Coming clean

by Alexis North, Williams Project Conservator

The renovation of our Mexico and Central America gallery will involve the conservation and installation of over 200 objects. Some are currently on display in the gallery, but many have never been exhibited before. One of these “new” objects (actually acquired from the World’s Columbian Exposition in Chicago in 1893) is this carved stone figure from Ecuador. It depicts a human man, possibly a king, seated on a throne.

Before treatment views of 12676, a stone figure from Ecuador.

It has an overall dark, somewhat shiny surface. At first glance, it looks like it may have been carved from a smooth black stone like hematite. However, once I was able to look at the figure more closely in the lab, I could tell there was something suspicious about its surface and overall appearance. The surface had a waxy feel, and upon closer inspection, I could see spots of wax on the surface. These waxy areas were very visible under ultraviolet light:

UV fluorescence image of the proper right side of the figure. The bright yellow-white spots are wax.

When I looked at the bottom of the figure, my suspicions were confirmed. Here you can see the bottoms of the feet of the figure and chair, which appear lighter and grey, and much more like stone than the odd waxy sheen of the rest of the surface.

Before treatment image of the bottom of the figure, showing the true surface and appearance of the stone.

I talked to the American section curator, keeper, and other conservators here in the lab, and we all agreed that this type of figure would not have had any sort of surface coating applied during its original use. It is likely that at some point after excavation, the piece was coated to give it more of an even, dark, shiny surface, which was seen as desirable by art dealers and collectors at the time, followed by a wax as a “protective” layer.

In order to prepare this object for display in our new gallery, the old surface coating had to go. It was misrepresentative of the object’s appearance, and the wax was collecting dust and grime. After our incredibly successful gel cleaning workshop with Professor Richard Wolbers, I decided that an emulsion gel would be ideal for removing this old coating.

I started by testing a number of aqueous cleaning solutions in a rigid agar gel. Small punches of gel with each solution were placed on the surface of the figure, and allowed to sit for 20 minutes. The small pores in the agar gel help it act as a sponge, holding the solutions against the surface and pulling the surface coating into the gel using capillary action.

During (left) and after (right) testing different cleaning solutions with a rigid agar gel.

The agar gel samples, after removing them from the figure’s surface.

And the results of my tests were pretty clear! All the solutions tested were successful in removing some of the surface coating (which is unusual!) but Solution A (deionized water with 0.5% citric acid, buffered to a pH of 6.0) clearly pulled the most grime and surface coating away. I performed a second test using Solution A in a xanthan gum gel, which is viscous but not rigid, resists penetration into the surface it is applied to, and has an emulsifying behavior when agitated which helps to pull out and hold on to the material being removed.

I also tested several solvents on the surface, and found that iso-octane would remove the wax, and acetone and benzyl alcohol both cleared some of the grime. I decided to make a xanthan gel mixture utilizing both cleaning Solution A and a combination of iso-octane and benzyl alcohol. This mixture, when tested on the surface, very successfully removed the surface coating better than Solution A on its own, revealing a lighter, gray-green micaceous stone underneath.

The results from testing xanthan gel mixtures by swabbing them on the surface.

Once the cleaning method was identified, it was simply a matter of systematically removing the coating. I worked in sections, by first applying a layer of octamethylcyclotetrasiloxane (D4), a silicone-based solvent which does not mix with water or the solvents used in the gel. The D4 fills the pores of the stone, and acts as a barrier that keeps the gel, solvents, or surface coating from penetrating into the stone during cleaning. Then I brushed on the xanthan gel mixture, and gently agitated it with a paintbrush over the surface to pull up the surface coating. Once the gel had turned a dirty brown, indicating that it pulled up the coating (see below), I removed the gel with cotton swabs and then cleared the area with deionized water. It was an extremely satisfying, if a bit goopy, process.

Left: After the left side of the seat was cleaned using the xanthan gel. Right: The cleared gel, you can see how dirty it got!

And here are some before and after photos of the figure. The difference is so clear! I believe the coating may have been applied to obscure the scratches you can see on the front of the figure, but overall it looks so much better now that the original material is visible.

After treatment images of the figure.

Front view after (left) and before (right) cleaning.

You can see this figure when we open our new Mexico and Central America gallery in late 2018!

BIG changes, little details

On November 1, our Museum announced the commencement of our  Building Transformation  campaign, a monumental project which will include a full renovation of our building structure and reinstallation of many of our signature galleries, including our iconic Egyptian Galleries.

The first glimpse of this work will be the opening of our Middle East Galleries in April 2018. This is not news for readers of this blog – you have been hearing about the conservation work for this project for awhile now (for reference, see these related blogposts).

Graduate intern Marci Jefcoat Burton (standing) and pre-program interns Fallon Murphy, Jennifer Mikes, and Alyssa Rina during an open window session in the Artifact Lab (with one of the al-Ubaid mosaic columns in the foreground)

In fact, you can get a glimpse of several exciting projects that are underway for our Building Transformation right now, on a daily basis, in either of our 2 public conservation labs.

In the Artifact Lab, you will mostly see objects being conserved for the Middle East Galleries and for our Mexico and Central America Gallery, opening in November 2018.

An assortment of artifacts for the Mexico and Central America Gallery in various stages of conservation treatment.

Our other public lab is down in our Lower Egyptian Gallery. Work in that space is dedicated exclusively to conservation treatment of the carved and painted limestone blocks from the Old Kingdom tomb chapel of Kaipure.

A view of the Kaipure tomb chapel lab space in Lower Egypt

Project Assistant Anna O’Neill at work on a block in the Kaipure lab

While you can watch the conservation team at work most days in the Kaipure lab, unlike the Artifact Lab, it does not include open window sessions. But have no fear – the Kaipure team has promised to write some blogposts about aspects of their work, so stay tuned for more information on this project!

