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!

 

Putting the finishing touches on the shabti box

I have put a lot of work into our troubled shabti box, including investigating and analyzing the varnish (more on the analysis in an upcoming post), doing some pretty cool imaging, and consolidating all flaking and unstable varnish and paint with methylcellulose. After consolidation of the surfaces, the box does not look much different than it did when I started the treatment (and this is a good thing). As a reminder, here is an image of the front of the box before treatment:

shabti box frontAt this point, I could call the treatment done, or take it a step further, by filling in some of the losses of the painted surface, which appear bright white since those losses expose the gesso below. After consulting with Dr. Jen Wegner in the Egyptian Section and with Lynn Grant, the head of our department, I decided to fill in some of the larger losses which really make it difficult to appreciate the object and “read” the designs. I have even heard some visitors refer to the box as “that badly damaged piece of wood”, and that is not what we want people to be thinking when they eventually see this on display. While I know I can never return the box to its original condition, I can reduce the appearance of some of the damage. But how to fill the losses on such a fragile surface, in a way that will be reversible/retreatable?

After some hemming and hawing and some failed tests, I ultimately decided to fill the losses by first placing a small piece of Japanese tissue paper into the loss, then applying a tinted fill mixture over the paper. I did this by doing the following:

1. I took a quick snapshot of the surface I was about to work on. I then downloaded the image and copied it into a Word document. Using the scale in Word, I was able to resize the photograph in order to print it approximately true to size, and then I printed the image in black and white. This took no more than 5 minutes.

2. I placed a piece of Mylar over the B&W print-out and traced the losses I wanted to fill with a black marker.

L-55-23A_template2

B&W image with Mylar template moved off to the right side

3. After trimming the Mylar around one of the tracings, I taped it to a piece of Japanese tissue paper with a small piece of blue tape.

L-55-23A_template34. I cut out the Japanese tissue paper and adhered it into the loss on the shabti box with a small amount of 5% methylcellulose.

5. I then applied a fill mixture over the Japanese tissue paper. The fill mixture is made of 5% methylcellulose, glass microballoons, and powdered pigment.

Fill mixture (in the jar and on the spatula)

Fill mixture (in the jar and on the spatula)

This may sound tedious, but the whole process works very smoothly and relatively quickly. It also minimizes the amount of time I need to spend touching the object and therefore minimizes damage that might be caused by touching the very fragile surface.

I’m not finished, but so far I’m pretty happy with how the front of the box is looking:

L-55-23A_dt01_compressed

Front view, during filling

It’s subtle, but to see the difference that filling makes, here are views before and after, side-by-side:

Picture1

Before treatment (left) and during treatment (right)

The only problem is, I feel like I’ve opened a can of worms. There are so many losses and I am not going to fill them all, but as soon as the larger losses are filled, I start seeing all of the small ones! I think it’s looking better though and I will get some feedback from my colleagues before proceeding further.

 

Wilfred or Wilfreda?

So, there has been some controversy over the fact that our mummy Wilfred is being referred to by a man’s name because there is some suspicion that this mummy may in fact be female!

Just before Thanksgiving, Dr. Janet Monge, Keeper and Curator-in-Charge of the Museum’s Physical Anthropology Section, along with colleagues Page Selinsky and Francesca Candilio, took at peek at the mummy and there was a hot debate over some of the features on the pelvis, but they all started leaning toward the conclusion that the mummy may be a woman.

The group huddled around the mummy. Photo by Nina Owczarek, copied from the Museum's Instagram account.

The group huddled around the mummy. Photo by Nina Owczarek, copied from the Museum’s Instagram feed.

The group felt like they needed to see the bones better. One of them (half-jokingly) asked if we could just lift the pelvis out. While we plan to take some new x-rays using our new digital radiography equipment, we have to do some work on the mummy in the lab first. But in the meantime, we can take a look at the x-rays taken in 1932 over at the Hospital of the University of Pennsylvania. The only notes from this old radiographic study say “adult”.

Radiograph of the chest area, showing the crossed arms, ribs, vertebrae.

Radiograph of the chest area, showing the crossed arms, ribs, vertebrae

Radiograph of the pelvis.

Radiograph of the pelvis

Radiograph of the feet.

