archaeological conservation – Page 5

RTI at Kurru!

Leave a Comment / Archaeological Research, Conservation, Fieldwork / March 17, 2016

JANELLE BATKIN-HALL, Graduate Intern in Conservation

I’ve just returned from a fantastic six-week fieldwork experience at the El Kurru archaeological site in North Sudan. There, Kelsey conservator Suzanne Davis and I documented ancient figural and geometric graffiti in a funerary temple at the site. Each day, Suzanne and I would make our way through a maze of mudbrick alleys to the edge of the village, where the funerary temple and several royal burial tombs and pyramids are located in the desert.

We photographed the graffiti using a process called reflectance transformation imaging (RTI) (fig. 1). RTI is an excellent technique for documentation because each pixel records surface texture in addition to color. Since sandstone is subject to ongoing disintegration and loss, the resulting RTI images provide an excellent record of the graffiti’s current condition, as well as a highly detailed image of the column’s surface texture.

The Kurru graffiti were documented using highlight image capture where the camera remains fixed and a portable flash is moved at intervals which create a dome of light over the surface. In a single photo sequence of one object (or in this case, graffito), approximately 48 digital images are taken. Two reflective black spheres are also fixed within the image frame, and the reflection of the flash on these spheres allows the processing software to calculate the light direction for each image. The resulting images are combined with software, resulting in a single file. In this file, the viewer can move the light source across the surface in order to examine the surface details and topography from any angle (fig. 2). As a result of using this technique, 64 “new” ancient graffiti were positively identified and additional surface details became visible. In a couple of instances, a graffito was initially misidentified. For example, in 2015 a particular graffito was identified as an arrow. After performing RTI, it was clearly a human figure.

Fig-2_RTIViewer_Screen_Capture — Figure 2. Screen capture of bull graffito using CHI’s RTIViewer software.

For me, this was a great experience because I was able to use a technique I recently learned in graduate school. Being able to apply it onsite and share the results with our colleagues was very rewarding.

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Ugly Object of the Month — March 2016

Leave a Comment / Conservation, Ugly Object / March 2, 2016

BY SUZANNE DAVIS, Curator for Conservation, Kelsey Museum of Archaeology

Our current special exhibition, Leisure and Luxury in the Age of Nero, features objects from the Villa Oplontis, one of the big Roman villas near Pompeii, Italy. Most of the objects are on loan to us from Italy, and let’s face it — they are gorgeous. But don’t worry, because when you start to swoon from the beauty, the Kelsey can apply smelling salts; we have some fantastically ugly objects from the same part of Italy.

Ugly_March — Iron hoe blade. Roman period, 1st century AD. KM 1948.

This one, a hoe blade, is one of my favorites. Roman villas were farm houses. Yes, some of them were very fancy farmhouses (witness Oplontis), but farming was occurring! Then and now, the grain for our daily bread does not grow itself. On the second floor of the Kelsey near the top of the stairs, you can see a variety of Roman farming implements, including this hoe. It is a large, industrial-sized hoe, much larger than my little garden hoe (although the Romans had small ones, too). A lot of the original metal is lost, but you can see some details. For example, at the top you can see the where the metal starts to curve upward — this is where the wood handle would have attached. You can also see how the sides start to curve in near the top, giving the hoe a shape sort of like a flat shovel blade. The chunks you see on this blade are little rocks that got stuck in the mineralized corrosion layer that formed while the blade was underground for almost 2,000 years.

If you feel like the Romans lived in a world apart, which is how it can seem if you imagine only the people who lived in fancy houses like Oplontis, take a few steps and reconnect with the reality of this hoe. If you are a gardener, you can also think about this when you turn your garden over for early spring planting (maybe this very month!); your springtime chore is one that has been performed by people for millennia.

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Keeping our heads on straight: custom mount design for Oplontis garden sculpture

Leave a Comment / Conservation, Exhibitions / January 19, 2016

BY CAROLINE ROBERTS, Conservator, Kelsey Museum of Archaeology

Over two hundred artifacts and sculptures are traveling from Italy to Ann Arbor for the upcoming exhibition Leisure and Luxury in the Age of Nero, opening in February. Among them are three marble heads that once stood in the north garden of Villa A at Oplontis. The heads will be displayed in the Kelsey’s temporary exhibition space as they once were in the garden: atop tall, narrow plinths. Sculpture like this might normally be held in place with a metal pin inserted into a hole in the base of the neck. These heads, however, lack such an accommodation, which meant that exhibition coordinator Scott Meier and I needed to come up with another way to secure the heads to their exhibit mounts.

