as a discipline distinct from the practice of art. For art historians of the nineteenth and early twentieth centuries, connoisseurship became an essential skill developed through intensive training of the eye in first-hand observation and visual analysis.

Today, very few of the historical paintings still in existence can be unequivocally traced back to their point of origin. This has given rise to the specialized field of provenance research, which reconstructs the historical record of ownership. This approach treats the painting as a material object whose authenticity is verified by documentary evidence without regard to its aesthetic character. Connoisseurship, conversely, begins from the intrinsic qualities of the object itself, aiming to discern characteristics that identify it as the product of an individual creative agent, or, at least, of a specific historical milieu. Some authors have asserted that results can be produced through methodical examination of style according to a prescribed set of criteria. The nineteenth-century theorist Giovanni Morelli, building on the ideas of earlier writers, such as De Piles, and on his own training in anatomy, argued that the touch of an individual artist can be recognized in the consistent treatment of familiar details (a curl of hair or a fingernail) that the artist repeats by rote.[viii] Yet, however systematic or even scientific the approach, the connoisseur’s conclusions remain hypothetical, a matter of judgment rather than fact.

Early modern art lovers enjoyed sharing and discussing their collections in the private setting of the home, but the emergence of public exhibitions (most famously the Salons sponsored by the Académie des beaux-arts in Paris beginning in 1725) also turned art appreciation into a popular pastime. Those who could not afford to purchase works of art for themselves could still be amateurs, cultivating familiarity with artists and art movements by studying works on public display. When we visit an art museum today, and especially when we share with others our observations and judgments about the works we see, we continue the tradition of connoisseurship as a form of sociability. The aggregate of our judgments creates a sense of period fashion or taste. Artists, in turn, may respond either by adapting their styles to prevailing tastes or by deliberately challenging expectation.

As an aspect of art appreciation, attribution to a particular hand has always mattered more for painting than for many other products of material culture such as ceramics, furniture, or textiles, which may be judged by the style of a period or workshop, but are seldom expected to be unique. In addition to the idiosyncrasies of touch (the analogy to handwriting is apt here), the fact that painting conveys not only abstract formal properties but also imagery constitutive of meaning—like the content of a novel or poem—plays a role in separating the creative masterwork from the copy: the artist, like the author, is expected to communicate with an individual and recognizable voice. In reality, thousands of artists have built productive careers as craftsmen whose gifts lie in faithful transcription or creative interpretation of the ideas of others. Yet, it is those masters whose voices strike us as original who most capture our imagination and esteem. Some, such as the Flemish Baroque master Peter Paul Rubens, were lucky to find validation of their efforts in their own time. For others, such as the Post-Impressionist Vincent van Gogh, recognition came too late for the artist himself to benefit.

The concept of quality as assessed by connoisseurs is typically comprised of excellent facture and satisfying approach to content, often spiced with a modicum of inventiveness, but it is also conditioned by cultural expectations. What is admired as beautiful or significant in one era may be denigrated in another. Even connoisseurship itself has been subject to the vagaries of fashion: by the mid-twentieth century it began to be dismissed by some scholars, those more engaged with questions of iconographic content and cultural context, as being too superficially concerned with appearances.[ix] For historians tracing societal trends, a work of art, as the product of its milieu, can serve as visual evidence for shared cultural values irrespective of individual authorship. Critics of connoisseurial methods have also argued, with good reason, that the evidence on which aesthetic judgments are based is often flawed and fragmentary.[x] Of the millions of paintings produced in early modern Europe, perhaps fewer than one percent exist today.[xi]

In spite of these challenges, the continuing value of connoisseurship can be claimed on both intellectual and practical grounds. Broad historical theories that build on works of art as evidence fall like a house of cards if assumptions about the authenticity of those works prove incorrect. Furthermore, the appraisal of an artist’s methods is not a superficial exercise. It involves the assessment not only of aesthetic elements, such as colour or brushwork, but also of how the artist deploys this visual language to convey meaning as well as to offer visual delight. Thus, as early writers like De Piles and Dezallier D’Argenville argued, the connoisseur must strive to understand the artist’s thought process as well as his techniques.[xii] In the marketplace, it seems likely that the high value of name recognition will also continue to drive efforts to identify authorship and originality, as well as to appraise quality.

While theoretical writings on connoisseurship have been concerned primarily with questions of style, authors have also paid attention to the material properties of paintings. For instance, the seventeenth-century French writer Abraham Bosse observed that copies sometimes fail to deceive because the copyist is unable to duplicate the original materials.[xiii] Given that writers like Bosse had nothing to rely on but their own faculties of sight and memory, their refined understanding of individual styles and artistic movements is truly remarkable. Today’s art historians, in contrast, have the benefit of a wide range of observational tools, from high resolution digital photography to infrared reflectography, as well as scientific methods of examining the materials of which paintings are made. Several of these methods are demonstrated in the present exhibition. Digital archives also allow us to compile, compare, and contrast data from diverse sources.

These objective methods would seem to render traditional connoisseurship obsolete. For instance, in 1997, the conservation scientist Karin Groen discovered that Rembrandt primed the enormous canvas for his famous group portrait The Night Watch with a medium that included an inexpensive filler, quartz. Since then, this mixture has been detected in numerous paintings by Rembrandt and his followers, but not in those of other Dutch artists. Thus, its presence may provide objective proof that a given painting came from Rembrandt’s atelier.[xiv] However, Rembrandt mentored dozens of other artists, and even chemical analysis may not be able to separate the hands of painters working in the same studio, on the same day, with the same materials, as associates in large workshops must often have done. This is where the connoisseur’s knowledge of an artist’s characteristic approach to style and facture can be brought to bear: even using the same materials, the brushwork of one artist may be discernibly different from another. So, too, may the interpretation of a familiar motif (the Morellian method), or the treatment of a formal problem such as perspective or shading. In assessing these features, intuition and experience, although theoretically contrasted, go hand in hand: the knowledge that enables a trained eye to recognize minute differences is built up over time through close acquaintance with the work of a given artist or movement until it becomes a matter of instinct as well as rational judgment.

In October 2014, the prominent art historian Mina Gregori made headlines with her discovery of what she believes to be an authentic painting by the Italian master Caravaggio. Although it is one of several close replicas of a well-known work depicting Mary Magdalene in ecstasy, Gregori is absolutely certain of its attribution to Caravaggio himself. In recognizing the subtle characteristics of the artist’s personal manner, she called upon what she terms the “memory archive” that seasoned art historians carry with them. “I have become a connoisseur,” the ninety-year-old Gregori told a reporter for the Guardian, “and I know a Caravaggio when I see one.”[xv]


[i] This brief summary is indebted to histories of connoisseurship such as Carol Gibson-Wood, Studies in the Theory of Connoisseurship from Vasari to Morelli (New York and London: Garland Publishers, 1988); Enrico Castelnuovo and Jaynie Anderson, “Connoisseurship. I. Western World,” Oxford Art Online, accessed November 3, 2014; Anna Tummers, Koenraad Jonckheere, eds., et al., Art Market and Connoisseurship: A Closer Look at Paintings by Rembrandt, Rubens and their Contemporaries (Amsterdam: Amsterdam University Press, 2008); and Anna Tummers, The Eye of the Connoisseur: Authenticating Paintings by Rembrandt and his Contemporaries (Los Angeles: J. Paul Getty Museum, 2011).

[ii] See Giulio Mancini, Considerazioni sulla pittura (1620), A. Marrucchi, ed., 2 vols. (Rome: Accademia Nazionale dei Lincei, 1956–7); Abraham Bosse, Sentimens sur la distinction des diverses manières de peinture, dessein, et graveure, et des originaux d’avec leurs copies (Paris, 1649); Roger de Piles, Conversations sur la connoissance de la peinture et sur le jugement qu’on doit faire des tableaux (Paris, 1677) and Abrégé de la vie des peintres, avec des réflexions sur leurs ouvrages, et un traité du peintre parfait, de la connoissance des dessins, et de l’utilité des estampes (Paris, 1699); Jonathan Richardson, Two Discourses. I. An Essay on the Whole Art of Criticism as It Relates to Painting, Shewing I. Of the Goodness of a Picture; II. Of the Hand of the Master; and III. Whether ’tis an Original, or a Copy. II. An Argument in Behalf of the Science of a Connoisseur, wherein is Shewn the Dignity, Certainty, Pleasure and Advantage of It (London, 1719).

[iii] The history of cultural consumption, artistic production, and the development of the art market has been the subject of much recent study. See, among others, John Brewer and Roy Porter, eds., Consumption and the World of Goods (London: Routledge, 1993); Michael North and David Ormrod, eds., Art Markets in Europe, 1400–1800 (Aldershot, UK: Ashgate, 1998); Richard Spear and Philip Sohm, Painting for Profit: the Economic Lives of Seventeenth-Century Italian Painters (New Haven, CT: Yale University Press, 2010).

[iv] Tummers, The Eye of the Connoisseur, 265. This statistic was borne out in my own research for a forthcoming article, first presented as a conference paper, “Rembrandt on the Market: A Case Study in the Value of Attribution,” at the Universities Art Association Annual Meeting, Toronto, October 25, 2014.

[v] Samuel van Hoogstraten, Inleyding tot de Hooghe Schole der Schilderkonst (Rotterdam, 1678): **3; see also Tummers, Eye of the Connoisseur, 183, 232.

[vi] See Eric Jan Sluijter, “On Brabant Rubbish, Economic Competition, Artistic Rivalry, and the Growth of the Market for Paintings in the First Decades of the Seventeenth Century,” Journal of Historians of Netherlandish Art 1:2 (Autumn 2009), accessed November 3, 2014, http://www.jhna.org/index.php/past-issues/volume-1-issue-2/109-on-brabant-rubbish. On the situation in Italy, see Spear and Sohm, Painting for Profit.

[vii] Gibson-Wood, Studies in the Theory of Connoisseurship, 84.

[viii] Giovanni Morelli, Italian Painters: Critical Studies of their Works, trans. Constance Jocelyn Ffoulkes, ed. A. H. Lanyard (London: J. Murray, 1892–93). See also Richard Wollheim, “Giovanni Morelli and the Origins of Scientific Connoisseurship,” in On Art and the Mind: Essays and Lectures (London: Cambridge University Press, 1974): 177–201; Jaynie Anderson, Collecting, Connoisseurship and the Art Market in Risorgimento Italy: Giovanni Morelli’s Letters to Giovanni Melli and Pietro Zavaritt (Venice: Istituto Veneto di Scienze, Lettere ed Arti, 1999).

[ix] See, among others, Max J. Friedlander, On Art and Connoisseurship (London: B. Cassirer, 1942); Edgar Wind, “Critique of Connoisseurship,” in Art and Anarchy: The Reith Lectures (London: Faber and Faber, 1963): 32–51; Jacob Rosenberg, On Quality in Art: Criteria of Excellence, Past and Present, A. W. Mellon Lectures in the Fine Arts (Princeton, NJ: Princeton University Press, 1964); Gary Schwartz, “Connoisseurship: the Penalty of Ahistoricism,” International Journal of Museum Management and Curatorship 7 (1988): 261–68; Gérard Mermoz, “Art History. III. Contemporary Issues,” Oxford Art Online (accessed November 14, 2014).

[x] Schwartz, “Connoisseurship.”

[xi] This statistic, proposed for Dutch seventeenth-century painting, seems plausible for the European market as a whole; see John Michael Montias, Vermeer and his Milieu: A Web of Social History (Princeton, NJ: Princeton University Press, 1989); Montias, Art at Auction in 17th Century Amsterdam (Amsterdam: Amsterdam University Press, 2002).

[xii] Discussed by Gibson-Wood, Studies in the Theory of Connoisseurship, 68, 73.

[xiii] Bosse, Sentimens, 64; Gibson-Wood, Studies in the Theory of Connoisseurship, 54.

[xiv] Rembrandt, The Night Watch, 1642, Amsterdam, Rijksmuseum; Karin Groen, “Investigation of the Binding Medium Used by Rembrandt,” Kunsttechnologie und Konservierung 2 (1997): 207–27; Groen, “Earth Matters: The Origin of the Material Used for the Ground in the Night Watch and Many Other Canvases in Rembrandt’s Workshop after 1640,” ArtMatters 3 (2005): 138–54.

[xv] Lizzy Davies, “Italian Art Historian Claims Magnificent Caravaggio Masterpiece Found,” Guardian, October 24, 2014, accessed Nov. 2, 2014, http://www.theguardian.com/artanddesign/2014/oct/24/italian-art-historian-claims-caravaggio-masterpiece-found.

Conservation Science and Paintings

en français

Alison Murray

Scientists have a long history of working with cultural objects.[i] For example, in the late eighteenth century, Claude-Louis Berthollet and André Thouin accompanied the Napoleonic army to the Italian peninsula, where, in addition to other duties, they evaluated the condition of artworks that had been confiscated.[ii] Archaeological pigments from Pompeii were identified in the early nineteenth century by Jean-Antoine Chaptal and by Sir Humphrey Davy.[iii] They made the first qualitative analyses of Egyptian blue, an artificial calcium copper silicate pigment.[iv] In 1850 Michael Faraday gave evidence at a select committee appointed by the British House of Commons on the effect of pollutants from the combustion of coal on paintings in London’s National Gallery. In 1859 Faraday was also part of a commission that studied the effects of the environment, including gaslight, on paintings. While working with these committees, he also promoted preventive measures, such as glazing and using backing materials for paintings, to slow down deterioration.[v] Wilhelm Röntgen first used X-rays in 1895, and soon afterwards they were applied to radiograph a painting.[vi] Scientists have examined other cultural objects in addition to paintings. In the twentieth century, the metallurgist Sir Cyril Stanley Smith investigated how ancient metal objects were made.[vii] He wrote, “the internal structure of a work of art in metal can often throw as much, or more, light on its origin as can be derived from stylistic analysis.”[viii] The earliest museum lab headed by a scientist was at the Staatliche Museen zu Berlin (National Museums in Berlin) in 1888. Other museums where scientists worked followed in the 1910s, 1920s, and 1930s including those at the British Museum in London, Harvard’s Fogg Museum in Cambridge, Massachusetts, the Louvre in Paris, and the National Gallery as well as the Courtauld Institute, both in London. Questions of identification, degradation, and condition of paintings, as well as preventive and cleaning treatments, are still being investigated today. This essay discusses the types of work that continue to engage scientists and how these scientists enter the conservation science field.

Conservation scientists perform analyses and undertake larger research projects, working with conservators, art historians, and curators. A conservation scientist is “a person trained in science who applies his/her knowledge to the conservation of cultural properties.”[ix] These professionals are also known as “heritage scientists” as their work involves more than conservation. A single artwork, a specific material, a collection, or even an artist’s entire oeuvre may be studied in order to learn about art materials, working process, or method of production. Identification of unexpected materials or techniques may indicate that a work is not, or not entirely, authentic. Conservation scientists also routinely work towards preventing problems that arise from the display or storage of artworks. The best environment, including safe light levels, relative humidity, and temperature, needs to be established for the many various materials found in a collection. For example, it is important to guard against changes in relative humidity that cause wood and paint layers in a panel painting to change in dimension and separate. A crucial relationship exists between the scientists and the conservators, who, from treating objects, can identify relevant issues; together they work to develop new conservation treatment techniques. Engineers and scientists also lend their expertise to help determine whether paintings and objects are stable enough to travel for exhibition and, if so, how they should be packed; inappropriate storage containers and packing material can emit noxious gases and cause degradation. In all these cases, professionals with scientific and engineering expertise undertake the basic research needed to answer questions on identification and degradation of cultural heritage materials.

The conservation scientist chooses the appropriate instrumental techniques, analyzes samples, and interprets the results in the context of cultural heritage. For example, ideally the amount of material selected for analysis is very small, with the specific amounts required varying for individual techniques. These selections require the careful planning of sample locations in order to ensure the results are meaningful for the issues being investigated and representative of the entire artwork. Can all the colours be sampled? Is the amount of material to be removed, even when it is microscopic, too large to be acceptable ethically or aesthetically? Does comparative material exist to give context to the results? Have the pigments faded, or has there been other decay to the material? Analysis exploring these questions can give surprising results. Scientists help to develop conservation treatments that must stand the test of time.[x] Scientists investigate newly developed products to see if they will improve the stability of cultural heritage objects undergoing conservation treatment. Extensive preliminary testing should prevent the use of harmful products that can cause deterioration, requiring conservators to undo previous treatments. Materials testing through accelerated aging and the use of samples that mimic actual cultural heritage objects can only give so much information. For work on actual artifacts, the principles of minimum intervention and continuing care and maintenance guide sound conservation practice today.

Newer techniques and instrument improvements continue to be developed, and there is a strong interest in applying these advances to the conservation and technical analysis of cultural heritage. An X-ray fluorescence spectrometer (XRF) for elemental analysis was used extensively when analyzing paintings for The Unvarnished Truth: Exploring the Material History of Paintings. Developments in the twenty-first century have made portable and lightweight units available. The Getty Conservation Institute (GCI) is one of several organizations that have developed noninvasive, portable X-ray diffractometers with XRF spectrometers (XRD/XRF).[xi] Had this combination of techniques been available to the researchers involved in this exhibition, it would have contributed greatly to The Unvarnished Truth as it would have given exact, nondestructive identification of crystalline pigments rather than only elemental analysis with XRF. Another recent development is the macro-scanning XRF spectrometry developed through a university-industry collaboration by the University of Antwerp in Belgium, the Delft University of Technology in the Netherlands, and Bruker Nano in Germany. This portable device allows paintings to be scanned with a high spatial resolution, identifying elements that make up the top surface and subsurface of the paint structure.[xii]

The clearly defined goals of any research project guide the scientist in choosing appropriate techniques. The information thereby gained is evaluated critically to determine its relevance. For some analyses, the art object may need to travel to a specific instrument, in which case the stability of the object must first be determined to ensure its long-term safety. New techniques are often expensive, and while analytical laboratories may be willing to perform some initial analysis free of charge, usually this cannot continue in the long term. Since achieving greater accuracy will often be more expensive, the scientist must ask if the likely results are worth the greater expenditure.

