A new material in the Lab

loadimg.phpWhile we primarily work on Egyptian materials in the Artifact Lab, we occasionally work on objects from other cultures as well. (http://www.penn.museum/sites/artifactlab/2013/12/21/ch-ch-changes-in-the-artifact-lab/) Recently, two new objects were brought to lab. They are two glass vessels from Cyprus, which were discovered in the archaeological site of Kourion. Their date is unknown.

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First of all, what is glass made of? Generally three materials are mixed together:

- A former, being the main component: silica, usually found in sand;

- A flux, lowering the melting point of the glass mixture, the melting point being the temperature at which the glass mixture becomes a liquid (from 1600-1713 Celsius for raw silica alone to 800 Celsius for silica + a flux); this material is an alkali or soda.

- A stabilizer, inserted inside the chemical structure of the glass to strengthen it; usually lime.

- A fourth material, metal oxides, can be added to obtain a specific color (manganese for purple, gold for red, silver for yellow…).

This composition and the percentages of each substance change according to times and places. Moreover, glass can take a wide range of different shapes.

Here is a picture of the objects before treatment:

The two glass objects before treatment.

The two glass objects before treatment.

Both are glass vessels. The vessel on the left was restored in the past; a coating was applied on its whole surface and it was glued with that same substance. This adhesive is now flaking off the object, leaving thin and transparent films. This become more obvious when observed under ultraviolet light.

The object viewed under UV light. The bright white-yellow material is the old adhesive.

The object viewed under UV light. The bright white-yellow material is the old adhesive.

The old adhesive is pretty obvious now, with its white-yellowish color. This substance is also soluble in acetone. These properties allowed us to conclude that it is cellulose nitrate, a well-known material used to restore glass objects in the past. In addition to not aging well, this adhesive was applied very thickly on the edges, preventing the fragments from being joined together correctly.

Example of a problematic cellulose nitrate deposit on the  edge of a fragment.

Example of a problematic cellulose nitrate deposit on the
edge of a fragment.

Both glass objects also show evidence of delamination of their surfaces. It takes the form of a white layer, which flakes off the object.

New Picture (3)This phenomenon, called delamination, can start in the burial environment especially when the object undergoes weathering. This weathering changes the refractive index of glass as well. Each glass artifact has a specific refractive index, indicating how the light passes through it. According to this, our eye will perceive the object a certain way. Any change in the material, such as delamination, will alter this refractive index and thus our perception of it.

Untitled-10Here is an illustration directly on the object itself:

Delamination of the glass; the delaminated layers are white whereas the ‘glass substrate’ show a brown amber color.

Delamination of the glass; the delaminated layers are white whereas the ‘glass substrate’ show a brown amber color.

This process, if not stopped, can end up delaminating the whole object, layer by layer, resulting in the loss of this artifact. Conservation treatment, and good environmental controls, can prevent this from happening.

We’ll write more about the treatment of these glass vessels in our next post!

 

 

 

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!

 

Ungluing, re-gluing and filling the jar.

Statuette of an egyptian potter at work (beginning of  the 2nd mill. B.C).

Statuette of an egyptian potter at work (beginning of the 2nd mill. B.C).

The next step for the Egyptian jar was un-gluing all the fragments …to glue them together again.

We had two different cases: fragments that remained adhered together and fragments that were already separated, bearing remains of an old adhesive on their edges. The old adhesive had to be removed since it had many negative issues. First, it prevented the fragments from being joined back together by creating an unnecessary thickness at their junction. Moreover, when reconstructing the ceramic, the old adhesive prevents the fragments from fitting together well.

This old adhesive had a light brown color and after a few tests, it was found to swell when warm water was applied on it.

Here is what it looked like:

Detail of the break edge of one of the fragments, after applying water steam.

Detail of the break edge of one of the fragments, after applying water steam.

To remove the adhesive from the break edges, we used a Preservation Pencil, a tool looking like a pen and emitting water steam. Once softened, the adhesive was very easily removed with a scalpel or a brush.

And here is the result :

The same fragment edge after the removal of the old adhesive.

The same fragment edge after the removal of the old adhesive.

For the fragments still adhered together, it was a little more difficult since the water had to penetrate inside the jar but not too much because of the water-soluble ink on the surface. Compresses, or poultices, of water were applied on the interior of the ceramic, to cover the breaks. Most of the fragmentsfell apart quite quickly contrary to areas where the jar was very thick.

