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.

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.

 

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

Considering Cleaning

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.

It’s time to check back in with the Ptah-Sokar-Osiris figure. In my last post, I mentioned a few of the condition concerns including a significant darkening over the front surface. The uneven surface poses interesting challenges for cleaning, and there are multiple approaches and methods to consider.

Before cleaning proceeds, it is important to understand both the nature of the surface discoloration and the properties of the paint layers. Egyptian objects are not always straightforward, and Ptah-Sokar-Osiris figures have a broad range of condition issues and treatment histories. Check out the British Museum’s online collection for a fascinating look at comparable figures. Discolored or yellowed varnishes have been observed on Egyptian painted surfaces, such as the shabti box described in a previous post. One way to assess surface discolorations is ultraviolet (UV) light illumination, a non-destructive lighting technique. In the UV portion of the energy spectrum, aged coating materials including varnishes and adhesives often fluoresce brightly. Areas that absorb more UV light appear darker in comparison. For this figure, areas of fluorescence do not appear to correspond to the pattern of discoloration, which is most noticeable on the platform under the feet.

L-55-29. In normal light (left), you can see the darkened surface of the front of the figure. In ultraviolet (UV) illumination (right), specific areas fluoresce. The pattern of UV fluorescence does not correspond to the discolored areas or suggest an overall coating.

Additionally, the surface darkening extends over large areas of damage and paint loss, suggesting that it occurred later in the object’s history. In an attempt to understand the darkened surfaces, I will take cross-section samples, which involve tiny (less than 1 mm) flakes of the paint layers. By looking at the edge of a paint flake under magnification, I can observe the stratigraphy from surface down to ground level. One way to visualize this technique is to think about slicing a cake to see the layers inside. To make handling tiny paint flakes easier, they can be mounted in resin for observation under magnification. Through normal light and UV light microscopy, the presence of discrete coating or soiling layers may be observed.

To characterize the behavior of the paint layers, solubility tests were conducted under magnification with small amounts of solvent on cotton swabs. For this painted figure, surfaces appeared to be water sensitive but relatively stable in other solvents. This finding is consistent with typical Egyptian paint binders such as gums or animal glues, which are both water sensitive. Once I know what affects the original surface, I will be able to think about designing a strategy to reduce darkening while avoiding disruption of the paint layers.

Dry surface cleaning is one of the first methods to test for a water sensitive surface. Cosmetic sponges and soot sponges lifted significant dirt and grime, although the appearance of the figure’s surface was not visibly improved. Water-based solutions and small amounts of solvent were tested in discrete locations to assess their efficacy. Water-based, or aqueous, cleaning solutions can be adjusted with buffers and chelators to more effectively lift dirt and break up staining. Chelators, such as citrate and EDTA (ethylenediaminetetraacetic acid) are complex ions that attach to metal ions, a key component of most types of dirt. A citrate solution at pH 8 was found to be very effective for lifting dirt and staining, but I wanted to minimize surface interaction with water. One method to manipulate these interactions is to work through silicone materials. Silicone gels, such as Velvesil Plus, can from stable emulsions that hold aqueous solutions. Silicone solvents, such as cyclomethicone D4, can saturate surfaces and act as a barrier layer to protect from water.

Testing dry surface cleaning with a cosmetic sponge on the figure’s base.

Testing aqueous cleaning solutions to reduce discoloration with a small cotton swab.

Could this be used as an overall cleaning solution? A larger test area suggested that the combination of materials, when applied carefully with brushes and worked over the surface, lifts dirt without visibly disturbing paint layers. However, the cleaning effect is slightly uneven, which raises concerns about whether this technique will significantly improve visibility and legibility of surfaces. Since this object is a long-term loan from the Philadelphia Museum of Art, continuing discussion with the PMA senior objects conservator, as well as Penn Museum curators, will help clarify these decisions.

In addition to aqueous cleaning methods, I researched the feasibility of laser cleaning. Conservators have successfully employed laser cleaning in many scenarios where discrete layers of soiling need to be removed from surfaces. For Egyptian artifacts, some of the primary challenges include fine control over complex surfaces and slight yellowing after cleaning. While the literature suggests that laser cleaning is unlikely to be the right solution in this scenario, we decided to experiment with a mock-up test panel to gain a sense of the technique’s future applications in the lab. This involved gathering typical Egyptian pigments, including the famous Egyptian blue and green, and mixing appropriate binders to mimic historic surfaces. The panel consists of an animal glue ground with gum arabic paint, coated with an additional layer of mastic varnish for half of the test areas. Mastic, a plant-based resin, is comparable to traditional Egyptian resins such as pistacia. After adding a little bit of “dirt,” a sticky mix of starch powder and pigments, I am ready to start exploring the efficacy of our laser cleaning system for painted surfaces.