At this time of limited budgets and fiscal restraint, conservation professionals are looking at ways to work more effectively and create greater impact. At the 2013 ICCROM[xiii] Forum on Conservation Science, “Conservation Science in Context,” professionals stressed that educating the public about the value of their work can generate numerous economic and social benefits.[xiv] The Unvarnished Truth is a wonderful example of bringing the analysis of cultural heritage to the attention of the public, and increasing awareness of scientific vocabulary, concepts, and techniques. The University of Delaware, funded by the Samuel H. Kress Foundation, recently launched a website aimed in part at providing project material for students in kindergarten to grade 12; it describes painting reconstructions and documentation techniques.[xv] The Art Gallery of Ontario’s recent exhibition Revealing the Early Renaissance: Stories and Secrets in Florentine Art included a display of pigments as well as the art objects themselves.[xvi] These three examples help the public to feel closer to artists by increasing understanding of their materials and highlighting the tangible aspect of creating works of art.

The applied field of art conservation often relies on interdisciplinary research groups that, in working together, face challenges arising from the priorities and vocabularies that vary according to discipline, and from difficulties in transferring research results into usable information. The 2014 report “Mind the Gap: Rigour and Relevance in Heritage Science Research” discusses these points as well strategies for effective collaboration, including pre-project time and funding to promote strong relationships before the actual start of a project.[xvii] The 2013 ICCROM Forum on Conservation Science also generated specific suggestions for increasing the impact of conservation science on heritage conservation. These included improving access to research facilities, making funds available for applied research projects, and running training courses that apply research outcomes. This last idea has been implemented for several years at the Cleaning of Acrylic Painted Surfaces Workshops organized by the GCI. Science researchers from the GCI and the Tate Modern discuss their current research with practising conservators, who then apply various cleaning methods to test samples and give their feedback directly to the science research team.[xviii] A simple method of inviting suggestions is used at the annual conference for the Canadian Association for Conservation, where conservators are routinely surveyed about where they feel scientific research is needed. Collaborative research is unquestionably valuable, but improved methods for implementation are needed.

Many of the world’s larger museums have scientists on staff; however, in Canada, we have a separate institution, the Canadian Conservation Institute in Ottawa, where a large group of scientists and engineers work with conservators. Conservation scientists in Canada also work at Parks Canada and various universities, such as the Art Conservation Program at Queen’s University. Training for conservation scientists has not been as formalized as it has been for conservators. Chemists (for example in analytical, organic, inorganic, or polymer science), biologists, material scientists, and mechanical and civil engineers may come into the cultural heritage field after completing their degrees or sometimes through fellowships. Some of these professionals enhance their expertise by taking a conservation treatment master’s degree, where they may work on paintings, works of art on paper, or objects. In North America and Europe, there are special programs for conservation science. For example, Queen’s offers a Master of Art Conservation degree, where science or engineering students carry out heritage science thesis research. More funded PhD opportunities would be welcomed, for example, through joint projects between professors in chemistry or materials science departments, and conservation programs, museums, or other cultural heritage institutions.

The world of cultural heritage offers numerous opportunities for scientific exploration. Conservation departments in art galleries and museums throughout Canada would welcome visits from interested scientists, possibly leading to future collaboration.

A heartfelt thanks to everyone who read and commented on my essay including colleagues on this project as well as Dorothea Burns, Michael O’Malley, and the project editor, Joan Padgett.


[i] Jilleen Nadolny, “A History of Early Scientific Examination and Analysis of Painting Materials ca. 1780 to the mid-Twentieth Century,” in Conservation of Easel Paintings, ed. Joyce Hill Stoner and Rebecca Rushfield (New York: Routledge, 2012), 336–40; Nadolny, “The First Century of Published Scientific Analysis of the Materials of Historical Painting and Polychromy, circa 1780–1880,” Reviews in Conservation 4 (2003): 39–51.

[ii] Cathleen Hoeniger, “Art, Science and Painting Restoration in Napoleonic Italy, 1796–98,” in Conservation in the Nineteenth Century, ed. Isabelle Brajer (London: Archetype Publications Ltd., 2013), 15–28.

[iii] Nadolny, “The First Century of Published Scientific Analysis,” 45.

[iv] Josef Riederer, “Egyptian Blue,” in Artists’ Pigments: A Handbook of Their History and Characteristics, vol. 3, ed. Elisabeth West Fitzhugh (New York, NY: Oxford University Press, 1997), 28.

[v] David Saunders, “Pollution and the National Gallery,” National Gallery Technical Bulletin 21 (2000): 77–94.; Nicola Costaras, “Richard Redgrave (1804–1888): First Curator of Paintings at the South Kensington Museum,” in Conservation in the Nineteenth Century, ed. Isabelle Brajer (London: Archetype Publications Ltd., 2013) 58–9.

[vi] Nadolny, “A History of Early Scientific Examination and Analysis,” 339.

[vii] Cyril Stanley Smith, “The Interpretation of Microstructures of Metallic Artifacts,” in A Search for Structure, Selected Essays on Science, Art, and History (Cambridge, MA: MIT Press, 1982) 69–111.

[viii] Smith, 109.

[ix] Marie-Claude Corbeil, “Training Options for Conservation Scientists,” in University Postgraduate Curricula for Conservation Scientists: Proceedings of the International Seminar Bologna, Italy, 26–27 November 1999 (Rome: ICCROM, 2000): 104.

[x] Giorgio Torraca, “The Scientist’s Role in Historic Preservation with Particular Reference to Stone Conservation,” in Historical and Philosophical Issues in the Conservation of Cultural Heritage, ed. Nicholas Stanley Price, M. Kirby Talley Jr., and Alessandra Melucco Vaccaro‬ (Los Angeles: Getty Publications, 1996) 439–44.‬‬‬‬

[xi] “New Portable X-Ray Diffraction/X-Ray Fluorescence Instrument (XRD/XRF),” The Getty Conservation Institute, last modified April 2009, https://www.getty.edu/conservation/about/science/portable_xrd_xrf.pdf; Alexandra Gianoncelli, Jacques Castaing, Luc Ortega, Eric Dooryhee, Joseph Salomon, Philippe Walter, Jean-Louis Hodeau, and Pierre Bordet, “A Portable Instrument for In Situ Determination of the Chemical and Phase Compositions of Cultural Heritage Objects” X-Ray Spectrometry 37 (2008): 418–23.

[xii] Matthias Alfeld, Joana Vaz Pedroso, Margriet Eikema van Hommes, Geert Van der Snickt, Gwen Tauber, Jorik Blaas, Michael Haschke, Klaus Erier, Joris Dik, and Koen Janssens, “A Mobile Instrument for In Situ Scanning Macro-XRF Investigation of Historical Paintings,” Journal of Analytical Atomic Spectrometry 28 (2013): 760–67.

[xiii] International Centre for the Study of the Preservation and Restoration of Cultural Property (ICCROM), based in Rome, Italy.

[xiv] 2013 ICCROM Forum on Conservation Science, “Conservation Science in Context,” /, last modified November 16, 2013, http://forum2013.iccrom.org/ and http://forum2013.iccrom.org/programme.

[xv] “Technical Art History Website,” University of Delaware, last modified February 25, 2015, www.artcons.udel.edu/about/kress.

[xvi] Revealing the Early Renaissance: Stories and Secrets in Florentine Art, last accessed November 16, 2014, http://www.ago.net/revealing-the-early-renaissance-stories-and-secrets-in-florentine-art.

[xvii] Nancy Bell, Matija Strlič, Kalliopi Fouseki, Pip Laurenson, Andrew Thompson, and Catherine Dillon, Mind the Gap: Rigour and Relevance in Heritage Science Research Report, The National Archives, Kew, Richmond, United Kingdom, last accessed November 16, 2014, http://www.nationalarchives.gov.uk/documents/mind-the-gap-report-jan-2014.pdf.

[xviii] “Cleaning of Acrylic Painted Surfaces,” The Getty Conservation Institute, last modified October 2013, http://www.getty.edu/conservation/our_projects/education/caps/caps_overview.html.

Conservation and Condition Issues

en français

Gianfranco Pocobene

Conservation encompasses a range of endeavours that seek to preserve and restore cultural material, such as paintings, drawings and prints, sculpture, and decorative arts, all of which deteriorate over time from the effects of environment, the inherent instability of the artistic materials, and misguided human interventions. A fundamental objective of conservation is to provide works of art with suitable physical and environmental conditions for their safekeeping. Modern-day museums with proper display and storage, controlled light levels that eliminate damaging ultraviolet radiation, and stable levels of temperature and relative humidity exemplify this concept of preservation. Moreover, conservation concerns itself with the physical condition and aesthetic appearance of the object, which may necessitate treatments to repair and alleviate a variety of condition problems. Conservation treatments are informed and guided by the careful visual examination and documentation of the work of art and take into consideration the short- and long-term effects of any material or procedure used. Critical in this process is a thorough understanding of artistic materials and how they age. Working collaboratively with conservation scientists, modern-day conservators employ a variety of sophisticated analytical tools in their work. During the study and conservation of a painting, much is learned about the materials and techniques used by the artist, which adds to a growing body of knowledge about the artistic process.

Works of art are composed of a variety of materials that react differently to the effects of light, temperature, and relative humidity. A traditional oil painting on canvas is composed of a linen fabric that is stretched over an adjustable wood frame. The linen is sealed and primed with an oil- or water-based ground layer onto which the artist executes the painting. The paint layers, which consist of pigments bound in a drying oil, such as linseed oil, ultimately harden to an inflexible film on the canvas surface. Finally, a varnish layer is typically applied to saturate and protect the paint layers. The differential expansion and contraction of these materials in response to fluctuating humidity and temperature creates stresses within the structure of the painting, causing cracks to form in the paint layers. Over time, further weakening of the paint and canvas support can lead to instability and paint loss. Nonetheless, when quality materials and sound artistic practice are employed, and environmental conditions are favourable, paintings can remain remarkably stable over long periods of time. By contrast, the use of poor materials or shoddy artistic technique can initiate degradation as soon as the object leaves the artist’s studio. Earth pigments are generally stable, but those composed of dye colours may not be and can fade irreversibly on exposure to light. Accidents can result in tears to the canvas or splits in wood panel supports. Less perceptible changes occur within the paint film itself, as volatile components leach out of the surface either from inherent deterioration processes or from the use of strong cleaning solvents during cleaning procedures. The slow deterioration of paint layers inevitably results in a dull paint surface no longer having the intensity of colour it originally possessed. Many paintings have been irreparably altered by owners and dealers who intentionally disassembled paintings for profit or repurposed them to satisfy changes in taste. The portrait of a man in the manner of Tintoretto (Cat. #) is an example of a painting where the original composition has been modified, having been cut down from a larger composition and subsequently relined to fit a new presentation format. The chemical and physical changes that occur to a painting over time can have a profound effect on its appearance and our comprehension of what the artist intended.

The terms conservation and restoration are often used interchangeably to describe the duties of the modern-day conservator, and while the two activities are closely interrelated, each has distinct objectives. Conservation is directed towards preservation of the work of art, typically involving stabilization methods to slow down deterioration and prevent further damage. For example, flaking paint, which might be lost if left unattended, is stabilized with an appropriate adhesive and then carefully reattached to the surface of the painting. The goal of conservation is to preserve as much of the original as possible. Even passive treatments, such as proper reframing and attachment of a protective backing board to the reverse of the painting, go a long way towards its conservation. Restoration efforts, on the other hand, focus on the appearance of a painting and strive to repair damages and alterations that have occurred to the work. The mending of tears in the canvas or the removal of an old, yellowed dammar varnish from the paint surface are examples of restoration procedures. Visually disruptive losses in the image are compensated for by inpainting, thereby “restoring” the composition and overall visual effect. While the term restoration implies that a work of art can be brought back to its original state, this is in fact not possible. Once physical and chemical changes (such as cracking of the paint layers and fading of pigments) have occurred, they are permanent and cannot be reversed. Another challenging problem for the conservator is the question of the artist’s intent. What did the painter actually intend the finished work to look like? Was the painting to be varnished or left unvarnished? The complexity of conserving and restoring paintings was considered by Gerry Hedley, who remarked that “we cannot return to the original intention and so must construct a new relationship between the artist’s original intention, the present work, and the passage of time.”[i] Working in collaboration with museum curators, art historians, and conservation scientists, it is possible for the conservator to interpret historical evidence and analytical findings to perform the most judicious conservation treatment possible, both for the painting’s long-term preservation and to make it visually engaging for the viewer.

Formalized training of conservators and research into artists’ materials and techniques based on scientific principles did not become a serious endeavour until the twentieth century. Before the eighteenth century, the task of cleaning and repairing paintings invariably fell to the hands of artists. A famous example of this occurred in 1603 when Peter Paul Rubens went to Spain to deliver paintings to King Philip III as part of a diplomatic mission. While en route, heavy rainstorms damaged a number of paintings, which were thought to be ruined. Instead of relying on others to perform the restorations, Rubens took it upon himself to repaint the damages, and onlookers at the Spanish court deemed his repairs to be of exceptional quality.[ii] In the eighteenth and nineteenth centuries restorers learned their trade empirically, carrying out their practice with little understanding of the degradation processes that afflict works of art. The results of these interventions, especially cleaning procedures, were mixed at best. The range of materials recommended for cleaning paintings included water, urine, and lye; the latter two are especially harmful to oil paint layers and the delicate glazes applied by artists as finishing touches to their work. The over-cleaning of paintings necessitated the repainting of damaged areas, often carried out in an excessive manner that obscured large portions of the original composition. Throughout the nineteenth and twentieth centuries, greater awareness of the variable quality of treatments, especially the cleaning of paintings, drew critical attention to restoration practices. The most famous controversy erupted in the mid-1840s at the National Gallery, London. The removal of heavy brown layers of varnish from pictures shocked some viewers and provoked an impassioned public debate, which led to the House of Commons appointing a select committee to investigate the manner in which paintings were being treated at the institution.[iii] The discussion concerning restoration and conservation procedures has continued unabated since then, and although many issues remain unresolved, a more reflective attitude has developed within the field. Where in the past, lining and cleaning of paintings were thought of as routine and required procedures—something to be done as a matter of course—conservation treatments have, over the last half-century, become far less invasive and frequent.

Today, conservators perform wide-ranging activities that go beyond conserving and restoring works of art. In the modern museum setting it is common for conservators to undertake many investigative procedures to answer questions about condition, artistic technique, and attribution. To do this they work closely with conservation scientists and use an array of imaging techniques including infrared reflectography and X-radiography. Minute paint samples are taken and examined as cross sections under high-powered microscopes to determine the stratigraphy and composition of paint and varnish layers, and the presence of restorations and grime. Many conservation labs are also equipped with non-destructive tools such as portable X-ray fluorescence analyzers that can quickly determine the elemental makeup of works of art. In the realm of cleaning paintings, great strides have been made with the introduction of gel cleaning systems as an alternative to more aggressive solvent mixtures. The pioneering work of Richard Wolbers enables conservators to apply controlled cleaning solutions to paint surfaces, thereby greatly reducing the risk of swelling and leaching of the paint medium.[vi] The innovations introduced over the past half-century provide the conservator with an unparalleled array of approaches unthinkable at the dawn of modern conservation. Combined with a more thorough understanding of past practices, ethical and philosophical considerations, and the history of the artwork, a more measured approach is possible when treatments and technical examinations are performed.

The paintings selected for this exhibition offer the viewer not only the opportunity to examine paintings composed of a range of artistic materials and techniques but also to consider some intriguing questions about their condition and conservation. Initially, they were examined by this author to determine their suitability for in-depth investigation. Previous conservation records were reviewed, and the paintings were examined visually and under ultraviolet light. Questions regarding their state of preservation and recommendations for further analytical work were detailed in written reports that were reviewed by the collaborating authors. Some of the paintings entered the McMaster Art Museum collection relatively unscathed and are in a pristine state of preservation, while others show signs of damage and multiple restoration interventions. For example, the painting by Rodchenko (Cat. #), executed with thin, translucent applications of paint directly on its softwood panel support, has a small vertical split just to the left of the artist’s signature, but otherwise shows no signs of ever having been cleaned or restored. By contrast, Vincent van Gogh’s Untitled, Still Life: Ginger Pot and Onions (Cat. #) has undergone invasive treatments including wax lining onto a linen support, selective cleaning of the varnish, and restoration of painting losses. To complicate matters further, Van Gogh himself appears to have reused a canvas on which he had previously painted an entirely different composition. To the naked eye, however, most of these condition problems are not readily apparent because, in the past, distracting damages or changes that occurred to the paint surface were hidden by restorers. It is only through the various imaging and analytical techniques recently performed on the group of paintings in this exhibition, and described in detail in the other essays in this volume, that we can better appreciate their physical condition and what has happened to them over time.