Now the building could begin ! … well almost since it was necessary to plan precisely how to proceed and in which order to arrange the fragments. First, we had to find where each of them was going, to estimate the losses. For that purpose every fragment was given a number and they were located on a map so as to keep track of their location.

The map; the numbers were indicated on the fragments with blue scotch tape.

The map; the numbers were indicated on the fragments with blue scotch tape.

Then the gluing really began, using the conservator’s favorite adhesive: Paraloid B72, diluted in acetone.

First steps of the gluing.

First steps of the gluing.

The more the jar grew, the more it needed a support, first on the outside, since its bottom is rounded….

A good support was provided by this bucket filled with glass balloons, heavy enough to stabilize the jar.

A good support was provided by this bucket filled with glass balloons, heavy enough to stabilize the jar.

…then on the inside to prevent it from collapsing on itself because of some particularly heavy fragments.

The jar was growing and needed internal support; the white material inside is a plastic bag filled with polyethylene fiber.

The jar was growing and needed internal support; the white material inside is a plastic bag filled with polyethylene fiber.

Losses in the ceramic had to be filled at the same time as the gluing to provide structural support to the jar and prevent it from collapsing.  Moreover those areas to fill would have been difficult to reach once the gluing was complete.

There was one large loss that definitely needed to be filled since one of the surrounding fragments was holding by only a few millimeters to another one.

Filling this area was a bit tricky. The fill material needed a support to be applied on the jar. Japanese tissue paper was glued inside of it and strengthened by applying several layers of Paraloid B72. It also needed to be shaped according to the curve of the jar.

On the left: The area to be filled.                        On the right: Japanese tissue paper used as a support to hold the fill material.

On the left: The area to be filled.  On the right: Japanese tissue paper used as a  support to hold the fill material.

On the left: The inside of the jar with the "tricky fragment" held in place by the japanese tissue paper.   On the right: Applying the fill material.

On the left: The inside of the jar with the “tricky fragment” held in place by the japanese tissue paper. On the right: Applying the fill material.

The fill material used is a mixture of Paraloid B72 and glass micro-balloons, looking like a very light white powder; plaster is also traditionally used to fill losses, but glass micro-balloons are lighter and don’t bring any salts to the ceramic. That kind of fill is also reversible and completely neutral towards the ceramic.

Here’s the fill once finished and polished with a heat spatula, ready to be painted.

The fill almost finished: the building can go on.

The fill almost finished: the building can go on.

More fills and building to come in a next post !

 

 

Cleaning the jar

Detail of the black inscription covering the jar.

A previous post introduced you to this demotic jar, currently on view in the Lab. The first step in its treatment was to clean the surface, which was very black due to dust.

It was necessary to make some tests on the ceramic to determine which way to clean was the best, meaning the safest for the object. Indeed, the black inscription on the jar is fragile and water sensitive. The first rule was to choose a non -aqueous method, that’s why I first thought about…erasers !

Image showing cleaning tests on a fragment of the jar.

Image showing cleaning tests on a fragment of the jar.

Test 1 : Sanford Magic Rub Eraser. index Test 2: Staedtler stick eraser.stadtlerTest 3 : Latex eraser.

Test 4: Ethanolethanol

Test 5: Wishab eraser.wishab

As you can see on the picture, the erasers seem to be the best choice, especially the n.2. Indeed, it can be applied with different levels of strength according to the amount of dust to remove.

Ethanol was also to be tried, being a “light” solvent; but the issue with a solvent is that you can’t control how it penetrates in the material, especially with a porous ceramic. So the best choice seemed to be the Staedler eraser.

It was then time to test this cleaning method on the inscription.

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Cleaning test with the eraser on an inscribed fragment.

The eraser appeared to work well, removing only the black grime and not the inscription. Of course, one has to be careful with this method, and not to press the eraser too hard or the black ink could disappear as well !

So I went on and cleaned all the other fragments.

Fragment before cleaning.

Fragment before cleaning.

The same fragment after cleaning.

The same fragment after cleaning.

 

In a general way, cleaning an object is very rewarding for a conservator, because the result can be seen at once. And pictures taken before and after are often impressive.

However, some things could not be improved; many demotic signs are lost due to water damage that occurred in the burial environment so the text isn’t complete. Moreover, a few fragments didn’t change after being cleaned, and still look dusty even if they aren’t.

Here is the general result, after all the fragments were cleaned.

General view of the fragments before cleaning.

