Completing the treatment of Tawahibre’s coffin

Things have been pretty busy around here lately, and I almost forgot to post some updates about several projects. One project in particular is the treatment of Tawahibre’s coffin. We have been working on this 2-part painted wooden coffin in the lab for the last year, and we recently completed its treatment.

As you may remember, when the coffin first came up here, it was covered with a thick layer of dust and grime, the paint was badly flaking in areas, several large pieces of painted gesso were pulling away from the wood support, and there were large cracks throughout.

Before treatment photos (clockwise from left): upper half of coffin showing layer of dust and large cracks and losses; large piece of painted gesso partially detached from top of head; large loss on wig, showing old animal glue adhesive from a previous restoration

Before treatment photos (clockwise from left): upper half of coffin showing layer of dust and large cracks and losses; large piece of painted gesso partially detached from top of head; large loss on wig, showing old, shiny animal glue adhesive from a previous restoration

After cleaning the surface with a brush and vacuum, followed by cosmetic sponges, I consolidated the paint with a methyl cellulose solution, filled in cracks and gaps using Japanese tissue paper and a mixture of methyl cellulose bulked with cellulose powder and glass microballoons, and then toned the fills with acrylic paint. This work is explained in further detail in previous posts, which you can find by clicking on the links included in blue above.

fillingcracks

A detail shot of the wig showing an area with several large open cracks before and after filling with Japanese tissue paper and methyl cellulose/cellulose powder/glass microballoons mixture

Based on a discussion with our Egyptian section curators, I also made some aesthetic fills to mask some large losses, including 2 losses on the wig. We chose not to fill the losses on the nose and chin because filling these losses would require too much guess-work as to the original contours of these features.

Large loss on wig before (left), after application of Japanese tissue paper layer (middle), and after application of fill mixture (right)

Large loss on wig before (left), after application of Japanese tissue paper layer (middle), and during application of fill mixture (right)

Detail of the head and wig before (left) and after (right) conservation treatment, with losses in before treatment photo outlined in red

Detail of the head and wig before (left) and after (right) conservation treatment, with losses on the wig outlined in red. The larger loss on the right is the featured in the previous series of images.

I carried out similar work on the base of the coffin, and now both are complete:

Tawahibre's coffin lid before (left) and after (right) conservation treatment

Tawahibre’s coffin lid before (left) and after (right) conservation treatment

The coffin base before (left) and after (right) conservation treatment.

The coffin base before (left) and after (right) conservation treatment

As you can see, we chose not to fill many of the losses, focusing instead on stabilization.

This work will enable future exhibition of the coffin, and just as importantly, it will make further study of the coffin possible. All along there have been some discrepancies between the name that has always been associated with the coffin (Tawahibre, a woman’s name) and a previous translation in 1946 of the hieroglyphic text on the coffin (which identified the name of a male court official, the son of J-se(t)-N-Ese). There has also been some confusion about the remains once housed in the coffin, which were previously identified as male, but in a 1975 autopsy the remains were confirmed as belonging to a female in her mid-30s. A bit confusing, but hopefully we’re now one step closer to getting this all straightened out!

 

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.

 

Opening Tawahibre’s coffin

I don’t think many people will argue with me about this – a day at work (heck, a day in my life!) can’t really get more exciting than opening a 2500+ year old Egyptian coffin. For the last several months, we have been carrying out treatment to stabilize the loose wood, crumbling gesso, and flaking and powdery paint on the lid of Tawahibre’s coffin. While there is still a lot of aesthetic work to carry out, we finally got the lid to a point where we deemed it stable enough to remove it from it’s base.

Removing the lid from an incredibly fragile 2500+ year old coffin doesn't happen without a lot of planning and discussions ahead of time.

Removing the lid from an incredibly fragile 2500+ year old coffin doesn’t happen without a lot of planning and discussions ahead of time.

Okay, okay, so, the coffin has been opened before, and we knew that there wasn’t a mummy inside anymore (she’s down in storage), but opening the coffin was monumental nonetheless, as the lid hadn’t been removed in decades and we didn’t really know what we would find inside.