[i] Gerry Hedley, “Long Lost Relations and New Found Relativities: Issues in the Cleaning of Paintings,” in Measured Opinions: Collected Papers on the Conservation of Paintings, ed. Caroline Villers (London: United Kingdom Institute for Conservation, 1993), 172–78.

[ii] Michael Jaffé, Rubens and Italy (Oxford: Phaidon Press, 1977), 68.

[iii] For a more detailed review of these issues, see Sheldon Keck, “Some Picture Cleaning Controversies: Past and Present,” Journal of the American Institute for Conservation 23, no. 2 (Spring 1984): 73–87; and also Report from the Select Committee on the National Gallery (London: National Gallery Archive, 1853), vi–xi.

[iv] For a comprehensive account of the history of technical studies and research at the Fogg Museum, see Francesca G. Bewer, A Laboratory for Art: Harvard’s Fogg Museum and the Emergence of Conservation in America, 1900–1950 (New Haven, CT: Yale University Press, 2010).

[v] Joyce Hill Stoner, “Changing Approaches in Art Conservation: 1925 to the Present,” Scientific Examination of Art: Modern Techniques in Conservation and Analysis (Washington, DC: The National Academies Press, 2005), 50.

[vi] For more on this seminal work, see Richard Wolbers, Cleaning Painted Surfaces: Aqueous Methods, (London: Archetype Publications Ltd., 2000).

[1] Gerry Hedley, “Long Lost Relations and New Found Relativities: Issues in the Cleaning of Paintings,” in Measured Opinions: Collected Papers on the Conservation of Paintings, ed. Caroline Villers (London: United Kingdom Institute for Conservation, 1993), 172–78.

[1] Michael Jaffé, Rubens and Italy (Oxford: Phaidon Press, 1977), 68.

[1] For a more detailed review of these issues, see Sheldon Keck, “Some Picture Cleaning Controversies: Past and Present,” Journal of the American Institute for Conservation 23, no. 2 (Spring 1984): 73–87; and also Report from the Select Committee on the National Gallery (London: National Gallery Archive, 1853), vi–xi.

[1] For a comprehensive account of the history of technical studies and research at the Fogg Museum, see Francesca G. Bewer, A Laboratory for Art: Harvard’s Fogg Museum and the Emergence of Conservation in America, 1900–1950 (New Haven, CT: Yale University Press, 2010).

[1] Joyce Hill Stoner, “Changing Approaches in Art Conservation: 1925 to the Present,” Scientific Examination of Art: Modern Techniques in Conservation and Analysis (Washington, DC: The National Academies Press, 2005), 50.

[1] For more on this seminal work, see Richard Wolbers, Cleaning Painted Surfaces: Aqueous Methods, (London: Archetype Publications Ltd., 2000).

Histories of Selected Artists’ Pigments

en français

Brandi Lee MacDonald

Artists’ pigments have long been a point of interest for researchers in cultural heritage. In the 1960s, Gettens and Plesters described the need for a handbook of painting materials that could serve the interests of chemists, conservators, curators, and collectors in the field of art.[i] Their efforts resulted in a series of volumes dedicated to the description of pigments by experts from around the world. That series, and others like it, are excellent sources of information on the extensive historical documentation of pigment history. This essay reviews a selection of commonly used artists’ pigments, and while not intended to be an exhaustive list of all pigments and their histories, our scope includes those materials we have identified as having been used to create the works included in this exhibition. The purpose of technical research on artists’ materials lies in the information it can reveal about which pigments the painters chose to use, their technique, and their process of mixing and layering paints. Data on the chemical composition of pigments are also used by conservators and conservation scientists for determining strategies for the restoration, preservation, and handling of works of art. Artists’ pigments fall within one of two broad categories: inorganic or organic. Inorganic pigments are derived primarily from mineral origins and have an extensive history of human use. Some of the first mineral pigments used by humans include red, purple, orange, and yellow iron oxides; kaolin clays; charcoal; and manganese dioxide; the earliest documented use of these include rock art sites across the globe.[ii] Organic pigments are generally carbon based, and their vivid colours are often derived from plant or animal origins. They are made using methods such as pulverizing insect husks, or by drying and grinding plant roots, and some examples include carmine yellow, indigo blue, and madder red. While the artists did employ both inorganic and organic pigments to create the works studied for The Unvarnished Truth: Exploring the Material History of Paintings, this survey focuses specifically on the mineral pigments used to highlight some of their unique histories.

Early and Modern Pigments: Development and Manufacture

For centuries before the Industrial Revolution, pigments were sourced, produced, and prepared on a local, small-scale basis, or imported from afar through extensive trade networks. A handful of pigment manufacturers and importers existed, such as the East India Company, which provided raw materials such as lapis lazuli from Afghanistan or vermilion from China. During the eighteenth century, however, pigment manufacturing became a widespread industry across Europe, giving rise to a range of new, synthetically prepared materials becoming readily available to painters. This transition resulted in some pigments, whose raw materials were easier to acquire, being more economically viable to manufacture, thus reducing cost; they were also safer to handle.[iii] In some circumstances, these newer synthetic materials were created to mimic and replace existing pigments that were expensive to import or process, were in short supply, or were difficult to access. For example, lapis lazuli was ground to create the vibrant blue pigment ultramarine, popular in use during the Renaissance and Baroque periods. In the 1820s, a synthetic replacement, sometimes referred to as French ultramarine, was produced by heating and grinding components including clay, sodium, sulphur, and charcoal. For many pigments produced after the late 1700s, their histories are typically well defined. It is possible to trace back through a timeline of manufacture the dates and locations of their production, if they were available to artists, and where other notable uses of the same paints are present. In some circumstances, the pigments themselves can be used as temporal markers, and in combination with other lines of evidence can be used for the attribution (sometimes referred to as authentication) of works of art. The proliferation of pigment manufacture in the eighteenth century changed the landscape of availability and accessibility to artists’ materials at an unprecedented rate.

Earth Pigments

Figure 1

FIGURE 1: Areas on The Drinker / The Bitter Draught where earth and other pigments were identified using X-ray fluorescence testing.

Earth pigments are primarily a group of iron and manganese oxides, as well as clays, ranging in colours from red to brown, yellow, orange, black, and white.[iv] They are known commercially by names such as ochre, umber, sienna, and green earth, and are some of the oldest pigments used in human history. Iron oxides (Fe2O3, FeO[OH]×nH2O), which are the foundation of ochres and umbers, are typically formed through the weathering of iron-bearing rocks. Umbers (Fe2O3+MnO2) are manganese-rich deposits of a similar form, and are often more black or violet in hue. Geologic sources of iron oxides are located on virtually every continent of the globe, however their quality and suitability for use as pigment is variable.[v] Historically, iron oxides have been some of the most inexpensive and longest-lasting pigments available to artists, and their presence in most works of art is ubiquitous. For most of the history of their use, earth pigments were used straight from the geologic source by grinding and mixing mineral ores; however, in the late nineteenth to early twentieth centuries, they were manufactured synthetically by oxidizing metallic iron via aqueous precipitation. Iron oxides were used in almost all of the paintings studied in The Unvarnished Truth, and examples from the old masters include a work in the manner of Tintoretto, and works attributed to Adriaen Brouwer, and Jan Gossaert. Figure 1 shows the use of earth pigments on Brouwer’s The Drinker / The Bitter Draught.

Lead and Chalk Whites

White pigments are perhaps one of the most significant materials used by artists as they were often employed both as a ground underneath the presentation layer and as an admixture to modify other hues. The ground layer is an important component of a painting’s composition as it primes the canvas or board for the application and buildup of pigment. White pigment is found in virtually every European oil painting and occurs primarily in two forms: lead white and chalk white. Lead white (2PbCO3×Pb[OH]2) is one of the oldest of all synthetically produced pigments,[vi] and written records describe its preparation during the Greek and Roman Empires, and in China.[vii] Chalk white occurs in three primary forms: chalk (CaCO3), anhydrite (CaSO4), and gypsum (CaSO4×2H2O), a hydrated form of anhydrite. Chalk is derived from limestone, which is composed of microscopic fossils, while gypsum and anhydrite are evaporite minerals associated with sedimentary geologic deposits.[viii] Lead and chalk whites were often mixed together to produce the imprimatura, or underpainting, creating the base upon which other pigments were applied. In the nineteenth century, lead and chalk whites continued to be used, but they were often mixed with kaolin (Al2Si2O5[OH]4), barytes (BaSO4), and zinc white (ZnO).

Figure 2a

FIGURE 2: a) A portrait of a man, showing locations where two paint samples were removed

Figure 2b

FIGURE 2: b) SEM cross-section image (20× mag.) of sample 2, showing the application of multiple layers of pigment

We identified lead and chalk whites in most of the paintings in this study. Using X-ray diffraction (XRD) and scanning electron microscopy (SEM-EDS) (described in greater detail in the essay “The Analysis of Inorganic Pigments Using Spectrometric Techniques” in this volume) on a tiny paint flake removed from the edge of a portrait of a man (Cat. #) in the manner of Tintoretto, we identified a mixture of lead, anhydrite, and gypsum minerals during our investigation of the faux frame, a built-up layer of pigments in the corners of the work (Fig. 2).

Cobalt Blues

Figure 3

FIGURE 3: Van der Neer used cobalt blue to colour the sky on Untitled, A Frozen Waterway with Villagers Playing Kolf and Skating and a Horsedrawn Sleigh (detail).

Cobalt blue (CoO×Al2O3) is derived from the heating of cobalt ore and aluminum oxide minerals. As an oil paint, it is often presented as a soft, cool light-blue pigment, commonly used for skies in landscapes. Historical records indicate that geologic sources of cobalt ore were located in the Saxony region of Germany as well as in Hungary, Burma, and Sweden.[ix] It was used for millennia to colour glass and for pottery glaze, and was employed extensively as an ingredient in Roman glassware manufacture. However, it was not isolated as a painter’s pigment until 1803–04 by Louis Jacques Thénard, at which point it was rapidly commercialized.[x] It dries slowly, but is stable to light, heat, chemical agents, and atmospheric chemical pollutants. It was used widely in European easel paintings, and using X-ray fluorescence we identified it in the section shown in Figure 3 in Untitled, A Frozen Waterway with Villagers Playing Kolf and Skating and a Horsedrawn Sleigh (Cat. X), attributed to Aert van der Neer.

Vermilion Red

Figure 4

FIGURE 4: Detail of Untitled by Rodchenko. The only mineral pigment identifiable is the red circle visible in the lower left area of the painting where the artist used vermilion.

Vermilion is the name given to the pigment derived from mercuric sulphide (HgS), also known as cinnabar. It has been used for millennia, and evidence shows it was used in eastern Asia, in the lands that made up the Greek and Roman Empires, and in areas of pre-European-contact North and South America. The pigment occurs geologically in many areas of the world, most notably in Russia, China, Germany, Italy, Croatia, Peru, Mexico, and in the American states of Texas and California.[xi] In seventeenth-century Europe, Amsterdam was the primary location for dry-processing vermilion until the advent of wet-processing in the mid- to late nineteenth century.[xii] Wet-processing involved the heating of vermilion ore in a solution of ammonium or potassium sulphide, which was more cost-effective than the dry-processing technique. Vermilion is still produced and used in Germany and England to this day. Vermilion was identified to some extent in every one of the paintings included in this study. Figure 4 shows the area of the Alexander Rodchenko work where vermilion, the only mineral pigment identifiable from the piece, was located via X-ray fluorescence.

Azurite and Copper Greens

Figure 5

FIGURE 5: SEM image of paint sample taken from the portrait of Maximillian, Archduke of Austria (50× mag.). Green-blue azurite crystals are visible, as is lead and chalk ground.

Azurite is a green-blue pigment composed of copper carbonate [2CuCO3×Cu(OH)2], and the group of associated copper greens includes variants such as emerald green [Cu(CH3COO)2·3Cu(AsO2)2], malachite [CuCO3·Cu(OH)2], and verdigris [Cu(CH3COO)2·nCu(OH)2]. Azurite is often found mixed with yellows to create blues and greens, and red lakes to create violet. Its synthetic counterpart, known as blue verditer, is almost chemically identical, and is produced by adding calcium carbonate to copper sulphate. The raw mineral azurite is found in many parts of the world, including Hungary, France, and Sardinia, and is historically known to have been used extensively in Egypt, eastern China, and Japan, as well as by pre-European-contact indigenous populations in central America. It has been described as one of the most important pigments used during the Middle Ages, the Renaissance, and later.[xiii] Using a combination of XRD and SEM-EDS, we identified azurite in the portrait in the manner of Peter Paul Rubens (Fig. 5). The pigment is known to have long-term discolouration and stability issues as it often turns to malachite over time, or darkens in the presence of sulphur fumes.

Chrome and Zinc: Modern Yellows, Blues, and Greens

Figure 6

FIGURE 6: Detail of Untitled, Still Life: Ginger Pot and Onions, areas showing where chromium- and copper-derived greens were identified.

A group of pigments synonymous with the modern age of pigment manufacture is derived from chrome- and zinc-rich minerals. Chrome oxides (chrome oxide, Cr2O3, and hydrated chromium oxide, Cr2O3 ×2H2O) produce green and green-blue pigments, ranging from dull to vibrant,[xiv] while another rarer occurrence, chromblaugrün is a richer blue (Cr2O3·CoO·Al2O3). These were introduced to artists’ palettes around the first half of the nineteenth century, and were known by names such as viridian, Guignet’s green, and Scheele’s green. Chrome-derived greens were known to have been used by Van Gogh during the late 1880s,[xv] and in our examination of Untitled, Still Life: Ginger Pot and Onions using X-ray fluorescence, we identified chrome-derived green in the brighter area of the jar, indicated in Figure 6. Other green areas around the jar that are duller in appearance are copper-derived greens.

Another group of chrome-, zinc-, and lead-based minerals are used to create yellow pigments, known commercially as chrome yellow or lemon yellow [PbCrO4 or, PbCrO4×PbSO4], or zinc yellow (K2O·4ZnCrO4·3H2O).[xvi] Chrome yellow was first produced in France in 1797 by Louis Vauquelin, but widespread production and use did not begin until the second quarter of the nineteenth century in France and the United States. It was originally extracted from the mineral crocoite (PbCr4O), but new methods of production, such as the precipitation of chromite (FeO·Cr2O3), created the potential for increased production. Zinc yellow, while chemically different from the chrome greens, was often used in combination with them. It was first synthesized in 1800, however it was not used extensively until 1850.[xvii] In our analysis of Murnau Landscape with Three Haystacks by Alexej von Jawlensky (Cat. #), we noted the presence of zinc—which could be associated with zinc yellow or zinc white—in many areas of the piece. This is discussed in greater detail in the essay “The Analysis of Inorganic Pigments Using Spectrometric Techniques” in this volume. Further investigation using chemical analytical techniques, such as X-ray diffraction of a removed paint sample, would verify this.

Artists’ pigments are an important source of information, and their study and documentation can reveal much, not only about artists, their techniques, and decision-making but also about broader historical and socioeconomic circumstances related to pigment manufacture that played out over time. Typically, a combination of expertise in technical art history and methodologies for chemical analysis are needed to achieve this end. The development and enhancement of new and existing technologies, such as macro X-ray fluorescence, X-ray diffraction, and scanning electron microscopy, have enabled researchers to discover previously unknown characteristics of pigments and to add to the records of historical literature on recipes, treatises on paintings, and manuscript sources related to painting technologies and practices. The essay “The Analysis of Inorganic Pigments Using Spectrometric Techniques” in this volume delves deeper into the scientific investigation of pigments, describing their chemistry, and the qualitative and quantitative methods and techniques for their analysis.

 


[i] Richard Buck, “Identification of the Materials of Paintings,” Studies in Conservation 11, no. 2 (1966): 52–3.

[ii] H. Valladas, J. Clottes, J.-M. Geneste, M. A. Garcia, M. Arnold, H. Cachier, and N. Tisnérat-Laborde, “Palaeolithic Paintings: Evolution of Prehistoric Cave Art,” Nature 413 (2001): 479.

[iii] R. D. Harley, Artists’ Pigments c. 1600–1835 (London: Butterworth Scientific, 1982), 58–9.

[iv] Brandi Lee MacDonald, R. G. V. Hancock, Aubrey Cannon, and Alice Pidruczny, “Geochemical Characterization of Ochre from Central Coastal British Columbia, Canada,” Journal of Archaeological Science 38 (2011): 3620–30.

[v] B. L. MacDonald, R. G. V. Hancock, A. Cannon, F. McNeill, R. Reimer, and A. Pidruczny, “Elemental Analysis of Ochre Outcrops in Southern British Columbia, Canada,” Archaeometry 55, no. 6 (2013): 1020–33.

[vi] “Lead White,” CAMEO: Conservation and Art Materials Encyclopedia, (Boston: Museum of Fine Arts), last modified, January 21, 2014, http://cameo.mfa.org/wiki/Lead_white.

[vii] R. J. Gettens, H. Kühn, and W. T. Chase, “Lead White,” in Artists’ Pigments: A Handbook of their History and Characteristics, vol. 2, ed. A. Roy (Washington, DC: National Gallery of Art, 1993), 67–81.

[viii] N. Eastaugh, V. Walsh, T. Chaplin, and R. Siddall, ed. Pigment Compendium: A Dictionary and Optical Microscopy of Historical Pigments (Boston: Elsevier, Butterworth-Heineman, 2004).

[ix] A. Roy, “Cobalt Blue,” in Artists’ Pigments: A Handbook of their History and Characteristics, ed. B. Berrie, vol. 4 (Washington, DC: National Gallery of Art, 2007), 151–77.

