UCLA/Getty Conservation Program

A graduate conservation training program focusing on the conservation of archaeological and ethnographic materials


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“Animal, Vegetable, Mineral?” – Identifying mystery fibers in the field

When conservators are working on archaeological excavations, their work often encompasses many different aspects of field conservation.  This can include materials identification and characterization, lifting fragile artifacts and aiding in archaeological research.  No matter what facet of the project they are involved in, the work can be challenging without the comforts of a well-stocked lab and requires lots of problem solving and improvisation.  Last summer while working on the Ancient Methone Archaeological Project, we were faced with the challenge of trying to identify an unusual looking fibrous material which required us to MacGyver a transmitted light microscope to aid in the examination and identification of the mystery fibers.

During the 2014 season, a team of geomorphologists working on the project were taking core samples in an area thought to be an ancient harbor.  In one of the cores, they pulled out a clump of fibers they thought might be cordage (fig. 1).  They brought the samples to the conservation lab to see if we could identify the fibers and determine if it was cordage or the remnants of woven fibers. Some samples were set aside for radiocarbon dating and the remainder of the sample, which was still bound in sediment, was examined.

Figure 1. Clump of fibers found in soil core by Geomorph team. Photo: Ancient Methone Archaeological Project

Figure 1. Clump of fibers found in a core sample taken by the Geomorphology team. Photo: Ancient Methone Archaeological Project

The initial macroscopic examination revealed that the fibers appeared translucent (fig. 2).  They seemed to be grouped into bundles and some of these bundles initially appeared to cross each other, giving the impression of a woven structure.

Fgiure 2. Detail of the fibers encased in the sediment.  The fibers are translucent and are grouped in bundles.  Photo: Ancient Methone Archaeological Project

Fgiure 2. Detail of the fibers encased in the sediment. The fibers are translucent and are grouped in bundles. Photo: Ancient Methone Archaeological Project

The fibrous material was encased in a gray, silty sediment, which appeared to include quartz, foliated phyllosilicates/sheet silicates (like mica, vermiculite, etc.) (fig. 3), as well as small shells, both fragmented and whole (fig. 4). The sample was initially wet, and was allowed to slowly dry out in the lab. The sediment was gently pushed away using a pin-vise under binocular magnification, to better define the structures and reveal diagnostic features of the material for its identification (fig. 5).  Photographs of the fibers were taken using the DinoLite USB microscope (7013MZT Series). During this examination and initial cleaning, the fibers were found to be very brittle.  Though they appeared to be in bundles, they were not actually bound to each other and could be easily separated.

Figure 3.  During cleaning, plate-like inclusions were found in the soil and between the fiber bundles.  These inclusions resembled sheet silicates like mica. Photo: Ancient Methone Archaeological Project

Figure 3. During cleaning, plate-like inclusions were found in the soil and between the fiber bundles. These inclusions resembled sheet silicates like mica. Photo: Ancient Methone Archaeological Project

Figure 4.  Small shells or shell fragments were also found in the deposit. Photo: Ancient Methone Archaeological Project

Figure 4. Small shells or shell fragments were also found in the deposit. Photo: Ancient Methone Archaeological Project

Figure 5.  After some initial cleaning to remove soil, more of the fiber bundles and associated materials are visible. Photo: Ancient Methone Archaeological Project

Figure 5. After some initial cleaning to remove soil, more of the fiber bundles and associated materials are visible. Photo: Ancient Methone Archaeological Project

Though examination with a stereomicroscope helped to reveal more about the fibers and the structure of the bundles, we were not able to clearly identify what the fibers were.  We felt that examination using transmitted light microscopy would be the most helpful since it could highlight any morphological features in the fiber that could aid in identification.  So we set out to make one armed with our DinoLite microscope and a flashlight. The set up turned out to be quite simple. We just needed to be able to shine a light through the fibers from below and examine the fibers at a high magnification using the DinoLite (fig. 6). We took a fiber bundle from the sediment and placed it on a multi-bulb LED flashlight (fig. 7).  This flashlight was flat and rectangular and the ideal shape for our light source since the fiber samples could be directly placed on the top surface of the flashlight.  The fact that the flashlight was flat also meant it was easy to position the light source under the microscope where needed (fig. 8).

