Should one strike when the solder is hot?

By Tatiana Perez

I am an undergraduate Classical and Near Eastern Archaeology student at Bryn Mawr College and this past summer, I began as a conservation intern within the Penn Museum’s Museum Practice Program. I am continuing this work through an independent study in the Museum’s Conservation Department this Fall. During my time here, I have treated a group of Egyptian faience shabtis.

Egyptian faience shabti prior to treatment.

Shabtis are statuettes that were made to be placed within ancient Egyptian burials for the purpose of assisting the deceased in the afterlife. The shabtis I worked on are made of Egyptian faience, a material made from silica, alkaline salts such as plant ash or natron, lime, and metallic colorants. The faience could be hand-shaped or pressed into molds, that when fired, would self-glaze. Although faience was made in many different colors, it is most often associated with a bright blue/turquoise color (using a copper colorant) as seen in many amulets, beads, and figurines.

The specific group of shabtis I worked with this summer differed in size, shape, and color. Many were previously repaired and some of these old repairs were failing. Unfortunately, these objects had become disassociated from their accession numbers and records, so there is no information on their provenance or previous conservation treatments. I was tasked with documenting their condition, and treating those that were broken or in need of re-treatment, either to remove failing old adhesives or remending those that were previously mended but now broken. As adhesives age, especially those used in the early 20th century, they can become discolored, may shrink or expand, or may become stronger. All of these conditions pose problems to the objects that can affect their future stability and ‘health’.

Since no record of the treatments existed, I used various methods to determine what worked best to remove the adhesives that were used. First, I used UV light to identify the type of adhesives. After observing that it was possibly shellac or animal glue, I spot-tested the adhesives using a variety of solvents. I found that acetone, ethanol, and deionized water worked best, so I left the shabtis in acetone vapor chambers for a few hours to allow the adhesive to dissolve.

After the old joins were taken down, one particular shabti caught my eye immediately. This lighter green-blue shabti had metal adhering one of the joins, with some adhesive underneath as well. After consulting with various conservators about this unexpected find and with help from the handheld pXRF instrument, we found that it was lead solder that was used to join these pieces. This is a very unusual (and outdated) technique for mending pottery and as head conservator Lynn Grant said, it’s likely whoever treated it last “struck when the solder was hot”.  In other words, the person who last treated this object might have used the solder because it was nearby and ready to use. This conservation method was not the best way to mend the shabti and doesn’t reflect current methods we use. The body, or core, of faience objects is very porous and absorbs whatever adhesive is applied. When the solder was applied it seeped into the body of the body of the object, and made it very difficult to remove.

Lead solder between first and second fragment (top). 60X magnification of the lead solder (bottom).

Though this conservation treatment doesn’t affect our understanding of the shabti, it got me thinking about how conservation ethics and practices have changed over time. As stewards of cultural heritage, conservators have the important job of fixing objects in a way that is reversible and that doesn’t compromise the object’s cultural integrity or future use. Conservators do their best to maintain the integrity of objects, for both research purposes and to preserve a piece of the culture these objects came from for future study and display. This means that conservators must also apply these ethics to objects that were treated before these standards were enforced, and take caution to prevent any further loss of information no matter how small.

With the shabti group I worked on, I used a technique that is commonly used to repair porous or low-fired ceramics. Before using an adhesive to repair the fragments, I applied a low concentration adhesive solution on the break edges to create a less porous surface and to prevent the adhesive from seeping into the body of the faience. I then used a higher concentration adhesive to put the pieces together. This specific treatment is reversible and will ideally last a century or more!

Mending artifacts can be a slow process in which a conservator attaches one piece a day. While working on this small group of shabtis for many weeks, I’ve grown very attached to them. They are all unique pieces with their own quirks, and I can’t wait to see them back together and ready for future use.

Shabti group after treatment (left). Shabti after treatment (right).

Analysis of the shabti box varnish

This is a long overdue post about the varnish on our beloved shabti box (in my last post I referred to the box as troubled…I’ve developed a tiny bit of a love-hate relationship with it, which I’m only now admitting).

A detail of the shabti box before treatment, showing the actively flaking and fractured orange-yellow varnish

A detail of the shabti box before treatment, showing the actively flaking and fractured orange-yellow varnish

Anyway, I’ve briefly mentioned that we believe that the varnish on our shabti box is a pistacia resin, but how did we come to this conclusion? I started out by doing some research into similar objects, and into painted wood from the New Kingdom in general. As I mentioned in a previous post, we know that some painted wooden objects were varnished with pistacia resin during this time period, and these varnishes often look like the coating we see on our shabti box. But there were some things about the coating, including the fact that it was actively flaking, and the fact that there are areas on the box where the paint is lost and where the coating extends over the loss onto the gesso below, which is strange.

In order to start characterizing the coating, I looked at the box under different light sources and did a microchemical spot test, all described here. All roads were leading toward the conclusion that the coating is pistacia resin, but since we had so many available samples (i.e. detached pieces of the varnish) I wanted to investigate further.