[x] Cobalt Blue,” CAMEO: Conservation and Art Materials Encyclopedia, (Boston: Museum of Fine Arts), last modified, January 13, 2014, http://cameo.mfa.org/wiki/Cobalt_blue.

[xi] R. J. Gettens, R. L. Feller, and W. T. Chase, “Vermillon and Cinnabar,” in Artists’ Pigments: A Handbook of their History and Characteristics, vol 2, ed. A. Roy (Washington, DC: National Gallery of Art, 1993), 159–82.

[xii] “Vermillion,” CAMEO: Conservation and Art Materials Encyclopedia, (Boston: Museum of Fine Arts), last modified, August, 1, 2013, http://cameo.mfa.org/wiki/Vermilion.

[xiii] R. J. Gettens and E. W. Fitzhugh, “Azurite and Blue Verditer,” in Artists’ Pigments: A Handbook of their History and Characteristics, vol. 2, ed. A. Roy (Washington, DC: National Gallery of Art, 1993), 23–33.

[xiv] “Viridian,” CAMEO: Conservation and Art Materials Encyclopedia, (Boston: Museum of Fine Arts), last modified, July, 24, 2013, http://cameo.mfa.org/wiki/Viridian.

[xv] R. Newman, “Chromium Oxide Greens,” in Artists’ Pigments: A Handbook of their History and Characteristics, vol. 3, ed. E. W. Fitzhugh (Washington, DC: National Gallery of Art, 1997), 273–90.

[xvi] “Chrome Yellow,” CAMEO: Conservation and Art Materials Encyclopedia, (Boston: Museum of Fine Arts), last modified, January, 13, 2014, http://cameo.mfa.org/wiki/Chrome_yellow.

[xvii] H. Kühn and M. Curran, “Chrome Yellow and Other Chromate Pigments,” in Artists’ Pigments: A Handbook of their History and Characteristics, vol. 1, ed. R. Feller (Washington, DC: National Gallery of Art, 1986), 187–217.

The Analysis of Inorganic Pigments Using Spectrometric Techniques

en français

Brandi Lee MacDonald 

A painting, as an object, consists of multiple components that, when analyzed together, have a unique story to tell about the artist, his or her practice, and the history of the piece. The supporting material, grounds, pigments, and varnishes that a painter chose to employ have the potential to reveal a great deal of information about the composition, context, and decision-making involved in the creation of a work, and their analysis contributes to our understanding of the artist’s oeuvre. Determining the chemical composition and identities of the pigments using spectrometric techniques is an essential component of the heritage scientist’s repertoire. Unsurprisingly, pigment analysis was a core component of the methods used to study paintings for The Unvarnished Truth: Exploring the Material History of Paintings. Artists’ pigments fall within one of two broad categories: inorganic and organic. Many resources exist that document histories of pigment types used over time,[i] and the essay “Histories of Selected Artists Pigments” in this volume provides a concise overview of selected types and the histories of their manufacture and use. Here we focus specifically on the analysis of inorganic mineral pigments that were used to execute the works attributed to Van Gogh, Jawlensky, and in the manner of Rubens. Four techniques were used to characterize the pigments: X-ray fluorescence (XRF), 2D macro-XRF (M-XRF), X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). It cannot be overstated that this research required the collaboration of individuals possessing expertise in areas of radiation physics, pigment and art history, and conservation science, and without their contributions, would not have been possible. The results of these tests provided valuable information for better understanding the works of art in question. 

Analysis of Pigments: Techniques and Limitations

The material analysis of pigments is a critical component of understanding a painter’s work. A range of tools for this are available to the heritage researcher, and deciding which technique(s) to use depends on the type and resolution of data that are required to answer the research questions. Paintings are created by mixing mineral pigments with a binding medium (often an oil), which are then applied to and dried on a surface, and subsequently painted over with additional paint layers and a coating of varnish. This creates a complex series of layered materials that are challenging to isolate individually and characterize; therefore, the analytical methods applied must be carefully selected bearing this in mind. Four different techniques were used for this study, each suited for different purposes to obtain elemental and chemical data.

XRF (including portable and macro-XRF) is a technique that measures the elemental composition of the surface and near-surface of an object, in most cases covering an area of a few milimetres.2 The method involves bombarding the surface of the painting with primary X-rays powerful enough to dislodge inner K-shell electrons from their respective shell configurations. The atoms become unstable, and the outer L- and M-shell electrons replace the inner-shell vacancies until the atoms are charge satisfied. The energy that is emitted, or fluoresced, during the inner-shell ejections produces X-rays that are characteristic of those elements. Those X-rays are measured by a detector, and through a series of computations, qualitative and semi-quantitative data on the elements present are produced. (Detailed descriptions of this technique exist elsewhere.[ii]) XRF is capable of qualitatively and semi-quantitatively measuring virtually all elements in the periodic table, although low atomic elements, such as sulphur, aluminum, and sodium, have weaker fluorescence signals, are difficult to measure, and require advanced instrumentation.[iii] Many higher atomic (high-Z) elements, including barium, iron, lead, and zinc, are of interest because they are major components of prepared pigments. XRF is an important screening tool for the heritage specialist as it is nondestructive, does not require the removal of sample material, and is relatively low cost. Recent advances in available portable technologies have enabled its use for the analysis of paintings and other objects in situ, which is of significant benefit as some artworks are too large, unstable to move, or must be measured where they are housed. However, there are a number of limitations to this technique. For the purpose of examining artists’ materials, this method measures elemental concentrations, not chemical compounds, and therefore some pigment compositions can only be inferred. For some pigment types, such as zinc white (ZnO) or titanium white (TiO2), pigment identification can be a straightforward task. However, some pigment groups, such as copper carbonates or acetates[iv] or iron oxides, have heterogeneous and complex chemistries, and to determine precisely what they are requires additional complementary information, such as chemical or mineralogical data. Further compounding the XRF measurement process is the depth at which primary X-rays penetrate the surface of a painting and the attenuation of the resulting fluorescence X-rays by the target material. Primary X-rays will penetrate the surface of the object at a depth ranging anywhere from a few microns to a few millimetres, the degree of penetration being influenced by the matrix density and chemical makeup. For example, primary X-rays can penetrate samples consisting of lower Z matrices (such as bone) more deeply than those of higher Z materials (such as metal)[v]. Therefore, when analyzing pigments one must consider not only the surface of the painting but also subsurface features such as the supporting material (canvas, wood panel, cardboard), the ground applied underneath the presentation layer (lead white, chalk, or mixtures of other materials), the pigment-binding medium, the homogeneity of the pigment (one or more materials used and their degree of mixing), the manner in which the artist applied the paint (impasto, thick buildup of paint), the different attenuating effects of all of these layers combined, and the influence they have on accurate instrumental measurements. This complex series of factors is why it is nearly impossible to accurately quantify the elemental concentrations of pigments via XRF, and it is considered primarily as a qualitative and semi-quantitative method.

In addition to XRF analysis, XRD and SEM-EDS techniques were used for this project. These methods are considered micro-destructive as they often require small samples to be physically removed from the surface of a painting. The decision to remove a sample of pigment from a work of art, regardless of how inconspicuous it may be, is never taken lightly. As technologies have advanced in sensitivity, accuracy, and precision, the quantity of sample needed for analysis has dramatically decreased, and when using XRD and SEM-EDS the minimum sample sizes required are smaller than the size of a pinhead. The removal of this small amount of paint from an inconspicuous area, which is subsequently retouched by a skilled hand, is virtually indistinguishable to the naked eye. XRD is a technique that determines crystal structures of inorganic and organometallic materials. It is used for determining the mineral bases of inorganic pigments, and provides information on the presence and relative proportions of these components. A sample is mounted in the path of a beam of primary monochromatic X-rays and rotated at different angles of orientation. The X-rays that hit the target sample scatter, or diffract, in a pattern that is characteristic to the molecular crystal structure. Those diffracted X-rays are measured and compared to a library of diffraction patterns of known chemical compounds for identification. An advantage to this technique is that it is possible, with only a microscopic sample, to determine the chemical compounds present and to differentiate classes of pigments that are indistinguishable on the basis of their elemental composition, for example, copper resinates and acetates, different iron oxides, or lead-based compounds. One drawback to this technique is that because such a microscopic fragment must be removed from the painting, the small sample size runs the risk of not fully representing the range of pigments or underlayers present.

Sample preparation for SEM-EDS requires the paint sample to be embedded in a resin and ground down to produce an optically flat cross section. A focused beam of electrons is applied to the sample to produce both a high-magnification image and elemental data through the analysis of characteristic X-rays produced through the imaging process. An advantage to this technique is that it allows for the linear exploration of elements along the cross-sectional surface of a sample, making it possible to target and identify individual mineral grains (Fig. 7). This is useful for identifying multiple layers of paint as well as the different constituents of paints that are chemically heterogeneous. Our use of XRD and SEM-EDS on the portrait of Maximillian, Archduke of Austria, in the manner of Rubens, described below, yielded valuable information regarding the pigment and ground layer compositions.

A Survey of Artists’ Materials: X-ray Fluorescence

Figure 1

FIGURE 1: Portrait of a man, circa 1520. Areas indicated where Fe, Pb, Cu, Hg, and Ca were identified via XRF.

For The Unvarnished Truth, we screened the nine paintings of interest using an Olympus Innov-X Delta Premium model handheld XRF. The unit has a rhodium anode X-ray tube, an SDD-type detector, and operates up to 40 kV and 0.1 mA. These devices can be configured to different modes, each applying different voltage, current, and filter combinations that optimize the fluorescence of different suites of elements.[vi] Readings were taken in 3-beam soil mode at 60 seconds each at varying currents and amperages. Focusing on testing as many different colours as possible, we targeted multiple areas of interest on each painting to obtain data on the elemental composition of the pigments used. Figure 1 shows areas of Gossaert’s portrait of a man (Cat. #) that were tested. The results indicate areas with iron, mercury, lead, copper, and calcium, and from this we infer that the painting was executed using earth pigments (Fe2O3), cuprite (Cu2O), vermilion (HgS), lead white (2PbCO3), and calcium carbonate (CaCO3). The iron oxides were likely used for browns and reds in areas of the background and in the flesh tones of the sitter. The cuprite, a red oxidized form of copper, was used in areas of the sitter’s shirtsleeve. Lead white was likely used throughout to lighten other hues and as part of the preparation ground. Calcium could represent chalk white used in the preparation ground, or bone black used to darken other hues, although chemical compound testing would be required to confirm this. Vermilion, a red-coloured mercuric sulphide, was found in trace amounts throughout. These pigments are typical of those used by a painter active during this time period.

Figure 2

FIGURE 2: Murnau Landscape with Three Haystacks, 1908–1909. Colour areas tested via XRF include green (A), violet (B), and yellow-red (C).

Figure 2 shows Jawlensky’s colourful piece Murnau Landscape with Three Haystacks and the areas that were tested via XRF. By the time this work was created in the early twentieth century, the mass commercial production of synthetic pigments was widespread. Mineral pigments whose components included chromium, zinc, lead, titanium, and cadmium were ubiquitous[vii]. Table 1 summarizes the areas that were measured, the elements that were detected, and corresponding commercial pigments that the elemental results could indicate. Jawlensky was known to have used many of the commercial pigments[viii] described in Table 1; therefore, we expected to see some of their elemental components in the XRF spectra. Figures 3a–3c are spectral representations and descriptions for measurements in green, yellow-red, and violet areas.

Figure 3a

FIGURE 3a: Spectrum from measurement of Area A (green). Elements present include calcium (Ca), titanium (Ti), chromium (Cr), iron (Fe), zinc (Zn), and lead (Pb), as well as a small cadmium (Cd) peak at 23.1 keV (not pictured).

Figure 3b

FIGURE 3b: Spectrum from XRF measurement of Area B (yellow-red). Elements present are Ti, Cr, Fe, Zn, Pb, and mercury (Hg).

Figure 3c

FIGURE 3c: Spectrum from measurement of Area C (violet), showing peaks for Ca, Ti, Cr, manganese (Mn), Fe, Zn, Pb, and strontium (Sr). The spectrum shows the probable presence of a small amount of manganese (@ 5.8, 6.4 keV), however it is difficult to resolve in the presence of chromium and iron. In this case, manganese violet would not be the primary pigment used for violet in this piece.

 

Table 1: Summary of areas measured, elements detected, and corresponding potential commercial pigments for the analysis of Murnau Landscape with Three Haystacks, 1908–09.

MeasurementArea and Colour Elements Detectedvia XRF in Order of Abundance Potential CommercialPigments in Common Use(post-1900)*
A: Light and darkgreen, lower area ChromiumLeadZincTitanium

Cadmium

Iron

Calcium

Chrome green (Cr2O3)Viridian (Cr2O3.2H2O)Lead white (2PbCO3×Pb[OH]2)Lead chromate (PbCrO4)

Zinc white (ZnO)

Titanium white (TiO2)

Cadmium yellow (CdS)

Black iron oxide (FeO×Fe2O3)

Chalk (CaCO3)

Bone black (C + Ca3[PO4]2)

B: Yellow and orange areas LeadZincChromiumMercury

Cadmium

Titanium

Iron

Lead white (2PbCO3×Pb[OH]2)Lead chromate (PbCrO4)Zinc white (ZnO)As a component of lead chromate

Vermilion (HgS)

Cadmium yellow (CdS)

Titanium white (TiO2)

Ochre (Fe2O3)

C: Violet area LeadTitaniumZincChromium

Strontium

Cadmium

Iron

Manganese

Lead white (2PbCO3×Pb[OH]2)Lead chromate (PbCrO4)Titanium white (TiO2)Zinc white (ZnO)

Chrome green (Cr2O3)

Viridian (Cr2O3.2H2O)

Strontium chromate (SrCrO4)

Cadmium yellow (CdS)

Ochre (Fe2O3)

Black iron oxide (FeO×Fe2O3)

Umber (Fe2O3 + MnO2)

Manganese violet (NH4MnP2O7)

*In use during the time that Jawlensky was an active painter.

This suite of elements suggests that the artist was mixing a range of pigments to create a colourful palette. The chemical compositions present are consistent with those of many of the modern commercial pigments noted above, and with those described in historical documentation confirming usage by the artist.[ix] There are several challenges and limitations for precisely identifying (via XRF) which paints were used for this piece including the degree and combinations of paint mixing, the variable thickness of application and topography of the surface, and the presence of multiple chrome-derived pigments. The mixing of different paints results in variability of the proportions of different elements present. This creates a chemically complex XRF spectra that not only exhibits overlapping and unresolvable peaks (e.g., Ka and La peaks for barium and titanium) but also renders it difficult, if not impossible, to attribute specific elements to specific pigments, potentially leading to misinterpretation. For example, chrome-derived pigments—of which there are multiple occurring in this painting—could include a range of hues, from yellows to greens and reds. Where multiple chrome-derived and other similar pigments are measured simultaneously, it is not possible to attribute them to commercial pigments without the use of additional techniques that measure chemical compounds. Our analysis of the Jawlensky piece also presents an example of the challenges of interpreting overlapping peaks. We have identified the possible presence of manganese (Ka1 @ 5.8 keV; Kb1 @ 6.4 keV) in the violet pigment sections (Area C) indicating the potential use of manganese violet pigment (NH4MnP2O7); however, in the presence of significant quantities of chromium (Kb1 @ 5.9 keV) and iron (Ka1 @ 6.4 keV), the presence or quantity of manganese is virtually impossible to resolve using this technique (Fig. 3c). Furthermore, the depth at which the pigments lie from the surface has an effect on the signal that the XRF technique can detect. Because of the variable surface topography of this particular work, and the multiple, thick layers of pigment that were applied, the XRF measures a combination of pigment layers simultaneously. Of the nine paintings surveyed using this technique, Murnau Landscape with Three Haystacks has, by far, the most complicated mixture of elements and pigments to identify, and serves as an example of the chemical complexity of modern commercial pigments and the importance of careful analytical interpretation of measurements from heterogeneous materials. Further work on this piece would involve chemical or molecular spectrometric techniques, such as XRD, to determine the compounds present.

Layers of Complexity: Mapping Pigments via Macro-XRF

Figure 4

FIGURE 4: Film X-radiograph (upper) and visible light photograph (lower), indicating area of interest.

Using imaging techniques, such as IRR as well as neutron- and X-radiography, it is possible to visualize and examine subsurface features of a painting such as underdrawings and multiple layers of pigment.[x] X-radiography of Untitled, Still Life: Ginger Pot and Onions, attributed to Van Gogh, revealed interesting features suggesting the application of multiple layers of pigment. Figure 4 compares the film X-ray and visible light images indicating where areas of variability in contrast are evident. In the X-ray image, the areas to the immediate centre left of the green jar show an amorphous shape of white contrast. However, on the visible surface of the painting there is no corresponding change in the pigments in shape or pattern. In an X-ray image, changes in contrast such as these are attributed to mineral pigments that contain heavy elements.[xi] When we compare the X-ray image with an elemental map created using macro-XRF, it is possible to create a visual representation of the elemental compositions of the different layers.[xii]

Macro-XRF is a technique that works on the same principles as XRF, but it is capable of scanning an array of points covering an area of interest resulting in a two-dimensional elemental map of the painting. For this experiment we tested the feasibility of a coarse analysis using a low-cost, low-powered benchtop X-ray tube[xiii] and then compared the results to the handheld XRF and X-ray image data. The system used for this test was a commercial X-ray tube that focused the X-ray beam to 0.5 mm × 1.0 mm in area. A custom holder was assembled to support the painting, and the holder was mounted onto a miniature jack to allow for controlled vertical and horizontal movement. A micrometer-driven linear stage was used to manually operate the movement of the painting. Figure 5 is a schematic representation of the layout. A He-Ne laser was used to identify the location of the X-ray beam, and a semiconductor detector was used to record the X-ray signals fluoresced by the painting. A series of 60-second measurements was taken for a total of 581 points measured covering a 70 mm × 45 mm area of the painting. The peak intensities measured at each data point were identified for all elements present. This provided a spatial representation of the distribution of individual elements across the scanned region of the painting, showing changes in the intensities of a corresponding element.