Fortunately, we were able to lift and move it without any problems:

DSC_0765DSC_0771DSC_0776(they really make it look like a breeze, don’t they?)

And now the lid is safely resting on a new palette, and the interior of the coffin is revealed to us for the first time:

Tawahibre lid and base separated

Yup, just another day in the Artifact Lab. We’ll fill you in later about what we’re learning and what’s going to happen next.

 

 

Field trip!

Sometimes getting started on a conservation treatment requires getting out of the lab for a bit, so this week, my colleague Julie Lawson and I took a field trip down to Baltimore to visit the Johns Hopkins Archaeological Museum and chat mummy treatments with their Curator/Conservator, Sanchita Balachandran. Sanchita and I connected at the American Institute for Conservation (AIC) annual meeting back in June – I had read about a treatment that she carried out on a human mummy at the museum, and when we realized that we both had animal mummies in our labs as well, we decided we’d get together for a brainstorming session to discuss treatment approaches, materials, and storage options for these fragile objects.

Julie Lawson admires artifacts in one of the cases in the Johns Hopkins Archaeological Museum

Julie Lawson admires artifacts in one of the cases in the Johns Hopkins Archaeological Museum

The Johns Hopkins Archaeological Museum is nestled in the center of the Johns Hopkins Homewood Campus in Baltimore, in a beautifully-renovated building, surrounded by classrooms and light-filled student study spaces. The museum was established in 1882 and since its founding, has been dedicated to inspiring and teaching students at the university.

One of the main features of the museum is the display of archaeological objects from ancient Greece, Rome, Egypt, the Near East, and the ancient Americas, displayed in glass case walls, allowing students, faculty, and visitors to view these pieces and peer into the museum itself.

museum2_compThe museum also displays pieces on loan, including an ancient Egyptian mummy from Goucher College.

Goucher mummyThis was the mummy that I had read about and was curious to learn more about from Sanchita. The Goucher mummy is an adult female mummy from the Ptolemaic Period (305-30 BCE), and I knew some details of the treatment from Sanchita’s article in the Journal of the American Institute for Conservation (JAIC), but this was a great opportunity for me to see this mummy up-close and to ask Sanchita more about how she approached this treatment and the specific materials and techniques she used. Since we are in the middle of working on the treatment of our mummy PUM I here in the Artifact Lab, this conversation was very timely.

Detail of the Stabiltex encapsulating the feet of the Goucher mummy

Detail of the Stabiltex encapsulating the feet of the Goucher mummy

The Goucher mummy has a fascinating history that I won’t get into here, but you can learn more about her in the “Object Stories” section of the museum’s website by following this link. One of the things I was curious to discuss more with Sanchita was her use of Stabiltex, a sheer polyester fabric, to protect fragile areas of the mummy’s wrappings, and the design and construction of the support the mummy is currently resting on in the exhibit. As I said, we’re working on encapsulating PUM I’s outer linen wrappings in a similar way, but using a different type of sheer netting fabric. After discussing techniques with Sanchita and seeing how successful her treatment of the Goucher mummy was, I returned to the Artifact Lab feeling good about our approach to PUM I’s treatment!

Sanchita also pulled out several animal mummies that she is currently working on, including these cuties:

Cat (above) and dog (below) mummies

Cat (above) and dog (below) mummies

We discussed the challenges of dealing with such fragile linen wrappings and our experiences with and use of different adhesives, as well as techniques for encapsulating fragile areas. Sanchita also showed us their handling and storage mounts, which go a long way in protecting these artifacts.

Sanchita lifts an ibis mummy from its storage box using a handling tray

Sanchita lifts an ibis mummy from its storage box using a handling tray

After discussing mummies at length, Sanchita took us back into their storage area, where we had the opportunity to see additional Egyptian artifacts, including several painted wood artifacts with a variety of condition problems. As readers to this blog may know, we have our own fair share of challenging painted wooden artifacts, including Tawahibre’s coffin, so I was eager to see how Sanchita was approaching the treatment of these pieces as well.

