Hello from Gordion!

Julia Commander is a third-year graduate student in the Winterthur/University of Delaware Program in Art Conservation. She is currently completing a curriculum internship at the Penn Museum.

As part of my internship year, I’m spending a month at the Gordion Excavations in the small town of Yassıhöyük, Turkey. This site, the capital city of ancient Phrygia, has been excavated by the University of Pennsylvania since the 1950’s. As a student interested in archaeological conservation, gaining experience with material in the field is an exciting learning process.

The Gordion dig house.

The conservation lab within the dig house compound.

Our home base is a small lab in the dig compound, where we work on processing whatever the excavators find. This year, we have a large amount of iron and copper alloy material. The metals are corroded and fragile, but many retain interesting details and clues about their use. Some of my favorite small finds so far are these two pairs of copper alloy tweezers, including a miniature version! Cleaning involves mechanical removal of dirt and corrosion products, followed by the application of a corrosion inhibitor for the copper alloy.

Two pairs of tweezers recovered as small finds and modern tweezers for scale. The miniature pair (left) has already been treated by reducing dirt and corrosion products.

We also consistently have a lot of ceramic material. Most of the ceramics are washed, sorted, and stored as bulk pottery, although particularly significant or interesting fragments come to the lab. This category includes painted tiles, inscribed or elaborately decorated fragments, and vessels that can be reconstructed. In the lab, we set up containers for desalination treatments, where ceramics are soaked in filtered water to slowly reduce salt content. These salts came from the burial environment, and they can cause damage over time if they remain in high concentrations. The process factors in ceramic weight, water volume, and time to tailor a treatment plan for each object.

Desalination set-up. Each container holds a ceramic object or fragment, and the soaking process reduces salts in the material.

In addition to keeping up with the current excavations, the conservation team works on projects with researchers and the local Gordion Museum. For researchers, accurately recording artifacts often involves detailed measuring and drawing. Conservators contribute to the process by joining fragments and reconstructing objects so that they can be documented. We also have ongoing preservation projects at the museum to make sure that objects are stored properly and stable over time. One example is the use of silica gel, which can help control humidity in storage housings.

Working on site moves at a quick pace, but there’s still time for exploring. One of my favorite near by sites is Midas City, known for its monumental rock carvings. Visiting different sites and museums, such as the Museum of Anatolian Civilizations, helps contextualize my work and adds to the experience. There’s still more to come from this busy season!

The Midas Monument at Midas City.

Two human figurines from Tureng Tepe

Preparations for the opening of our new Middle Eastern Galleries are well underway. Take a peek into either of our lab spaces (both the Artifact Lab and our main lab spaces) and you’ll see a multitude of artifacts being treated for this upcoming exhibition.

I recently treated two ceramic human figurines which will be going into a case with several other figurines from Tureng Tepe, a site in northeastern Iran.

Map of archaeological sites in Iraq and Iran, with a red star next to Tureng Tepe. Base map image credit: University of Chicago.

One is female, and mostly complete, and the other is a male torso.

Like most objects for the Middle Eastern Galleries, both of these objects needed treatment. And they represent two different reasons for treatment, which we commonly seen in our lab.

The female figure had a couple different problems. First, and most obviously, her head was detached.

A detail of 32-41-68, before treatment.

The other problem stemmed from the fact that she had been treated before. In the 1980s, she was desalinated by soaking in water, and consolidated with PVA-AYAF, a polyvinyl acetate resin. Both of these interventions were important for the long-term structural stability of this piece. But the problem related to old treatment was an aesthetic one – there were areas on the body that were very discolored/gray, which made for a splotchy appearance overall. You can see these gray patches in the images above. These gray patches were also very shiny, and were related to a coating that had been applied to the figure at some point – possibly the old PVA consolidant.

Treatment of this figure included removing the darkened coating by swabbing with acetone, and some mechanical removal with bamboo skewers. The head was reattached with Paraloid B-72. There were some areas where the ceramic body was flaking and these areas were consolidated with a dilute solution of Paraloid B-72 in acetone and ethanol.

32-41-68 before (left) and after (right) treatment

In contrast, the male figure had never been treated. When I first laid eyes on him, I thought to myself, “Terrific! This piece looks like it will just involve documentation. It will be in and out of the lab within a day or two.” Well, looks can be deceiving, and I quickly realized that the male figure had a soluble salt problem, related to the burial environment. I actually haven’t discussed soluble salts on this blog before. You can read a nice explanation of soluble salts, how they affect archaeological objects, and what we do about them, in Tessa de Alarcon’s blogpost on the Penn Museum blog.