Scott’s idea is to create a two-part mount custom fit to each head’s neck base. The mount will essentially serve as a clamp, immobilizing the head and preventing it from tipping off the plinth if it is accidentally bumped. In order to create such a mount we needed a cast of each sculpture’s neck. Scott and I were able to do this in person in June 2015, when we traveled to Oplontis with curator Elaine Gazda. First, I covered the ancient marble surface with a temporary layer of Parafilm® M, a stretchable plastic film, in order to protect the stone from any staining that might be caused by the mold-taking material.

Carrie applies protective Parafilm® M to the base of each neck.

For the mold-taking material we used silicone rubber putty, which Scott applied in a thick layer to the surface.

Scott creates a mold of the neck using silicone rubber.

The putty cured overnight, leaving us with three hollow, rubber neck molds — which we dubbed the “blue brains” because, well … that’s what they look like.

Carrie and Scott pour plaster of Paris into the molds.

These “brains” eventually served as receptacles for plaster, which we used to create duplicates of the neck bases.

Plaster duplicate of one of the three neck bases.

The duplicates are being used to cast the two-part mounts in epoxy resin. Once it’s cured, the epoxy will fit perfectly around the bases of the necks and hold the heads in place with the help of metal brackets. You won’t be able to see the custom-fit mounts when the heads are on display, but you will be able to appreciate the many steps that took place in order to recreate the sculptures’ original plinth presentation. See the marble heads and more in Leisure and Luxury next month at the Kelsey!

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IPCAA field conservation workshops — Spring 2015

2 Comments / Conservation, Students / April 22, 2015

BY CARRIE ROBERTS, Conservator, Kelsey Museum of Archaeology

The Kelsey Conservation Lab recently hosted two hands-on conservation workshops for PhD candidates in the Interdepartmental Program in Classical Art and Archaeology (IPCAA): one covering ceramics and the other copper alloy (bronze) conservation. Our goals were to help familiarize the students with archaeological conservation best practices, learn about condition issues and field recovery, and gain some useful hand skills. In essence, we wanted to provide them with conservation information they could take with them into the field.

The first workshop covered ceramics conservation, beginning with an overview of deterioration phenomena. We spent some time looking at artifacts that demonstrated springing, spalling, and other structural condition problems; and we talked about lifting, transport, and temporary storage, as well as long-term ceramic storage considerations. We then proceeded with the hands-on part: the smashing and subsequent reconstruction of thrift store ceramics (the most challenging object proved to be the purse-shaped cookie jar adopted by Shannon Ness). The students learned how to make their own Paraloid B-72, a conservation-grade adhesive, and label their homemade adhesive tubes with hazardous materials labels. Fun times!

IPCAA students Dan Diffendale and Alison Rittershaus reconstruct broken ceramics.

The second workshop covered copper alloy conservation. This time we discussed deterioration, field recovery, and the goals of cleaning small metal finds (to stabilize artifacts and reveal information). The students participated in a cleaning exercise, where they learned how to use various tools — from bamboo skewers to scalpels — to clean archaeological copper alloy artifacts. They wore Optivisors during this step of the workshop. These magnifiers allowed them to better see the progress of their cleaning. The Optivisors also provided a fun talking point, as they basically transform the wearer into a lab tech/Star Trek-looking character. We finished by making Ethafoam cavity-cut supports for their artifacts and talking about the pros and cons of using silica gel in microclimate storage.

We conservators had a lot of fun working with the IPCAA students. They had many questions for us and participated in the hands-on sections with real enthusiasm. I think they’ll be taking some useful information with them into the field. We’ve benefitted too; teaching drives home the fact that one of the best preservation strategies we have is to share our knowledge with others. We hope to provide interested students with other conservation workshops in the coming years!

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A Romano-Egyptian lion takes a bath

Leave a Comment / Conservation / March 3, 2015

BY CARRIE ROBERTS, Conservator, Kelsey Museum of Archaeology

When it comes to conserving works of art, how do you treat what you can’t see?