Radiograph of the feet

Dr. Monge offered to share these images with her colleague Dr. Morrie Kricun, Emeritus Professor of Radiology, Hospital of the University of Pennsylvania. Dr. Kricun was able to manipulate the image of the pelvis to view it as it would look like if it was undisturbed.

Manipulated radiographic image of the mummy's pelvis

Manipulated radiographic image of the mummy’s pelvis

He’s also leaning toward female, but wants to do some additional imaging, which we plan to do soon. I promise to update the blog as soon as we do this! But for now, I feel like I may need to start calling this mummy Wilfreda.

 

Meet Wilfred

I swear, sometimes I think we’re just trying to outdo ourselves. There has been a whirlwind of activity lately – in the museum, in the conservation department, and in the Artifact Lab. Between “finding” a 6500 year-old skeleton in storage, to moving into our new conservation suite, it’s been so busy that I haven’t been very good about writing updates (but I promise to post some of the stuff about our new digs and equipment on the blog soon). Just when I thought things were settling down, this mysterious crate showed up at my door:

Wilfred crate

Okay, so at this point, it wasn’t a complete mystery – I knew what was in that crate (more or less) because last summer, some brave souls in the Egyptian Section managed to get this crate down from a very high shelf in storage. Once it was down, they found this note pinned to the top of the box:

Wilfred label

Well, hello, Wilfred. As you can see, the team was very happy with themselves afterward, even if they had to get a little dirty in the process.

"Team Wilfred" (Dr, Joe Wegner, Jean Walker, Jamie Kelly)

“Team Wilfred” (Egyptian Section Associate Curator Dr. Josef Wegner, Assistant Keeper Jean Walker, and volunteer Jamie Kelly). Photo by innocent bystander Dr. Jen Wegner

So who/what is Wilfred, exactly? Well, inside the crate we found this:

Wilfred crate open

It’s an old, dirty mattress, with a wooden stick resting on top. And inside that mattress, we found…

wilfred in crate

A mummy! A badly damaged, but nonetheless very well-preserved mummy.The upper half of the body is where most of the damage is visible, exposing the human remains underneath, while the lower half appears pretty well-wrapped.

Today, my colleagues and I hoisted Wilfred out of the crate onto a temporary support. Here is what he looks like, sitting out on a table in the lab:

Wilfred on table

And there’s more. But I won’t write any more about him in this post, except to say that no, this isn’t the first time he’s been studied since coming to the museum in 1911 (he was x-rayed in the 1930s), but it is the first time that any of us here at the museum are really getting a good look at him.

There will be much more to follow…so stay tuned!

 

Tawahibre, front and center

As promised, Tawahibre’s coffin lid is now on display, front and center, in the Artifact Lab.

Tawahibre's coffin lid on display at the entrance to the Artifact Lab

Tawahibre’s coffin lid on display at the entrance to the Artifact Lab

Getting this Late Period painted wooden coffin lid ready for display required months of treatment to clean the surface and to stabilize the flaking paint, powdery and crumbly gesso, and loose wood components. I blogged rather extensively about the treatment – follow this link to view some of my previous posts.

Here are some treatment images that were posted on the museum’s Facebook page last week, showing details of the head/upper body before, during, and after treatment:

E885CbeforeduringafterCome visit Tawahibre in the lab, where you can examine the coffin lid up-close, read the conservation treatment report (which includes some materials identification reports), see more before, during, and after treatment images, and discuss the treatment with the conservator during open window times.

 

Hello, goodbye

We have had a very special object in the Artifact Lab for a few weeks – this Predynastic ritual vessel in the shape of a woman:

E12281_at01_compressed

E12281, after treatment

This vessel was excavated at Abydos, and we estimate that it is at least 5000 years old.
Here is a view of the vessel from the top:

E12281_at06_compressedI have worked almost exclusively on organic materials in the Artifact Lab, so getting to work on this ceramic was a nice diversion. Conservation treatment, which involved some light surface cleaning and minor mending, was requested because this object will be featured in an upcoming publication. It will leave the lab today, but I didn’t want it to leave without posting an image of it on the blog! Once the publication comes out, I’ll be sure to include a link to it.