The most obvious signs of soluble salts were the small flakes of ceramic sitting under the figure in its storage support. A quick spot test for chlorides was positive, so I made the decision to desalinate the figure by immersion in water for several days. After desalination, I readhered the small flakes, and the treatment was complete.

Before (left) and after (right) treatment images of the male figure from the side. Small flakes were reattached in the area indicated by the red arrow.

32-41-62 before (left) and after (right) conservation treatment.

As I mentioned, these artifacts will go into a case with several other human figurines from Tureng Tepe. We have, or will be treating a number of figurines from several different sites for the Middle Eastern Galleries. I am including images of some of these figurines below. Personally, I like the ladies with their hands on their hips.

Human figures. Link to larger images and more information by clicking on their numbers (listed from left to right): 32-41-25, 31-43-450, 43-29-3, 58-4-3, 31-16-733, 31-16-734

A final look at Ptah-Sokar-Osiris

Julia Commander is a third-year graduate student in the Winterthur/University of Delaware Program in Art Conservation. She is currently completing a curriculum internship at the Penn Museum.

When we last checked in with the Ptah-Sokar-Osiris figure, I was working on finding a satisfactory cleaning approach. The figure has a darkened layer over the front surface, which obscures the beautiful patterns, colors, and hieroglyphs. My goal for cleaning was to clarify designs and improve legibility, although the sensitivity of the paint layers has made this an interesting challenge.

After cross-section analysis, I looked into instrumental techniques to better understand the condition issues. One promising technique was gas-chromatography mass-spectrometry (GC-MS) since the darkened layer was potentially a coating material. I took a sample by swabbing the dark layer from the wood substrate. Since only a small amount of material can be gathered this way, I collected several swabs in a glass vial for analysis. I sent this down to Winterthur Museum’s Scientific Research and Analysis Laboratory (SRAL), which has previously collaborated on samples from the Artifact Lab. Dr. Christian Petersen, a GC-MS specialist, sent back my spectra with some interesting results. He described the mixture as “waxy dirt,” which helps to clarify what likely happened to the surface. Wax may have been applied to consolidate the badly flaking paint, and this layer could have trapped dirt over time as the figure rested face-up in storage.

Focusing on the wax component did not immediately produce better cleaning results, and I continued testing gels with variations on solutions, application method, and timing. I eventually tried an application of Pemulen TR-2 gel, a polymeric emulsifier, with a proportion of solvent added. This gel was more effective for lifting the waxy grime and did not require excessive action on the surface. Used along with a silicone solvent barrier layer, I was able to lightly clean without lifting pigments from the surface. While I had some initial ideas about cleaning, this method was something that I only found through the process of trial and error.

L-55-29 detail, cleaning test

Even though I cleaned slowly in very small sections, the actual treatment step took much less time than the research, testing, and planning phases. Take a look at the results below.

L-55-29, before cleaning (left) and after cleaning (right)

Aside from cleaning, a few other steps were taken to stabilize the statue. The headdress, which is constructed from multiple pieces of wood, had a large gap that allowed the pieces to move individually. To add support and decrease movement, removable fills were made from Volara foam and Japanese tissue. These materials were turned into small “pillows” that were then pressure-fit into place.

L-55-29 headdress, shaping and fitting Volara foam fills

The figure, headdress, and base do not fit together in a stable arrangement. Instead of intervening further with the object itself, an exterior mount will be constructed to hold the components in place. This method has worked well with a similar Ptah-Sokar-Osiris figure, which you can see displayed in the Upper Egypt Gallery!

Another Ptah-Sokar-Osiris figure on display in Upper Egypt, showing the back of the figure and the mount holding the three pieces together.

Overall, this project provided quite a few challenges and an opportunity to explore cleaning techniques. Thanks for following along on this experience with Egyptian painted surfaces!

Update on one of the Al-Ubaid Friezes

The treatment of the two Al’Ubaid Friezes has progressed since the last post. This post is going to focus on what we have been doing with the marching bull frieze (B15880). This frieze is made up of shell pieces for the bulls (probably made from large conch shells) on a background of black stone pieces with copper alloy borders at the top and bottom of the frieze.

B15880, frieze of 6 bulls

The archaeologists who excavated these materials in the 1920’s set the mosaic into plaster over a wooden backing. Overtime, this support had started to flex, causing the plaster to separate from the wood. This lead to movement of the mosaic frieze casing pieces to loosen and detach as well as causing breaks in the stone. Over the years detached pieces were re-adhered using a variety of different adhesives depending on when the work was done.