When a carved limestone lion from Karanis came to the conservation lab a few months ago, grain-sized bits of stone were coming away from the sculpture’s pitted, weathered surface. It was the type of deterioration conservators often associate with salt activity. Egypt has salty burial conditions, and objects that are porous — like ceramics and stone — absorb salty water into their bodies.

Sodium chloride, or table salt, is a common type of water-soluble salt found in archaeological artifacts. When moisture levels in the air fluctuate, sodium chloride crystallizes and liquefies. This action is called “cycling,” as the salt goes through cycles of change from liquid, to solid, to liquid phases. With these phase changes come changes in volume — an expansion and contraction of the salt. In the crystalline phase, salts are sometimes visible on an artifact’s surface; this is called “efflorescence.” Crystallizing salts can grow right through the surface of an artifact, sometimes even pushing it off. Imagine salts cycling inside an artifact, and, well, you can see why so many ancient stone sculptures are in such bad shape!

A close look at the Karanis lion revealed no salt crystals visible on the surface. However, salts can be present even if visible efflorescence is not. I had a hunch. I took a small sample of stone powder that had detached from the surface, and tested it for chloride salts. Sure enough, the test came back positive.

Lion in bath — The limestone lion during desalination treatment.

Since salts are so sensitive to fluctuating humidity levels, and since the lion was slated for display outside its usual climate-controlled storage environment, I decided it was time for the lion to take a bath. Soaking artifacts in a water bath is an often-used method for extracting potentially harmful salts, and by measuring the amount of salt in the water bath over time, we could monitor this extraction in a quantitative way. After a few hours in a bath of purified, or deionized, water, quite a bit of salt was removed from the lion, and with it much of the risk of potential damage from salt activity.

Carrie taking measurements — Conservator Carrie Roberts tests salt levels in the bath.

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Conserving a dog skull

2 Comments / Conservation / February 10, 2015

BY MADELEINE NEIMAN, 2014–2015 Samuel H. Kress conservation fellow at the Kelsey Museum

This past Friday marked the opening of our new exhibition at the Kelsey: Death Dogs: The Jackal Gods of Ancient Egypt. My favorite object in the exhibition is a desiccated dog skull excavated from Karanis, a Roman-period village in Egypt. Here at the conservation lab we have affectionately named the skull Kalbi, or “my dog” in Arabic.

While he is not the prettiest specimen, the conservator in me is amazed by Kalbi’s phenomenal state of preservation. Large portions of the dog’s skin were preserved by the arid desert environment at Karanis. Even his eyelids and nose remain! Today, I thought I would share with you the challenges of displaying Kalbi, as well as how we overcame those challenges.

Challenge 1: The dried skin covering the skull is extremely fragile. Skin is composed of a network of collagen fibers — chains of amino acids that are spiraled together to form fibrils that, in turn, bundle together to form fibers. As the skin covering the skull dried, the fibers shrank and stuck together, causing it to become brittle and cracked. In several locations along the edges, the delicate skin was in danger of completely falling off.

Solution 1: Cracks in the skin were stabilized by gluing small pieces of Japanese tissue beneath the cracks. The tissue acts like a splint; it bridges/reinforces splits in the skin and secures loose pieces in place.

Gluing Japanese tissue mends under cracks in the skin.

Challenge 2: Several of the teeth had fallen out of the dental aveoli — the small voids in the jaw that hold the roots of the teeth. While we could easily secure the teeth in place with a small amount of adhesive, figuring out their correct anatomical location was trickier.

Solution 2: For assistance, we turned to Richard Redding, a Kelsey Research Scientist and zooarchaeologist (specialist in archaeological faunal remains). Richard determined the proper placement of each tooth, and we glued them into place.

Challenge 3: We needed to find a way to put the head back together. The dog’s head came to the lab in two pieces; without muscles to hold them together, the skull and jaw had separated. Unfortunately, the fragile teeth and delicate skin along the lower jaw meant that the skull could not safely rest on top of the jaw.

Solution 3: A mount. The creation of mounts is typically the domain of our talented exhibition preparator Scott Meier. When objects are particularly fragile, however, Scott and the conservation staff collaborate. In this case, we combined forces to create a mount that would allow the skull to float above the jaw, giving the appearance of a complete head without allowing the two pieces to touch. Scott made a raised support using a carved wood block and brass dowels. To the top of the wood block, I attached carved pieces of ethafoam, which keyed into raised areas along the base of the cranium, locking it into place. With the skull held above, the jaw could be slid into place below. Each piece is separately supported, but Kalbi’s head appears complete.