Creating a mock-up panel to test laser cleaning on painted surfaces. Materials include Egyptian pigments mixed with gum arabic binder, an animal glue ground, and mastic varnish.

Selected resources:

Korenberg, C., M. Smirniou, K. Birkholzer. 2008. Investigating the use of the Nd:YAG laser to clean ancient Egyptian polychrome artifacts. Lasers in the Conservation of Artworks: 221-226. London: Taylor and Francis Group.

Larochette, Y. 2012. Wolber’s world: A review of a textile wet-cleaning workshop held in Oaxaca, Mexico. Western Association for Art Conservation (WAAC) Newsletter 34(1): 24-26.

Roundhill, L. S. 2004. Conservation treatment considerations for an Egyptian polychrome wood coffin. Objects Specialty Group Postprints 11: 89-102.

Ptah-Sokar-Osiris and Treating Painted Surfaces

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 a conservation intern working in the Artifact Lab, I was able to go shopping through shelves of Egyptian objects and scope out interesting treatment projects. A painted wood statue, depicting the composite god Ptah-Sokar-Osiris, immediately caught my eye. The figure has intricate painted designs decorating the mummiform figure and its base, as well as gilded details in the face and headdress.

Ptah Sokar Osiris Statue, L-55-29A-C

L-55-29C, detail of paint and gilding

High-status burials in 19th dynasty Egypt often included this type of mummiform statue. Comparable examples of the popular object type exist in collections worldwide, such as the British Museum and the Metropolitan Museum of Art. Common characteristics include carved wood, a preparatory gesso layer, polychrome design, and in some cases, a coating of varnish. Ptah-Sokar-Osiris statues also frequently feature small compartments carved into the wood figure or base. These cavities could contain small papyrus scrolls or textile wrappings. While examining the object with this in mind, I noticed a faint rectangular shape on the reverse of the figure’s head.

X-radiography, a non-destructive imaging technique that helps clarify construction details, was perfectly suited for the question of the compartment. Without disturbing the delicate painted surface, we were able to observe that a rectangular cavity is in fact cut into the head of the figure. Although the cavity appears to be empty, this interesting construction detail is consistent with similar Ptah-Sokar-Osiris figures.

L-55-29A detail (left) and X-radiograph (right). Image captured from 55 kV, 2 mA, and 6 second exposure.

The statue has several condition issues, such as actively flaking paint and significant darkening over the front surface. Additionally, the figure is unable to stand upright in the base, and the components do not fit together securely. Upcoming treatment aims to address these issues, and I will be searching for the right approach to cleaning and consolidation. The complex surface made of wood, gesso, and paint will require detailed testing to find appropriate solutions.

To further investigate painted surfaces and possible coatings, I used multispectral imaging (MSI), which incorporates multiple light sources to reveal details that cannot be seen in visible light. Interesting findings included the presence of Egyptian blue in the figure’s wig and broad collar, as well as the headdress. This pigment shows up in visible-induced infrared luminescence and is easily distinguishable from surrounding pigments.

Detail of multispectral imaging, highlighting Egyptian blue pigment. Normal light (top), visible-induced infrared luminescence (center) with Egyptian blue shown in white, and false color image (bottom) with Egyptian blue shown in red.

Learning more about the object’s structure and surface will help inform treatment decisions about this complex figure. Check back to see what else we learn and how treatment will proceed!

’tis the season for…removing BJK dough

I had heard about this material, BJK dough, since graduate school but had never actually seen it on an object until coming to the Penn Museum. Now that I’ve encountered it, I know it when I see it. It’s often found as fills on ceramics in our collection that were treated in the 1970s and 80s. It’s brown, fibrous, and really hard. Sometimes it is painted but in some cases it is left unpainted because its brown, matte appearance worked well for filling archaeological ceramics (and other similarly-colored objects).

I first read about BJK and its predecessor, AJK, in this great JAIC article by Steve Koob, Obsolete Fill Materials Found on Ceramics. AJK was developed in the University College London (UCL) conservation lab in the 1960s, by mixing Alvar (polyvinyl acetal), jute, and kaolin in solvents, to create a putty. In 1980 Alvar was discontinued so was replaced by Butvar (polyvinyl butyral), to make BJK dough. Both AJK and BJK were used extensively in conservation labs during these decades to fill ceramics and for other gap-filling on objects. Some fills were made by creating a lattice-support with narrow strips. This terrific blogpost goes into detail about AJK and BJK and includes a recipe for making strips of dough for filling archaeological ceramics. This recipe is interesting for understanding the old treatment materials and methods, but just to be clear, is NOT recommended for conservation treatment any longer. We use materials that are now known to have better long-term aging properties, such as Paraloid B-72 bulked with glass microballoons.