Diagram of B15880 showing the 1920’s backing materials in relation to the copper, shell, and stone materials of the frieze.

Because of these issues the mosaic has now been removed from the 1920’s support. One of the perks of having the pieces free from the support, is that we can see both sides of each piece. While we knew from the X-ray that in antiquity they had been attached to the original support using copper alloy wire twists, we can know see those twists.

Detail of the shell showing the remnants of a copper alloy twist/fastener

Detail of the stone showing the remnants of a copper alloy twist/fastener

Now we are working to stabilize each individual piece. The shell bulls are in very good shape, so that has just been cleaning to remove the plaster, areas of over-paint, and adhesive residue. The stone pieces are, however, in much worse shape. We have been consolidating them to restore the cohesion of the stone, joining broken fragments, and cleaning to reduce plaster and old adhesives.

Image showing the progress on cleaning and stabilizing the mosaic pieces.

The next step will be to adhere the clean and stable pieces to a new backing with new grouting around them to keep them in place. Exactly what materials we will use and how that will be done is something we are still working on, but here you can see some of the test tiles that we are making to help make that decision!

Test tiles with bone beads and different possible grouting materials.

 

Treatment of a Huron cigar case

To prepare this jewel of a cigar case for exhibition, lifting and detaching moose hair and splits in the birch bark had to be stabilized.

Before treatment image showing the cigar case from the side, with arrows indicating lifting and detaching moose hair (red ) and splits in the birch bark (green)

A small piece of twisted Japanese tissue paper used to replace some of the missing threads

 

Some of the lifting moose hair was stabilized with dabs of 5% methyl cellulose. For the lifting moose hair around the edges of the case, much of this damage was exacerbated by the missing brown thread stitches. For these areas, after re-positioning the moose hair, I recreated the missing threads with twisted Japanese tissue paper fibers, toned with acrylic paint.

 

The fibers were adhered in place with Lascaux 498, an acrylic emulsion.

Before (left) and after (right) treatment images, with red arrows indicating the locations of the replacement stitches

Unstable splits in the birch bark were repaired from the interior with Japanese tissue and Lascaux 498. Additional support splints made of twisted Japanese tissue fibers were added to the exterior in one place on the lid.

Before (left) and after (right) treatment images of the lid. The red arrows indicate the location of the split and the repair splints used on the exterior.

The cigar case is now on exhibit in our Native American Voices gallery. I only learned after it was installed that it dates to 1850 – much older than I realized! Its age makes it an even more remarkable piece.

The cigar case on display in the Native American Voices gallery

Moose hair and birch bark

Moose hair and birch bark. Those are 2 materials that we have not written about on this blog before. But now that we are working in the Artifact Lab on objects for all of our upcoming exhibitions and loans, we are seeing a wider variety of artifacts and materials in the lab.

This embroidered birch bark case will be installed in our Native American Voices gallery later this month, so it is in the lab for examination and treatment.

Views of both sides of a small birch bark and moose hair case (45-15-1328) 

The 2-part case (the lid is a separate piece) was purchased by the museum in 1945. It is attributed to being Huron and from Canada.

The case itself is made of birch bark and it is embroidered with moose hair. The intricate details are difficult to appreciate without being able to see them up close. So, let’s take a closer look at the decoration:

Details of the moose hair embroidery, 7.5X magnification

Details of the moose hair embroidery, 20X

The case and lid are edged with bundles of moose hair attached with thread:

Details of the moose hair embroidery, 7.5X magnification

As you can see in the image above, some of the threads attaching the moose hair bundles along the edges are missing, causing hairs to become lost. These areas, as well as splits in the birch bark, will have to be stabilized before this case can go on display.

Check back for post-treatment photos, and visit the museum to see this case on exhibit by the end of May.

Two Al-‘Ubaid friezes

There will be a heavy rotation of objects from Iraq and Iran in the Artifact Lab as we work on objects that will be installed in our new Middle Eastern Galleries, scheduled to open in April 2018. Two of the newest pieces to come into the lab (but 2 of the oldest things in here) are these friezes from Tell Al-‘Ubaid, a site located west of Ur in Iraq, which date to the Ubaid period (ca. 6500-3800 BCE).

B15880, frieze of 6 bulls.

