When is cleaning coins not like cleaning coins?

Alexis North, Williams Project Conservator

 

This sounds like a joke that only archaeological conservators would enjoy, but it’s actually an honest question! The answer is (in this case at least), when those coins are reused in other objects.

Before treatment photo of 42-35-370.

This necklace comes from Coban, Guatemala. It is made from black glass roundelle beads, interspersed with 144 coins from Guatemala, Mexico, and Spain. It was collected in the early 20th century, but the coins all date to before 1900.

photos of the obverse and reverse of a Guatemalan 50 cent coin, 1870; a Mexican 2 Reales coin (date illegible); and a Spanish 2 Reales coin, 1835.

There are also a number of other beads and charms, including two crosses, two round silver beads, and a black faceted stone charm in a silver bezel. The necklace is in good condition, and the only treatment it needs is a nice overall cleaning.

This necklace is being prepared for display in our new Mexico and Central America gallery, along with this necklace, also made from coins:

Before treatment photo of 42-35-41.

The pendant on this necklace is made from a large 1 Sol coin, dated 1892, surrounded by 8 small 1/4 Real coins, all from Guatemala. On top of the 1 Sol are two small deer, and suspended below are 2 quetzal birds, and a cross.

Coins are important in Guatemalan culture. These necklaces would have been symbols of wealth, and be passed down from mother to daughter within a family. Even today, when a couple decides to get married, the groom will often give the bride a gift of 13 coins in a small box, called an arras.

Come see these pieces when they go on display in our new gallery!

Ancient faces in the Middle East Galleries

Our new Middle East Galleries open next week and they will feature over 1200 artifacts from our collection, including many iconic objects like the Ram in the Thicket, the Bull-headed lyre, and Queen Puabi’s headdress. Oh, and for those of you who are always asking about our cuneiform tablets, do we have a treat in store for you – there are dozens and dozens in the galleries. The majority of the objects in the exhibition were excavated by Penn archaeologists, many nearly a century ago.

ALL of these objects came through our Conservation Labs to prepare them for the galleries and many needed significant treatment in order to ensure their stability for long-term display. Our Middle East Galleries (MEG) team has worked diligently and tirelessly on this project – you can read more about some aspects of this work on the Penn Museum blog here.

The triumphant column team poses next to the 4 recently conserved mosaic column drums from Tell al-‘Ubaid, Iraq. This project took months to complete.

In just over a week, visitors to the Museum will have the opportunity to get up close and personal with these newly-conserved objects. Everyone will be drawn to the highlight pieces mentioned above and here, but the other pieces are worth lingering over too. It’s usually impossible to see them as closely as we do during the conservation treatment process, so I thought I’d give you the opportunity to see 2 small but beautiful objects closer than you can in the galleries.

B8997 (left) and B9026 (right)

These 2 female figures, both excavated from Nippur, Iraq, will be on display in the same case in the Middle East Galleries. They’re small, just several inches long. The figure on the left was likely a doll which would have had articulated arms; you can see the holes where they were once attached. Fortunately, both artifacts required very little treatment. B8997, the figure on the left, does have a large, but stable crack that did not require any treatment. Examination under the binocular microscope revealed small amounts of burial dirt on both figures which had escaped previous cleaning campaigns, so both were carefully surface cleaned to remove this soil.

Detail of B9026 before (left) and after (right) cleaning, 7.5X magnification

As I worked on these figures, I captured some images with the camera attachment on our Leica microscope. Both objects are made of bone and are delicately carved. The reverse side of the doll’s head has an unworked area that nicely shows the cancellous (or spongy) bone features.

B8997 detail of front (left) and reverse (right), 7.5X magnification

Their time in the lab was brief – they only stayed for a day or 2. But in the midst of the hustle and bustle of preparing for these galleries, it’s nice to take a moment to appreciate the details.

The Middle East Galleries open to the public on Saturday, April 21. Our department has a few loose ends to wrap up with that project (and a few loose ends on the blog – stay tuned for a last blogpost on the mosaic column treatment) but we’re already turning to our next big tasks – the renovation of our Mexico & Central America Galleries, Africa Galleries, and Egyptian Galleries.

Many new faces in the lab…

by Williams Project Conservator Alexis North

Yesterday, I was able to make several new friends, when the American section brought these objects up to the lab, in preparation for the reinstallation of our Mexico and Central America gallery:

 These are a group of Zapotec ceramic effigy vessels from Mexico. These types of vessels are usually found in tombs, and their meaning depends on where and how they were buried. They are often found in groups, and with other associated burial materials.

Each of these effigy vessels is elaborately and uniquely decorated. Some have human faces, some are wearing masks, and some even have animal features.

These two vessels (NA6361; 29-41-707) depict humans wearing masks.

Most of these vessels are in good condition, intact or with only small losses. At least two, however, will need a little more conservation to get them ready to display. This vessel was originally covered with a white stucco coating:

Vessel 29-41-702, depicting a masked seated figure.

The stucco is now starting to lift from the surface, and any handling can cause small pieces of the stucco to fall off. It will need to be carefully stabilized before the vessel can go on display.

Detail of the headdress of 29-41-702. The red arrows show areas where the stucco is lifting off the surface of the ceramic.

And this vessel shown below has some loose fragments which will need to be rejoined. Thankfully the amazing duck bill on his face is still intact!

Before treatment photo of 31-26-1.

For (a lot) more information and other examples of these types of vessels, check out the Foundation for the Advancement of Mesoamerican Studies, Inc., and their database on Zapotec effigy vessels.