General view of the fragments before cleaning.

view after step1

General view of the fragments after cleaning.

Next step: de-gluing the fragments !

 

The heads in color.

If you’ve been following the Artifact Lab blog you are now familiar with the two Egyptian wooden heads and the work in progress on them. Those heads are complex since they are composed of several materials that the conservator has to understand to treat them.

So let’s explore an important but now almost lost of their aspects: polychromy. Indeed, 99% of the colors on the heads are lost but some remains allow us to figure out what colors were originally theirs.

Mapping of E17911 – To show the remaining polychromy on the heads, the colors were enhanced using Adobe Illustrator.

Mapping of E17910 red paint layer.

Mapping of E17910 red paint layer.

Let’s have a look at the real colors left on the heads:

E17911 – On the left: Detail of red paint on the left ear (x 10 magnification) ; On the right: detail of blue paint on the the wig located on the right of the head (x 10 magnification).

E17911 – On the left: detail of black paint on the the wig located on the right of the head (x 10 magnification) ; On the right: Detail of red paint on the left ear (x 10 magnification).

E17910 – Detail of the red paint above and under  left eye and red paint below the right eye (x 10 magnification).

E17910 – Detail of the red paint above and under left eye and red paint below the right eye (x 10 magnification).

The wig is black (even if it looks blue on the picture !). The red is ochre, produced by reducing iron oxides to powder.

All Egyptian statues (and generally statues from other ancient civilizations) were completely painted. Only a few of them had their polychromy preserved, and it is especially rare on wooden artifacts because of many alteration factors that damaged these objects. The two heads were buried in a grave, several feet underground and the groundwater could rise very irregularly and completely overflow the tomb and its contents. The wood suffers a lot from humidity changes: indeed, this material always tries to keep its own moisture content stable, according to the environment moisture. That involves cycles of giving off and taking moisture; if those cycles occur too many times, the wood can’t follow and breaks generally appear.

If the wood is covered with a polychromy layer, it falls off since it can’t follow the movements of the wood. The wood is also susceptible to damage by other substances, like different types of salts and other alkaline substances whose action is increased by humidity.

That’s what explains that on the heads, the few areas of color left are in a bad condition; let’s try to explain what’s going on under the sediment!

To give you an idea, here is a stratigraphic representation of what a nice and undisturbed polychromy (if that exists!) should look like:

stratiThe wood is covered with a preparatory layer; it allows the surface to be even so that the paint layer can stick better to it. That’s it about the theory, let’s see what we have in reality:New PictureA lot less pretty and legible ! We can’t say whether the preparatory layer exists or not, and the paint is covered with a modern application of paraffin wax that wasn’t applied correctly on the wood; indeed the white material that covers some areas of the surface and of the polychromy is a paraffin deposit.

White paraffin deposits on the paint and the wood.

White paraffin deposits on the paint and the wood.

E17911 - The paint layer is poorly attached to the surface and termites didn’t spare it.

E17911 – The paint layer is poorly attached to the surface and termites didn’t spare it.

The paint layer is poorly attached to the wood and the paraffin used to strengthen the heads in the field (during the 19th century) is the only thing maintaining them.

While we are grateful that there is still some polychromy remaining…paraffin isn’t such a good thing ! It will be the topic of a next post to come.

Ch-ch-changes (In the Artifact Lab)

Visitors to the Artifact Lab these days will see a slightly different scene.

A variety of Native American objects currently in the Artifact Lab, including a war bonnet, baskets, a harpoon, a beaded vest and a wooden helmet.

A variety of Native American objects currently in the Artifact Lab, including a war bonnet, baskets, a harpoon, a beaded vest and a wooden helmet.

Rockwell Project Conservator Molly Gleeson will be on leave for the next few months, spending time at home with her baby daughter. While she’s away, our intern Laura Galicier will continue to work on Egyptian artifacts such as the wooden heads or the demotic jar. But she’ll be joined by other members of the Penn Museum Conservation team, who will be working on a variety of projects. Because of various upcoming deadlines, a lot of what you’ll see worked on will be Native American artifacts from Penn Museum’s collections.

Penn Museum Conservation intern Alexis North, working on moccasins for the Native American Voices Exhibition.  Photo by Steven Minicola, University Communications

Penn Museum Conservation intern Alexis North, working on moccasins for the Native American Voices Exhibition.

