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Art at the ‘cutting’ edge: Cross-section sampling of paintings

Last month, I led a handful of members of the IMA’s Second Century Society through a special behind-the-scenes workshop in my laboratory exploring the practice of cross-section sampling in conservation science. A cross-section is a miniscule sample cut from an artwork so as to contain all the layers of the painting – from the topmost varnish to the lowest preparation layer. When examined under a microscope or probed using micro-analytical techniques, a cross-section tells the story of the artwork’s inception, creation, and aesthetic techniques in a way that no other analysis or connoisseurship can. Although the collection and preparation of these samples can take days, we whisked participants through the many steps of sampling, mounting, and analysis of a cross-section using materials prepared in advance – much like a cooking show – in order to explain this invaluable technique for understanding and interpreting artworks in the collection.

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Figure 1. The horizontal red and white element (#2013.443B) is seen in the foreground.
Roy Lichtenstein, Five Brushstrokes, designed 1983-84, fabricated 2012.
Gift of the Roy Lichtenstein Foundation with additional support from the Robert L. and Marjorie J. Mann Fund.
© Roy Lichtenstein Foundation

Recently, we installed Roy Lichtenstein’s Five Brushstrokes on the Sutphin Mall. The extraordinary process of carefully positioning and stacking these monumental artworks – one that involved cranes, work crews, and conservators – was captured on time-lapse photography. The morning after the installation, I found a plastic baggie with two small paint samples on my desk. As I turned the chips over in my hand, it was obvious they told a story of the sculpture’s creation – so I prepared a cross-section to check it out.

The five components of Brushstrokes are made of painted aluminum. One of the samples came from the horizontal red and white brushstroke (Figure 1), and it is obvious from the cross-section (Figure 2) that the white highlights were painted first and then the sculpture was masked off to add the red passages – you see the red layer over top of the white in the cross-section meaning that the red paint had to be the last to be applied. But what is all that thick pink stuff below? An industrial product similar to Bondo! Yes, it is an epoxy version of a fairing compound like that used in bodyshops to level dents and scrapes on your car. When an aluminum sculpture is fabricated, the surface isn’t always smooth, and so an epoxy or polyester filler is troweled on top and sanded smooth to give an even surface that is then painted.

Figure 2. A magnified view of a mounted and polished cross-section from the horizontal red and white element of Five Brushstrokes. 1000 µm = 1 mm.

Figure 2. A magnified view of a mounted and polished cross-section from the horizontal red and white element of Five Brushstrokes. 1000 µm = 1 mm.

This layered structure seems complex, but cross-sections can get much more interesting! Check out this cross-section from a wooden shutter salvaged from a historic property on the Dupont’s Winterthur Estate, Figure 3. Because the building was regularly repainted, the section shows over a dozen different paint schemes. Furthermore, irradiating your sample with ultraviolet light and imaging the visible fluorescence from the paints can help to identify additional layers in what looks like a single, thick white paint coat toward the bottom of the section – the shutter has obviously been touched up with the same color a few times too!

Figure 3. Visible (left) and ultraviolet-induced visible fluorescence (right, reversed) photomicrographs of a wooden shutter from a building on the Dupont’s Winterthur Estate in Delaware.

Figure 3. Visible (left) and ultraviolet-induced visible fluorescence (right, reversed) photomicrographs of a wooden shutter from a building on the Dupont’s Winterthur Estate in Delaware.

Cross-section sampling is, by its nature, a destructive technique since a small sample of paint must be sacrificed. However, these samples can be vanishingly small, oftentimes less than the width of a hair, and yet they yield an enormous amount of information about the materials, craftsmanship, and condition of an artwork.

 

The IMA in Egypt, Part 3: ‘Wrapping up’ our Mummy Coffin Research

Today’s blogger is Dr. Gregory Dale Smith, the Otto N. Frenzel III Senior Conservation Scientist at the IMA. Dr. Smith is reporting through a series of blog posts on the IMA’s involvement in an exhibition at the Kelsey Museum of Archaeology in Ann Arbor, Discovery! Excavating the Ancient World.