In the meantime, to learn more, follow this link to check out a video discussion of a similar vessel, in the collection at the Brooklyn Museum:

Brooklyn Museum female figure

 

Glowing in the dark: multispectral imaging and Egyptian blue

There is something I’ve mentioned before on this blog, but never actually shown, and that is the ability to “see” Egyptian blue on objects using multispectral imaging. On many objects Egyptian blue is very well-preserved, so there is no need for special examination techniques in order to spot it. But there are cases in which being able to accurately identify this pigment is important. Sometimes Egyptian blue deteriorates either by changing color (to green or black) or by becoming lost altogether, making it difficult to know which areas may have originally been blue, or if blue was used at all.

And then there are objects like this one:

Front view of the shabti box in normal lighting conditions

Front view of the shabti box in normal lighting conditions

You’ve seen it before, it’s our painted wooden shabti box. I have been working on the treatment of this box for awhile now, mostly to stabilize the flaking paint and varnish. And this thick, orange-yellow varnish, which we believe is original, and is pistacia resin, makes it difficult to see the painted surface, both the details and the colors. While I could see that there is some green and possibly blue paint on this box, between deterioration of the paint and/or pigment, and the thick application of pistacia resin, I couldn’t say for sure which areas may have originally been painted blue…until now…

Taking advantage of the fact that Egyptian blue has luminescent properties when illuminated with visible light and captured in infrared, we can detect where Egyptian blue was applied. And wow, look at these results:

Visible-induced IR luminescence image of the shabti box. Light source: SPEX Mini Crimescope with 600nm band-pass filter. Captured with a Nikon D5200 modified camera with an IR 87C filter.

Visible-induced IR luminescence image of the shabti box. Light source: SPEX Mini Crimescope with 600nm band pass filter. Captured with a Nikon D5200 modified camera with an IR 87C filter.

This is the same surface of the shabti box seen in the first photo, but zoomed in a bit, and taken under different lighting conditions and captured with a different camera. The areas that appear white are where Egyptian blue was applied. Because everything else pretty much disappears on the box in this image, to better visualize where the Egyptian blue is in relation to other details, we created a false-color image in Photoshop:

False color image of the shabti box. The areas painted with Egyptian blue appear red.

False color image of the shabti box. The areas painted with Egyptian blue appear red.

In this false color image, the areas that appear red are where the Egyptian blue was applied. It’s not perfect (you can see that the bands in the hair of the figure on the right don’t really show up) but we could play around with the photographs a bit to improve this.

We did this imaging on all surfaces of the box, and on the box lids. Here is a regular photo, a visible-induced IR luminescence photo, and a false color image of one of the box lids, also showing lots of Egyptian blue:

Shabti box lid, normal light

Shabti box lid, normal light

Visible-induced IR luminescence photograph

Visible-induced IR luminescence photograph (areas in white = Egyptian blue)

False color image (areas in red = Egyptian blue)

False color image (areas in red = Egyptian blue)

You can use any regular/visible light source to produce the luminescence, but in this case, we used our fancy-schmancy new Mini Crimescope, which was developed for forensic work, but is useful to us because it allows us to examine objects under specific wavelengths of UV and visible light. We found that using a peak emission 600nm light source worked best for the excitation of the Egyptian blue.

In order to “see” the luminescence, we have to capture images using a modified digital camera, with an 87C IR filter.

In summary, we’re having lots of fun with our new equipment, and finding that these Egyptian objects are perfect subjects for learning how to use the Crimescope and the modified camera, because they produce such great, dramatic images.

 

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!

 

Sizing up our child mummy

Everyone loves Tanwa, our child mummy, but a lot of people ask about her size. “Isn’t she kind of small for a 5-year-old?” they’ll ask. Without knowing a whole lot of 5-year-olds myself, I usually say, yes, I guess, but you have to remember that she’s wrapped really tightly and that people were generally smaller in stature 2000 years ago. We also don’t know how she died, so theoretically, her size could have been affected by a disease or something that eventually caused her to die. But the truth is, I don’t know how she compares to the size of kids today.

But today I had the perfect opportunity to size her up, and a willing subject, my niece Luisa. Luisa is “almost 4-years-old” (this is a direct quote). We held Luisa up next to Tanwa for a little height comparison.

luisa and tanwaLuisa is the tallest in her class and she’s “almost four”, and she’s just about the same height as Tanwa. So I would say that Tanwa isn’t so short after all. What do you think?