Mystery fiber update

Posted on February 23, 2013 by mollygleeson

A quick update on our mystery fiber (see my previous post for details):

Today I decided to do a chemical spot-test to see if I could determine if the fiber was cellulose or protein-based. Chemical spot tests are inexpensive, generally simple procedures that conservators may use to characterize materials on artifacts. These spot tests are often carried out on small samples removed from artifacts using chemical reagents. In the case of my mystery fiber, I cut a small piece off of one of the fiber samples I previously examined under the microscope-this small piece was enough for a spot test, and there was no need to remove more material from the coffin in order to do this.

The first test I chose to carry out was the Biuret test for protein (according to instructions in Material Characterization Tests for Objects of Art and Archaeology), using copper(II) sulfate. After placing a drop of copper (II) sulfate solution on the sample, I waited for a few minutes, then soaked up the excess solution and added a drop of sodium hydroxide solution to the sample. It immediately turned purple (see below), which indicates the presence of protein (and just in case it’s not clear on your screen, believe me, it is purple!).

Magnified image of the sample used for the protein spot test. The purple hue indicates a positive reaction for presence of protein. 50X magnification

What this means is still unclear, but it’s another clue. It is possible that my earlier comparison of this fiber to sinew was not a bad suggestion! But it’s also possible that this fiber was coated in a protein-based glue before it was incorporated into the gesso (or something like this).

This calls for further investigation!

Mystery fiber

Posted on February 23, 2013 by mollygleeson

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…

Art conservation students visit the Artifact Lab

Posted on February 21, 2013 by mollygleeson

Last Saturday, I was pleased to give a special tour of the Artifact Lab to a group of students from the University of Delaware.

Group photo in the Artifact Lab

This group was made up of graduate students in the Winterthur/University of Delaware Graduate Program in Conservation (WUDPAC), a pre-program intern currently working at Winterthur, and undergraduates majoring in art conservation at the University of Delaware.

Several students gathered for our open window session

They arrived during our open window session, and then we continued the tour afterward, which gave me the opportunity to present some of my ongoing work and experiences working in an open lab. While I speak about my work every day, discussing my work with students who are learning some of the latest treatment techniques and analytical methods, and who have this information fresh in their minds, was incredibly useful for me. Since their visit, I have received some generous offers of sharing material samples and articles. I know that visiting the Artifact Lab must have been a treat for them, but I think it was equally rewarding for me!

Giving our falcon a little love

Posted on February 12, 2013 by mollygleeson

One of my favorite artifacts in the lab is a falcon mummy, which I described in an earlier post. While he is a fascinating object, this poor little guy hasn’t been able to be exhibited, or even handled very much, because some of his linen wrappings are quite deteriorated, brittle, and breaking apart, causing serious structural issues.

Overall shot of our falcon mummy

Recently, I worked to stabilize the linen wrappings on his feet, which were partially detached, and in some areas, barely hanging on by a few threads.

Side view of the falcon’s “feet” showing the fragile, partially detached linen wrappings

Before carrying out any treatment, I did a little bit of research and carried out some testing to determine what materials I might want to use to repair the textile. I knew that a stitched repair would not be possible, as the linen fibers are far too weak and this would likely cause further damage, so I started investigating different adhesives and support materials to use instead. As part of this process, I consulted with Nancy Love, a local conservator in private practice who specializes in textiles. Nancy recently visited me in the Artifact Lab, and among the other materials I was trying, she suggested that I experiment with nylon bobbinett, a heatset nylon net.

I did some experimentation with it, and I really liked how it behaves, both as a support fabric and as an overlay to protect fragile areas-it drapes well and can be toned easily with dyes or paint. After feeling satisfied with the results of some of my tests, I set out to repair the damaged linen over the falcon’s feet.

I started by toning the bobbinett with Golden acrylic paint. Then I backed the fabric that was dangling off the back of the foot with the toned bobbinett lightly coated with 10% methylcellulose in water. I then used the bobbinett support fabric to raise the partially detached fabric up into place, secured temporarily with pins.

After positioning the linen, I covered the entire back of the foot area with another piece of toned nylon bobbinett.

The back of the foot area with an overlay of the toned nylon bobbinett, after treatment

Finally, I tacked down the strip of linen over the top of the feet, which was also partially detached but otherwise fairly stable, using small beads of methylcellulose. Reattaching the linen over this area also hid the edge of the nylon bobbinett overlay.

View of the front of the foot wrappings, after treatment

I’m pleased with the results, and I can now breathe a sigh of relief that we’re not going to lose any more of the linen from this area. My next task will be to address the falcon’s partially detached head/neck area. Hang in there, little guy!

A sticky issue: choosing a consolidant for our painted coffin

Posted on February 9, 2013 by mollygleeson

In a previous post, I described some of the issues we’re facing in the treatment of our painted coffin of Tawahibre.

The top of the coffin before treatment – note the large losses and areas where the paint and gesso are just barely hanging on by a (plant fiber) thread

We’ve managed to clean much of the painted surface, but there are many areas of the paint and gesso that are so fragile, you get the feeling that a deep exhale – not to mention a sneeze – would send fragments flying. (And when I say gesso, I’m referring to the calcium carbonate preparatory layer/ground, which has plant fiber inclusions, that I’d like to investigate further).

Such areas require consolidation. We use this word, consolidation, a lot in conservation, and many of our treatments involve this process. Consolidation is essentially the reunification/reinforcement of a weak or powdery substance through the application of a material that we refer to as a consolidant. Consolidants often consist of dilute adhesive solutions, and they may be applied directly to artifacts with a brush or syringe, by spraying onto the surface, and in some instances, it may be appropriate to immerse an artifact in a consolidant solution. Ideally, a good consolidant must be stable (good aging properties), reversible (can be removed if necessary), and should not change the appearance of the artifact.

