Tag Archives: digital radiography

Ptah-Sokar-Osiris and Treating Painted Surfaces

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Julia Commander is a third-year graduate student in the Winterthur/University of Delaware Program in Art Conservation. She is currently completing a curriculum internship at the Penn Museum.

As a conservation intern working in the Artifact Lab, I was able to go shopping through shelves of Egyptian objects and scope out interesting treatment projects. A painted wood statue, depicting the composite god Ptah-Sokar-Osiris, immediately caught my eye. The figure has intricate painted designs decorating the mummiform figure and its base, as well as gilded details in the face and headdress.

Ptah Sokar Osiris Statue, L-55-29A-C

L-55-29C, detail of paint and gilding

High-status burials in 19th dynasty Egypt often included this type of mummiform statue. Comparable examples of the popular object type exist in collections worldwide, such as the British Museum and the Metropolitan Museum of Art. Common characteristics include carved wood, a preparatory gesso layer, polychrome design, and in some cases, a coating of varnish. Ptah-Sokar-Osiris statues also frequently feature small compartments carved into the wood figure or base. These cavities could contain small papyrus scrolls or textile wrappings. While examining the object with this in mind, I noticed a faint rectangular shape on the reverse of the figure’s head.

X-radiography, a non-destructive imaging technique that helps clarify construction details, was perfectly suited for the question of the compartment. Without disturbing the delicate painted surface, we were able to observe that a rectangular cavity is in fact cut into the head of the figure. Although the cavity appears to be empty, this interesting construction detail is consistent with similar Ptah-Sokar-Osiris figures.

L-55-29A detail (left) and X-radiograph (right). Image captured from 55 kV, 2 mA, and 6 second exposure.

The statue has several condition issues, such as actively flaking paint and significant darkening over the front surface. Additionally, the figure is unable to stand upright in the base, and the components do not fit together securely. Upcoming treatment aims to address these issues, and I will be searching for the right approach to cleaning and consolidation. The complex surface made of wood, gesso, and paint will require detailed testing to find appropriate solutions.

To further investigate painted surfaces and possible coatings, I used multispectral imaging (MSI), which incorporates multiple light sources to reveal details that cannot be seen in visible light. Interesting findings included the presence of Egyptian blue in the figure’s wig and broad collar, as well as the headdress. This pigment shows up in visible-induced infrared luminescence and is easily distinguishable from surrounding pigments.

Detail of multispectral imaging, highlighting Egyptian blue pigment. Normal light (top), visible-induced infrared luminescence (center) with Egyptian blue shown in white, and false color image (bottom) with Egyptian blue shown in red.

Learning more about the object’s structure and surface will help inform treatment decisions about this complex figure. Check back to see what else we learn and how treatment will proceed!

What’s inside those animal mummies?

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Last week we x-rayed 8 animal mummies from our collection. These mummies were previously in storage and are in the Artifact Lab for much needed treatment and storage upgrades. As you can see in the images below, some of them are incredibly fragile with extensive damage. X-radiography is completely non-invasive and is one of the best tools we can use to study these mummies.

Recently we heard that researchers at the Manchester Museum and the University of Manchester found that about 1/3 of their mummies are “fakes” (and we use this word rather loosely – read the article in the link to find out more).

How do ours measure up? Well, even though we have a much smaller sample size, we found our stats to be a little bit better – 7 of the 8 that we just x-rayed contain animal remains, and one contains the remains of 3 animals, so the number of animals actually outnumbers the number of mummies in this instance!

Below we’ve posted paired images of the animal mummies and their radiographs. Our initial findings are written in the captions for each image. See if you can figure each one out, and if you see something that doesn’t make sense or something that we haven’t explained, please write into the comments below this post and we’ll follow up! All radiographs were captured with a GE Inspection and Sensing Eresco 65MF4 tube on a digital x-ray detector at 35kV 6mA for 6 seconds.

Cat mummy (left) and x-ray image (right) showing a complete cat body inside.

L-55-13: Mummy (left) and radiograph (right) showing a complete cat body inside.

ibismummy4

97-121-27: Mummy (left) and radiograph (right) showing an ibis in the lower 2/3 of the wrappings.

Mummy (left) and radiograph (right) showing a fragmented ibis body inside.

97-121-28: Mummy (left) and radiograph (right) showing fragmented ibis remains inside.

Mummy (left) and radiograph (right) showing an ibis inside.

E3539: Mummy (left) and radiograph (right) showing an ibis inside.

Mummy (left) and radiograph (right) showing an ibis inside, plus an extra bone and part of the ibis beak.

E3541: Mummy (left) and radiograph (right) showing an ibis inside, plus an extra bone and part of the ibis beak lying outside the mummy bundle.

Mummy (left) and radiograph (right) showing nothing inside the wrappings.

CG2015-4-1080: Mummy (left) and radiograph (right) showing nothing inside the wrappings (it was likely intended to be a hawk or falcon mummy).

kittenmummy

CG2015-4-9: Mummy (left) and radiograph (right) showing a young kitten in the upper half of the wrappings, missing its head.

snakemummies

97-121-8: Mummy (left) and radiograph (right) showing at least 3 snakes inside (scale not included, but this mummy is about the length and width of an iphone).

X-raying fragments of a painted wooden coffin

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I recently completed the treatment of these coffin board fragments.

E12617A-C, boards from a painted wooden coffin, before treatment

E12617A-C, boards from a painted wooden coffin, before treatment

In addition to the cleaning, which I blogged about before, the treatment involved stabilization of loose and powdery gesso and paint, filling losses where needed for structural support, and x-radiography, multispectral imaging, and portable X-ray fluorescence (pXRF) analysis. It has also enabled a translation of the text. I’m going to write a few shorter posts to highlight the different components of this project, starting with the x-radiography.

During my initial examination of the boards, I could see that the boards represent just a portion of the front, head end of the coffin. The rest of this side of the coffin would have continued much further to the left, but at some point these pieces were cut down and finished off on the left side to a smooth edge. This is most evident when you look at the hieroglyphic text, which obviously should continue to the left.

I could see that these 3 boards were originally joined with wooden dowels, because there are wooden dowels protruding from the join edges. I also noted some large cracks in the painted surface of the largest (center) piece in the image above, which led me to realize that this central piece was made of more than 1 piece of wood. I turned to x-radiography to get a better understanding of what is going on below the surface.

Here is a composite image showing the radiographs of the 3 boards:

E12617A-C x-ray image

E12617A-C x-ray image

The dowels joining the 3 pieces together are very clear in the x-ray image above. There are some darker (almost black) areas, which represent the holes that were drilled out for inserting the dowels. The denser (whiter) areas within those voids are the wooden dowels themselves. I’ve outlined these areas in green in the image below.

E12617xraymapped-1The x-ray image also helps clarify how the center piece is constructed, with 3 pieces of wood, which I’ve outlined in red above. Where those 3 pieces of wood join correspond directly with the cracks observed in the painted surface on the exterior.

Also visible in the x-ray image are two small nails driven into the lower edge of the bottom board. These nails are historic additions, likely added at the time when the boards were cut down and modified, although their purpose is unknown.

In my next post, I’ll focus on what cleaning, pXRF, and multispectral imaging has revealed about the painted surface, and I’ll include some after-treatment images.