Figure 6.  We created a transmittled light microscope using the DinoLite USB microscope and an LED flashlight which acted as the transmitted light source. Photo: Ancient Methone Archaeological Project

Figure 6. We created a transmittled light microscope using the DinoLite USB microscope and an LED flashlight which acted as the transmitted light source. Photo: Ancient Methone Archaeological Project

Figure 7. We placed samples of the fibers directly onto the flashlight during examination. Photo: Ancient Methone Archaeological Project

Figure 7. We placed samples of the fibers directly onto the flashlight during examination. Photo: Ancient Methone Archaeological Project

Figure 8.  Using our transmitted light  microscope to examine the fibers.  Macguyver would be proud. Photo: Ancient Methone Archaeological Project

Figure 8. Using our transmitted light microscope to examine the fibers. Macgyver would be proud! Photo: Ancient Methone Archaeological Project

Looking at the fibers in transmitted light, we observed a central void within some of the fibers.  Since we were considering the possibility of the fibers being organic in nature, we thought these central voids could be the medulla or lumen of an organic fiber (fig. 9). However, no other morphological features were present that helped us determine at this point what the fibers were.

Figure 9. Looking at the fibers under transmitted light, we could see they had a central void, which initially made us think this was the lumen of a plant fiber or medulla of an animal fiber. Photo: Ancient Methone Archaeological Project

Figure 9. Looking at the fibers under transmitted light, we could see they had a central void, which initially made us think this was the lumen of a plant fiber or medulla of an animal fiber. Photo: Ancient Methone Archaeological Project

We were also able to take a look at the cross-section of the fibers with the addition of a polarizing lens on the DinoLite (fig 10). Some fibers appeared hexagonal in section (fig. 11).  Some of the ends of the fibers ended in a point or were triangular in shape.

Figure 9.  With the addition of a polarizing lens on the DinoLite we were able to see the cross-sections of some of the fibers.  Some appeared hexagonal or triangular in section. Photo: Ancient Methone Archaeological Project

Figure 9. With the addition of a polarizing lens on the DinoLite we were able to see the cross-sections of some of the fibers. Some appeared hexagonal or triangular in section. Photo: Ancient Methone Archaeological Project

Figure 11.  Details of the fibers showing their shape in section.  Photo: Ancient Methone Archaeological Project

Figure 11. Details of the fibers showing their shape in section. Photo: Ancient Methone Archaeological Project

Further cleaning revealed a tiered growth structure that resembled the growth of minerals more than plant or animal fiber bundles (fig. 12).  The inclusion of sheet silicates in relation to the fibers, either located between bundles or within them further suggested these fibers were mineral.  In searching the literature we came across images of asbestos minerals which looked similar to our mystery fibers.  Several types of asbestos minerals are fibrous in appearance (fig. 13), and can occur near phyllosilicate deposits.  Armed with this information we concluded that the fibers were definitely mineral in nature and could possibly be asbestos.

Figure 12.  Fiber bundle after cleaning. Photo: Ancient Methone Archaeological Project

Figure 12. Fiber bundle after cleaning. Photo: Ancient Methone Archaeological Project

Figure 13. An image of crocidolite, a fibrous form of the mineral riebeckite, and one of the 6 recognized forms of asebstos minerals.  © Raimond Spekking / , via Wikimedia Commons https://upload.wikimedia.org/wikipedia/commons/b/b3/Krokydolith_-_Mineralogisches_Museum_Bonn_%287385%29.jpg

Figure 13. An image of crocidolite, a fibrous form of the mineral riebeckite, and one of the 6 recognized forms of asebstos minerals. © Raimond Spekking / , via Wikimedia Commons https://upload.wikimedia.org/wikipedia/commons/b/b3/Krokydolith_-_Mineralogisches_Museum_Bonn_%287385%29.jpg