Fig. 1.  A portion of a painted headdress from a Late Period wooden coffin. The annotations provide the unique data label, the chemical elements identified by X-ray fluorescence spectroscopy, and the most likely pigment inferred from the elements found.

Fig. 1. A portion of a painted headdress from a Late Period wooden coffin. The annotations provide the unique data label, the chemical elements identified by X-ray fluorescence spectroscopy, and the most likely pigment inferred from the elements found.

A year ago this week, I boarded a plane for Egypt carrying a small “mobile lab” to take part in a collaborative fieldwork project studying ancient wooden funerary objects. As I reported earlier, the goal was to determine better conservation methods for stabilizing these beautiful, but fragile painted artifacts, which include decorated sarcophagi and statues. As the group’s chemist, my job was to use portable analytical instruments to identify the pigments, adhesives, and binding media used in the surface decoration of these deteriorated objects. On this one year anniversary, I wanted to wrap up my blog series by presenting some of our results from this exploratory season in the field at Abydos.

Our analyses showed that the ancient Egyptian artists used natural materials to decorate the tombs of their dead (Fig. 1). The binding agents for their paints included glue made from boiled animal skins and resinous gums exuded from plants. The colorants were also largely natural minerals including white chalk, yellow and red earths, soot black, and the poisonous arsenic containing yellow mineral orpiment. The primary blue pigment, however, was synthetic; Egyptian blue, a copper-containing glass frit was first made in Egypt as early as the 4th Dynasty around 3000 BC. Armed with this information about the paint composition, conservators are able to choose the most appropriate consolidants to stabilize these often disintegrating artifacts.

Fig. 2. A composite “eye” from a Ka statue composed of copper sheet, marble, and obsidian. The left eye is shown in pieces while the right one has been reassembled by conservators.

Fig. 2. A composite “eye” from a Ka statue composed of copper sheet, marble, and obsidian. The left eye is shown in pieces while the right one has been reassembled by conservators.

We also encountered other decorative elements including the inlaid eyes (Fig. 2) from wooden Ka sculptures found in the chapels associated with royal tombs. These are composite structures that include metal eyelids identified as pure copper sheet soldered together with lead and limestone whites of the eyes carved around a central black pupil of imported volcanic obsidian. The black gemstone was held in place with a plug of beeswax. Future work might include using chemical analysis to trace the foreign source of these luxury trade items.

Fig. 3. A display panel from the Kelsey Museum of Archaeology’s exhibit Discovery! Excavating the Ancient World showing the Abydos wood project team onsite.

Fig. 3. A display panel from the Kelsey Museum of Archaeology’s exhibit Discovery! Excavating the Ancient World showing the Abydos wood project team onsite.

One further outcome of this highly successful exploratory field season is the exhibit Discovery! Excavating the Ancient World at the Kelsey Museum of Archaeology at the University of Michigan.  The work of the conservation team was included in the exhibition’s didactics to show the diversity of disciplines that contribute to our understanding and preservation of archaeological materials (Fig. 3). All of those who were part of this field season are extremely grateful to our home institutions for the latitude to come together to participate in this exciting project, and to the American Research Center in Egypt (ARCE) who along with the University of Michigan funded the expedition. Aside from being a fascinating study with components of ancient technology, complex biodeterioration, and delicate preservation interventions, our work in Egypt was a lot of fun (Fig.4)!

Fig. 4. Team leader and Kelsey Museum conservator Suzanne Davis shows off the Ka statue inlaid eyes after reassembling the excavated pieces.

Fig. 4. Team leader and Kelsey Museum conservator Suzanne Davis shows off the Ka statue inlaid eyes after reassembling the excavated pieces.

 

The IMA in Egypt, Part 2: Have Gun – Will Travel

Today’s blogger is Dr. Gregory Dale Smith, the Otto N. Frenzel III Senior Conservation Scientist at the IMA. Dr. Smith is reporting through a series of blog posts on the IMA’s involvement in a new exhibition at the Kelsey Museum of Archaeology in Ann Arbor, Discovery! Excavating the Ancient World.