Figure 5

FIGURE 5: An overhead schematic of the 2D macro-XRF scanner setup.

Figure 6

FIGURE 6: 2D macro-XRF elemental map of area of interest for the element lead. Similar patterning in “hotspots” of elements occurs for iron, zinc, and mercury.

 

Features in the 2D XRF map follow similar trends in the X-radiograph, with an angled feature visible in both modalities. This is most strikingly visible for lead (shown in Fig. 6) as well as for iron, zinc, and mercury. These features, when considered alongside the X-ray image, suggest that a different composition (although visually unresolvable) exists underneath what is visible on the surface layer. There is the potential that Van Gogh may have recycled this canvas, and it is documented that during his time in Nuenen in the Netherlands he used zinc white to re-prime previously used canvases as a way of reusing expensive materials.[xiv] Based on our handheld XRF survey of this piece, zinc was present throughout the painting. Zinc white is an inexpensive extender that dries poorly in oil[xv]and is known to result in characteristic surface cracking over time. Under high magnification, it is possible to see this cracking, and in the area of interest, we can see between those cracks to what appears to be a lighter pigment layer underneath (see Fig. 7 micrograph). While the form of this underlying image is unresolved in X-ray and IRR imaging, it is still possible to see that there are areas where whiter pigments lie underneath visible layers, and the handheld and macro-XRF elemental data support this interpretation. For this piece, perhaps Van Gogh had abandoned an earlier work, or scraped down a previous work to the point of obscurity. Others have reported that during the same months that he painted Untitled, Still Life: Ginger Pot and Onions at least another ten of his works that were analyzed using XRF and X-radiography exhibit the same pattern of overpainting and reuse.[xvi] Higher resolution techniques, such as those described by Legrand et al.,[xvii] or the combination of techniques used by Dik et al.[xviii] (portable-, macro-, and micro-XRF, infrared reflectography, XANES[xix], SEM-EDS, and synchrotron radiation XRF), could potentially resolve the underlying image of Untitled, Still Life: Ginger Pot and Onions. However, this would require overseas transportation of the work, which is, unfortunately, cost prohibitive. 

FIGURE 7: Micrograph (7× mag.) of region of interest of the Van Gogh painting. Cracks and pale yellow paint layer below are visible.

FIGURE 7: Micrograph (7× mag.) of region of interest of the Van Gogh painting. Cracks and pale yellow paint layer below are visible.

 

SEM-EDS and XRD of Maximilian, Archduke of Austria

Our preliminary XRF survey of the portrait of Maximillian, Archduke of Austria, in the manner of Rubens, showed that elemental analysis alone was insufficient for determining all of the materials used. Testing of the area that serves as background to the sitter indicated the presence of copper-derived pigments, which one might expect to show as a brighter, vibrant green hue. However, in visible light the area appears to be a muted black-brown. Most copper-derived pigments are impossible to differentiate on the basis of elemental data alone. Because the attribution of the piece remains in question, our goal was to determine precisely which pigment was used and what the application of paint layers could reveal about the painting’s composition. To do this, we removed two tiny paint fragments for XRD and SEM-EDS analysis. Figure 8 shows the areas from which the samples were taken.

FIGURE 8: Areas of the portrait of Maximillian, Archduke of Austria, where two samples were taken for XRD and SEM-EDS analysis. Inset: image showing the size of the paint sample needed, visible at the tip of the scalpel blade.

FIGURE 8: Areas of the portrait of Maximillian, Archduke of Austria, where two samples were taken for XRD and SEM-EDS analysis. Inset: image showing the size of the paint sample needed, visible at the tip of the scalpel blade.

The first paint sample was submitted to McMaster’s Analytical X-ray Diffraction Facility for XRD2 rapid-phase analysis. It was mounted between two Mylar films and analyzed in air using a Bruker Mo Smart APEX2. The system is equipped with a Rigaku RU200 Cu Kα(bar) rotating anode, a Bruker Smart6000 CCD area detector, Bruker 3-circle D8 goniometer, and Göebel cross-coupled parallel focusing mirrors. The detector was calibrated using corundum powder, and three 300-second frames were collected at -20, -40, and -60 degrees 2Θ. The power setting was 50kV, 90mA, and a 0.5 mm collimator was used, and the data were collected using standard Bruker-AXS software. Figure 9 shows the spectral results, indicating that the copper-derived pigment consisted primarily of azurite with traces of chalcopyrite (CuFeS2). Chalcopyrite is a copper mineral that oxidizes to azurite, which is then prepared as a pigment through a process of grinding, washing, levigation, and sieving.[xx]

FIGURE 9: Spectral results of XRD analysis showing presence of diffraction patterns for azurite, lead oxide, chalcopyrite, and others.

FIGURE 9: Spectral results of XRD analysis showing presence of diffraction patterns for azurite, lead oxide, chalcopyrite, and others.

 

Figure 10

FIGURE 10: SEM-EDS back-scattered electron image in the manner of Rubens paint sample (20× mag). The ground layer contains lead, iron, and calcium, while the upper presentation layer shows azurite, calcium, lead, and iron

Sample 2 was embedded in epoxy resin and ground down to produce an optically flat cross section for SEM-EDS analysis. The cross section was examined in a JEOL JSM-6460LV scanning electron microscope with an Oxford Instruments INCAz-sight energy dispersive X-ray spectrometer, and a 133 eV resolution at 5.9 keV. Uncoated samples were examined in low vacuum mode (35 Pa) at 20 kV at a working distance of 10 mm. Images were taken with the JEOL BSE (back-scattered electron) detector in “shadow’” mode (Fig. 10), which combines a typical BSE image with some topographical information. The results of the X-ray spectroscopic analysis revealed that the ground layer is composed primarily of lead white. Directly above the ground layer, another layer—perhaps an initial application of tone—contains a combination of calcium, lead, and copper, and the upper three-quarters of the paint layers also contain copper. Consistent with the XRD results, these are likely azurite and chalcopyrite crystals. It is important to also note here that the cross-section image reveals that in the two layers of paint described, there is not a smooth or clean transition between them. The boundary is somewhat amorphous and disrupted in appearance, suggesting that the upper, or “presentation,” layer was applied very soon after the previous one. This leads us to believe that the background was not repainted at a later time, and in its original form may have appeared to be a green-blue hue. We suspect that the reason the painting now looks very dark is a result of successive applications of oil or resin varnishes applied after cleaning, and of the well-documented phenomenon of azurite pigments fading to dark over time. Gettens and Fitzhugh[xxi] describe how thick layers of azurite in oil become very dark green, in some cases almost black, and list other examples of this. This exploration of paint samples via XRD and SEM-EDS provided insight on the pigment composition and condition, as well as the layering of multiple applications of paint and ground.

Figure 11

FIGURE 11: Overlay of visible light, X-radiograph, and 2D elemental map of area of interest.

As techniques for the visual and chemical analyses of paintings become more widely available, heritage scientists are using these tools to conduct an increasing amount of research into the techniques and materials used by painters, and the condition and life histories of works of art. When these data are combined with art historical information, these explorations have the potential to reveal significant information that would otherwise be unknown. For The Unvarnished Truth project, XRF analysis of Jawlensky’s Murnau Landscape with Three Haystacks verified the presence of a series of modern (post-1850) materials used by the artist such as titanium white, zinc white, and strontium yellow, and also highlighted the limitations of this technique for the examination of chemically complex paint layers. When combining visual modalities such as X-radiography and high-resolution microscopy with elemental mapping, it is possible to glean information on the pigments and condition, as demonstrated in our examination of Van Gogh’s Untitled, Still Life: Ginger Pot and Onions. While the image shown in the X-radiograph and the macro-XRF elemental mapping indicates the presence of an earlier work and the potential recycling of this canvas, this issue remains unresolved until higher resolution techniques can be applied. Furthermore, the analysis of paint samples removed from the portrait of Maximillian, Archduke of Austria via XRD and SEM-EDS provided valuable information regarding its composition and history including confirmation that the use of azurite as a pigment and that the portrait would have likely had a green-blue background rather than a dull black-brown one. The results from these explorations are a testament to the potential for interdisciplinary research in heritage science and what the use of these tools can contribute to our understanding of art history.


[i] Pigment classes and histories are described in further detail in the essay “Histories of Selected Artists’ Pigments” in this volume.

[ii] For extensive discussions on the physics, configurations, and limitations of XRF, see Michael Mantler and Manfred Schreiner, “X-ray Fluorescence Spectrometry in Art and Archaeology,” X-Ray Spectrometry 29 (2000): 3–17.

[iii] Michael Mantler and Manfred Schreiner, “X-ray Fluorescence Spectrometry in Art and Archaeology,” in X-Ray Spectrometry 29 (2000): 3–17.

[iv] Chris McGlinchey, “Handheld XRF for the Examination of Paintings: Proper Use and Limitations,” in Handheld XRF for Art and Archaeology, ed., Aaron Shugar and Jennifer Mass (Leuven, Belgium: Leuven University Press, 2012), 131–58.

[v] For more detailed discussion of X-ray mass attenuation coefficients for different materials of heritage interest, see Michael Mantler and Manfred Schreiner, “X-ray Fluorescence Spectrometry in Art and Archaeology,” in X-Ray Spectrometry 29 (2000): 3–17.

[vi] Nathan Goodale, David G. Bailey, George T. Jones, Catherine Prescott, Elizabeth Scholz, Nick Stagliano, Chelsea Lewis, “pXRF: A Study of Inter-instrument Performance,” in Journal of Archaeological Science 39 (2012): 875–83.

[vii] See the essay “Histories of Selected Artists’ Pigments” in this volume for detailed descriptions of pigment manufacturing history.

[viii] Roy S. Berns, Lawrence A. Talpin, Francisco H. Imai, and Ellen A. Day, “A Comparison of Small-Aperture and Image-Based Spectrophotometry of Paintings,” in Studies in Conservation 50 (2005): 253–66

[ix] Stefan Zumbuehl, Nadim C. Scherrer, Alfons Berger, and Urs Eggenberger, “Early Viridian Pigment Composition: Characterization of a Hydrated Chromium Oxide Borate Pigment,” in Studies in Conservation 54 (2009): 149–59; and Maria Jawlensky, Lucia Pieroni-Jawlensky, and Angelica Jawlensky, Alexej von Jawlensky, Catalogue Raisonné of the Oil Paintings, Vol 1, 1890­–1914 (London: 1991).

[x] For detailed descriptions of imaging techniques, see the essays “Imaging Using X-rays and Neutrons” and “The Technical Art Historian’s Methods on Investigation” in this volume.

[xi] B. I. Reiner, E. L. Siegel, K. J. French, R. S. Dentry, W. T. Mazan, M. J. Maroney, “Use of Computed Radiography in the Study of an Historic Painting,” in Radiographics 17, no. 6 (1997): 1487–95; Olivier Schalm, Ana Cabal, Piet Van Espen, Nathalie Laquiére, and Patrick Storme, “Improved Radiographic Methods for the Investigation of Paintings Using Laboratory and Synchrotron X-ray Sources,” in Journal of Analytical Atomic Spectrometry 26, no. 5 (2011): 1068–77.

[xii] K. Janssens, G. Vittiglio, I. Deraedt, A. Aerts, B. Vekemans, L. Vincze, F. Wei, I. De Ryck, O. Schalm, F. Adams, A. Rindby, A. Knöcgekm, A. Simionovici, and A. Snigriev, “Use of Microscopic XRF for Non-Destructive Analysis in Art and Archaeometry,” in X-ray Spectrometry 29 (2000): 73–91.

[xiii] M. Zamburlini, “In Vivo Measurement of Bone Strontium with X-ray Fluorescence,” (PhD diss., McMaster University, 2008).

[xiv] R. Haswell, L. Carlyle, C. T. J. Mensch, and M. Geldof, “The Examination of Van Gogh’s Painting Grounds Using SEM-EDX,” in Van Gogh’s Studio Practice, ed. Marije Vellekoop, Muriel Geldof, Ella Hendriks, Leo Jansen, and Alberto de Tagle (Brussels, Belgium: Mercatorfonds, 2013), 202–15.

[xv] Ella Hendriks and Louis van Tilborgh, Vincent Van Gogh, Paintings, Volume 2: Antwerp and Paris 1885–1888 (Zwolle: Waanders and Amsterdam, the Netherlands: Van Gogh Museum, 2011), 115–16.

[xvi] L. Megens and M. Geldof, “Van Gogh’s Recycled Works,” in Van Gogh’s Studio Practice, 306–29.

[xvii] Stijn Legrand, Frederik Vanmeert, Geert Van der Snickt, Matthias Alfeld, Wout De Nolf, Joris Dik, and Koen Janssens, “Examination of Historical Paintings by State-of-the-Art Hyperspectral Imaging Methods: From Scanning Infrared Spectroscopy to Computed X-ray Laminography,” in Heritage Science 2 (May 2014): 2–13.

[xviii] Joris Dik, Koen Janssens, Geert Van der Snickt, Luuk van der Loeff, Karen Rickers, and Marube Cotte, “Visualization of a Lost Painting by Vincent van Gogh Using Synchrotron Radiation Based X-ray Fluorescence Elemental Mapping,” in Analytical Chemistry 80 (2008): 6436–42.

[xix] XANES stands for X-ray absorption near edge structure.

[xx] R. J. Gettens and E. W. Fitzhugh, “Azurite and Blue Verditer,” in Artists’ Pigments: A Handbook of their History and Characteristics, ed. A. Roy, vol. 2 (Washington, DC: National Gallery of Art, 1993), 25.

[xxi] Ibid., 27.

 

The Technical Art Historian’s Methods of Investigation: Some Tools and Practices

en français

Nenagh Hathaway

Paintings are complex, multilayered objects, of which we can usually only see the surface layer. These objects result from a series of processes involving the selection and application of painting materials and techniques. The painter chooses a support for the painting (often wood or canvas), a ground material on which to apply the paint, and pigments that are bound in a medium of the artist’s choosing. Before paint layers are applied, an underdrawing, or an initial plan for the overall composition, might be set down to help guide the subsequent stages. The paint can be applied thinly or thickly, roughly or smoothly, and in one or multiple layers. Once the painting is finished, varnish can be applied to protect the paint below and saturate the colours, but the artist might also desire a matte finish and decide not to use varnish. There are many variations to this process, which are usually influenced by the place and period in which the painting was created. Technical art historians study these aspects of a painting to help answer questions on issues such as the attribution and the dating of an artwork. By combining an array of art historical and scientific tools, we can approach questions about artists’ working methods. Technical art history is, by definition, a highly interdisciplinary effort, since it draws on instruments and expertise from fields outside the humanities. Through such exchanges, scientists can better understand their own equipment: its limitations, extensions, and possible improvements. Technical art history also brings together curators and conservators whose experience and knowledge deepen our understanding of the artworks and their state of preservation.[i] The McMaster Museum of Art’s exhibition, The Unvarnished Truth: Exploring the Material History of Paintings, demonstrates that science can provide essential data to further enhance our understanding of the creative processes that produced the fascinating and beautiful objects on display.

The Electromagnetic Spectrum

The human eye is the first tool used to examine paintings. Using only a very small range of the electromagnetic spectrum (Fig. X), our eyes are able to detect a wide range of colours, hues, and tones, through which we experience the world. The colours that we can see are a function of wavelength, all arranged within this visible range of the spectrum, between approximately 400 to 700 nanometres (nm), or billionths of a metre. From short to long wavelengths, the visible spectrum runs from violet, blue, green, yellow, and orange to red.

After this initial visual analysis, a decision can then be made to proceed with examinations using forms of radiation that cannot be detected by the human eye. Beyond the red end of the visible spectrum lies the range of infrared (IR), with wavelengths that are longer than 700 nm. The wavelengths of ultraviolet (UV), on the other hand, are too short to be seen by humans; they are beyond the purple end of the visible spectrum. X-rays have even shorter wavelengths and, thus, more penetrating energy. All these different types of radiation provide complementary information about applied materials and techniques and, typically, about layers that lie below the surface of a painting. However, before using these other parts of the spectrum to analyze a painting, it is possible to learn a great deal about the painting’s condition simply by closely examining its surface.[ii] As paintings age they are transformed: varnishes yellow, some paint mixtures become transparent, and the surface can crack. Human intervention is another factor that often affects the way a painting ages. Over the course of history, many paintings have been subject to alteration by people including amateur painters and professional conservators. These attempts may be an effort to address the effects of age. Such interventions can often be detected with the human eye, sometimes simply by manipulating a light source. For example, shining a light from behind a painting produces light that is transmitted through the painting’s surface. When a painting that is executed on canvas is illuminated using transmitted light, it is possible to see variations in the thickness of paint. Raking light, or light that is shone from one side of a painting, emphasizes surface texture. The surface texture is very informative about the state of preservation of a painting. Using our eyes, we may also see more than the uppermost layer of a painting. For instance, certain paint layers will become increasingly transparent as the work ages, making it possible to see the underdrawing, if present, through these layers.