Luckily we were able to bring a sample of the fibers back with us and conduct some analysis in the UCLA/Getty Conservation labs. And we were quite surprised by the results!  It turns out we were correct in deducing the fibers were mineral in nature, but we were incorrect about which mineral. XRF and XRD analysis did not find any asbestos minerals in the sample, but instead the fibers were identified as calcite (fig. 14).  Though we had never seen calcite that was fibrous in appearance, it is one of the mineral’s crystal forms. An example is shown in fig. 15 where you can see the SEM image of “lublinite”, a needle-type of calcite whose form is thought to be associated with the activity of microorganisms.

Figure 14. XRD analysis results showing the fibers were composed of calcite.

Figure 14. XRD analysis results showing the fibers were composed of calcite.

Figure 15. SEM image of lublinite, the fibrous form of calcite.  Image taken from: http://www.speleonics.com.au/jills/bymineral/lublinite.html

Figure 15. SEM image of lublinite, the fibrous form of calcite. Image taken from: http://www.speleonics.com.au/jills/bymineral/lublinite.html

Even though we were not able to identify the fibers as calcite in the field, the use of a stereomicroscope and our makeshift transmitted light microscope certainly helped distinguish their mineral nature and rule out plant or animal origins.  And now that we’ve figured out how to make a transmitted light microscope and tested it out, we’re ready for any future material ID questions that would require one.

MacGyver looks on and smiles at our ingenuity.  Photo: http://macgyver.wikia.com/wiki/List_of_problems_solved_by_MacGyver

MacGyver looks on and smiles at our ingenuity. Photo: http://macgyver.wikia.com/wiki/List_of_problems_solved_by_MacGyver

Written by the 2014 Ancient Methone Archaeological Project Conservation Team: Heather White (UCLA/Getty Program Grad Student, Class of ’16), Vanessa Muros (Conservation Specialist/Lecturer, UCLA/Getty Program) and Anna Weiss (Campus Art/Artifact Collections Coordinator, Conservator, Univ. of Chicago)


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Class of 2016 Summer & 3rd Year Internships

The quarter is coming to an end and students are busy finishing up treatments and thesis projects, as well as writing papers and studying for finals. On top of all that, they’re busy getting ready to leave LA for their summer and 3rd year internships. Below is a list of all the great places they’ll be working at in the upcoming year.

We wish them good luck on their internships and safe travels!


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RTI of Etruscan Bucchero Fragments at Poggio Colla

My first summer internship with the Mugello Valley Archaeological Project (MVAP) at Poggio Colla has wrapped up, and it was an incredible season with exceptional finds! Under the guidance of head conservator, Allison Lewis—a UCLA/Getty alum (‘08 )—and with the sponsorship of The Etruscan Foundation’s 2014 Conservation Fellowship, I was afforded the amazing opportunity to participate in this project, which has been underway for the last several decades. MVAP has significantly contributed to the study of ancient Etruria with their work at Poggio Colla, the site of a hilltop settlement and sanctuary that spanned the 7th-2nd centuries B.C.E.

A particularly groundbreaking find happened in 2011, when a student participating in the MVAP field school found a stamped bucchero fragment that appears to depict a woman in the midst of childbirth. This imagery is the earliest documented in Italy and nearly unparalleled in the ancient Mediterranean, however study of the finely recessed scene is difficult due to its small size and worn nature. It takes just the right angle of raking light to highlight the surfaces and make the scene legible (Fig. 1), which is often the case with these stamped and incised bucchero vessel fragments.

Fig.1. The birthing stamp (inv. PC 11-003), found on a bucchero fragment, measures just around a centimeter in height and is worn, requiring magnification and raking light to study its imagery. [Photos courtesy of Dr. Phil Perkins, The Open University].