Sanchita and Julie in storage

Sanchita and Julie in storage

All in all, it was a fun and productive day! These types of professional exchanges are incredibly valuable, and I’m not only inspired to tackle some treatments and try new things back in the lab, but to make more time in the future to visit other colleagues and collections. A huge thanks to Sanchita for hosting us and for sharing so much about her work at Johns Hopkins.

 

Conservators-in-training

For over 10 years, our museum has organized an “Anthropologists in the Making” Summer Camp, and today we hosted 66 of these summer campers in the Artifact Lab for an afternoon of conservation training.

IALSummerCamp1This year the camp is being held over 8 weeks, with different themes each week, including Can you Dig it?, all about archaeology, and Visions and Dreams, which explores the significance of dreams and the roles of shamans and mystics (this one is coming up in August).

The camp theme this week is Mummies Unwrapped so of course we had to give the campers a taste (but not literally) of mummy conservation, in addition to what they are learning about mummies and ancient Egypt.

We organized 3 different activities for the 7-13 year olds (they were split into 2 groups according to age) to test their hand and observation skills. All 3 activities were created to mimic some of the work that we’ve been doing in the Artifact Lab, including:

- an excavation station, which challenged the campers to pick out the remains of a beaded shroud from a bin of mummy debris (similar to recovering PUM I’s beads)

IALsummercampexcavation2

- a cleaning station, where campers tried different cleaning tests to remove dirt from a painted ceramic tile (like the cleaning that we’ve been doing on our painted coffin of Tawahibre)

IALsummercampcleaning4

- a materials ID station, where the campers had the opportunity to examine “mystery” materials under magnification and then had to identify what they were looking at (an example of one of the material ID challenges we’ve encountered in the lab can be found here)

A camper compares reference materials to the magnified image of the "mystery" material on the monitor

A camper compares reference materials to the magnified image of the “mystery” material on the monitor

For each activity, we had the kids fill out worksheets to record their observations, to give them a sense of the documentation involved in our work. Before moving on to the next station, each camper needed to get their supervising conservator to sign off on their worksheet. On their way out the door, all campers received certificates declaring them “Junior Conservators for-the-day”.

certificateWe had lots of fun, not only preparing for the camp

Arts and crafts day in the Artifact Lab (left) and the painted tiles before "dirtying" them for the campers (right)

Arts and crafts day in the Artifact Lab (left) and the painted tiles before “dirtying” them for the campers (right)

but also working with the kids at each of the stations. We were impressed with their observations and how quickly they picked up on each activity (rolling swabs can be hard at first!). Special thanks to our Education Department and to all of the summer campers for increasing our department more than tenfold for the afternoon!

IALsummercampcleaning1

 

Slowly, but surely

Sometimes when working on a large, complex project, it can be hard to see progress – once certain areas are addressed/stabilized I just start focusing on all of the other problems. In these cases, I find it really helpful to write about the work, to go through the photos I’ve taken so far, and to reflect on how far we’ve come. One of the more complex treatments we’re working on in the Artifact Lab is Tawahibre’s coffin.

The last time you saw Tawahibre on the blog, she was all tied up, Lilliputian-style.

Tawahibre capturedSince that last post, we actually have made quite a bit of progress, and have started realigning and filling areas where the gesso and smaller wood components have cracked and separated from the wood ground below.

One very precarious area has been a large section on the lower proper left side of the coffin – when the coffin came into the lab for treatment, this section was only just barely attached along the top, with the help of two wooden dowels as well. In addition to being just about ready to detach, this section was also very distorted and misaligned, with areas of the painted surface overlapping and abrading each other.

tawahibre PL detail BT with arrows

Before treatment detail of this large partially detached section. It was just barely attached along the top (indicated by red arrows) and by 2 wooden dowels (circled in green).