Magnification

A great deal of information can be gathered while still using the visible part of the spectrum through magnification of the surface of a painting. This is achieved with the help of lenses. Such lenses can be handheld, or can be attached to a headband and worn as a visor to allow both hands to be free (Fig. X). The close examination of the surface of a painting can tell us about the condition of the work, the presence of additions, and the painting technique. Cameras are also capable of producing magnified images of a painting’s surface; macro photography uses a special lens to create detailed images of a small area of a painting (Fig. X).

Photography is an important tool for creating more permanent records of this type of analysis by making it possible to print hard copies of an image. Like analog photography, digital photography requires direct access to the paintings. Once created, digital image files are more accessible because they can be shared with relative ease over the Internet. This enables researchers without firsthand access to artworks to conduct research from afar. Digital photographs can also be effectively compared with digitized X-radiographs, IR reflectograms, and other photographs, facilitating comparisons of the different layers of a painting. For The Unvarnished Truth, digital photographs of all nine paintings were taken and uploaded to a website for sharing among experts. Digital copies of the UV images, IR reflectograms and X-radiographs were also placed on this website. This allowed specialists to examine the paintings in detail before participating in discussions at the museum.

Microscopy

Stereomicroscopes can help direct research because they produce extreme close-ups of the surface of a painting, which cannot be achieved by a camera lens of the type discussed in this essay. Magnification of this strength can allow researchers to see into cracks in the paint surface. This type of microscope generally uses the visible range of the electromagnetic spectrum (about 400 to 700 nm). Stereomicroscopes have two objective lenses (lenses that are closest to the object being examined) that create a three-dimensional image. By making it possible to get a detailed sense of the landscape of a painting, the stereomicroscope yields valuable information about the material composition and the way these materials were applied. Another type of microscope that is often employed in technical analysis of paintings is the research microscope. It is used to examine cross sections, which are tiny samples that are removed from a painting. Research microscopes can also use UV light (approximately 30 to 400 nm) to analyze the structure and materials of the cross section.

INFRARED REFLECTOGRAPHY

IR radiation is composed of longer wavelengths than visible light (between about 700 to 1 000 000 nm or 1 mm). This range is subdivided into the following groups: near infrared (NIR) extends from approximately 750 nm to 2500 nm, mid infrared (MIR) from about 2500 nm to 30 000 nm, and far infrared (FIR) from approximately 30 000 nm to 1 000 000 nm. NIR is used for the analysis of paintings and is a part of the IR spectrum that is not involved with heat detection.

Initially, conservators used IR photography to assess the condition of paintings. Later, the idea developed that this technique might be able to reveal the painting’s underdrawing. Once the support had been prepared for painting, artists were able to apply their compositional designs to it; this is what is called the underdrawing.[iii] Examining underdrawings reveals a great deal of information about the creative process and can assist in clarifying issues of attribution, for example. While IR photography was successful at producing images of the underdrawing beneath most paint mixtures, it is limited as a tool because it is not capable of penetrating some blues and greens. Infrared reflectography (IRR), which uses longer wavelengths than IR photography, was developed by J. R. J. van Asperen de Boer in the 1960s to address this limitation.

Early Netherlandish paintings are particularly well suited to examination with IRR because these works typically include an underdrawing made of a carbon-containing medium applied on top of a white chalk ground. Carbon absorbs IR, whereas white chalk reflects this radiation, creating a high-contrast image of the underdrawing layer. IR is also absorbed by carbon-containing materials used in other layers of a painting besides that of the underdrawing. A careful comparison of the painting as it appears in regular light and in the IR image is therefore necessary to avoid confusing these layers. The entry in this volume on the painting attributed to Jan Gossaert provides a good example of IRR analysis.

Ultra Violet Examination

UV light lies just beyond the purple end of the visible light spectrum (between approximately 30 and 400 nm). UV lamps are useful tools for examining the surface condition of a painting. UV excite fluorescence in materials contained in the uppermost layer of an artwork.[iv] Photographs of paintings under UV light (also known as UV fluorescence photography) can be taken to create a more permanent document for analysis.[v]

It is possible to identify substances based on an understanding of the way particular materials appear when they fluoresce. Different varnishes exhibit characteristic fluorescence, making it possible to classify them under UV illumination. For example, an aged natural resin varnish appears bright greenish-blue under UV. One of the most common uses of the UV lamp is to identify recent areas of retouching, applied within approximately the last several decades (although this range may vary). These retouches will typically appear dark under the UV lamp. UV illumination was used in the analysis of the painting by Aert van der Neer; for more details, see the entry on this particular work in this volume.

X-Radiography

X-radiography uses radiation of the electromagnetic spectrum that falls below about 0.01 to 10 nm. The technique was invented in 1895 and was soon applied to the study of paintings.[vi] X-rays are potentially able to penetrate the entire layered structure of a painting, all the way through the support to anything that is attached to the back of the artwork. X-radiography allows us to visualize the materials of a painting and its support because different elements absorb X-rays in distinctive ways. Areas of paint that contain elements of high atomic number, such as lead white and vermilion, appear as white areas in X-radiographs, and are thus easily identified. In contrast, elements of low atomic number, which are usually part of earth pigments—including umbers, earths, and siennas—appear dark. The negatives of X-radiograph films are used for interpretation because, under regular illumination, the lighter colours on the painting’s surface often appear more like the X-radiograph negatives rather than the developed X-radiograph films.

X-radiographs provide useful information about the construction of a painting as well as the artist’s technique. Compositional changes made in a dense material like lead white, which took place at an early stage of the painting process and are now hidden by subsequent layers of paint, can be revealed by X-radiography. Patches of paint loss that have been filled with a material of high atomic number can also be detected in X-radiographs. As with other methods, it is critical to compare X-radiographs with results from other methods, like IRR. These techniques complement each other, enriching our understanding of artists’ working methods. A practical application of X-radiography can be found in the entry on Adriaen Brouwer’s The Drinker /The Bitter Draught in this volume.

X-Ray Fluorescence Analysis

With X-ray fluorescence (XRF) analysis, a small area of the painting’s surface is exposed to X-rays (between approximately 0.2 to 0.1 nm). These X-rays excite atoms contained in a small spot on the sample and cause X-ray radiation or photons to be emitted. This radiation can then be detected and analyzed to identify the elements that make up the object. Each element reacts differently when exposed to this type of radiation, meaning that qualitative XRF analysis can help identify pigments present in an area of a painting. XRF provides semi-quantitative information about the relative concentrations of these elements within a sample spot. Whereas earlier XRF equipment required samples be removed from a painting for analysis, modern equipment for XRF is nondestructive. For some time, to use nondestructive XRF required that the painting be brought to the instrument. More recently, portable, handheld XRF devices have been developed that can be taken into a museum or conservation studio.

The interpretation of XRF data is often complex. The high-energy X-rays used for XRF analysis are capable of penetrating the entire layered structure of a painting and, therefore, can detect elements located below the surface. XRF can also provide important insights about the physical history of paintings because it can also detect non-original materials including fills that have been added in areas of loss. A preliminary examination with a microscope can help establish the condition of the sample area and detect whether or not non-original materials may be present. It is also useful to identify, with as much certainty as possible, what pigments may be present in the sample spot before conducting XRF as this will facilitate the interpretation of the results. Here, the interdisciplinary nature of technical research is of primary importance, since art historians and conservators collaborate with scientists to interpret the spectra. XRF analysis was used to examine Alexej von Jawlensky’s Murnauer Landscape with Three Haystacks, discussed elsewhere in this volume.

Harnessing the power of the electromagnetic spectrum and combining scientific analysis with art historical research reveals new information that is hidden within a painting. The Unvarnished Truth exhibition demonstrates the way in which the study of paintings is deepened by technical art history’s application of scientific methods. By conducting this valuable interdisciplinary research, new insights have been generated that shed light on artistic processes and issues such as dating and attribution.


[i] Both conservators and curators tend to the protection and preservation of artworks. Curators are the caretakers of artworks within a collection and have a wide range of responsibilities. These duties include, but are not limited to, conducting research, organizing exhibitions, and performing administrative tasks related to objects in their collection. Conservators examine artworks to determine their condition and perform treatments to ensure that these works are preserved in the most stable state possible. To this end, the conservator can make adjustments to the storage environment or artwork itself.

[ii] Stephanie S. Dickey’s essay “The Art of Connoisseurship” in this volume discusses an important method of analyzing paintings using the visible range of the electromagnetic spectrum and the keen visual memories of this type of specialist.

[iii] Some artists did not include this underdrawing stage in their creative process. Furthermore, in some parts of the world, the material used for the underdrawings did not contain carbon, meaning that these underdrawings are invisible to IRR.

[iv] Fluorescence is the emission of longer wavelength radiation from atoms stimulated or irradiated with shorter wavelengths of electromagnetic radiation. These longer wavelength emissions can be in the visible spectrum and show up as colours.

[v] Although not used as part of this exhibition, another technique involving this wavelength group is UV reflection photography. This involves taking photographs with a UV-sensitive camera of the UV light that is reflected by a work. See R. de la Rie “Fluorescence of Paint and Varnish Layers (Part I)” and “Fluorescence of Paint and Varnish Layers (Part II)” in Studies in Conservation 27, no. 1 (1982): 1–7 and 65–9.

[vi] Ron Spronk, “More Than Meets the Eye: An Introduction to Technical Examination of Early Netherlandish Paintings at the Fogg Art Museum,” Harvard University Art Bulletin 5, no.1 (1996): 5.

Imaging Using X-rays and Neutrons

en français

Dr. Fiona McNeill

X-Radiography

Fiona Figure 1

FIGURE 1: The first X-ray image, Frau Röntgen’s hand, taken in 1895.

The first X-ray image was taken by Professor Wilhelm Röntgen in 1895, a mere two weeks after he had first discovered the phenomenon he called “X-rays.” The remarkably obliging Frau Röntgen allowed her hand to be fixed between the X-ray source and a photographic plate: the image shows the clear pattern of the bones of her hand, the ghostly outline of the skin and muscles, and a ring that was studded with small jewels (Fig. 1). Röntgen recognized immediately the medical implications of his basic physics research, and the first medical use of X-ray imaging occurred three months later at Dartmouth College in Hanover, New Hampshire. Röntgen never applied for a patent, as he felt strongly that his discovery should be freely available. His generosity of spirit has resulted in millions of lives having been saved around the world. He could have been a millionaire, but instead died nearly bankrupt.

The “X-rays” that Röntgen discovered were, in fact, an electromagnetic wave. Radio waves, microwaves, light, and X-rays are all electromagnetic waves: X-rays are in the high-frequency (high-energy) part of the electromagnetic spectrum. X-rays are so useful to us for medical imaging because of the fortunate coincidence that our human bodies are made of distinct types of materials: bone and soft tissue. An X-ray image is possible because when X-rays pass through a material, they have a probability of interacting with the electrons in the atoms of the material. A denser material has more electrons per unit volume, so an X-ray is more likely to interact in dense material. In addition, elements with a higher atomic number have more electrons per atom, and so an interaction is more likely. In the case of humans, our soft tissue is made up of low atomic number elements such as hydrogen, carbon, oxygen, and nitrogen, and it has a density very similar to water. Bones are made from higher atomic number elements, such as calcium, and are denser. Higher density, higher atomic number bones therefore interact more strongly with X-rays than lower density low atomic number muscle and fat, so when X-rays pass through our bodies, more X-rays are absorbed or scattered in bone than in soft tissue (Fig. 2). This means that X-rays mostly pass through soft tissue, but are stopped by bone, so areas of soft tissue are bright on the X-ray image because the film is exposed. Areas of bone are dark on the image because fewer X-rays pass through and there is less exposure of the film. Broken bones, degraded bones from arthritis, and hairline fractures all show up readily in images because of the distinct contrast between bone and soft tissue.

Fiona Figure 2

FIGURE 2: Fewer X-rays can pass through a volume of bone compared to the same volume of muscle.

The same principle, that different material types result in more and less X-ray interaction, can be used to study paintings. A common use of X-radiographs in art is to look for areas that have been painted over, or for canvases that have been reused. High atomic number materials attenuate X-rays strongly, that is, they allow few X-rays to pass through a material (Fig. 3). Commonly occurring high atomic number elements include metals such as lead and mercury. These are often found in the pigments used in oil paintings. If a single pigment was used in an even wash over the canvas, there would be no distinction on an X-ray image. All of the X-rays would be attenuated by the same amount, and the X-ray image would look flat and grey. However, paintings are often made with different pigments and are layered with different thicknesses of pigment. Sometimes, an artist will have painted on a canvas, and then decided either to reuse the entire canvas or change the image and paint over a section. This can sometimes (with luck!) mean that a pattern is observed on an X-ray image that is not seen by the naked eye. The X-ray shows the layers of pigment that are under the surface if (and only if) the combination of thickness, density, and atomic number of the pigment underneath the surface layer is different enough from other parts of the painting so that it attenuates the X-rays differently.

In The Unvarnished Truth: Exploring the Material History of Paintings, X-radiographs were used to investigate all of the paintings, and in the case of Van Gogh’s Untitled, Still Life: Ginger Pot and Onions, the X-radiographs were indeed different from the image observed with the naked eye. He had either reused the canvas, or repainted a section of the work. Fortunately for us, the pigment underneath was distinct enough in composition from the surface layer that it attenuated the X-rays, allowing the hidden image beneath to be detected. For further discussion on this, see the essay “The Analysis of Inorganic Pigments Using Spectrometric Techniques” in this volume.

 

FIGURE 3: X-rays are attenuated exponentially by material. For paintings with multiple layers of pigment, more X-rays will be attenuated, resulting in the visualization of those layers underneath the visible surface.

FIGURE 3: X-rays are attenuated exponentially by material. For paintings with multiple layers of pigment, more X-rays will be attenuated, resulting in the visualization of those layers underneath the visible surface.

In the case of Brouwer’s The Drinker / The Bitter Draught, materials behind the paint caused an interesting problem in the X-ray image. The Brouwer work is attached to a wooden cradle. When the X-ray was taken of the painting, the X-ray image (Fig. 4) was a really good picture of the cradle, rather than the painting itself. We were able to use an X-ray attenuation “trick” to reduce the impact of the cradle on the image by matching the attenuation of the cradle. Wood is a material that is mostly composed of the elements hydrogen, carbon, nitrogen, and oxygen. In X-ray terms, plastics can be considered to be very similar to wood because they are composed of hydrogen, carbon, and oxygen and have a very similar density. Elvacite is a product that consists of tiny (<1 mm) acrylic resin beads, and by using this it and pouring the beads into the back of the Brouwer painting, we could fill in the gaps in the cradle. The acrylic resin beads match the attenuation by the wooden cradle, and this means there is less contrast in the image between the cradle and the air (Fig. 5). We can therefore see the X-ray image (Fig. 6) produced from the layers of paint more clearly. The beads were poured back out after the X-ray, leaving the painting unharmed.

fig. 4 01XRADDI01

FIGURE 4: Film X-radiograph of The Drinker / The Bitter Draught, without Elvacite. The wooden cradle on the back of the painting obscures the other details of the painting.

 

Fiona Figure 5

FIGURE 5: Elvacite, a beaded acrylic resin, whose composition (in X-ray terms) is similar to that of wood, was poured into the gaps in the cradle on the reverse side of the painting. The X-ray attenuation was matched, which resulted in the cradle being less obvious in the new X-ray image.

In modern medicine, most X-ray images are taken digitally, which means film is not used to record the X-rays so images can be taken and read immediately. There is no need to wait for film to be processed and images can be stored on a server for immediate access by the radiologist. However, for the studies of the paintings, film radiographs were used instead because the image resolution, which is how fine a spot or line size can be discriminated, was extremely important. Digital images are composed of a series of “dots” called pixels in a two-dimensional array. The resolution of the image depends on the total number of pixels in the image. A more blurred image is the consequence of fewer pixels in the array (Fig. 7). For our purposes, the digital X-ray scanners available to us did not have the high resolution we required. Their ability to detect fine detail, such as the lines in a canvas, was not good enough. However, films are still available that allow better resolution images to be taken than if using a camera. We ordered special high-resolution industrial X-ray film that was exposed by positioning the paintings face down on the film and taking the X-ray from above.

01XRADFI02-sm

FIGURE 6: Film X-radiograph of The Drinker / The Bitter Draught, with Elvacite. The wooden cradle is now less of a visual interference for the interpretation of the image.

 

FIGURE 7: One X-ray image shown at two resolutions. The resolution of the X-ray detection system affects the quality of the image and the information that can be obtained.

FIGURE 7: One X-ray image shown at two resolutions. The resolution of the X-ray detection system affects the quality of the image and the information that can be obtained.

Using high-resolution film also allows us to view the threads on a canvas. The analysis of the pattern and density (per cm) of the weave of a canvas support of a painting, also referred to as thread counting, can provide important information regarding the piece. Research has shown that it is possible to compare the canvases of paintings attributed to the same artist and determine if they were cut from the same bolt.[i] The researcher will take a high-resolution X-ray film of a painting, scan it to a digital format, use a software algorithm to characterize the density and angles of the warp and weft pattern of the canvas, and then compare to a database of other paintings. The Thread Count Automation Project, co-directed by C. R. Johnson Jr. and D. H. Johnson, is the primary developer of this technique, which we applied to the Van Gogh painting. For a detailed discussion of this, see the entry on dendrochronology in this volume.