Fig.1. The birthing stamp (inv. PC 11-003), found on a bucchero fragment, measures just around a centimeter in height and is worn, requiring magnification and raking light to study its imagery. [Photos courtesy of Dr. Phil Perkins, The Open University].

As an 2014 Etruscan Foundation Conservation Fellow, I proposed a special project to the Foundation involving the documentation of bucchero fragments using Reflectance Transformation Imaging (RTI), which Allison has wanted to test at Poggio Colla for several field seasons. This technique, created by Cultural Heritage Imaging (CHI), involves a low-cost, easy photographic set-up that can be macgyvered in the field with fairly basic supplies (Fig. 2). RTI essentially blends a series of photos of an object under different angles of light to create an interactive file (a polynomial texture map) that one then explores using a “virtual torch” in various rendering modes. In other words, instead of researchers straining their eyes and handling the object in different raking light or studying static images, they can explore the features and subtle details of the object’s surface in a single, high-resolution image with an adjustable light source that they can control.

Fig. 2. We were able to disassemble a standard desk lamp to become our movable light source, much to our excitement! This imaging technique was affectionately called “A Thousand Points of Light” amongst the staff, and it was pointed out that it’s quite a ritualistic process (appropriate for the sanctuary site) as we huddle on the floor around an ancient artifact with a single torch lighting us.

Fig. 2. We were able to disassemble a standard desk lamp to become our movable light source, much to our excitement! This imaging technique was affectionately called “A Thousand Points of Light” amongst the staff, and it was pointed out that it’s quite a ritualistic process (appropriate for the sanctuary site) as we huddle on the floor around an ancient artifact with a single torch lighting us.

Our set-up was simple. We picked a relatively closed-off room adjacent to the field conservation lab where we could have good control over ambient light; as you can see, it doesn’t have to be a special room-nor a room at all if you’re on-site! We used the lab’s point-and-shoot Canon G10 digital camera with a remote so as not to shake the camera when capturing the images, a copy stand, a disassembled desk lamp that we tethered to a string, and small, black reflectance spheres purchased by the conservator prior to the season (Fig. 2).

The black spheres are required in the frame near the object, in order to reflect the location of the light source for the software during image processing (Fig. 3). Any black, reflective sphere can be used; Allison purchased 1/4” and 7/16” silicon nitride (Si3N4) ceramic balls used for ball bearings (Boca Bearing Company), which we mounted in frame with Benchmark wax, at times stuck to bamboo skewers to be held level with the object’s surface. The string tied to the lamp was measured to roughly 4x the diameter of our object, becoming the fixed radius at which we moved the light around the object for each photo (Fig. 2).

Fig. 3. Items inserted in frame for image processing or posterity (such as the black spheres, grey scales, or labels) can be cropped out in the final stage of processing in RTIBuilder so that your final product is simply your subject, to be navigated and explored in RTIViewer.

Fig. 3. Items inserted in frame for image processing or posterity (such as the black spheres, grey scales, or labels) can be cropped out in the final stage of processing in RTIBuilder so that your final product is simply your subject, to be navigated and explored in RTIViewer.

Keeping the camera in a stationary position with our object and black spheres in focus, we proceeded to take around eighty images per object, with each object taking roughly fifteen minutes to shoot; one person snapped the photo while the other moved the light. We continued taking photos until we felt we covered a full “umbrella” of light around the object in our series of images.

The photos were then processed using the RTI software (RTIBuilder), which is available for free on CHI’s website, along with RTIViewer for navigating the final product. RTIBuilder can be finicky and particular, especially in naming files. No spaces, hashtags or other similar characters are acceptable in file names. We also found that the program did not recognize capitalized file extensions (for example not .JPEG files, only .jpeg) so if you can’t control which file type you’re capturing in on your camera, you’ll need a computer with Photoshop or an equivalent image processing software that can convert them. For optimal quality, CHI recommends capturing images in RAW and then converting to jpegs (RTIBuilder can only process jpeg files). Processing items inserted in frame (black spheres, gray scale, label, etc.) can be cropped out at the end before the images are converted into the single digital file, which can be interactively viewed by anyone who has downloaded the free RTIViewer (Figs. 3-5).