Big projects like the Building Transformation campaign come down to a lot of little details, and no one knows details like the Conservation Department. We hope you visit us to learn more about these details, and all the work underway to make these big changes possible.

Sometimes you just can’t get close enough (intern Celine Wachsmuth in the Kaipure lab)

To learn more about the vision of our Building Transformation, check out this ~3 minute video which captures the grandeur of the project (and features Project Conservator Tessa de Alarcon!).

A Columnar Matter Part I: The Technical Examination of a 3rd Century BCE Mosaic Column from Al Ubaid

Marci Jefcoat Burton

My first project as a curriculum intern with the Penn Museum Conservation Department involves the conservation of a mosaic column from the Ninhursanga temple site of the ancient Mesopotamian city of Tell al-Ubaid in Iraq (column in digital collections: (B15887.1 – 15887.4). Dated as 2400 – 2250 century BCE, the column was excavated sometime between 1919 – 1924 as a pattern of alternating triangular and diamond shaped shell, pink limestone and shale tiles. Fortunately, the years of resting in the compacted dirt of the burial environment preserved the shell and stone tesserae and maintained their original conformation. The original column interior, more than likely palm logs, did not survive the centuries of burial.

Figure 1 (left): Before treatment image of the four column sections stacked together to make a mosaic column.
Figure 2 (right): Reconstructed façade of the Ninhursanga temple of Tell al Ubaid. The columns were originally believed to be outside the entrance of the temple doorway, although it is not certain if both columns were on the exterior or interior of the building. (Both images courtesy of The Metropolitan Museum of Art. (2003). Art of the First Cities: The Third Millennium B.C. from the Mediterranean to the Indus. The Metropolitan Museum of Art: New York)

Without a support, the delicate tesserae were lacking a method of storage and display. Working with the materials available on site and with technology available in the early 20th century, the archaeological team constructed four drums to mount the tesserae into four stackable sections. Although reports attribute the original 3rd century BCE binding medium as bitumen (i.e., asphaltum, tar, pitch) to hold the tesserae in place on the original wooden supports, the 20th century excavation team reconstructed the shell and stone mosaic pieces with a grey plaster. In addition, only half of each drum holds original tesserae, and the remainder of each section is filled with a painted plaster reconstruction.

Figure 3: c. 1920s, on-site with the recently assembled tesserae onto the wire mesh and wood drums. (Image courtesy of http://www.mesopotamia.co.uk/tombs/story/page07b2.html).

X-radiography of one of the drum sections revealed that each drum is constructed as a hollow metal mesh cylinder with wooden caps on each end, and several nails to keep the cylinder together. After 100 years in this conformation, the drums have become problematic for the long-term display of the tesserae. Fluxuations in temperature and humidity, as well as the weight of the tiles and the thick, rigid plaster have caused opposing shifts in the internal structure, leading to the formation of cracks in the plaster and several tiles to dislocate and fall from the support.


Figure 4: X-radiographs of column section B15887.3 detailing the inner drum structure consisting of an open wire mesh and hollow interior. (Left (a)): X-radiograph of the column section side reveals the radiopaque grid pattern indicative of a metal mesh. (Right (b)): X-radiograph of the column section top, revealing numerous nails in various locations that hold the cylindrical drum together. (X-radiographs courtesy of Julia Commander (2016)).

The column, with all four sections, is one of the many objects selected for exhibition in the upcoming Middle Eastern Gallery (scheduled to open in Spring 2018). Therefore, it was decided it was time for the over 4,000 year old tesserae to be removed from the hollow wire mesh supports and then remounted onto a structured, solid support made with materials that will prevent structural damage and be sustainable for its preservation and long-term display in the gallery. Following a treatment protocol implemented successfully on one of the four column sections by Julia Commander (WUDPAC, Class of 2017), I will deconstruct the tesserae from the current supports, clean and repair each piece, and remount the tesserae in their same arrangement to new cylindrical supports made from solid, very dense Ethafoam measured to the exact shape for each section awaiting treatment. Stop by the Artifact Lab to see the progress of the column treatment, which is already underway, or stay tuned for a follow up blog post!

Figure 5: Start of the disassembly of the shell, pink limestone and shale mosaic tesserae from column section 2. Note the color difference of the large painted plaster fill on the left versus the original tesserae on the right. Several breaks are also observed in the inlays (most notably the beige shell pieces) and a layer of dark, brown grime has accumulated on the surface overall.

A lion relief from Nippur

Yesterday we received a new artifact in the lab: this terracotta lion relief from Nippur, Iraq.

B20014: the lion relief in fragments

Some may argue that this object could be a candidate for the Ugly Object of the Month club. Well, we like him, and one of our conservators pointed out that he looks a lot like one of these wonderful characters from William Steig’s Rotten Island.

Illustration from William Steig’s “Rotten Island”. Image courtesy of scienceblogs.com

This relief was excavated in the University of Pennsylvania’s Babylonian Expedition to Nippur in 1899. Like the Nippur slipper coffin currently on display in the Artifact Lab, it was previously repaired with metal staples and (at least one type of) adhesive, likely around the same time as the slipper coffin.

The staple-like wire tires used to repair the relief are visible in this view of one of the break edges.

More evidence of the old repairs on this fragment.

Getting this relief ready for exhibition in the Middle Eastern Galleries will not only require significant conservation treatment, but also a custom mount so that it can be displayed safely. We will provide updates as we work on this.

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

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.

B15883, 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.

 

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