First, we turned to a resource that we have in-house: Fourier transform infrared spectroscopy, or FT-IR. FT-IR is a method of infrared spectroscopy, where IR radiation is passed through a sample, and some of the radiation is absorbed and some of it is passed through or transmitted. A spectrum is produced that represents the molecular absorption and transmission, which is unique to that material. I collected samples of detached varnish from the shabti box and from one of the shabti figures, and passed them along to Tessa de Alarcon, a conservator in our department, and consulting scholar Dr. Gretchen Hall. Here is what the spectra look like for each:

FT-IR spectra for samples of varnish from the shabti (top) and the shabti box (bottom).

FT-IR spectra for samples of varnish from the shabti (top) and the shabti box (bottom). The characteristic peaks are labeled on the top spectrum.

They look virtually identical, which confirms that the varnish on the box is the same as the varnish on the shabtis.

Dr. Hall then compared the spectrum for the shabti box sample to spectra for mastic (Pistacia lenticus) and terebinth (Pistacia terebinthus), both pistacia resins.

Spectra for (from top to bottom): the shabti box sample, a sample of terebinth, a sample of mastic from Chios purchased in Athens, and a sample of mastic from Kremer Pigments (the Kremer Pigment mastic sample spectrum was found in the IRUG database). IRUG = Infrared and Raman Users Group

Spectra for (from top to bottom): the shabti box sample, a sample of terebinth collected from the Uluburun shipwreck, a sample of mastic from Chios purchased in Athens, and a sample of mastic from Kremer Pigments Inc. (the comparative spectra were found in the IRUG database, IRUG = Infrared and Raman Users Group)

They all look very similar, with characteristic resinous acid peaks that occur between 1700 & 1720 cm-1 (carbonyl stretching) & the acid OH stretching that occurs ~1460 cm-1.

In order to see if we could classify the shabti box resin even further, Dr. Hall took a sample to Dr. Chris Petersen, Affiliated Associate Professor in the Winterthur/University of Delaware Program in Art Conservation (WUDPAC), where they analyzed it using Gas Chromatography-Mass Spectrometry (GC-MS). GC-MS is a technique that combines 2 methods of analysis, and in conservation we use it to analyze organic compounds.

Dr. Hall and Dr. Petersen ran the sample and here is what the GC-MS chromatogram looks like:

L-55-23A_GCMSlabeled2Dr. Petersen labeled the peaks and included their structures. The structures are consistent with pistacia resin, either mastic or terebinth. They did identify a peak for 28-norolean-17-en-3-one (#3 above), characteristic of heated pistacia resin, which could indicate that the resin was heated before application (which would have turned it from clear to a yellowed varnish). We cannot be certain what color the varnish was when it was first applied, but the analysis does confirm the fact that the shabti box and the shabtis all have aged pistacia resin coatings.

We are grateful to both Dr. Hall and Dr. Petersen for their work on this analysis!

 

I spy with my little eye…

A long time ago I posted an image of our Mummy Gallery, circa 1930s. Well, I find myself returning to this photograph again and again as I work on new objects in the lab.

The "Mummy Room" ca. 1935

The “Mummy Room” ca. 1935

Can you find two of the objects that we’re working on right now, the beautifully preserved painted wooden coffin and the shabti box and shabits, all from the New Kingdom? Here are images of these objects, just to help you out:

Overall view of the interior of the coffin from above

Overall view of the interior of the coffin from above

The shabti box and one of its associated shabtis

The shabti box and one of its associated shabtis

Did you find them? I’ll post the image of the mummy room below, with these objects circled in red.

mummy room with coffin and shabtis circledAnd here is a cropped version of this image, to better show these objects:

31011_mummyroom_1935-croppedWhile it’s just cool to see an image of these objects in a previous display, it’s also helpful to me as a conservator. I can see how they were mounted for exhibit (the coffin is standing upright, the shabtis are on little platforms) and I can also get a sense of condition at this time (for instance, the middle lid of the shabti box is missing in this image, and I can see some losses to the painted surface as well).

I’m am nearly finished working on the shabti box and shabtis, and the coffin will also be completed this year, so we will finally be able to put these objects back on exhibit.

Coming up next week, I will be posting some multispectral images of the shabti box and shabtis, which is helping us better understand the original colors and also to see some of the painted details, which are now largely obscured by the orange pistacia resin varnish.

 

Consolidating a painted wooden shabti

This one-minute video captures what I did at work today, times about 250.

Shabti paint consolidation (click on the link to view the video)

To put it into context, I was working on this painted wooden shabti, which I’ve mentioned on the blog before.

The area blocked out in yellow is the area I'm working on in the video.

The area blocked out in yellow is the area I’m working on in the video.

