Consolidating and reconstructing glass objects

* A new post from former Artifact Lab graduate intern Laura Galicier, contributing from a distance in Paris!

Reconstruction of a fish-shaped vessel from ancient Afghanistan (picture from a video of the British Museum, that can be viewed at https://www.britishmuseum.org/channel/exhibitions/2011/afghanistan/video_glass_blowing.aspx

Reconstruction of a fish-shaped vessel from ancient Afghanistan
- picture from a video on the British Museum website, that can be viewed by  following this link

Two glass objects from Cyprus were previously introduced to you. After an initial examination, several treatment steps were decided.

First, the surface showed evidence of delamination and was slightly flaking. We chose to consolidate the surface because if this destructive process went on it could lead to the complete loss of the object. An acrylic resin (Paraloid B72, that you’re now pretty familiar with) in acetone was chosen to do this light stabilization.

Then, we tried to see if the pieces from each object could be built up. We found that while the jug (n.63-1-196) would be able to reconstructed, the fragments of the bowl (n.63-200) didn’t fit together.

On the right: the glass jug    On the left: the glass bowl

The glass jug                                                                         The glass bowl

So the building work for the jug began! We had to find where every fragment was supposed to go. If you read our blogpost about the Egyptian Demotic jar, you’ll realize that building up a glass object is very different. Of course, the size of these glass fragments is considerably smaller than the jar fragments. Besides, the edges of a ceramic are irregular, which can help with reassembly, whereas the edges of glass are smooth.

Glass fragments glued together

Glass fragments glued together

In terms of thickness, a glass object can be very irregular, especially after deterioration, such as delamination of the surface. Generally, you hope that two fragments of similar thickness belong to the same area of the object, but with glass, delamination makes it possible for two fragments of very different thickness to fit together. Moreover, compared to ceramic, glass fragments have a very different way to adjust to each other.

Despite these differences, the methodology to reconstruct glass and ceramic has some similarities: it is necessary to map out the joins so as to know precisely where each fragment goes.

After a bit of work the fragments were put in the order to be joined.

The fragments arranged in the right order

The fragments arranged in the right order

Then, the fragments were temporarily reconstructed using scotch tape. Taping the joins clarifies where each fragment goes and exactly in which order to build them up. This order isn’t always the most obvious but if it isn’t respected, a fragment could prevent another one to fit.

The fragments were built together with scotch tape.

The fragments were built together with scotch tape.

Then, the scotch tape was removed and the fragments were glued with an adhesive (Paraloid B72). Three groups of fragments were reconstructed: fragments of the top, fragments of the bottom and a few fragments that should be placed in-between. The in-between fragments couldn’t be glued to the top or to the bottom because there’s a wide gap between them and the other fragments. This is why it was necessary to make fills so as to support these before going any further.

The three groups of fragments reconstructed and glued together.

The three groups of fragments reconstructed and glued together.

The fills will be explained in a post to come!

 

Peptide Mass Fingerprinting (PMF)

Motivated to learn more about the fur and animal hair found in our Predynastic mummy bundle, I popped up to Boston yesterday for a workshop entitled “Identifying collagen-based materials in cultural objects using peptide mass fingerprinting“.

The workshop was organized by a group at Harvard, including the Peabody Museum of Archaeology and Ethnology in collaboration with the Straus Center for Conservation at the Harvard Art Museums and the Harvard FAS Division of Science. The team received NCPTT funding for a project to develop a new application of an analytical technique called peptide mass fingerprinting (PMF).

PMF uses mass spectrometry to analyze very tiny samples of proteinaceous objects and identify the mammalian source to the species level. It actually can be used to analyze materials made of collagen and keratin, but the group at Harvard is focusing on collagen-based materials. The procedure essentially breaks up the protein into smaller peptides, and the mass of the peptides is measured using a mass spectrometer such as a MALDI-TOF. The peptide masses are compared to known reference samples, which allow for identification. This type of analysis falls under the category of proteomics, or the large-scale study of proteins, and it is sometimes referred to by this name as well.

The Harvard project is focused on applying this technique to objects made of gut, skin, sinew, and membrane from Alaska, the Northwest Coast, Northern California, and the High Plains. Another goal of the project is to bring this type of analysis, which typically takes place in large industrial or academic labs, to museum labs. You can learn more about the project on their blog.

The workshop included 3 presentations by the project’s primary analytical investigator/scientist Dr. Dan Kirby, project research associate Madeline Corona, and Kress fellow Ellen Promise. Between the 3 of them, they covered how PMF works, what it can tell you, and how it is applied to cultural artifacts, using a project on Alaskan kayaks as a case study.

After Q&A led by Peabody Museum conservator T. Rose Holdcraft, we were led on a tour of the Peabody conservation lab, where we were able to feast our eyes on some of the impressive Native Alaskan objects that they are investigating as part of the project.
A view of the Peabody Museum conservation lab, with several Native Alaskan skin and gut objects on view

A view of the Peabody Museum conservation lab, with several Native Alaskan objects on view

We also toured the impressive Mass Spectrometry and Proteomics Resource Lab, where we had a chance to see the Bruker MALDI TOF/TOF instrument and a demonstration of how samples are prepped for analysis.
The Bruker MALDI-TOF/TOF instrument and Madeline Corona demonstrating sample prep

The Bruker MALDI-TOF/TOF instrument and Madeline Corona demonstrating sample prep

The sample prep area showing the equipment used, including the MALDI plate (lower right)

The sample prep area showing the equipment used, including the MALDI plate (lower right)

Here at Penn, we are excited by this technique – not only for the minute sample size required (the samples used are just barely detectable to the naked eye) but also for its accessibility. We have a lot of animal-based materials in our collection and we are hoping to pursue using PMF to analyze these materials. Actually, we are already working to see if its possible to use this technique to identify the sources of the fur and basketry hair fibers from our Predynastic mummy, thanks to help from Smithsonian MCI fellow Caroline Solazzo, whose work focuses on keratin-based materials. PMF supposedly works on all types of samples, including those that are very old and/or are in poor condition, so we thought we’d put this to the test by starting with samples from our oldest Egyptian mummy (he’s well over 6000 years old). We will let you know how it seems to work.