Here are some examples of BJK dough that we’ve found on objects that are currently in the Artifact Lab:

31-17-318, painted ceramic vessel from Ur, before treatment (left) with painted BJK fills, and during treatment (right) with BJK fills removed. One of the removed BJK fills is pictured in the center.

73-5-557, Detail of iron sword from Hasanlu (Iran) with BJK fills (before treatment)

E8436, cup from Karanog, Nubia, Meroitic Period (ca. 100 BCE-300 CE) with large painted BJK fill. The black arrow points to a new crack that developed in the ceramic due to shrinkage of the BJK fill post-treatment.

Due to damage that we have observed on objects with BJK fills (see image above), and to prevent damage from occurring in the future, we often remove BJK when we find it on objects being treated in the lab. Fortunately, the BJK can be removed by poulticing with acetone, which causes it to become flexible and gummy enough to be scraped or gently pried away from the original object.

I think I can safely say that all of us in our department have done our fair share of picking off BJK from objects. Spending time undoing old treatments allows us to reflect on these past treatment choices and on our own decisions. We are very fortunate today to be able to learn from past treatments, to have decades of research and published observations to rely on for our own decision-making, and to have the technologies to allow us to better track condition of objects and materials over time.

As it is, this is a good time of year for reflection, but also to look forward to a new year ahead, and the certainty of new challenges and discoveries to be made. There will be no public access to the Artifact Lab from December 31 until April 8, but we will continue to update the blog as we work in the lab on new projects. Stay tuned, and Happy New Year, from all of us in the Conservation Department!

Conserving Egyptian mummies…and more

Recent visitors to the Artifact Lab may have noticed this new sign posted on one of the lab windows:

signdsc_0539

Since we opened in fall 2012, you might have occasionally caught us working on non-Egyptian things, but if you visit us now, you will definitely see us working on things from other parts of the collection, especially artifacts that we are preparing for our new Middle East Galleries. Right now, we are focusing a lot of our efforts on treating ceramics and lithics, most from Iraq and Iran.

We have tens of thousands of ceramics and lithics in this museum’s collection, but somehow, in my over 4 years here, I have gotten away with working on only a handful.

tessa4

Conservator Tessa de Alarcon reconstructing a ceramic vessel. This is a common sight in our main lab (behind the scenes) but not so much in the Artifact Lab…until now.

So this is how, after spending over 4 years working on mummies and coffins, working on a small ceramic vessel becomes a novelty. And that is why I am going to walk you through some of the fairly routine steps of treating a ceramic, because I’ve never gotten a chance to write about it on this blog before, and honestly, I’m excited about it.

This small ceramic vessel with a simple striped pattern was excavated in 1931 in Ur, which is a site in modern day Iraq. It dates to the Ubaid Period, so is at least 6000 years old.

31-17-318

31-17-318, before treatment (BT)

As you can see in the above BT image, it was previously broken and repaired. In order to get it ready for exhibition, those old repairs need to be removed. We don’t always remove old repairs (and we never remove repairs that date to when the objects were still in use), but based on observations of the vessel and referencing an old conservation treatment report, I knew that the repairs had to be undone –  if left in place those old materials are likely to fail and possibly cause more damage to the object. Another goal of the conservation treatment is to improve the appearance of the vessel, as there was excess adhesive and overpaint in areas and many of the joins were not well aligned.

Based on that old treatment report and tests in the lab, I knew that the old adhesive is soluble in acetone and that the material used to fill missing areas would soften in acetone enough to allow it to be removed. So the first treatment step, after documenting the piece fully, was to put it in an acetone vapor chamber:

cup-dtdsc_0042

An acetone vapor chamber isn’t anything fancy – in this case it was created with a plastic bag. I placed the vessel and 2 small containers of acetone in the bag and then clamped the open end to prevent the acetone from leaking out. Sometimes an object only needs a few hours in a vapor chamber before it can be taken apart. This little vessel required 24 hours before even one piece could be taken off. The whole thing was finally deconstructed after a week of sitting in the chamber on-and-off and poulticing and swabbing the joins with acetone.

During treatment, after the first piece detached

During treatment, after the first piece detached

During treatment, after about half the vessel was taken down

During treatment, after more than half the vessel was taken down

Success! All the pieces are finally apart, placed on images of the vessel in order to keep track of everything.

Success! All the pieces are finally apart, placed on images of the vessel in order to keep track of everything.

Once the pieces came apart, I had to swab all the joins with acetone to remove excess adhesive and fill material. I’m now at the point where I will start joining the pieces together again.

Swabbing a break edge of a ceramic to remove excess old adhesive

Swabbing a break edge of a ceramic to remove old adhesive

Stay tuned for more posts about our work on these objects, and our continued work on the Egyptian collection and other projects!