Fig. 4. When you open RTIViewer, you have several options at your disposal: you can control your light source; you can zoom in and out on your subject and move around over its surface; you can take a snapshot of your field of view (which saves as a .jpg and XMP file); and you can play with a diverse range of rendering modes available in the dropdown menu.

Fig. 4. When you open RTIViewer, you have several options at your disposal: you can control your light source; you can zoom in and out on your subject and move around over its surface; you can take a snapshot of your field of view (which saves as a .jpg and XMP file); and you can play with a diverse range of rendering modes available in the dropdown menu.

Fig. 5. The different rendering modes can emphasize or deemphasize particular surface characteristics, and some modes allow you to study the surface without the distraction of surface pigment/colors.

Fig. 5. The different rendering modes can emphasize or deemphasize particular surface characteristics, and some modes allow you to study the surface without the distraction of surface pigment/colors.

As you can see, this imaging technique offers a different, versatile way of studying the morphological and topographic features of an object’s surface, no matter how minute, without the need to access the object itself. Given the various rendering modes available in the RTIViewer, it can be used as a supplementary tool in examining the object, and it can also be offered as an alternative format for researchers wanting to study the piece, limiting unnecessary handling….which we conservators like to hear! We found RTI to be an especially useful field tool for recording and studying worn, stamped bucchero decoration, fabrication related marks on bucchero surfaces, and incised characters on ceramic and stone surfaces (Figs. 6-8). After a great pilot program, the MVAP conservation staff and other project members hope to continue exploring its potential applications at Poggio Colla in future seasons.

Fig. 6. An incised and stamped bucchero sherd (inv. PC 13-075).

Fig. 6. An incised and stamped bucchero sherd (inv. PC 13-075).

Fig. 7. A bucchero sherd (inv. PC 14-062) with reticulate burnishing, nearly invisible under even light (note the ‘Default’ image). Modes like ‘Normal Unsharp Masking’ can reveal the very subtle, recessed burnishing marks, and others like “Diffuse Gain’ can contrast them.

Fig. 7. A bucchero sherd (inv. PC 14-062) with reticulate burnishing, nearly invisible under even light (note the ‘Default’ image). Modes like ‘Normal Unsharp Masking’ can reveal the very subtle, recessed burnishing marks, and others like ‘Diffuse Gain’ can contrast them.

Fig. 8. An inscribed stone base (inv. PC 05-105).

Fig. 8. An inscribed stone base (inv. PC 05-105).

Heather White (’16)


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Class of 2016 Summer Internships

The quarter is coming to end in a few weeks and our 1st year students are all getting ready to head off on their summer internships. “Where are they going?”, you ask. Take a look at the list below and see all the exciting places they’ll be working this summer.

We hope they enjoy their time at their internship sites and we can’t wait to hear about it in the fall!


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Class of 2014’s Summer/3rd Year Placements

It’s finals week and the students are getting ready to head off (or some have already left) for their summer internships and 3rd year placements.  Here’s a list of all the exciting places they’ll be working at:

We wish them lots of success during their internship year and will see everyone again in Spring 2014!


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Summer Internships 2012

The quarter is over and summer begins for the class of 2014. This means that everyone is gearing up to start their summer internships. This summer we have students working in 6 different countries, at museums and archaeological sites.

The summer internship placements  for our 2nd years (congratulations on completing your 1st year!) are listed below. We hope they have an amazing time this summer and we can’t wait to hear about their experiences when they are back in the fall.

tattooing_header


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The Inherent Vice of a Tattooing Instrument

What do you do with an object, purchased as a central part of an exhibition, which is corroding on display? This was the question conservators were faced with at the Pitt Rivers Museum at the University of Oxford (where I have been completing part of my third year internship) when deciding what to do with a tattooing instrument which was exhibiting signs of deterioration while on display.