Here is a view of this section, before treatment, from above (the red arrows are just pointing out the area that I’m talking about, for clarity).

tawahibre PL detail overhead BT with arrowsAfter working to humidify and realign this area as much as possible, I prepared it for filling and stabilizing by lining the wood support below and the inside surface of the detached section as possible with Japanese tissue paper, adhered with methyl cellulose adhesive. The Japanese tissue paper will serve to make these fills more easily reversible in the future.

Tawahibre PL detail DT with arrows

Preparing this section for stabilization and filling. The red arrows are indicating the Japanese tissue paper used to line the inner surfaces of the coffin before filling.

To secure this section to the rest of the coffin, I applied a fill mixture between the large partially detached section and the wood support below. The fill mixture was made using 5% methyl cellulose adhesive in 1:1 water/ethanol bulked with a 1:1 ratio of alpha cellulose and 3M glass microballoons. The alpha cellulose and microballoons were chosen to create a lightweight, relatively dry, and easily moldable fill – they also make this mixture a bright white color. After applying the fill material, this section was again bound with the twill tape and ethafoam blocks to hold everything together while the fill dried.

Detail of this section after filling. Note-no straps are needed to hold it in place!!!

Detail of this section after filling.

And here is a detail showing this section from above – I think it makes a nice comparison with the before treatment shot from a similar angle, above.

Tawahibre PL detail above DT2So far this has been a successful course of treatment and we have filled several areas on the coffin. Our current goal is to get the lid stabilized enough so that we can separate it from the base, so that we can continue to work on both sections with better access to some of the very unstable, fragile areas.

Special thanks to my conservation colleagues for their help with brainstorming, problem-solving, and carrying out this treatment!

 

Reimagining an ancient Egyptian material

Have you checked out our In the News section of this blog? Periodically, we try to update this page with some interesting articles related to our Egyptian collection, stories about projects and discoveries in Egypt, and even our own lab highlighted in the press.

One of the more recent stories that we’ve posted is about a new discovery related to Egyptian blue, one of the world’s first synthetic pigments. The ancient Egyptians made it by heating together copper, silica (sand), lime (calcium oxide) and an alkali such as natron (sodium sesquicarbonate) and it is found on objects from as early as the 4th Dynasty through to the Roman Period. We see this pigment on artifacts here in the lab, including Tawahibre’s coffin (and for more details read our blogpost on how we know this.)

A detail of Tawahibre's coffin. Based on analysis, this pigment has been determined to be Egyptian blue.

A detail of Tawahibre’s coffin. Based on analysis, this pigment has been determined to be Egyptian blue.

One thing that has been discovered about Egyptian blue is that it has luminescent properties-this luminescence cannot be seen in normal light conditions, but can be detected using infrared light. Using an infrared light source, it is possible to not only positively identify Egyptian blue using a completely non-invasive technique, but it is also possible to discover very small traces of Egyptian blue pigment on surfaces of objects. The British Museum provides a great overview of this phenomenon on their website. It is our hope that we might be able to try this technique to examine some of the artifacts in our collection.

A painted wood uraeus on display in our Upper Egypt gallery. The paint has not been analyzed, but based on appearance the blue is most likely Egyptian blue. Examination with an IR source could confirm this.

A painted wood uraeus on display in our Upper Egypt gallery. The paint has not been analyzed, but based on appearance the blue is most likely Egyptian blue. Examination with an IR light source could confirm this.

Furthermore, it is now understood that this luminescence is produced by the nanostructure of the pigment – scientists have discovered that the calcium copper silicate in Egyptian blue can be broken into nanosheets, which produce infrared radiation similar to beams that communicate between TVs and remote controls and car door locks. It is now being envisioned that these nanosheets could be used for future near-infrared-based medical imaging techniques and security ink formulations!! Talk about a new life for such an ancient material.

You can read and hear more about this by following this link to our In the News section of this blog. Have you read or heard about something recently that you think we should share on our blog? Leave a comment here and we’ll try to incorporate these suggestions whenever possible.

