UCLA/Getty Conservation Program

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


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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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RTI Rock Art Documentation at LA County Parks & Rec

Last Monday, we joined Ansley Davies, Associate Curator for the LA County Department of Parks & Recreation, at a local rock art site with both painted and carved elements in order to carry out a photographic technique called reflective transformation imaging (RTI). The rock art elements are at risk of vanishing because they were painted on and inscribed into massive sandstone rocks, the surface of which is easily destroyed by particles carried by wind, rainfall, movement by animals, and lichens, which are growths on rock made up in part by algae and part by fungus. Vandalism by visitors also places the rock art at risk. The goal of the project then was to start creating a photographic record of each of the elements so that the information carried by the elements can be preserved and interpreted by archaeologists for years to come, even if the physical paintings and drawings cannot be preserved. Joining us for the project to learn the technique were Sarah Brewer, a local archaeologist who grew up in the area, and Jairo Avila, a graduate student studying archaeology at Cal State Northridge who plans to write his thesis on the paints used on rock art sites in Southern California.

Developed by Cultural Heritage Imaging (CHI), RTI is a way to create a digital image of a flat surface that when processed with special computer software, allows the texture of the surface to be examined using a moveable virtual light source. Special filters can also be used to emphasize the surface features, as well. Students in our class learned how to set up the camera and special equipment to capture images in the fall of 2011, when the staff of CHI taught a workshop at the Getty Villa.

The set-up involves placing a camera on a stable tripod in a position allowing the desired image to be framed and in focus. Two small, black, shiny reflective balls are also placed in the image, attached to long sticks that are held steady by tripods. A series of 24 – 72 images are taken with a bright light source such as a portable flash in a different location each time, while the camera stays in the same position. Afterwards, the images are fed into a computer program that recognizes the location of the highlight on the shiny black balls from the flash. It uses the information to calculate the direction and distance of the light from the object in each image, adding them together to make a single image (without the balls). When the image is viewed on a computer, the viewer can use a mouse to move a virtual light source, showing the highlights and shadows of the surface from different angles. This technique is especially good for documenting rock carvings that might not be easily visible with normal lighting.

We had never carried out RTI in an outdoor setting before, and were met with some challenges. The first was hiking with all the equipment out to the site! Another issue was the brightness of the mid-day sun, which can sometimes cause problems with trying to use another light to create shadows. This wasn’t as much of a problem as we expected though, because the rock face happened to be in shadow itself, allowing the flash to do its job. We made up for the extra light by taking the images with slightly shorter exposure times. Another problem was that we did not have enough tripods. We solved this problem by picking up some dried yucca stalks lying on the ground, mounting the balls on the ends with plastic ties, and propping them up with our backpacks and small rocks lying on the ground nearby! We were quite proud of this innovation.

It was a beautiful day to be out in the park admiring the rock art, and we can’t wait to go back!

Image

Brittany Dolph (’14) and Geneva Griswold (’14)


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The UCLA/Getty Program goes “C.S.I.”: The use of a forensic light source for the examination and documentation of archaeological evidence

Conservators are always looking for new techniques that will aid in the examination and documentation of art. The UCLA/Getty Program purchased a forensic light source, the Mini CrimeScope (from Horiba Scientific), to investigate its application in conservation. The CrimeScope is an alternate light source used by crime scene investigators to look for blood stains, latent fingerprints or any other forensic evidence they could utilize for solving crimes. The wavelength of the emitted light in the CrimeScope is controlled by filter wheels that allow material to be examined from ultraviolet to infrared. Instead of solving crimes, students in the conservation program have been using it to solve archaeological mysteries through the study of ancient and ethnographic objects. Artifacts analyzed include pre-Columbian ceramics and polychrome African wooden masks. They have been using the light source to look for evidence to answer questions about materials, technology and manufacture of artifacts, areas of deterioration and signs of previous conservation interventions. Our CrimeScope has also been used by colleagues at the J. Paul Getty Museum to look at the faint remains of a drawing on a white ground lekythos.

The CrimeScope is being employed to compliment other techniques of analysis and provide a first screening during the examination of materials. With the use of a forensic camera and a series of different camera filters the students have also been able to record the fluorescence and luminescence of materials and to see beneath their surface. The results are remarkable and we are currently exploring other potential applications of our CrimeScope to investigate and document different archaeological and ethnographic treasures.

The image above shows how the CrimeScope helped to highlight the decoration on a pre-Columbian vessel that was not as evident when viewed in visible light (left image) or ultraviolet (UV) light (central image). When examined in visible light, the decoration on the vessel is faint and obscured by burial deposits. Examination using a UV light at λexc max=365nm allowed for the decoration to be more visible. However, using the CrimeScope with a filter at λexc max=415nm the decoration was more distinctive and stood out. In particular the "S" shaped design on the upper left side of the vessel, which is slightly visible in the central image under UV, is much clearer in the image taken using the CrimeScope. (Vessel image courtesy of the Fowler Museum at UCLA. Photo taken by A. North, 1st year conservation student)


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Royce Hall Mural Documentation Project

During the first quarter of the first year, the UCLA/Getty Conservation Program offers a course on documentation and imaging techniques used for art, archaeology and conservation. In the class, students are introduced to a range of techniques used to document objects and sites and are given a project where they can put what they have learned in the lectures into practice. This year one of the projects focused on documenting the condition of a mural painting located on a building on UCLA’s campus. Three students had the opportunity to examine and document the condition of a section of a mural on the ceiling of the eastern cloister of Royce Hall, one of the four original buildings on the campus. Using various photographic and recording techniques, the students were able to provide a condition assessment of a small section of the murals in this part of the building. In addition to learning how to apply the techniques they learned and become aware of their advantages and limitations, the students were able to provide some information to those responsible for the building on the condition of the mural and issues that may need to be addressed to ensure the preservation of the decorated surfaces.

The presentation below was prepared by the students working on this project and provides a brief summary of the techniques they used for documenting the murals and their results.