We have mixed up a variety of consolidant solutions to have on hand in the Artifact Lab – here are a few, along with some brushes, a plastic pipette, and syringes

Choosing an appropriate consolidant requires testing ahead of time. To start, it is important to test a variety of solvents (such as water, acetone, ethanol) – knowing which solvents can be used safely on a particular artifact will likely narrow down the range of adhesives that can be used (due to the fact that many adhesives are only soluble in a select number of solvents). In the case of our painted coffin, this involved testing all of the colors of the painted surface as well as the gesso substrate. Testing was carried out by rolling a swab dampened with each solvent over a discreet area and then observing the area for changes.

Solvent testing on an area of blue paint

After carrying out these tests, I did some research into what other conservators have used successfully for similar treatments on similar artifacts. In our field, we are fortunate to have a good body of published literature, and there is increasingly more information that can be found on the web as well. The sources I referred to included articles in the Journal of the American Institute for Conservation (JAIC), and a variety of books that have been published on the subject of conservation of Egyptian collections. Websites/blogs that I have found really useful include Inside the Conservator’s Art: A behind-the-scenes look at conserving Egyptian artifacts at the Phoebe A. Hearst Museum of Anthropology, conservator’s entries on the Brooklyn Museum blog, and the British Museum’s online collections database, which has many records with detailed conservation treatment information. There are actually lots of great blogs and websites out there, and I am grateful to my colleagues for actively sharing information in this way.

After this work, I selected several consolidants, and conducted another round of testing. During my testing I discovered that water was the key to getting the paint and the gesso to relax. Unfortunately, the painted surface is sensitive to water, but I found that a 50:50 mixture of water and ethanol is acceptable for use, especially when applied in a solution behind the lifting paint. In the end, we’ve chosen to consolidate the very fragile paint with a solution of methyl cellulose (a water-soluble cellulose ether) in a 50:50 water/ethanol mixture. To re-adhere larger flakes and chunks of gesso, we are experimenting using higher concentrations of methyl cellulose alone, and in combination with other adhesives, including Lascaux, a water-based acrylic resin.

An area near the foot of the coffin, before (left) and after (right) readhering detached gesso and consolidating paint

As I’ve stated before, this will be an ongoing project in the Artifact Lab – we will continue to report on our treatment progress, and any interesting discoveries made along the way (which is inevitable!).

Don’t just DO SOMETHING, SIT THERE!

Posted on February 3, 2013 by artifactlab

Artifact Lab Conservator Molly Gleeson, just sitting there (with laptop)

by Lynn Grant
Last month, Artifact Lab Conservator Molly Gleeson was talking about her experiences being the public face (and hands, and body) of Conservation at the Penn Museum to PACA, a group of Philadelphia Area conservators. She said that one of the occasionally difficult things about work in the ‘fishbowl’ is that visitors expect to see her “doing something” (ie., interacting directly with the mummies or other artifacts in the lab) and she worries about disappointing them when she’s just sitting at the computer or thinking quietly. I’ve noticed the same thing on my stints in the Artifact Lab (although Molly is the Main Attraction, the other Penn Museum conservators all spend time in the lab when Molly’s off).

But In the Artifact Lab: Conserving Egyptian Mummies isn’t meant as performance art; we want to give our visitors a real look at how conservation happens and that includes the fact that we don’t spend 100% of our time actually laying hands on ancient artifacts. Before a conservator does touch any object she’s working on, she’ll spend a lot of time:
• Examining the object carefully to see how is was made, how it was used, what’s happened to it over time, what needs fixing and (as importantly) what doesn’t.
• Writing up her findings. Conservators document everything we see, think, or do with regards to an object. This is essential for various reasons: other researchers may be interested in our observations; if the treatment doesn’t go as planned, knowing what was done will make it possible to undo; if the treatment is a success, knowing what was done makes it possible to apply the same knowledge to other objects. I often find that this process really helps clarify treatment issues in my own mind.
• Researching the artifact’s past and conservation research and treatments on other, similar artifacts. If you look at the books, blue binders in the seating corner of the Artifact Lab space or at some of these sites shown on the right sidebar, you’ll see examples of the kinds of resources we use every day. The Internet is a wonderful tool, as well. There are many online resources for conservators, especially a series of discussion groups where conservators all over the world pool their information about materials, treatment options, experience, etc.

And the ‘sitting time’ doesn’t end there. With a whole host of options for treatment at her fingertips, the conservators needs to spend time just thinking through all the possible results and repercussions of her active treatments. Many of the treatments carried out by conservators are not that difficult or complex (rolling a cotton swab across a surface isn’t rocket science) but the decision-making process behind choosing the treatment is why we need to spend years preparing to get into conservation training, years in that training, and continuing to learn every day of our working lives.

Conservators Julie Lawson (left) and Nina Owczarek, with intern Naomi Shohami (foreground) consulting over a laptop in the Artifact Lab.

So
• if you see the Artifact Lab conservator at the computer, she is probably still doing conservation. She could be: documenting her work; consulting other experts; researching web resources; writing a blog post(!); or even answering a question on our blog. Got a question? Post it here.
• If you see her talking to someone, she is probably still doing conservation. She could be: seeking advice or information from a colleague; teaching an intern; communicating a cool new finding; or asking them to contribute a blog post.
• If you see her just sitting or standing looking into thin air, she is probably still doing conservation. She could be: thinking about treatment options; deciding to consult a resource; considering the results of a recent treatment; or planning a blog post.

Of course, she could also be checking her Facebook page; calling a friend; making plans for lunch; or even just taking a rest because conservators are real people too and, even in the Artifact Lab, no-one is ‘on’ 100% of the time!