A glimpse of upcoming changes

There are a few new objects on display in the Artifact Lab this week, which give visitors a glimpse of upcoming changes in the museum.

Newly-installed case with objects slated for the renewed Mexico & Central American Gallery

These 4 pieces were recently conserved in the Artifact Lab to prepare them for installation in our forthcoming Mexico & Central America Gallery (from left to right: a stone metate from Costa Rica 11819, two burnished ceramic jars from Mexico 31-41-34 & 87-42-1132, and a ceramic tripod vessel from Costa Rica 2013-11-1) .

You can see many other objects that will be going into that gallery, both on display in our current Mexico and Central America Gallery as well as being worked on in the Artifact Lab.

Artifacts currently being treated in the Artifact lab.

Visit our Building Transformation website to learn more about this gallery, which will look something like this:

A Columnar Matter Part II: The Conservation Treatment of a 3rd Millennium BCE Mosaic Column from Al ‘Ubaid

By Marci Jefcoat Burton

As a follow up to my previous blog post, conservation treatment of the second of four sections comprising a mosaic column from Tell al-Ubaid, Iraq is well on its way! For a quick recap, the column is dated to 2400 – 2250 BCE (Figure 1). After centuries of burial, the triangular and diamond shaped shell, pink limestone, and shale tesserae (also referred to as tiles), were excavated in 1919 – 1924. The original wooden column interior did not survive the centuries of burial, so after excavation, the tesserae were mounted with plaster to four hollow cylindrical supports of metal mesh covered with burlap. After nearly 100 years, shifts in the internal support have caused structural instability to each section.

Figure 1: (left) Before treatment image of the four column sections stacked together to make a complete column. Image 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) (right) Column section 2 detail, before treatment.

First step of treatment: Remove tesserae from the current support.

The plaster was softened with distilled water applied by brush, then carved away to expose the sides of the each tessera. The tesserae could then be separated from the plaster and burlap backing one by one (Figure 2). Like the first slice of pie, the first piece was the most difficult to remove. Once extracted, access to adjacent tesserae became easier.

Figure 2: (left) Removing plaster surrounding the tesserae with a scalpel blade. Plaster was first softened with distilled water. (middle) Carefully extracting a shell tessera from the plaster. (right) Shell tessera after removal from column section.

The tesserae were removed from the support and placed on an enlarged reference photo in a tray to maintain the order of composition (Figure 3).

Figure 3: All tesserae were removed from the support and placed on top of a rolled out image of the column section to maintain their original placement. All that remains on the exterior of the cylindrical support is a layer of grey plaster and previously filled areas. As a bonus, the Egyptian female child mummy named Tanwa can be seen in the background, just outside of the Artifact Lab window!

Second step of treatment: Cleaning

After removal from column section 2, all tesserae were covered with a layer of powdery plaster, which was removed with distilled water applied with hand-rolled cotton swabs. Medical scalpels were used to gently lift and remove thick remnants of plaster as well as adhesive from previous repairs. In addition, years of dark-brown dirt, dust and grime were removed with distilled water, and Stoddard solvent (a petroleum-derived organic solvent) was applied to the pink limestone and shell pieces to remove greasy grime trapped in the surface (Figure 4).

Figure 4: (left) Removal of adhesive and plaster remnants from a diamond shaped tesserae using a medical scalpel. (right) Shell tesserae being cleaned with distilled water. Note the dark grey-brown grime picked up on the cotton swab.

Third step of treatment: Repair

Once cleaned, tesserae that exhibited breakage such as cracks, detachment, and delamination were repaired with a thin layer of a semi-viscous solution of Paraloid® B-72 (ethyl methacrylate (70%) and methyl acrylate (30%) copolymer) resin in acetone. The majority of the shell tesserae experienced separation between the layers comprising the shell. Some even separated into several pieces, making their reassembly somewhat of a puzzle (Figure 5)!

Figure 5: (left) A triangular shell tessera delaminated (separated) into six pieces. (right) The same shell tessera with all pieces adhered together with Paraloid® B-72.

The shale was even more temperamental to remove from the column section (Figure 6). Shale is a soft sedimentary rock composed of mud, clay, and minerals, such as calcite and quartz. The inherent nature of the shale causes breakage and crumbling. Water can remove particles from the shale surface, therefore these pieces were cleaned with dry brushes and if needed, cotton swabs lightly dampened with distilled water.

The most resilient material was the pink limestone. While some pink limestone tesserae are weathered on the surface, most likely from centuries of burial, these tiles exhibited very little breakage and cleaned up nicely with distilled water and Stoddard solvent (Fig. 6).

Figure 6: (left) A diamond shaped shale tessera exhibiting a lack of cohesion, best observed around the edges, which caused cracks and areas of material loss. (right) A resilient triangular pink limestone tessera with a weathered surface, noted by the lighter, speckled locations. The pink limestone tesserae have strong cohesion and required very little repair.

After a month of cleaning and repair of the shell, pink limestone and shale tesserae, their overall appearance is quite transformative. The tesserae look brighter and truer to their original colors (Figure 7). This is especially the case for the pink limestone, which went from a dark peach-brown, to a brighter light-pink hue.

Figure 7: (left) Shell, pink limestone and shale tesserae after removal from the former support, and kept in their original arrangement. (right) All tesserae after cleaning and repair, ready for re-mounting to a new support.

…..What’s next?

The next phase of treatment for section 2 of the mosaic column is to mount the shell, pink limestone, and shale tesserae to a new solid cylindrical support. More information and updates on the column treatment progress will be featured in an upcoming post, so please stay tuned!

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