NEUTRON RADIOGRAPHY

The principle of neutron radiography is very similar to X-radiography. A beam is passed through an object and a film (or digital camera) records the parts of the beam that are transmitted through the material. The McMaster Nuclear Reactor has a radiography beam port that is designed to allow imaging through objects using thermal neutrons, that is, low-energy (room temperature) neutrons. X-rays interact with the electrons around an atom, whereas neutrons interact with the nucleus of the atom itself. Because the interactions are based on different physical properties, X-rays and neutrons image different things. X-rays are excellent at imaging metal (because there are lots of densely packed electrons in metal), while neutrons are excellent at imaging materials containing hydrogen. Hydrogen has a high probably of interacting with thermal neutrons; in physics terms, we say hydrogen has a high thermal neutron capture cross section. There are other elements with high thermal neutron capture cross sections, two being cadmium and gadolinium. However, hydrogen is by far the most common element with a significant thermal neutron capture cross section, because it is an element in water, wax, and plastics, and therefore most radiographs are predominantly a result of interactions with hydrogen.

FIGURE 8: Comparison of neutron- and X-radiographs of a lighter, illustrating the differences between the attenuation of neutrons and X-rays for metallic and hydrogenous (butane) materials.

FIGURE 8: Comparison of neutron- and X-radiographs of a lighter, illustrating the differences between the attenuation of neutrons and X-rays for metallic and hydrogenous (butane) materials.

Combinations of X-radiographs and neutron radiographs can show complementary information. In the image of the lighter (Fig. 8), taken at the McMaster Nuclear Reactor by Nray Services Inc., the X-radiograph shows the metal striker and flint. The neutron radiograph shows the level of butane, which contains a lot of hydrogen, inside the lighter. In this project, Nray Services Inc. used neutron radiography to capture an image of Untitled by Rodchenko. We knew the image was painted on a spruce board. We used neutrons to image the painting for two reasons: we were interested in whether there was cadmium in the pigments; and because wood contains hydrogen, we hoped we could gain information about the wood. The resulting ghostly neutron image of this work showed the knots in the wood and a clear image of what looks like a panel board. It also showed an unfortunate crack in the centre of the painting (Fig. 9).

 

FIGURE 9: Neutron radiograph of the work on spruce panel by Rodchenko. The woodgrain panel is visible, as is the crack through the middle of the piece, which otherwise would not be visible on the surface of the painting.

FIGURE 9: Neutron radiograph of the work on spruce panel by Rodchenko. The woodgrain panel is visible, as is the crack through the middle of the piece, which otherwise would not be visible on the surface of the painting.

[i] A. G. Klein, D. H. Johnson, W. A. Sethares, H. Lee, C. R. Johnson Jr., and E. Hendriks, “Algorithms for Old Master Painting Canvas Thread Counting from X-rays,” Signals, Systems, and Computers: Proceedings of the 42nd Asilomar Conference (2008): 1229–33.

Limits of the Eye and the Engine of Curiosity

en français

Dr. Ihor Holubizky

The Unvarnished Truth: Exploring the Material History of Paintings project began as a modest but focused transdisciplinary examination of nine paintings from the McMaster Museum of Art collection. The prime objective was to explore specific and precise material conditions: how were these artworks made and what was the material history, including changes and alterations over time. The information gleaned from these explorations then allowed reflection on why these objects were made in relation to ascribed meanings, interpretation, and the history of art. The why is no more stable than the material condition. Eighty years ago, art historian Ludwig Goldscheider wrote, “in reality the past changes as rapidly as the present,” an observation that has been expressed by others.[i] But if the past is never static, how does this concept relate to what we know and believe to be true.

In practical terms, the paintings for this project were chosen for their broad range of supports and mediums, from historical to the modern period, and for their dimensions, which could be accommodated by the available technical equipment. Early on, one of the project’s contributors, Dr. Spronk, commented that a key to knowing more is posing good questions. Therefore, another factor in the selection process was intuition, choosing works that might offer interesting questions and problems to address. Over the course of the project, questions developed and shifted from the specific to the general and back again. Testing was modified, adjusted, and refined because of uneven—and unexpected—specific findings and results.

From the outset, the limits of the eye was an implicit governing principle; that is, not accepting the visible (the surface) as the primary way of looking and thinking about art. By the same token, deferring to the established schemata of art history, although essential in comparing the known with the unknown, can be a habit of mind—to leave well enough alone, and to consider “minor” works of art as a means to serve “merely” as illustrative examples. While this project did not have an explicit objective to prove or disprove attribution (authorship), through imaging data, diagnostic examinations, and project team discussions, some attributions shifted, as noted in the catalogue entries and throughout the essays in this volume.[ii] Science alone cannot provide an answer, but in tandem with an inquisitive, art historical methodology, new avenues of inquiry are opened up with the understanding that the work of a museum does not end with the acquisition of a work of art. David M. Wilson, a former director of the British Museum, stated that “a good museum curator is above all things curious about all objects, whether they be in his own subject or [an] entirely different area [of expertise].”[iii] Indeed, the very act of removing works from their position in the collection and hence, art history—even if temporarily—creates an opportunity in which the engine of curiosity functions.

 

146,000 Days and Counting

 

The topic of collecting and collections is not exclusive to the museum, but inside the museum it takes on a weight and responsibility, even for the most basic question of how did this get here, and why? (There is an accountable museum due process, which is rarely communicated to the public.) We can also ask, why do we collect? Historian Herbert Read rightly noted, “the pursuit [of collecting] is ambiguous because in the first place it does not necessarily serve any rational purpose,”[iv] yet we invest meaning in objects and works of art that is not wholly quantifiable or measurable—what we call intrinsic value. Susan S. Pearce wrote, “objects are not inert or passive; they help to give shape to our identities and purpose to our lives.” And as George Kubler stated, “the only tokens of history continually available to our senses are the desirable things made by men [and] to say that man-made things are desirable is redundant, because man’s native inertia is overcome only by desire, and nothing gets made unless it is desirable.”[v]

Collecting is a foundation of museum activity,[vi] although the process is complicated: “policy, accident and serendipity all play their part.”[vii] Private collectors, however, are not obliged to justify their choices, but can exercise the impulse to share personal interests and passions with the public through loans to exhibitions, gifts that have been the foundations of now major museums, and the establishment of private museums.[viii]

By happenstance, five of the nine works selected for this project were part of a donation made to the McMaster Museum of Art in 1984 by the late Herman Levy, a Hamilton collector. This gift dramatically altered the scope and magnitude of the Museum’s collection. These nine works represent an arc of five hundred years, or one hundred forty-six thousand days (and counting), without a typical curatorial assertion. Other questions formed: What is the relationship between private and public collecting, as one impacts on the other? How does a focused and intense examination of works of art “in isolation” relate to what is often called and inevitably accepted as “the canon”?[ix] Can these works return to the collection “changed”?

There is another important aspect to a work of art. Even though it is a prime document of singular authorship, it can also express and convey a complex array of aesthetic and social (political and religious) values that speak of the times; these are all the elements of culture and history. Yet, as with all historical texts and documents, the further away we are from the moment of creation or inception, the more likely it is that specific references will be weakened because society and culture is ever-changing. What may have seemed obvious three hundred years ago can become obscured or cloaked. Kubler expanded on this flux:

Historical knowledge consists of transmissions in which the sender, the signal, and the receiver all are variable elements affecting the stability of the message. Since the receiver of a signal becomes its sender in the normal course of historical transmission…we may treat receivers and senders together under the reading of relays. Each relay is the occasion of some deformation in the original signal. Certain details seem insignificant and they are dropped, [while] others have an importance conferred by their relationship to events occurring in the moment of the relay and so they are exaggerated.[x]

Rather than a flaw in our thinking, what Kubler mapped out is an inherent, human condition, the implicit personification of art history; great artists make great art—hence, the “canon.” Less fortunate artists are relegated to the position of journeymen and can remain unknown and nameless, a case in point for two of the paintings in this project. In the schemata of art history, the artist without a name “characterizes” and points to more important artists and works.[xi] Context rules the story of art, but connoisseurship—as the authoritative voice—as well as taste, fashion, and desire (all subjective areas) dominate the inherent or intrinsic merit of any given object.

 

Connoisseurship, Taste, and Fashion: Collections, Collectors, and the Museum

 

Connoisseurship emerged in the nineteenth century as a critical device in the assessment of artistic merit and authenticity. The key figures in its development—essays and books published between 1880 and 1942—include Giovanni Morelli, Bernard Berenson, and Max Friedländer. This “classical” approach can be understood (if not wholly defined) as the refined and informed eye registering and comparing compositional factors. Bernard Berenson defined his methodology as the examination of formal characteristics in order to determine an artist’s stylistic “fingerprint”:

Connoisseurship…proceeds, as scientific research always does, by the isolation of the characteristics of the known and their confrontation with the unknown [and to] take all of [an artist’s] works of undoubted authenticity [in order] to discover those traits that invariably recur…but not in the works of other masters.[xii]

Although Berenson invoked science, he left the penultimate verification to the subjective, what he named and defined as “The Sense of Quality [which] is indubitably the most essential equipment of a would-be connoisseur.”[xiii] Connoisseurship, therefore, cannot be wholly separated from taste and fashion—taste as the objectification of preference, and fashion as a currency that comes and goes.[xiv] “Taste,” as Stephen Bayley wrote for a formative exhibition on the topic, “derives its force from data that is a part of culture rather than pure science.”[xv] Art historian Francis Haskell explained:

Taste, however capricious, always depends on more than taste. Any aesthetic system, however loosely held together, is inextricably bound up with a whole series of forces, religious, political, nationalist, economic [and] intellectual.[xvi]

Max Friedländer’s different (or adjusted) view questioned the assertion of a “universal validity.”[xvii] He proposed an informed “intuition and the first impression”[xviii]: “[The] inner certainty [of authorship] can only be gained from the impression of the whole; never from an analysis of the visible forms.”[xix] However, Friedländer also raised a caveat: “Intuitive judgment may be regarded as a necessary evil. It is to be believed and disbelieved [and] intuition resembles the magnet needle, which shows us our way whilst it oscillates and vibrates.”[xx] In other words, in the reach for eternal or universal values, one step forward can be two steps back.

Connoisseurship, regardless of the contested debate on methodologies or recipes for connoisseurship, has had a significant impact on collecting in the late nineteenth century and the first half of the twentieth, and particularly in the United States where major collections of European historical and modern art were being assembled.[xxi] The cult of connoisseurship, however, also blurred the lines between the art historian (as connoisseur-advisor), the art dealer, the private collector, and the museum.[xxii] In a (capitalist) market economy, there is an ever-present monetary and exchange value that can exaggerate worth and create desirability in the same breath. [xxiii] The transfer of a private collection into the public realm (and trust) validates it, along with the aggregated values that can include ownership power and prestige. Arguably, connoisseurship continues to operate within the contemporary art world, but under different terminology. We can also say that the acquisition of privately held works by major public galleries cements reputations through validation and legitimacy. (The lines between private and public can also blur depending on the insistence of the private collector as a museum stakeholder.)

“What a wonderful collection” is a phrase that may be uttered by a museum visitor. It can mean one of two things, or a blend of both: what I see reflects and reinforces what I know and admire; or, what I see has broadened my understanding and appreciation. For some, the dutiful visit to a museum is akin to an annual check-up—never pleasant, but “good for you.” The argument that good art makes good citizens sits at the core of many museum mission statements, as if an unassailable principle.

The easiest and the most radical thing is not to collect;[xxiv] not to be held accountable for the vicissitudes of history and ever-changing tastes. The rise of the temporary exhibition space reflects that view—the kunsthalle or institutes of contemporary art.

Case Studies – Knowing and Framing

As noted earlier, science alone does not offer a complete answer, which leads to ruminating on a hypothetical “dream” instrument capable of determining everything; “When was it made? Who made it? Where was it made? How was it made? Of what material was it made?”[xxv] Each work studied in the McMaster project generated different forms of data, rather than equal and cumulative research; different ways of thinking came forward.

The infrared reflectography image of the painting attributed to Jan Gossaert delivered perhaps the most distinct and remarkable image from a curatorial point of view. Chalk lines on the oak wood support were revealed. Here was tantalizing evidence of the formation of composition—a “day one” (or thereabouts), as if we are looking over the shoulder of the artist, and an aspect of the work unseen for five hundred years (excluding, of course, examples of unfinished or abandoned works). To leave this as mere foundation in the how of art is to disregard the miracle of art. Through the habit of mind and the imprint of authoritative connoisseurship, too often only the outcome is judged and admired, and not the process. Process as “idea and concept” is equated with art of the modern age and contemporary times. Yet the reflectance transformation imaging for the Alexej von Jawlensky, a modern painting, presented evidence of process that has not been expressed in considerable extant writing about the artist and interpretations of his work.

Can we dismiss process for pre-modern art where it is too often relegated to the enchantment of the eye (the limits of the eye), a craft of the art rather than the art in the crafting? Formal elements are not the only way to understand and know art of the past.

The Rubens painting fragment is another and different case. It was acquired by Herman Levy fifty years ago from London dealer Henry Roland, who had purchased it at auction and believed that it was a Rubens sketch rather than a work by the Spanish painter Juan Bautista Martínez del Mazo (active during Rubens’s time), as described in the auction catalogue. There is dual connoisseurship at work; while there must be a degree of trust between collector and dealer, Levy did not merely accept at face value Roland’s assertion that the work was a Rubens, but drew on his own study and knowledge of art to make his own assessment. Nevertheless, much was left unexamined. The Rubens has been in the McMaster collection for a quarter of a century with the generalized description, “head of a man with grey beard and white ruff.” This is a common titling strategy for historical portraits of unknown sitters, and over time it becomes the de facto title. Why was the sitter not uncovered when it seemed “so simple”? A different version of an image of the same sitter is in the Rubens catalogue raisonné, published in 1987, three years after the donation to the Museum. If curiosity is a driving force in acquiring knowledge, a lack of curiosity is too often acceptable, to leave well enough alone. A portrait is always of someone, and in this instance—though certainly not in all—the name of the sitter was recoverable: Maximilian III, Archduke of Austria (1558–1618).

The Venetian painting, in the manner of Tintoretto, was a different scenario. In his purchase discussions, Herman Levy did not accept the dealer’s Tintoretto attribution, yet agreed to buy it if it was sold as “Venetian,” and with the appropriate discount in price. Levy was expressing his connoisseurship through a belief in the “Sense of Quality,” even if artist and sitter remain unknown. [xxvi] Another critical condition was revealed in the technical examination, pointing to taste and fashion. The painting had been altered several times in order to conform to what undoubtedly was a market for Venetian paintings, and not to adhere to custodial principles or ethical practices for the work. That history of change (who did what, when) may never be known. This is also likely true for the Rubens fragment. It may have been more readily saleable as a face-only portrait (“of the period”) than as what it may have been originally, a three-quarter portrait of an Austrian Archduke.

From another perspective, we can take imperfect condition for granted, and even celebrate it. The Winged Victory of Samothrace is an apt example. Although missing the head and arms (other parts have been discovered, but not reattached), this statue is nonetheless admired as a masterpiece of Hellenistic sculpture and, for many stands for classicism and beauty.[xxvii] It has been displayed prominently at the Louvre in Paris since 1883, with the exception of its removal for safety during the Second World War. However, it is only goods “damaged” by time. Are we celebrating the passage of time and the miracle of survival?

The issue of painting frames was not a consideration for The Unvarnished Truth, but came forward because of the necessity of removing the works from their frames for a complete examination. The Adriaen Brouwer painting had been mounted in a rebate frame, a practical and conventional way of securing paintings. The rebate, however, compressed the composition by concealing the edges. In a small work that is painted to the edge, every centimetre counts. The decision was to “float” the panel so the edges could be seen, but not so easily reached. There was a compromise in revealing bits of framing felt that had transferred to the painting’s edges over time. Through discussion and consultation, the attempt to remove or restore the frame was not advised. It meant living with this “flaw” in order to see the whole painting. Ironically, the felt residue left on the edges of the painting had been noted in a conservator’s examination in 1986, yet the painting was returned to the frame.

The paintings by Vincent van Gogh and Aert van der Neer had been framed in the taste of the time, a seventeenth-century Baroque style that spoke of value and importance. This style of frame is an anachronism for both works: Van Gogh painted in the late nineteenth century; and, while he lived and worked during the Baroque period, the governing principle was to change the frame for a style sympathetic to a Dutch genre scene.

What We Can Never Know

Ironically, what was learned in the project underscored what we can never know. As noted at the outset, the objective was not to establish attribution where there was uncertainty; the examination of materials, condition, and changes beyond the limits of the naked eye was the primary task. And indeed, due to a lack of time to dedicate to research as well as an absence of absolute information or consensus, there will remain works we will never know, as W. McAllister Johnson observed:

What emerges from [extant] literature is the constant flux of attributions and provenance [and that] the number of works that can be identified at any one time and that lend themselves to discussion are few indeed. Faced with this uncertainty, it is the apparatus of criticism and connoisseurship that permits at least the educated guess, proposes likelihoods [and] offers documentation” [or, opinion].[xxviii]

We can never know the creative act, and attempting to do so through descriptive language and analytical terms enters into the persuasiveness of erudition. Likewise, science cannot “unmake” and reveal the act—the creative moment—or reverse its arrow of time. If the creative act and impulses of the past may never be fully known or recoverable, the active engine of curiosity—and understanding our limits (of the eye)—keeps art alive. Not knowing—and acknowledging that—is as important as claiming to know everything, the conceit of an empiricism without the “shred” of doubt. Much has been written on the not-knowing in positive terms. Here is one example, from curator Bryan Robertson (I have interjected the term “compelling” where he has used “great”), citing the contradictions that may be unavoidable in the creative act:

A [compelling] painting or sculpture denotes forces in our imagination, which transform life.