In addition to Native American Voices, our new exhibition opening March 1, 2014, we will be loaning Native American objects to exhibitions at three other museums in the new year: the Quai Branly Museum in Paris, France; the Autry National Center of the American West in Los Angeles; and at Penn’s own Arthur Ross Gallery. At other times you may see a conservator working on material from ancient Cyprus or material from the Museum’s excavations at Ur. Whenever you come, there’s sure to be something interesting to see and our conservators will be happy to talk to you about whatever they’re doing or whatever you’re interested in at our open window times (weekdays, 11:15 – 11:45 am and 2:00 – 2:30 pm, and weekends, 12:30 – 1:00 pm and 3:30 – 4:00 pm). And you’re always welcome to submit questions or comments via this blog. We’ll continue to post regularly on the doings of the Artifact Lab and Molly may even find some time to write in from home.

A demotic jar

A pottery workshop (from LICHTHEIM Miriam, Ancient Egyptian literature, 1973)

A pottery workshop (from LICHTHEIM Miriam, Ancient Egyptian literature, 1973)

Among the objects that an archaeological conservator treats, a very important one regarding the quantity is ceramic. Ceramic artifacts are widespread on time and many very different places; a lot of (if not all) civilizations on Earth made ceramics, so if you haven’t met one of those yet in a museum, it’s only a matter of time!

The one we have in the Artifact Lab is an Egyptian jar, from one of the past Penn Museum’s excavations on this site. Jars were used to contain fluids and are covered inside with a mixture of water and clay, to make it waterproof.

Here is a picture of the fragments before any intervention:

The jar before treatment.

This ceramic is covered with inscriptions painted in black ink (most likely a carbon ink) and the writing appears to be demotic. The Egyptian writing knew three different forms: hieroglyphic, which is the one you’re used to see on monuments; hieratic, which is a simplification of hieroglyphs, allowing the scribes to write faster for their administrative work on papyrus or pottery and rock fragments; and the demotic is a simplification of the hieratic, used from the VIIth century B.C. It is one of the writing that you can see on the Rosetta Stone.

rosetta stone

Demotic writing on the Rosetta Stone.

Detail of the black inscription covering the jar.

Detail of the black inscription covering the jar.

This black ink is water soluble, meaning that water is highly prohibited to clean the inscribed areas !

Concerning its condition, the main problem of course is that the jar is broken into about 50 fragments. It was restored in the past so it still bears remains of an old adhesive on the edges and many fragments are still glued together. Moreover, the surface and the inscription are covered with dust and need to be cleaned.

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Example of a particularly dirty fragment. The inscription is barely visible.

The next step will be to remove the old adhesive and to put the fragments together again. Eventually, we may have to fill some gaps in the ceramic, so as its handling could be easier and safer.

Those steps will be more detailed in several blogposts to come !

 

X-rays and the statues eyes

left eyeIn a previous post, we told you that the two wooden heads were going to be X-rayed and CT-scanned, alongside with some other artifacts from the Lab.

In this post we will deal with what we learned about the wooden heads’ eyes from the X-radiographs only.

A lot of our readers will probably know what X-rays are, for they may have experienced them in a hospital. X-rays are also successfully used in Art and Archaeology (for a general overview and some examples, see SCHREINER et al, “X-rays in Art and Archaeology – An overview). The principle of the X-ray is to expose a material to x-ray energy of a particular wavelength. According to the molecular weight of the material, the x-rays will, or won’t, be allowed to go completely through it. The energy that does penetrate passes through to a detector.

In digital radiography, the data is then processed by a computer and, eventually, we obtain a picture where dense (high molecular weight) materials appear white and lighter ones (low molecular weight) are black.

X-ray photograph of E17911

X-ray photograph of E17911 – We can see a lot of termite tunnels and the big hole inside the head, on the right-hand side, and the shining eyes.

E17911, in profile - This picture allows us to see more clearly the structure of the eyes.

E17911, in profile – This picture allows us to see more clearly the structure of the eyes.

New Picture (2)

E17910 – Also helpful about the inserting of the eyes.

In these radiographs, we clearly see the structure of the inlaid eyes. In fact, those eyes are quite similar to those studied at the Louvre Museum on Kay’s statue (ZIEGLER, Les statues égyptiennes de l’Ancien Empire, Musée du Louvre, 1997, p.256). This statue is from the Vth Dynasty, not so far in time from our heads.

Eventually, we can conclude that the eyes are made of a metallic sheet soldered in the back, which is flat. It is shell-shaped and the hippo ivory is inserted inside. Then the black pupils (made of obsidian?) are placed in the ivory, maintained inside by an adhesive (resin ? plaster ?).