 

Tawahibre all tied up

When I wrote about the fantastic image we retrieved from our Archives a couple weeks ago showing our Mummy Gallery in 1935, I promised to provide an update on the treatment progress on Tawahibre’s coffin.

Well, why don’t I start with this:

A view of Tawahibre's coffin from above

A view of Tawahibre’s coffin from above

While you may not be sure what you’re looking at here, this looks like progress, doesn’t it? I’ll tell you what you are seeing – the coffin is tied in several places with cotton twill tape, holding small pieces of white Volara foam and blueboard (acid-free, lignin-free corrugated board) in place against the coffin surface.

A detail of the Volara foam and blueboard held in place with cotton twill tape

A detail of the Volara foam and blueboard held in place with cotton twill tape

The purpose of this system, other than looking kind of intriguing, is to place select pressure in areas on the coffin (whenever I say this I always think of the useful book The Gentle Art of Applied Pressure-the title speaks for itself). As I have described previously, the coffin is pretty distorted in areas, due to the fact that many of the individual wood elements have separated and moved apart and that the plaster has separated from the wood substrate. We are trying to realign these pieces as much as possible using humidification with a Preservation Pencil, which allows us to direct a small stream of warm humidified air in select areas, which helps the plaster and wood relax a bit and encourages movement. Once we get an area to move sufficiently, we then apply pressure to the area to hold everything in place.

Here Nina is directing a stream of humidified air with the Preservation Pencil and I am applying pressure with my hands.

Here Nina is directing a stream of humidified air with the Preservation Pencil and I am applying pressure with my hands.

We’re also continuing to consolidate the painted surface and readhere loose pieces of plaster and wood.

We don't usually work in teams, but yesterday we had a little group humidification and consolidation party!

This treatment has been a team effort, and yesterday we had a little group humidification and consolidation party!

While we’re making progress and becoming pretty comfortable with the coffin and the treatment, there are still some scary areas to deal with. This is an area that I’ll be tackling next:

A detail of a badly damaged area on the coffin, showing significant cracking and flaking and detached and displaced fragments

A detail of a badly damaged area on the coffin, showing significant cracking and flaking and detached and displaced fragments

Wish us luck as we continue this work!

From the Archives

The Penn Museum Archives is an incredible resource for us here at the museum.

A view into the Penn Museum Archives

A view into the Penn Museum Archives

When we begin working on objects in the conservation lab, we carry out preliminary research, which often includes searching for related materials in the Archives. Among the materials we may be interested in are archaeological field notes, letters between curators and archaeologists or collectors about the acquisition of specific artifacts, and old photographs.

Recently, Senior Archivist Alex Pezzati scanned some images for me, including this one, a shot of the Egyptian “Mummy Gallery” in 1935.

31011_mummyroom_1935_compressed

I was excited to see some of the artifacts we’re working on in the Artifact Lab right now in this photo. Can you pick some of them out? In the image below I’ve circled some of them in red.

The objects circled in red above are either being worked on in the Artifact lab or are on display in our accompanying exhibit

The objects circled in red above are either being worked on in the Artifact lab or are on display in our accompanying exhibit

These old exhibition photographs can be extremely valuable to conservators. Not only does this particular image tell us that certain artifacts were definitely on display, and when (which may not be recorded elsewhere), but it also shows us how they were displayed. In some cases, seeing the way that artifacts were previously displayed may help to explain damage, such as excessive fading on one side or adhesive residues left behind by an old mount. We can often make good guesses about this type of damage, but it’s always nice to have some proof!

What particularly excited me about this photograph is that it shows the coffin of Tawahibre in the gallery. We are currently working on this coffin in the lab, but it is still too fragile to separate the lid from the base to allow for examination of both pieces individually.

The coffin of Tawahibre in the Artifact Lab.

The coffin of Tawahibre in the Artifact Lab.

Just recently, Curator Dr. Jen Wegner was up in the lab and we were discussing the coffin and some of my observations, and she wondered out loud if the back had any text written on it. I had wondered the same thing myself but I knew that until we carried out further work, we wouldn’t be able to know.