Figure 1. A Bruker Tracer III-V portable XRF spectrometer positioned vertically in a bench top stand alongside a Bruker Alpha FTIR spectrometer. Dr. Smith uses the FTIR to analyze the organic binder in small fragments of paint.

Figure 1. A Bruker Tracer III-V portable XRF spectrometer positioned vertically in a bench top stand alongside a Bruker Alpha FTIR spectrometer. Dr. Smith uses the FTIR to analyze the organic binder in small fragments of paint.

An X-ray gun that is! In a previous post, I described a collaborative project with the University of Michigan’s Kelsey Museum of Archaeology and the American Research Center in Egypt that sought to find a better means of excavating, stabilizing, and preserving beautifully-decorated, but incredibly fragile painted funerary artifacts. My role in the 2013 field season was to identify the materials of these coffins, statues, and wooden objects in order to better inform the approaches to their conservation. To do this, I needed to transport several scientific instruments to our field site in Abydos, Egypt. The IMA’s X-ray fluorescence (XRF) spectrometer, a.k.a. the X-ray gun, was one of those analytical tools, ideal for determining the elemental composition of the objects’ inorganic components (metals, minerals, stone) and small enough to be easily transported to a dig site lab (see Figure 1).

Figure 2. The Abydos dig house wet chemistry laboratory was used to test for proteins and polysaccharides in the paints used to decorate wooden funerary objects.

Figure 2. The Abydos dig house wet chemistry laboratory was used to test for proteins and polysaccharides in the paints used to decorate wooden funerary objects.

For the organic components (paint binders, wood, resins, waxes, textiles, glues), a Fourier-transform infrared (FTIR) spectrometer loaned by Bruker Instruments complemented wet chemical tests conducted in our makeshift field lab, shown in Figure 2.

Figure 3. Blue tape solves the persistent problem of loose electrical adapters while a tea kettle and insulated thermos replace a lab hotplate for warming reaction test tubes.

Figure 3. Blue tape solves the persistent problem of loose electrical adapters while a tea kettle and insulated thermos replace a lab hotplate for warming reaction test tubes.

Operating a field lab in the desert requires a good deal of patience and creativity. Daily power outages, loss of the internet, and an omnipresent layer of dust can complicate analyses that would be quick and routine in the IMA’s state-of-the-art laboratories (see Figure 3).  Stay tuned for the final installment describing the results of our research and some future research directions.

 

The IMA in Egypt, Part 1: Science in the Sand

Today’s blogger is Dr. Gregory Dale Smith, the Otto N. Frenzel III Senior Conservation Scientist at the IMA. Dr. Smith is reporting through a series of blog posts on the IMA’s involvement in a new exhibition at the Kelsey Museum of Archaeology in Ann Arbor, Discovery! Excavating the Ancient World.

This spring I was part of a multi-disciplinary team tackling tricky archaeology in Egypt. The University of Michigan’s Kelsey Museum of Archaeology, under the direction of Egyptologist Dr. Janet Richards, excavates a famous cemetery site there, the Abydos Middle Cemetery (AMC). Abydos, positioned mid-way up the Nile River, was the burial site of Egypt’s earliest kings. Archaeologists commonly encounter beautifully-decorated funerary materials at the site, like the painted wood coffin shown below.

Figure 1. A painted coffin being unearthed at the Abydos Middle Cemetery excavation. Photo, S. Davis, courtesy of the Kelsey Museum of Archaeology.

Figure 1. A painted coffin being unearthed at the Abydos Middle Cemetery excavation. Photo, S. Davis, courtesy of the Kelsey Museum of Archaeology.

Although these artifacts look well preserved, they are anything but! The wood has been attacked by fungi and termites to the point that only a brittle web of debris, insect frass (a.k.a. bug poop), and mud is holding it together. On top of this delicate matrix is an eggshell-thin layer of gesso and paint. How does one excavate and lift these fragile objects without crushing them? Archaeologists and conservators currently use a variety of methods to preserve these artifacts, but none work very well. The goal of this project was to find better approaches that could be used in the harsh desert conditions.

Figure 2. Dr. Smith descending into a cistern at Sepphoris, Israel.