New Picture (3)

X-ray radiography photograph of Kay’s statue eyes (from ZIEGLER, 1997, p.256).

Structure of Kay's eyes (from ZIEGLER, 1997, p.259); the back of the metallic part is flat and the edges were folded so as to form the eyelids.

Structure of Kay’s eyes (from ZIEGLER, 1997, p.259); the back of the metallic part is flat and the edges were folded so as to form the eyelids.

Structure of Kay's eyes and identification of the materials we have on Adu's eyes (from ZIEGLER, 1997, p.259)

Structure of Kay’s eyes and identification of the materials we have on Adu’s eyes (from ZIEGLER, 1997, p.259)

 

 

 

 

 

 

 

 

 

 

Fortunately, the Penn Museum has some inlaid eyes in storage, allowing us to figure out more clearly what we have on the heads.

New Picture (7)

The eye n.E6789B – Limestone and obsidian.

 

Back of the eye n.E12905A - Copper alloy.

Back of the eye n.E12905A – Copper alloy.

 

 

 

 

 

 

 

 

 

 

 

Again, fortunately for us (yes, fortunately!), the Louvre Museum has a very interesting statue, also from the Old Kingdom, with missing eyes. This statue of a nobleman named Tcheti informs us on how the inlaid eyes were inserted into the wood.

Tcheti statue, Louvre Museum n.E11566 - Detail of the missing eyes.

Tcheti statue, Louvre Museum n.E11566 – Detail of the missing eyes.

We can see that a hole was cut in the wood, fitting the eyes’ size. We can suppose that an adhesive was used to prevent the eyes from falling off the statue.

As you can see, a conservation intervention, apart from treating the objects, can also allow us to study them more closely and to know them better.

We will talk about the CT-scan in a next post and, in the meantime, you’re more than welcome to visit us at the Lab or to post a comment below !

 

Flippin’ coffins

We’ve been threatening to do it, and this week we followed through on our promise – to flip over the base of Tawahibre’s coffin.

As readers know, we have been working on Tawahibre’s coffin lid, and recently lifted it away from the base. Once we removed the lid, we could see that the interior of the base was undecorated, with plaster smoothed over the wood joins. There was also some textile remaining, presumably from the mummy who once was inside.

inside tawahibre

An interior view of the base of Tawahibre’s coffin

While the interior is undecorated, we know the same isn’t true for the exterior, based on a photo recovered awhile back in the Archives. After a bit more digging in Archives recently, we found even more detailed photographs of the coffin lid and base, taken sometime before they were put on exhibit back in the 1930s.

tawahibre front and back

Image from the Archives showing the front of the coffin lid and the back of the coffin base

Recovering old images like this is exciting because they potentially have a lot to tell us. In this case, this photograph is a good record of what the condition of the coffin was like soon after it was acquired by the museum. Like in the exhibit photograph I had recovered earlier, I could see that a lot of the damage we’re seeing on the coffin lid today was present then. But there was no way of knowing, until this week, how the current condition of the coffin base compares to the condition seen in this photograph.

And I have to tell you, I was a bit worried – until just a few days ago, all I could see of the coffin base was from these views:

Detail views of the proper right and proper left sides of the coffin lid and base, before treatment

Detail views of the proper right and proper left sides of the coffin lid and base, before treatment

Those large chunks of plaster and paint on the wood support below weren’t very promising. I had a sinking feeling that a lot of the paint and plaster on the back of the coffin base was unstable as well, and going to fall away when we tried to lift and flip it over.

The first step in getting the coffin base flipped over was to stabilize the plaster and paint on the inside and sides of the base, as much as possible. I carried out this work using the same methyl cellulose adhesive solution and fill material mixture as I have been using on the lid.

Then we did a test lift, to see how stable it felt, and to determine if we needed to temporarily stabilize any areas on the back before turning it over.

test liftThe test lift was encouraging, so we decided just to go for it!

How many conservators do you need to flip over a coffin base? Eight, it turns out.

flipping over1Fortunately, the procedure went smoothly, smoothly enough that we even allowed our Public Relations Coordinator Tom Stanley post a video of us turning the base over on the museum’s Instagram account.