A side note – a quick trip to Boston wouldn’t be complete without a stop at the Museum of Fine Arts. I spent most of my time there ogling the Ancient Egypt exhibits, admiring the massive, yet delicately decorated and inscribed coffin boards of Djehutynakht’s outer coffin (same time period and style as Ahanakht’s coffin)

The interior of the lid of Governor Djehutynakht's outer coffin (left) and detail of the false door (right)

The interior of the lid of Governor Djehutynakht’s outer coffin (left) and detail of the false door (right)

and many of the other treasures of this collection, such as this bead net dress made of faience and gold from the 4th Dynasty.
Detail of a 4th Dynasty beadnet dress (ca. 2551-2528 BCE)

Detail of a 4th Dynasty beadnet dress (ca. 2551-2528 BCE)

Breathtaking, really. I also found this shabti in a miniature coffin very charming.
Shabti of Queen Neferu with  miniature coffin, from Deir el-Bahri, tomb of Queen Neferu, 11th Dynasty (ca. 2061-2010 BCE)

Shabti of Queen Neferu with miniature coffin, from Deir el-Bahri, tomb of Queen Neferu, 11th Dynasty (ca. 2061-2010 BCE)

And while the MFA does not have conservators working in a gallery, as we are doing here at Penn, they do have some great “behind the scenes” galleries, one with interactives that engage visitors to think about conservation ethics and decision making. One of my favorites was an example using Maya Cylinder vases, examining condition issues and treatment decisions.

Some screen shots of the Maya vase example in the MFA's "behind the scenes" gallery

Some screen shots of the Maya vase example in one of the MFA’s “behind the scenes” galleries

All in all, a great trip. We’ll keep you updated on the whole peptide mass fingerprinting technique and how we might be able to use this for our collection.

 

More about our Predynastic mummy

Last year we posted some information about Bruce, our Predynastic mummy (and the oldest Egyptian mummy in the museum) here in the lab. Bruce has been on ongoing project, but he is often tucked toward the back of the lab unless we are actively working on him. While he’s often not front-and-center, when visitors enter the gallery and they catch a glimpse of him, they know that he’s special, even if they don’t know what he is, exactly.

Bruce on his cart, near the back of the lab, as viewed through the Artifact Lab windows.

Bruce, near the back of the lab, as viewed through the Artifact Lab windows.

As soon as he is spotted, I am often asked “what is that?” “is that a mummy?” and “what are you doing with him?”. In conservation, we are not always actively treating objects (or in this case, mummies); some of our projects involve close examination and study of objects (often referred to as technical studies). These technical studies may be a precursor to conservation treatment, but they may also be independent of treatment.

We are not currently carrying out conservation treatment on Bruce. Our focus at the moment is careful examination and some analysis, in consultation with other specialists. At the moment, we are focusing on trying to identify the type of animal hide that he’s wrapped in:

The red arrows are pointing out pieces of the animal skin bag wrapped around Bruce.

The red arrows are pointing out pieces of the animal skin bag wrapped around the mummy.

and also the animal hairs used to make the finely woven baskets included in his burial bundle:

E16229_basketsThese baskets are actually made of plant and animal fibers – the baskets are twined, and the passive elements (or warps) are made of plant fibers, while the active elements (wefts) are made of light and dark animal hairs. We know that the wefts are animal hairs based on our examination of these fibers using our polarized light microscope (PLM).

Views of the light-colored hair (left) and a cross-section of the hair (right) at 100X magnification

Views of the light-colored basketry fiber at 10X (upper right), at 50X (lower left), and a cross-section (lower right) at 200X magnification

Views of the darker hair (left) and a cross-section of the hair (right) at 100X magnification

Views of the darker basketry fiber at 10X (upper right), at 100 X (lower left), and a cross-section (lower right) at 200X magnification

Sometimes animal hair can be identified based on the features observed under a microscope, by comparing the unknown hairs to known reference samples. Some great animal hair ID sources on the web include this great resource on the FBI website and the Alaskan Fur ID website.

While we can clearly see that these fibers from the basket are animal hairs, we have not been able to identify them based on microscopy alone, so we are pursuing other analytical methods of identification, such as peptide mass fingerprinting (PMF). PMF uses a mass spectrometer to analyze the peptides in a proteinaceous sample, which can identify mammalian material to the species level using a micro-sized sample. Next week, I am attending a collagen identification workshop at Harvard, where I will learn more about PMF and its application to cultural artifacts.

We are excited by the possibilities this technique offers – being able to identify the skin(s) Bruce is wrapped in and the materials used to make the baskets found in his bundle will add to our understanding of very early technologies and funerary practices in Egypt. We will certainly share our findings as we learn more.