A [compelling] work of art proclaims that two plus two equals five: this truth cannot be rationally communicated, only imaginatively apprehended, and it needs time to grow.

The first task of a museum is to give maximum life to a work of art…untrammeled…and thus to grow in the imagination of visitors.[xxix]


[i] Ludwig Goldscheider, foreword to Art Without Epoch (Vienna: Phaidon Press/New York: Oxford University Press, 1937), np. Art critic Lawrence Alloway wrote, “The past is always interpreted according to present knowledge and topical interests; it changes as quickly as our comprehension of the present changes,” in “The American Sublime” in Topics in American Art since 1945 (New York: W.W. Norton & Company, 1975), 39. (The article was originally published in 1963.)

[ii] In 2007, Director of the National Gallery of Victoria (Australia), Dr. Gerard Vaughn, stated with respect to the tip-over of a Van Gogh attribution in the collection, “The reattribution of paintings is part of the daily life in any major gallery with a large and complex collection. We regularly change the labels to reflect new research and scholarly opinion.” “It’s tough to canvas an opinion,” Sydney Morning Herald, December 29, 2012, www.smh.com.au/entertainment/art-and-design/its-tough-to-canvas-an-opinion-20121228-2bz6m.html. In the same article, Jaynie Anderson, professor of fine arts at the University of Melbourne commented, “No one should be frightened of real knowledge.”

[iii] David M. Wilson, The British Museum: Purpose and Politics (London: British Museum Publications, 1989), 41.

[iv] Herbert Read, introduction to Niels von Holst, Creators, Collectors and Connoisseurs (New York: G. P. Putnam’s Sons/London: Thames and Hudson, 1967), 3.

[v] George Kubler, The Shape of Time: Remarks on the History of Things (New Haven, CT: Yale University Press, 1962), 1.

[vi] There are variations of the museum foundation “pillars.” Five responsibilities are cited by Joseph Veach Noble: “to collect, to conserve, to study, to interpret, and to exhibit,” in Stephen E. Weil, “Rethinking the Museum: An Emerging New Paradigm” in Reinventing the Museum: Historical and Contemporary Perspectives on the Paradigm Shift, ed. Gail Anderson (Oxford: AltaMira Press, 2004), 74. Weil in turn cites Peter van Mensch who proposed that the “essential functions of museums [can be] reduced to three: to preserve…to study…to communicate.” Ibid., 74–75. This, however, is a parlour game of terminology, or the impulse to assert “new paradigms.” Fundamentally, the roles remain the same and, as Weil noted, are closely intertwined.

[vii] Wilson, The British Museum , 24.

[viii] The founding collection of the National Gallery, London, England, in 1826 was the bequeathed collections of banker John Julius Angerstein and painter-collector Sir George Beaumont. See “Collection History,” National Gallery, accessed February, 27, 2014, http://www.nationalgallery.org.uk/paintings/history/collection-history/. Among the renowned private collection museums in the United States are the Isabella Stewart Gardner Museum, Boston, founded in 1903; the Barnes Foundation, Philadelphia, established in 1922; and the Frick Collection, New York, which opened to the public in 1935. Gertrude Vanderbilt Whitney established the Whitney Studio to present exhibitions of living American artists. When her offer to donate her collection, with an endowment, was refused by the Metropolitan Museum of Art, she formed The Whitney Museum of American Art in 1930. See “History of the Collection,” Whitney Museum of Art, accessed February 27, 2014, http://whitney.org/About/History. There is a similar private collection beginnings story for the Guggenheim Museum. See “History,” Guggenheim Foundation, accessed February 27, 2014, http://www.guggenheim.org/guggenheim-foundation/history. See also Pierre Cabanne, The Great Collectors (London: Cassell & Company Ltd., 1963), a study of collectors from Catherine of Russia to Peggy Guggenheim.

[ix] Among the earliest and most celebrated visualizations of a canon is Raphael’s fresco School of Athens (1509–1511), which depicts Greek philosophers in a hierarchical order, the embodiment of knowledge and learning. It was a model for Paul Delaroche’s Hémicycle mural commission at the École des Beaux-Arts in Paris. Delaroche depicted the seventy-five greatest artists of all time. While such conceits and fabrications are discredited as an expression of taste and fashion, strategic position continues today in published anthologies where the term “great” is replaced by the word “today.”

[x] Kubler, The Shape of Time, 21–22.

[xi] In his paper on the university museum and collections, John R. Spencer touches on the dilemma of the “equivalent” in “Cross stands for Seurat, Giampietrino for Leonardo, a Rembrandt etching for a Rembrandt painting,” in Museums in Crisis, ed. Brian O’Doherty (New York: George Braziller, 1972), 139.

[xii] Bernard Berenson, Rudiments of Connoisseurship (New York: Schocken Books, 1962), 123–124. Berenson’s book was written in 1902, and he notes in the preface that the rudiments chapter was written eight years before.

[xiii] Ibid., 147.

[xiv] Francis Haskell noted that “the eighteenth century was deeply—almost obsessively—concerned with the problem of Taste, and the possibility of determining fixed canons whereby it could be established.” Haskell, Rediscoveries in Art: Some Aspects of Taste, Fashion and Collecting in England and France (Ithaca, NY: Cornell University Press, 1976), 5.

[xv] Stephen Bayley and Stafford Cliff, Taste: An Exhibition about Values in Design (London: Boilerhouse Project, Victoria and Albert Museum, 1983), 14.

[xvi] Haskell, Rediscoveries in Art, 23.

[xvii] Max J. Friedländer, On Art and Connoisseurship (Boston: Beacon Press, 1960), 169–170.

[xviii] Ibid., 172.

[xix] Ibid., 173.

[xx] Ibid., 175.

[xxi] See W. G. Constable, Art Collecting in the United States of America (London: Thomas Nelson and Sons Ltd., 1964).

[xxii] See Dictionary of Art Historians, accessed February 27, 2014, https://dictionaryofarthistorians.org/berensonb.htm.

[xxiii] See Gerald Reitlinger, The Economics of Taste: The Rise and Fall of Picture Prices 1760–1960 (London: Barrie and Rockcliff, 1961). Much of this continues in the current contemporary art market, both for historical and contemporary works. The notion of collecting has become a sociological topic of study too. See Susan M. Pearce, On Collecting: An Investigation into Collecting in the European Tradition (London: Routledge, 1995).

[xxiv] “Initially, the Gallery had no formal collection policy, and new pictures were acquired according to the personal tastes of the Trustees. By the 1850s the Trustees were being criticised for neglecting to purchase works of the earlier Italian Schools, then known as the Primitives.” From “Collection History,” National Gallery, accessed February 27, 2014, http://www.nationalgallery.org.uk/paintings/history/collection-history/collection-history/*/viewPage/2.

[xxv] Victor F. Hanson, “The Curator’s Dream Machine,” in Application of Science in Examination of Works of Art (Boston: Museum of Fine Arts, 1973),18.

[xxvi] McMaster Museum of Art files, letter from Herman Levy to Brod Gallery, 14 March 1967. The original sales invoice drops the attribution to “by a Venetian master…attributed to Tintoretto.” Yet at the same time, Levy accepted the Collier attribution for a “manner of” work. In a letter sent to Mr. Levy a year later, Brod Gallery persisted in the Tintoretto claim, and cited that Bernard Berenson had seen the work and declared it to be a Tintoretto. McMaster Museum of Art files.

[xxvii] H. W. Janson, History of Art (New York: Harry N. Abrams, 1986), 146. The Winged Victory of Samothrace is illustrated on the dust cover of the book.

[xxviii] Johnson, 39.

[xxix] Bryan Robertson, “The Museum and the Democratic Fallacy” in Museums in Crisis, 87.

Disciplines in Motion: The Changing Roles of Museum Curators, Art Conservators, and Conservation Scientists

en français

Ron Spronk 

The research and exhibition project The Unvarnished Truth: Exploring the Material History of Paintings, organized by the McMaster Museum of Art, is another welcome example of a fruitful interdisciplinary collaboration of art historians, art conservators, and conservation scientists. Nenagh Hathaway and Brandi MacDonald, both PhD candidates (at Queen’s University and McMaster University, respectively), did an exemplary job of coordinating this project. The results of this four-year venture are laid out in this publication. The McMaster Museum of Art and McMaster University deserve much praise for embracing and supporting The Unvarnished Truth from its very conception, and for realizing the project in close collaboration with colleagues from Queen’s University and other institutions. Over the last century, university art museums in the United States have played a major role in this highly interdisciplinary field of art conservation science, and it is exciting to see that this tradition is now also spreading to Canada. By its very name and nature, a research university brings together the different disciplines within the arts and sciences. The Unvarnished Truth exhibition also shows that relatively small museums can make major contributions to this field, when such work more typically takes place in large museums that have specialized art conservators and conservation scientists on staff. It is in this latter arena that recent changes in models of collaboration among the disciplines can be most clearly noticed.

Museum curators and art conservators share the responsibility of conserving artworks in public collections.[i] According to the Shorter Oxford English Dictionary, to conserve is “to keep from harm, decay, loss or waste, especially with a view to later use.”[ii] A curator—traditionally, an academically trained art historian—is largely responsible for the research, management, and display of a museum’s permanent collection, and for making artworks and the information about them accessible. In addition, a curator often organizes temporary exhibitions, using works from the institution and, at times, loans from other collections.

The primary task of an art conservator, by comparison, is to monitor, research, and safeguard the material condition of artworks through preventive actions and, when necessary, to execute conservation or restoration treatments, or both. Historically, a restorer was typically trained in the traditional master-apprentice model. Today, the modern conservator, like the curator, is academically trained, but this is the result of a relatively new development that has been long in coming. Pioneering conservation specialist George L. Stout once wryly characterized art conservation as “the mongrel pup that had crawled through the academic fence.”[iii]

The responsibilities and tasks of curators and conservators within the museum sometimes overlap and can even be at odds. The organizers of the 2012 CODART (Curators of Dutch Art) conference on the topic did not mince words when they laid out areas of contention:

The crossover of responsibilities sometimes leads to conflict: Who decides on the conditions in which works of art are exhibited? Who determines the restoration priorities? Who has the final say in approving loan requests? Yet despite the occasional frictions among curators and conservators, technical research plays an increasingly significant role in the art historical interpretation of works of art and has become standard practice in studying museum collections.[iv]

These highly important points deserve some context, especially since these issues are relatively new and seem to have developed in parallel with the increased recognition of the importance of art conservation and the contributions of art conservators. Previously, whether as museum director, curator, or art history professor, it was the art historian who initiated and directed conservation projects. As a result, there are a number of examples of problematic restoration treatments, in the rather short history of the conservation field, that could have been avoided if art conservators had had shared influence over the direction of these projects.[v]

In today’s museum practice, it is a given that curators and conservators work closely to conserve artworks. The roles of the curator and the conservator have been transformed over the years, since the shared arenas of their activities, art museums, have changed so dramatically. In the past, the relationship between art historian and art conservator was generally more hierarchical, and thus clearer. While they now work more collaboratively, the traditional pattern of the art historian having a much larger say in decision-making than the art conservator still persists in many places. Nevertheless, over the last half-century or so, the art conservator has, on the whole, gradually claimed a better position at the negotiation table and has found a louder, clearer voice in deliberations on the “crossover of responsibilities” outlined above. That this voice is much needed is also obvious, since the numbers of loan exhibitions have increased dramatically in the last decades, and artworks seem to be travelling more than ever before.

But let us be careful to focus not only on conservators and curators as they do not make decisions in isolation. There are registrars, education departments, exhibition departments, and other groups that are legitimate stakeholders in these discussions. Restoration treatments have become exhibition driven, which can create significant problems in prioritizing and financing; and, perhaps worst of all, there is the issue of very rigid deadlines for the treatments themselves. All the players involved in the conservation of artworks have distinct tasks and responsibilities. However, the final responsibility for conserving the collection lies not with the individual curator or conservator, but with the museum director. If there are insurmountable problems between the curator and the conservator, it will be up to the director to find solutions and to make final decisions. It is also the director who must strive to achieve an optimal infrastructure for conserving the collections, and to weigh the different and often conflicting needs of the departments in regard to financing, real estate, and staffing.

The importance of institutional infrastructure is hard to overestimate. The conservator is a much-needed and valuable asset to museums, and should have a major voice in matters of collection care, loan requests, preventative actions, and prioritizing restoration treatments; many institutions have granted conservators the right of de facto veto on these matters. However, many institutions, the McMaster Museum of Art included, do not have conservators as permanent staff, relying instead on freelancers (or centralized government facilities). But how often may one expect a conservator to weigh in with an unpopular opinion when hired on a temporary contract? In my opinion, it should be a clear priority for museums with substantial volumes of loan traffic to have at least some of their conservators appointed to permanent positions.

The changing role of the conservator has probably become most visible outside the museum setting in the field of technical research, the last of the shared tasks listed by the CODART conference organizers. This is because conservators have become increasingly involved in technical studies of objects in the museum collections. Over the last decades, such studies have become part of mainstream museum activities, a development evidenced by the growth in publications and exhibitions on the subject, to which we now can add The Unvarnished Truth. But when you put your ear to the ground, it is possible to hear directors, and especially curators, complain about conservators performing too few treatments because of their increased activities in research. The changed role of the conservator in relation to technical research is directly related to a rather dramatic shift in the very nature of that type of research.

The study of materials and techniques is, by definition, an interdisciplinary field, where art historians, conservators, and scientists have collaborated effectively for many years. Traditionally, it was often the art historian who mediated among the disciplines and who formulated the underlying research questions. Generally speaking, however, over the last two or three decades a shift has occurred, and the role of the scientist has become increasingly important in such teamwork, and for many good reasons. Conservation science has swiftly developed into a fully established discipline, and the equipment for instrumental analyses has become increasingly complex, triggering further specializations within the field. Other sciences have also become rapidly more important, and artworks are now routinely examined with instruments such as synchrotron particle accelerators, high-resolution 3D microscopes, and optical-coherence tomography.

It is more and more difficult for the interested art historian to keep track of these developments or fathom the outcomes of the research, let alone steer such activities. Digital imaging is becoming progressively more sophisticated as well. One could, of course, set out to master MATLAB programming language and software to perform algorithm-based image stitching or registration of high-resolution images, but it is probably more efficient to work with imaging specialists and computer scientists. In addition, scientific research is often grant driven, and granting agencies tend to fund more requests from the harder sciences than from the humanities. Regardless of one’s feelings about the changing nature of conservation, overall this field is expanding exponentially, and the art historian is not always the most logical arbiter among the players involved. Rather, we now often find that it is the modern, academically trained conservator who is better equipped to bridge the multiple disciplines and to take on the central role of mediator.

This new role for the conservator is directly linked to changes in education and training. Over the last few decades, the study of art history has largely moved away from the art object itself, whereas in the same period the training of conservators at the academic level has significantly improved. By default, the training of conservators remains focused on the physical evidence of the artwork. In addition, many professionals are crossing the academic fence between disciplines at an individual level; more and more practising conservators now also have advanced degrees in art history. And although this would appear to improve the general parameters for interdisciplinary research, this is not always the case. In some research projects, there remains too little overlap of disciplines, and a lack of common language can hamper collaboration, especially between the art historian and the scientist.

The changing role for the art conservator and the scientist in the studies of materials and techniques appears to be reflected in how we refer to this field. Rather than “technical art history”—a very apt term, I think, coined by David Bomford some two decades ago—we now increasingly see the term “art technological research,” from the German word Kunsttechnologie. The development of technical studies separate from art history and the art historian is logical and organic, but it comes with the risk of losing an essential component. In my opinion, the more interesting interdisciplinary projects in this field are driven by broader research questions that have firm roots in art history, rather than in advances of technology or conservation treatments alone. It is the very study of materials and techniques that often allows us an intimate discernment of the artist’s intent. For me, this remains the holy grail of art history.


[i] This text is a much-abbreviated version of the author’s keynote presentation at CODART 15 (Curators of Dutch Art) held 18–20 March 2012 in Brussels, Belgium. The theme of this conference was “Conserving the arts: The task of the curator and the conservator?” The conference program with the full text and accompanying PowerPoint images of my presentation can be downloaded from http://www.codart.nl/images/RonSpronkFullText.pdf and http://www.codart.nl/images/Spronk_CODART15.pdf, accessed October 10, 2014. I am grateful to Dawn Carelli for a first edit of that presentation, and to Joan Padgett for further editing.

[ii] Lesley Brown, ed. The New Shorter Oxford English Dictionary (Oxford: Oxford University Press 1993), 485.

[iii] George L. Stout, introduction to Wash and Gouache, by Marjorie B. Cohn (Cambridge, MA: Center for Conservation and Technical Studies, Fogg Art Museum, 1977), 8.

[iv] Quoted from the CODART 15 program notes; see note 1.

[v] In my presentation at CODART 15, I discussed three such events from the 1890s, the 1930s, and the 1970s. These concerned, respectively, the splitting of six wing panels from the Ghent Altarpiece in Berlin by sawing them lengthwise; the restoration of Rogier van der Weyden’s Saint Luke Drawing a Portrait of the Virgin while it was in Nazi Germany, now in the Museum of Fine Arts, Boston; and the stripping of the early Italian panel paintings at Yale University; see note 1.

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