BUT, since this 1935 photograph shows both the lid and the base of the coffin on display, we don’t have to wait any longer!

The lid and the base of Tawahibre's coffin, side by side in the Mummy Gallery in 1935.

The lid and the base of Tawahibre’s coffin, side by side in the Mummy Gallery in 1935.

As you can see in the above image, there is writing on the back! Now only if we could just hasten the conservation treatment so we can examine it for ourselves…

Another thing that is useful about this image is that is shows that much of the damage we’re seeing on the coffin today was present in 1935. This includes both major structural damage and extensive paint loss in areas. It is likely that the coffin came into our collection with this damage, which is somehow reassuring to me. I will also note this in my documentation.

Tawahibre's coffin in 1935 (left) and today (right). Much of the major damage we see today had already occurred by 1935. To highlight this, I've circled some of the damaged areas in red in both images.

Tawahibre’s coffin in 1935 (left) and today (right). Much of the major damage we see today had already occurred by 1935. To highlight this, I’ve circled some of the damaged areas in red in both images.

We continue to plug away on the treatment of the coffin and we are hoping to soon reach the point where we can separate the lid. I will provide an update shortly about some of the more recent work we have been carrying out on this artifact!

 

 

Mystery fiber

In a recent blog post I mentioned that I am working on the painted coffin of Tawahibre, which has fibers mixed into the ground layer (gesso). In my examination prior to starting treatment, I had noted these fibers, and observed that they are present all over the coffin lid, mixed into the ground layer just below the painted surface. They are exposed in many places where there are losses-here is an image of one area where the surface of the coffin is badly damaged, revealing these fibers:

Fibers visible in the ground layer of the painted coffin lid

There are quite a lot of these fibers in some areas (as seen in the photo above), and then in others, there are very few. They are found in areas where the ground is thick and also where it is applied very thinly. They are not arranged in any particular way-they appear to have been mixed haphazardly into the ground. The fibers are light brown in color, and while most of them are very stiff, they react almost immediately to moisture, becoming very flexible when wet. I had initially assumed that these were plant fibers-possibly flax-but they always seemed a bit odd, and to be honest, these fibers remind me a little bit of sinew (animal tendon).

As I have been working on the coffin, several of these fibers “presented themselves to me” for sampling-meaning, as I’ve been working to stabilize some of the areas with these fibers, a couple became detached, allowing me to investigate them further using PLM. So far I have looked at 2 samples, and both look the same. I prepared the fibers by mounting each one on a glass slide with water. When looking at them in plane-polarized light, they look like this:

Two different fibers from the coffin ground layer viewed at 50X magnification

I didn’t really know what I was seeing-it was difficult to pick out any really distinguishable features, so I then viewed both fibers under crossed polars. This is what I saw:

Same two fibers viewed under crossed polars at 50X magnification

What the heck is that? I’ve never seen anything like this before. When I showed this to a few other people, the first reaction has been-it looks like a worm! And it totally does. This very regular banding pattern has got to be characteristic of something-I just don’t know what.

I thought I had a lead last week-I found this image in a book, showing a bundle of sisal fibers with a commonly-seen spiral element:

Sisal sample showing a characteristic spiral element. Image from “Color Atlas and Manual of Microscopy for Criminalists, Chemists, and Conservators” by Nicholas Petraco and Thomas Kubic, p. 94.

However, just last week I obtained a sisal sample from one of the Winterthur art conservation graduate students and I’m pretty sure that’s not what I have. The sisal sample looks distinctly different to me-here it is in both plane polarized light and under crossed polars:

Sisal reference viewed at 400X magnification in plane polarized light (left) and crossed polars (right). Also, note the difference in magnification between these fibers, viewed at 400X, as opposed to the coffin mystery fibers above, viewed at 50X.

For the moment, I’m stumped. But I’m continuing to investigate this and to get input from colleagues, and I’m open to suggestions/ideas! I’ll also certainly provide more information when I know more. To be continued…