Figure 2. Dr. Smith descending into a cistern at Sepphoris, Israel.

So why me? To develop new conservation methods, the AMC conservators needed to understand the paints, pigments, and other materials present on the artifacts. Any new conservation treatment they designed would have to be sympathetic to these materials and not cause unexpected harm. Since no artifacts, or even samples of artifacts, are allowed to leave Egypt, the scientist and the necessary equipment would have to travel to Egypt with the project team. As it happens, I have a background in both chemistry and archaeology. While a chemistry graduate student at Duke University, I spent my summers excavating at Sepphoris in Israel’s Galilee region (Figure 2). With my conservation science expertise, the necessary portable instruments, and previous experience in archaeology, I was a natural fit.

ima_egypt_fig3_101513The project team would spend several days in Cairo consulting with local conservators and visiting museums with artifacts similar to those at the field site. Then we were off to Abydos for a week of analysis and conservation trials. Our group, pictured below in front of the modern-day Abydos village, consisted of:

  • AMC/Kelsey Museum conservators Suzanne Davis and Claudia Chemello
  • Smithsonian Institution conservator Rae Beaubien, a specialist in the excavation of fragile archaeological materials
  • The MFA Boston’s Pamela Hatchfield, who has considerable expertise in the conservation of Egyptian antiquities
  • Dr. Robert Blanchette, professor of plant pathology and specialist in archaeological wood at the University of Minnesota
  • Mycologist Dr. Ahmed Abdel-Azeem, from Egypt’s University of Suez Canal, who has studied the fungi of North Africa

Stay tuned for part two of the story as I discuss working in the field!

 

 

CSI: Conservation Science Indianapolis

Part One in a series of blog posts on the ongoing technical examination of a purported 1874 Alfred Sisley Impressionist painting.

Has a crime been committed?  Where will the evidence lead?  I recently began teaching a course for graduate students in IUPUI’s Chemistry and Biological Chemistry department and the Forensic and Investigative Sciences (FIS) program. The course, Chemical Analysis in the Detection of Fakes, Forgeries, and Misattributions, explores the role of the physical sciences in unmasking ersatz artworks.  But this isn’t like any normal seminar course – the students not only receive lectures on the chemistry of artists’ materials and the instrumentation used to characterize them, they also work with me in the laboratory scrutinizing, imaging, sampling, and analyzing an artwork from the museum’s collection.

Painting attributed to Alfred Sisley (1839-1899), “House in a Village,” dated at bottom, May 16, 1874, oil on canvas, James E. Roberts Fund, 52.33.

For the past two weeks, the students have been learning about the IMA’s Impressionist painting, House in a Village, ascribed to the hand of the British painter Alfred Sisley who spent his adult life working in France. IMA Associate Curator for Research, Annette Schlagenhauff, has had her suspicions about the Sisley painting, which was purchased by the museum in 1952 for $3000. Many of the questions arise from the notorious scandal in 1962 in which many of the paintings included in a touring exhibition of Walter P. Chrysler Jr.’s collection were refuted by art experts as fakes. These paintings included works by the likes of Monet, Picasso, Matisse, and yes, two by Alfred Sisley.  The relationship between these debunked artworks and the IMA’s painting exists in the dealer responsible for both sales, J. P. Hartert of New York City.  Dr. Schlagenhauff has examined the museum’s documentation on the sale, including letters from Mr. Hartert to the museum’s curator.  Through online databases she has tracked the painting’s dubious provenance provided by Hartert, identifying several non-existent collectors and fictitious “experts” who are said to have owned or examined the painting.  These discrepancies, while troubling, do not necessarily invalidate the work.  Dr. Schlagenhauff’s challenge to the class is to identify any anachronisms in materials or inconsistencies in technique that would clearly place the painting outside the lifetime and painting style of Alfred Sisley. Stay tuned…

 

About gdsmith

Title: Senior Conservation Scientist Interests: Home brewing Favorite Movies: The Hangover Favorite Music: folk Favorite Food: chocolate & coffee, together or separate Pets: No, thank you. Something Extra: Lived in London and loved it.

Greg has written 7 articles for us.