E15883, frieze of 3 ducks

These frieze fragments were excavated by Charles Leonard Woolley in 1924 as part of the British Museum/University Museum Expedition to Al-‘Ubaid. They both have been heavily reconstructed, displayed a lot, and loaned several times, so this is not their first time in the conservation lab. Due to some condition issues and because we are preparing them to go on long-term exhibition here at the museum, we have decided to deconstruct the old repairs and reassemble the friezes using materials that we expect will last longer and provide greater protection for the original pieces.

Conservation treatment of the frieze with the bulls began a week ago:

The bull frieze after 2 days of treatment.

One week later, even more progress has been made:

The bull frieze after 1 week of treatment.

Detail of the first bull freed from the frieze, 7.5X magnification. The bulls are made of shell and are in excellent condition.

Prior to treatment, the friezes were x-rayed to provide a better understanding of their construction and previous repairs, and to guide conservation treatment.

A digital x-ray radiograph of a portion of the bull frieze showing ancient methods of attachment (some are circled in red), modern nails (circled in blue), and a large fill made as part of a previous conservation treatment (circled in green).

Check back for updates on this exciting and complex treatment.

 

Cleaning Questions and Cross-Sections

Julia Commander is a third-year graduate student in the Winterthur/University of Delaware Program in Art Conservation. She is currently completing a curriculum internship at the Penn Museum.

The investigation of the painted Ptah-Sokar-Osiris figure continues. Previously, I mentioned that I would be taking cross-section samples to gain a better understanding of the paint layers. This type of sampling involves taking tiny (less than 1 mm) flakes of paint to capture the stratigraphy. Once I have a slice showing all of the layers, I can look at the edge under magnification to observe the structure from surface down to ground level.

In this case, I took four samples from representative areas on the figure in order to compare the layers. Before sampling, I looked at each area under magnification and made notes about surface characteristics and conditions. To sample, I continued working under magnification with a fresh scalpel blade.

L-55-29, cross-section sample areas. You can also see the darkened appearance of the front surface.

As you can probably imagine, handling a tiny little paint flake can be tricky. To make observation possible, conservators embed cross-section samples within a mounting material, typically a clear resin. Mini ice cube trays are perfect for making small blocks of resin for this purpose. After embedding the sample between two resin pours, one face of the cube is polished to a glossy finish. The polishing process helps to get a clean cut of the sample from an edge-on perspective.

Mounting cross-sections with a clear polyester resin, molded in a mini ice cube tray. The cubes are then polished with Micro-Mesh cushioned abrasive cloths.

You never know exactly what your cross-section will end up looking like until it’s under the microscope. Flakes can shift while the resin cures or be affected by polishing, so it’s an exciting moment to see the results. Sample X2, below, shows a clear view of the layer structure. Similar to the way conservators use ultraviolet (UV) light during object examinations, cross-sections are often viewed with various light sources to show different properties. Here, you can see the sample in visible light and UV light (365 nm).

Sample X2, 100X total magnification, in visible light (right) and ultraviolet light (left). Samples were viewed on a Zeiss Axio Scope.A1 polarized light microscope.

We can see a few interesting features here. The sample area appeared to have predominantly red paint, although it was heavily obscured by the surface darkening. The uppermost layer of dark material could be related to a discrete layer of soiling or coating, or we could be seeing black paint. Since the front surface of the figure is intricately painted, it’s difficult to completely rule out paint as a possibility. Aged coating materials often fluoresce in UV light, which can help to distinguish them from underlying paint layers. In this case, we can see small flecks of fluorescence (indicated by the red arrows) but not a distinct fluorescent layer. We can also observe faint fluorescence in the ground layer, which is consistent with the idea of an aged animal glue binder.

Another sample, X4, came from an area of plain red paint without any adjacent black designs. This area was also affected by the surface darkening issue, although to a less severe extent. Here, instead of a discrete layer of dark material, we can see small specks above the red paint layer (indicated by the red arrows). These dark specks are most likely related to soiling or discolored coating and unlikely to be original applied paint.

Sample X4, 200X total magnification, visible light (right) and ultraviolet light (left). Samples were viewed on a Zeiss Axio Scope.A1 polarized light microscope.

The cross-section samples offered some insights into the multi-layered nature of the delicately painted surface. As with most analytical techniques, results lead to more questions than clear-cut answers. Luckily, my colleagues here in the lab got together to talk about this complex condition issue and offer different perspectives and approaches. To clean or not to clean the darkened layer? Clarifying the surface details would be helpful for interpretation, but an even more gentle cleaning system will be needed to avoid damage to paint layers. The consensus: further testing needed!