Here is a still shot of the area I’m working on in the video, taken at 10x magnification using our binocular microscope:

IC800006The paint is actively flaking in many areas on this object. In the video, you can see me applying a 2% solution of methyl cellulose in water by brush to a loose flake of paint, and then after allowing the flake to relax, tapping it into place using a silicone colour shaper. It’s slow-going, but it’s working!

 

A new challenge in the lab

I am always pleased to see returning visitors to the Artifact Lab. And of course, people who have been here before want to know, what’s new? Visiting the lab is the best way to find out about our latest projects and progress, but this blog is the next best thing.

So, what is new around here? Well, I’ll let you take a look for yourself:

shabti boxThis object was featured in the “What in the World” series on the museum’s Facebook page this week. There were a wide range of guesses as to what this is; my favorites being a breadbox, an Egyptian mail box, a papyrus organizer, a holder for cat mummies, and an ancient Egyptian Matchbox-car garage.

Seriously though, this is a shabti box. Here is a shabti box that is similar in style, at the British Museum. Shabti boxes were used to house shabti figures. Shabtis were included in burials as servant figures that would carry out heavy work on behalf of the deceased. They were depicted as mummified and were inscribed with spells which, when recited, magically caused them to come to life and perform work for the deceased in the afterlife. Here are 3 shabtis that were originally housed in our shabti box:

shabtisThe shabti box and shabtis are made of wood, covered with a thin layer of gesso, and painted. They are in the lab for treatment because their surfaces are actively flaking. Not only is the paint flaking, but there is a yellow-orange coating over the painted surface that is badly flaking as well.

This yellow-orange coating is applied over the entire surface of the shabtis and the box (inside and out), and it is very thick in areas.

A detail of the shabti box showing areas where the coating is particularly thick (pointed out here with the red arrows).

A detail of the shabti box showing areas where the coating is particularly thick (pointed out here with the red arrows).

My first question is, what is this coating? Is it an original varnish or is it a later restoration?

The box and the shabtis date to the New Kingdom, ca. 1200 BCE. We know that varnishes such as those containing pistacia resin were used on painted wood in the New Kingdom, and these varnishes often appear yellow, although they may not have been yellow when first applied. We also know that these varnishes were applied unevenly – the application of the pistacia resin varnish has even been described as “messy” and it is acknowledged that its purpose was not an aesthetic one, but rather intended to make such objects more divine, or suitable for the afterlife (Serpico and White 2001). This description may help explain the rather sloppy appearance of the yellow-orange varnish on our shabti box and figures.

We cannot, however, discount the idea that this coating may be a later restoration. We know that archaeologists frequently stabilized artifacts in the field to allow for their safe recovery. Materials such as paraffin wax, gelatin, shellac, and cellulose nitrate have been used for this purpose in the field or once the objects found their way into museum collections (like the wooden heads Laura has been working on).

There are several ways in which we can try to determine what this coating is and when it may have been applied. We already have some clues, but we’ll share those in an upcoming post. Stay tuned for updates as we learn more!

 

Update from Abydos

A few weeks ago I wrote about Penn Museum Curator Joe Wegner and his team who are currently excavating in Abydos at the mortuary complex of Pharaoh Senwosret III. Recently the team has been battling exceedingly high temperatures and consistent loss of power (so no internet and water) but despite all of this, graduate student Kevin Cahail has been kind enough to continue sending me photos and information about their latest discoveries.

Many visitors to the Artifact Lab ask if mummies are still being discovered in Egypt. The answer is yes, and now I can point to the recent discovery of a mummy just outside of one of the tombs that was recently excavated.

View of the burial chamber from tomb CS.5

View of the burial chamber from tomb CS.5

The shot above was taken after excavation of a tomb (named CS.5) – this is actually the same tomb that contained the curious bricks with the dots in them that I included images of in my last post. Excavation of this tomb revealed that the burial had been long-since removed, but soon after excavation, a skull, and then the rest of a body, was found in the sand nearby. It appears that she(?) was at some point thrown out of her tomb by robbers.

Mummy upon discovery, before excavation (left) and after excavation (right)

Exposed skull found in the sand (left). Removal of the skull revealed the rest of the body, shown here after excavation (right)

Removing and transporting unexpected or unwieldy archaeological finds often requires a bit of resourcefulness. In order to move this mummy into a box for transport back to the dig house, Kevin recovered an old laundry detergent sack, which they then slid under the mummy,

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and used as a sling to lift the mummy into a box.

in boxReconstruction of the skull of this mummy is now underway.

In addition to the field work, the team also spends time in the lab, which sometimes includes minor conservation work. This shabti figure was found in two pieces:

shabtiKevin used Acryloid B-72, an acrylic adhesive commonly used in conservation for repairing ceramics (among many other things) to re-adhere the fragments:

Kevin holding the recently repaired shabti figure

Kevin holding the recently repaired shabti figure

As you can see, Joe, Kevin, and the rest of the team have been busy, and they only have about another week left in the field. As I hear more from them during their last days in Abydos, I will follow up with further information.