As you can see, the preparation of objects for exhibition is a team effort! We hope you will come by to visit Kalbi and all of the other artifacts on display in Death Dogs: The Jackal Gods of Ancient Egypt.

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Conserving a Seleucian Incantation Bowl

1 Comment / Conservation / January 7, 2015

BY MADELEINE NEIMAN, 2014–2015 Samuel H. Kress conservation fellow at the Kelsey Museum. During her time here, Madeleine’s work will focus on the technical analysis and treatment of objects from the Seleucia collection.

KM 31455 — Incantation bowl (TMA 1931.455) from the site of Seleucia on the Tigris. The object is a wheel-thrown, buff-colored earthenware bowl the surface of which has been painted with black pseudoscript (small lines meant to mimic Aramaic writing) and images of anthropomorphic figures.

The vessel was excavated in the 1930s from Seleucia on the Tigris, a site approximately 18 miles south of modern-day Baghdad, Iraq. Magical bowls like this one were placed in the corners of houses or under thresholds as a means to protect their owners from evil spirits. The text and images drawn served to combat demons or other supernatural beings that might harm the object’s owner. Today incantation bowls, including this one, are important for the study of ancient magical and religious practices.

Can you guess why the bowl came to the conservation lab?

How about if you compare it to another incantation bowl in the Kelsey collection?

Incantation bowl (KM 33756) from the site of Seleucia on the Tigris. The object was found alongside the above-pictured bowl.

Yes. That’s right. There is a thick, dark crust covering much of the interior and exterior of the bowl, and it hides the decoration on the bowl’s surface. Curators here at the Kelsey have asked the conservation lab to remove the crust so that the decoration on the surface is easier to see. Before the crust can be removed, however, conservators must figure out what this strange material is.

Based upon a close examination of the surface, we suspect the crust is most likely one of two things.

Option 1: Salts! This bowl was buried under ground for approximately 2,000 years. During that time the porous ceramic vessel was likely exposed to groundwater containing a range of salts; chlorides, nitrates, phosphates, and sulfates are all commonly present in soil and are, as a result, often found within the fabric or on the surface of ceramics recovered from archaeological contexts. While salts typically appear as areas of white crystalline efflorescence on an artifact, they may also occur as dark, hard surface accretions similar to the material visible on the bowl.

Option 2: A modern coating. It is possible that the darkened surface is due to the application of a modern coating. During the 1930s, when this object was excavated, archaeologists and conservators often covered artifacts with a resin or glue in an attempt to protect and strengthen surfaces. While these materials were applied with good intentions, they can alter over time in unexpected and undesirable ways. A once clear, coherent coating could become dark and brittle like the coating on the bowl.

However, as Sir Arthur Conan Doyle notes, “it is a capital mistake to theorize before one has data.” So … how will conservators here at the Kelsey get the data necessary to determine what is covering the bowl?

Like historians, conservators look at archival records. The Seleucia archive at the Kelsey Museum holds a range of primary source documents created by archaeologists at the time of excavation, including journals, object lists, and photographs. We will examine these documents for any clues to what the bowl looked like at the time of excavation (e.g., was the bowl’s surface dark when removed from the ground?) as well as the conservation methods that might have been used on the bowl. We will also utilize a range of scientific examination techniques available across the University of Michigan campus to study the chemical makeup of the crust.

I hope you will check back with us in the coming months as we work to uncover the surface of this bowl.

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Using UV light to examine ancient paint

1 Comment / Conservation / December 9, 2014

BY MADELEINE NEIMAN, 2014–2015 Samuel H. Kress Conservation Fellow at the Kelsey Museum. During her time here, Madeleine’s work will focus on the technical analysis and treatment of objects from Seleucia on the Tigris, a site approximately 18 miles south of modern-day Baghdad, Iraq.

One of my major projects here at the Kelsey is conducting a survey of artifacts from the Seleucia collection. The goal of this work is to answer three questions:

What are the artifacts made of and how are they made?
What is the condition of the object? More simply, is there any evidence of damage or deterioration (e.g., breaks, cracks, discoloration) present?
Have the objects been modified (e.g., repaired or reused) in any way by modern or ancient people?

Conservators utilize a number of tools to help us answer these questions. Today I thought I would share with you a bit about one of our most commonly employed techniques — examination under ultraviolet light.

