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!

Artifact Lab on hiatus

Happy New Year! As I’ve mentioned in my 2 previous posts, the Artifact Lab exhibit/viewing area will be closed to museum visitors until April 8, 2017. During this time we will be working in the lab and updating this blog, but you will not be able to visit us in person. When we reopen there will be some changes in the lab and gallery space so please do come back and visit us in a few months! You can find up-to-date information on our gallery closures and re-openings on the Penn Museum’s website, here. See you in April! (but don’t forget that we will continue providing updates about our work on the blog).

’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!

Ancient Egypt Open House

The museum is hosting an Ancient Egypt Open House today. This open house was put together for all local students who are taking Dr. David Silverman’s Introduction to Ancient Egypt and Its Civilization on Coursera, an online platform which allows students from all over the world to enroll in the course (more than 20,000 people have signed up for the first offering). But you don’t have to be enrolled in the class to take part in the open house, which will include a talk by Dr. Silverman, Egyptian gallery tours, a mummification workshop, a hieroglyph workshop, book signings, and a special open window session in the Artifact Lab. The full schedule is posted on the museum’s website – follow this link for more information. You can also read about the course and the Open House in the Inquirer article from earlier this week:

Penn online course on Ancient Egypt – The Philadelphia Inquirer

If the open house isn’t alluring enough, remember that this is one of the last weekends to visit the Artifact Lab before we go on hiatus at the end of the year. We will be closed temporarily from December 31 but we will reopen to the public on April 8, 2017. As usual, we have some pretty interesting things in the lab that you can see when you visit, including our Egyptian mummy Hapimen, a Graeco-Roman terracotta coffin lid, and several artifacts that have been selected for our new Middle Eastern Galleries, slated to open in 2018. Here are a few images to show you how our work is coming along:

A detail of Hapimen (E16220A), showing the damage to his wrappings and body, likely caused by tomb robbers. Conservator Alexis North is working to stabilize the damage and get Hapimen ready to go back on exhibit.

Graeco-Roman terracotta coffin lid from Meydum (32-42-1107) (before treatment)

Djed-Hapi’s cartonnage mask with a temporary facing applied (during treatment) (E3413D)

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!

Symposium follow-up

Thanks to the hard work of so many individuals, including our incredible speakers, I think I can safely say that our symposium last month was a smashing success. Nina Owczarek wrote a nice summary post on the Museum blog that includes imbedded video footage of Head Conservator Lynn Grant’s introduction, which contains some terrific images of the Conservation Department and the Museum over the last 50 years.

In addition to 30 paper presentations, the symposium featured 4 short talks entitled “Penn Stories”, and a keynote lecture. Video footage of these 5 presentations is now available on the Penn Museum YouTube channel. Check them out by following this link: Engaging Conservation video clips

 

50 years of Conservation at the Penn Museum

2016 marks the 50th anniversary of the Penn Museum’s Conservation Department, which was founded in 1966 through the efforts and generous support of the Museum’s Women’s Committee. It is thought to be the first archaeology and anthropology museum conservation lab in the United States to be staffed by professional conservators.

Views of the Conservation Lab ca. 1968

Views of the Conservation Lab ca. 1968

To commemorate the establishment of the department, we are hosting a symposium from October 6-8, 2016: “Engaging Conservation: Collaboration Across Disciplines.” The Symposium will feature 31 paper presentations by conservators, archaeologists, anthropologists, and specialists in related fields, which will address topics related to the conservation of archaeological and anthropological materials and the development of cross-disciplinary engagement over the past half century. In addition to these presentations, there will be an evening keynote address by Dr. Brian Rose, Director of the Museum’s Gordion Archaeological Project in Turkey. The full schedule and abstracts can be found on the symposium website by following this link:

Engaging Conservation: Collaboration Across Disciplines

Views of the Conservation Lab ca. 2016

Views of the Conservation Lab ca. 2016

We look forward to seeing some of you in Philadelphia in October for this event!

 

A little tip

This week, I just have a quick “tip” to offer. A lot of the work that we do in the Artifact Lab involves repairing very fragile organic material and consolidating delicate painted surfaces, and these treatments often rely on the use of adhesives that take awhile to fully set (dry).

To ensure that the areas that we glue together set in just the right position, we rely on the use of gentle finger pressure while the adhesive dries. But instead of sitting there with our finger on an artifact for minutes, if not hours (totally impractical), the finger pressure we apply doesn’t involve our hands at all!

Let me introduce to you the finger weight:

2 finger weights applying gentle pressure to the painted surface of a cartonnage pectoral

2 finger weights applying gentle pressure to the painted surface of a cartonnage pectoral

These little weights are made by snipping off the fingers of nitrile gloves, filling them with the material of your choice (sand, glass microbeads), and then tying off the open ends with a small piece of thread. In our field, we use a wide variety of weights and clamps, many of them fancy and custom-made, but these simple, cheap finger weights are often just the ticket when it comes to finding the right amount of weight and pressure for a fragile, delicate surface or mend.

I can’t take any credit for these – I’m sure many conservators use them, but I was introduced to them by my colleague Alexis North, who has been making them for use in the Artifact Lab. Now she is going to know who is stealing all of the wonderful little weights she makes!

Coolness vs. cuteness

We have been carrying out our work in front of the public here in the Artifact Lab for nearly 4 years now. Despite the fact that visitors can peer in from various points around the room and watch us working for as long as they have the patience for it, it’s not always clear what we are doing, especially when the work is very detailed and only requires us to make the smallest of movements for hours on end (several of us have overheard museum visitors quietly whispering “is she real?”).

So even though we are “demystifying” our work by bringing it out in full public view, we sometimes have to rely on labels, signs, a slideshow we have running here in the lab, and, hey! this blog, to describe what it is we are doing.

For example, I have been working on this Ptolemaic pectoral cartonnage piece, and most recently started backing and filling losses and tears in the linen support. Most of what I’ve done so far is really difficult to see or appreciate, even though I’m working right by one of the lab windows.

Detail image before (left) and after (right) filling a loss

Detail image before (left) and after (right) filling a loss

These images above show a detail of an area that I backed and filled. There is nothing elaborate or dramatic about this work. As you can see, the fills are small and subtle, mimicking the surrounding areas of paint loss. These repairs were made by backing the losses with Japanese tissue paper and filling with a mixture of Klucel G, alpha cellulose powder, glass microballoons, and powdered pigments.

There are a few areas that I could not access from the front, so I decided to flip the piece over to continue the treatment. In order to protect some fragile areas while the piece is turned over, I temporarily faced them with small pieces of Japanese tissue impregnated with Paraloid B-72.

A detail of the upper half of the pectoral showing facing in progress

Below, you can see what the piece looks like from the reverse. Unfortunately, this means that for the time being, visitors will not be able to see the beautiful painted decoration.

Reverse of E352

Reverse of E352

But have no fear! We have other interesting things on view, and to keep us company as we do this detailed, subtle work. We have our mummy Hapi-Men, who is front-and-center in the middle of the lab, and for those visitors who may not see the “coolness factor” of the mummies, there is this little guy who is currently sitting right by one of the lab’s windows:

E11474: Ptolemaic cartonnage cat head from Abydos

E11474: Ptolemaic cartonnage cat head from Abydos

Because who can resist a cute kitten? We sure can’t, which is why we figure that if this adorable kitty is in the window, even if our work doesn’t appear particularly exciting at the moment, there will be something interesting for everyone to see (and the cat head actually does need treatment and a new storage support, so he is up here for a real reason too!).