Back in business

Saturday April 8th is the official reopening of the Artifact Lab, complete with a modified name and some new objects on exhibit and in the lab.

View of the Artifact Lab, ready for reopening on Saturday April 8th

The Artifact Lab: Conservation in Action looks a lot like it did before we closed in December, but as you can see from the shot above, our focus has shifted from Egyptian mummies and funerary objects to a wider range of artifacts, with a special focus on objects being prepared for installation in our Middle East Galleries next year.

This glazed clay slipper coffin from Nippur, excavated by our museum in the late 19th century, is front and center in the Artifact Lab:

The slipper coffin (B9220) on display in the Artifact Lab

It has a fascinating history, including its restoration here at the museum in the 1890s, which is noted on its catalog card as being carried out by the restorer William H. Witte. The restoration work allowed this coffin and several others to be displayed for the opening of the new museum building in 1899, where they remained on display for 40 years. We are particularly tickled that this coffin was displayed in this very same gallery where the Artifact Lab is now housed, the Baugh Pavilion.

The Baugh Pavilion, one of two galleries devoted to the museum’s Babylonian expeditions, as it appeared in 1899 with four slipper coffins on display. UPM Neg. #22428

118 years later, the slipper coffin has once again been installed in this space. It’s exhibition this time would not be possible without the extensive treatment carried out by conservator Julie Lawson in 2005. You can read more about its history and her work in her article in Expedition Magazine. For those interested in a more in-depth discussion of the conservation treatment, Julie also wrote an article that was published in the American Institute for Conservation’s Object Specialty Group Postprints, Volume 13, 2006.

There are many more stories to share about the objects and work being done and we’ll continue to write about them on our blog. In the meantime, come visit us now that we are open again! Our open window times also have changed slightly – they are now as follows:

Tuesday – Friday 11:00 – 11:30 and 1:30-2:00

Saturday – Sunday 12:00-12:30 and 3:00 – 3:30

Hidden in plain sight

I like to think that even though the Artifact Lab is essentially a fish bowl, when we are in here we are often hiding in plain sight. People in our department have been known to come up to the Artifact Lab to work on treatments because they are less likely to be interrupted up here. That sounds strange, I know, but it’s true. And sometimes our visitors don’t even think that WE are real, so we can kind of operate under the radar even when people are looking right at us. This is not the case all of the time, of course, and we do get plenty of visitors who tap on the glass and try to talk to us even when our backs are turned and we have earbuds in.

Aside from the people working in the lab, I think that there are a lot of things that go unnoticed too. Now, there are some things that people ask about all the time, like, “what is that Chock full o’Nuts can for?” and “what is in that jar?”.

These are pretty normal accessories in conservation labs, but of course most people would be puzzled by them at first. (The coffee can has been re-purposed as a sharps container, for disposal of old scalpel blades for example, and the jam jar is being used for disposal of cotton swab tips.)

Then there are things that go unnoticed but are arguably more fascinating, and puzzling. For example, we have never been asked, “why do you have an autopsy table in the lab?”. We probably have never been asked this because I would imagine that most people do not know an autopsy table when they see one. Our department inherited this table many years ago and when we opened the Artifact Lab in 2012 it somehow seemed appropriate to bring it up here (but really, we are NOT autopsying or unwrapping mummies, I swear). We have used the table on a daily basis, both for supporting mummies and large (people-sized) artifacts for treatment, and for prepping materials for re-housing artifacts.

Tawahibre’s coffin on the autopsy table during pXRF analysis. Link to original post here.

Unfortunately, it is not the most useful table, because it has a lip around the edge, the table surface is slightly inclined, and there is a hole on one end for the drain. But we made it work for us for over 4 years!

The autopsy table

The Artifact Lab has been closed to the public since December 31 and in the meantime we have been working away in here, but we are gearing up to reopen on April 8. When we reopen there will be some changes to both the lab space and the exhibition space. The most noticeable changes for visitors will be some new objects on exhibit, new graphics and text panels, and some other nice additions which I’ll write about in an upcoming post. But the change that we are feeling slightly sad about is that we are getting rid of the autopsy table. It has served us well but it just isn’t functional for our purposes anymore. And since many of you may not have noticed the table before, I didn’t want it to go away without mentioning it here.

We are hoping to find a good home for the table. Who might want an old autopsy table, you might ask? Well, this exists, so anything is possible. And actually, we can think of a lot of people who might like it.

Stay tuned to hear more about the other changes to the Artifact Lab, and what we’ve been doing in the meantime.