Once we turned the base over, we were rewarded by being able to see that the back is still remarkably well-preserved, with very little changes from when that old photograph was taken:

Tawahibre's base in the 1920s (left) and today (right)

Tawahibre’s base in the 1920s (left) and today (right)

Can you spot the differences in these two photographs? I’ll post another copy of this image soon, circling the changes that have occurred.

 

Looking inside our falcon mummy

Last Friday, 7 of us from our conservation department took a group of objects from the museum to the GE Inspection Technologies Customer Solutions Center in Lewistown, PA for x-radiography and CT scanning.

Our group gathered around the CT scanner, being operated by Becky Rudolph, GE's North American Radiography Sales Manager for Academia

Our group gathered around the CT scanner, being operated by Becky Rudolph, GE’s North American Radiography Sales Manager for Academia

Now, wait just a second, you might be thinking. Doesn’t Penn have its own x-ray and CT scanning equipment? Why did we have to take these objects all the way to Lewistown for this work? Good questions, and we have a good answer. We just received word that in early 2014, construction will begin on our new conservation labs, which will include a digital x-ray suite. We plan to purchase the x-ray unit from GE, so a visit to their facilities was a chance for us to demo the equipment using some of our own artifacts!

The object I was most eager to image was our falcon mummy. X-ray and CT (computed tomography) scanning technology allow us to “virtually unwrap” this mummy, helping us understand how it was made and what is inside (and as visitors to the lab have heard me say, we can’t assume that there are any falcon remains inside-we can only hope!).

The falcon mummy laying on its storage support on the x-ray plate (within a lead-lined room)

The falcon mummy lying on its storage support on the x-ray plate (within a lead-lined room)

The quickest way to get a peek inside the falcon mummy’s wrappings is by taking an x-ray image. Digital x-ray technology is amazing – with a push of a button, 135 kV (kilovolts, measurement of the voltage), 2.0 mA (millamperes, measurement of the current) and 4 seconds later, we saw this:

falcon xray annotatedHooray! In this first attempt, we could already see that there are bird remains inside. The bright white material concentrated in the center of the mummy wrappings is the skeletal remains. In radiographic images, materials that are denser appear white because they do not allow x-rays to pass through. Materials that are less dense (such as the textile wrappings surrounding the bird bones) appear darker, because the x-rays are penetrating and passing through these materials. We can see in the image above that there are no skeletal remains in the “head” and the “feet” of the falcon mummy – these areas appear to have been sculpted with fabric. The slightly brighter white area near the feet just reflects an overlap of textile in that area.

While we were excited by this image, it immediately prompted more questions. We can see bird bones, but where is the skull? How much of the bird body is present? Are there any clues as to how the body was prepared for mummification? To answer these questions, we turned to the CT scanner.

CT scanning uses x-rays to produce cross-sectional images of an object, which can then be combined to produce three-dimensional views. CT provides a much more detailed look inside objects, and better distinction between different materials.

The CT unit at GE does not look like a medical CT scanner that many people may be familiar with. To scan the falcon, we had to stand the mummy upright in its box, which we then secured to the rotating stage inside the CT chamber with masking tape.

Right: Lynn Grant and I taped the falcon mummy in his box to the stage inside the CT chamber. Left: another view of the falcon mummy's box secured inside the CT chamber.

Left: Lynn Grant and I taped the falcon mummy in its box to the stage inside the CT chamber Right: another view of the falcon mummy’s box secured inside the CT chamber

The CT scanning took a bit longer than 4 seconds, but again, produced much more detailed images. Here is what one of the cross-sections looks like:

falcon cross section annotatedIn this image, the bones are visible as the most radio-opaque materials (so they are bright white). We were also excited to see the feathers, clearly visible as little circles reflecting the cross-section of the feather shafts, which are hollow. The various layers of linen wrapping are also very clear – clear enough to count! But other details are not so immediately clear to us, including the presence of the skull, and exactly how the remains were prepared.

Here is a screen shot from the program we are using to view the CT images, showing 3 different cross-sections, and a basic 3D rendering of a section of the falcon mummy. In this 3D rendering, we can clearly see the falcon’s talons, circled in red!

falcon CT 3 views annotatedWe will need to spend time with the images, and consult other specialists, to better understand what the CT scans have revealed.

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UCLA/Getty graduate intern Alexis North and I puzzle over the CT images of the falcon mummy

We will follow up later with more images and interpretations of the falcon mummy CT scans, plus more about the other objects we were able to examine.

A special thank you to Becky Rudolph and Hank Rowe at GE for spending the day with us, and for their expertise!