The tattooing instrument (2001.41.1) was made by a tattoo artist and donated to the Pitt Rivers Museum for its Body Arts display in 2001. Since the object’s installation, it has been displayed along with other components of modern western tattoo application such as different colors of ink in plastic bottles, tracing paper, and needles. A museum guard noticed its corrosion in the winter of 2011 and drew the attention of conservation to it.

The Body Arts display with the tattooing instrument in the upper left corner.

The tattooing instrument consists of the body of the instrument, a needle, and the power cord. There is a coiled wire around the power cord where it attaches to the instrument’s body. This coil had developed loose white needle-like corrosion crystals covering most of its surface.

The object before treatment

Detail of corrosion on tattooing instrument.

The conservators reviewed the object’s condition and decided that it would be best to try and analyze the corrosion that had separated from the tattooing instrument before deciding to remove it because of the central role it played in the display. The loose white powdery corrosion below the object was collected and brought back to the lab. Spot tests for chlorides and carbonates were conducted using the protocols in Odegaard et al. (2005). The corrosion products tested negative for carbonates and positive for chlorides.

A lead spot test was conducted using the Plumbtesmo papers, which produce a pink color in the presence of lead. However, the area around the sample turned orange. A known sample of lead turned the paper a pink color, indicating that the orange result was not due to issues with the test paper but to the sample.

The Plumbtesmo papers with the known lead on the left and the unknown sample on the right

Due to the inconclusive spot tests, the tattooing instrument was removed from display for analysis with XRF. The coil and corrosion products were examined with X-Ray Fluorescence spectroscopy (XRF) (Bruker Tracer III-V). Based on the XRF results, the coil is composed of iron coated with cadmium. The corrosion product, when analyzed on its own, had a strong cadmium peak indicating that it was the cadmium that was corroding. When the exhibition case was opened to remove the object, it smelled strongly of pesticides like dichlorobenzene or naphthalene. There is a possibility that the organic acids from the pesticides or other materials in the case reacted with the cadmium, as discussed by Scott and Derrick (2007).

Portable XRF spectrum showing the presence of cadmium.

Once the corrosion product was identified as cadmium, which is hazardous to our health, we took additional health and safety precautions by wearing particulate masks in addition to gloves and lab coats when handling the object and samples. The corrosion product was removed from the object with a scalpel and brush and kept inside a glass jar for later analysis that might be able to indicate the cause of the corrosion. After removal of the loose white corrosion, the coil had a dull fogged silver-white appearance consistent with cadmium corrosion (Scott and Derrick 2007). The surface of the coil was slightly uneven in sheen and not uniform in appearance.

The object after treatment.

Detail of the coil after treatment.

After deliberation, we decided to place the object back on display even though the exhibition environment may be contributing to its corrosion. The tattooing instrument comprises a central part of the exhibit and was made and donated for the purpose of being displayed in it. These factors were weighed against the fact that the object had taken ten years to develop the corrosion we had just removed and therefore we expect that it will take several more years for the corrosion to return. Its condition will continue to be periodically monitored for the growth of additional corrosion. Now after examination and treatment, the tattooing instrument can be viewed again within the context of various components used for Western tattooing and enjoyed by visitors to the Pitt Rivers Museum.

The tattooing instrument back on display after treatment.

Bibliography
Odegaard, Nancy, Scott Carroll and Werner S. Zimmt. Material Characterization Tests for Objects of Art and Archaeology. London: Archetype Publications Ltd, 2005.

Scott, David A. and Michele R. Derrick. “Deterioration of Cadmium-Coated Instruments in Museum Storage.” Studies in Conservation 52 (2007): 59 – 68.

Robin Ohern (’12)



All text and images on this blog are © Pitt Rivers Museum, University of Oxford. The posting is the opinion of Robin Ohern and doesn’t necessarily reflect the Pitt Rivers’ position, policies or opinions.

http://www.prm.ox.ac.uk/

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