Light is a form of electromagnetic radiation and exits as part of a large electromagnetic spectrum. Ultraviolet radiation, often called UV light, refers to that area just below what is visible to the human eye. While we can’t see UV light, when it illuminates the surface of an artifact, certain types of materials, including some dyes, minerals, and resins commonly found on archaeological objects, fluoresce. These materials glow different colors!

Let’s look at an example.

Among the over 13,000 objects in the Seleucia collection are a group of bone figurines. Several of these are decorated with a reddish-pink paint that displays a unique orangey-pink fluorescence.

Images of bone figurine (16187) with pink paint captured under visible (left) and UV (right) illumination. — Images of bone figurine (KM 16187) with pink paint captured under visible (left) and UV (right) illumination.

In antiquity, people created paints using mineral pigments as well as organic colorants found in plants and animals. Among the most common sources of red were the pigments hematite (iron oxide), cinnabar (mercury sulfide), and red lead as well as the dyes kermes (from the Kermes vermilio insect) and madder (from the plant Rubia tinctorium). When viewed in visible light all five appear red. However, when examined under UV light, one stands out: madder. Madder contains four principal colorants: alizarin (red), purpurin (red), pseudopurprin (red) and xanthine (yellow). The purpurin and pseudopurpurin glow a bright orangey-pink when exposed to UV light, making it easy to distinguish.

By examining the figurines under UV light we can tell that an ancient artist used madder to decorate these figurines!

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News from the Conservation Lab

Leave a Comment / Conservation / September 30, 2014

The Kelsey Conservation Lab is pleased to welcome Madeleine Neiman as our new Samuel H. Kress Fellow for the 2014–2015 academic year.

Madeleine is a recent graduate of the UCLA/Getty Program on the Conservation of Archaeological and Ethnographic Materials, and has an undergraduate degree in anthropology from Bryn Mawr College. She just completed a year-long graduate practicum internship at the Arizona State Museum (University of Arizona) and has also previously worked at the Colonial Williamsburg Foundation, the Alaska State Museum, and the Anchorage Museum, where she focused on the conservation and technical analysis of ethnographic and archaeological materials.

At the Kelsey, Madeleine’s research will center on conservation projects for the Seleucia collection. For example, she will research and treat an incantation or “demon” bowl from Seleucia, an unglazed ceramic bowl painted with magical spells designed to entrap demons. The inscriptions on this bowl are obscured by a darkened surface layer (possibly a modern coating) and by the presence of chunky salts, probably deposited while the bowl was buried. Important goals of conservation treatment will be to stabilize the bowl’s inscription and make it more legible.

In addition to the bowl, Madeleine will survey and study a group of bone figurines from Seleucia. The figurines are carved in both stylized and naturalistic human forms, and some are painted. Madeleine will collaborate with zooarchaeologist Dr. Richard Redding, as well as materials scientists at U-M and elsewhere, to answer a variety of research questions about the figurines.

We are thrilled to have Madeleine here to research and treat these unique artifacts, and we’re grateful to the Samuel H. Kress Foundation and the Foundation of the American Institute for Conservation for supporting her fellowship. Welcome, Madeleine!

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News from the Conservation Lab

Leave a Comment / Conservation / September 3, 2014

Meet Shelley Almburg, microscope repairperson extraordinaire.

Shelley works for the Microscopy and Image-analysis Lab at the University of Michigan. She is the one and only microscope troubleshooter for the University, traveling from lab to lab with a bag of tools designed to tweak, align, degrease, re-lube, and fix whatever ails microscopes. As a conservator, I use our polarized light microscope quite often, to look at fibers, pigments, salts that might be growing on an excavated pot, you name it. But when the lightbulb in our Olympus BH-2 burned out, did I know the first thing about how to fix it? Nope. Not a clue.

“Make sure not to touch the new bulb,” Shelley told us as she pulled the replacement light from her bag and installed it with the greatest of ease into the microscope’s base. She then proceeded to disassemble the microscope piece by piece, with the deliberateness of a master clock worker inspecting the parts of an intricate, antique timepiece. I realized then that my fear of breaking the scope had prevented me from ever exploring its inner workings, preventing it from ever working properly! It takes some serious knowledge and guts — and maybe a little WD-40 — to take something like this apart and know that you’ll be able to put it together again, and make it better in the process.

Thank you, Shelley!

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