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].

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.

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.

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. 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. 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).

Heather White (’16)

2012 ANAGPIC Conference

Next week we will be heading to New York City to attend this year’s ANAGPIC conference hosted by the Conservation Center of the Institute of Fine Arts, NYU from April 12-14. Here’s a sneak peak at what our 1st and 3rd years will be presenting:

Papers
The ‘dead-bucket’: An inexperienced conservator’s guide for evaluating setbacks
Ayesha Fuentes and Geneva Griswold

Setbacks are an often-unacknowledged reality of conservation practices. This paper examines various types of setbacks, shortcomings, and mistakes in conservation practice, including unsuccessful treatments, errors in judgment, and the limits of intervention. While it may be tempting for a young conservator to anticipate these types of experiences as ‘failures,’ we argue that these situations provide opportunities for growth and development. While a senior professional may readily recognize the value in setbacks and contextualize them by drawing upon their past experiences, we seek to explore the ways in which a less seasoned practitioner may productively reinterpret or reevaluate such situations in terms of our expectations, achievements, and sense of personal responsibility. Categories of setbacks will be illustrated with specific examples from personal experiences and those of our cohort-at-large as pre-program trainees and students.

This project was first inspired by the attempted re-treatment of a ceramic object during the Fall of 2011 at the UCLA/Getty Conservation Training Program. While the objectives of the assigned exercise were unmet — the object was returned to the lending institution in the same condition that it arrived at our training labs— the student learned appreciably about the effects of material degradation, the decision-making process for designating an object as un-treatable, and the ethical considerations such conclusions require. Further examples of setbacks include errors in judgment — such as removing original polychromy by wheeling a tall, wooden sculpture into a low door frame — and a lack of self-awareness with drastic consequences for object safety when a ceramic figure was knocked off a table as a result of fatigue. By reflecting on and discussing the setbacks we encounter as inexperienced conservators, it is possible to glean lessons about our limitations and expectations of conservation practices, and to integrate these into our evolving working methods. Strategies for reevaluating these experiences include viewing them in terms of their positive role in developing long-term goals and practical methodologies as well as promoting a non-punitive and professional culture of honesty, humor, and acceptance. We hope that our attitude will help establish, in the words of Marincola and Maisey (2011), ‘a more fruitful learning culture’ for the benefit of both the field of conservation and its mission to protect and preserve historic and artistic materials.

We hope that by encouraging a collaborative and collective acknowledgement of our limits and, simply put, humanity, will help redefine learning goals for emerging conservation professionals. We believe that fostering an open dialogue amongst our peers, and eventually the conservation community-at-large, will promote a deeper understanding of our methods and the body of wisdom from which we draw as a discipline. Additionally, we would like to promote the idea and organization of an online, perhaps anonymous, forum for practitioners at all stages of their careers to report similar experiences.

 
Unmasking the surface: A technical analysis of eight polychrome Kuba masks
Geneva Griswold and Madeleine Neiman

The Kuba region, positioned in south-central Democratic Republic of Congo, between the Sankuru, Kasai, and Lulua Rivers, is widely renowned for its vibrant masking tradition. Funerals and initiation ceremonies often include a masquerade, honoring the initiate through dance, masks, clothing, and associated accouterments. While the fields of anthropology and art history have devoted significant time and study to the Kuba masquerade traditions, technical analysis of the methods and materials used in the masks’ fabrication is limited. During the fall of 2011, the first year students at the UCLA/Getty Program in collaboration with their colleagues in the Material Science and Archaeology departments conducted a technical study of a suite of eight Kuba masks in the Fowler Museum’s Wellcome Trust collection. Students employed both non-invasive and invasive techniques including: forensic imaging, X-ray fluorescence spectroscopy (XRF), and ultra-violet-visible-near-infrared (UV-Vis-NIR) spectroscopy, optical microscopy under white, plane, and cross-polarized light (PLM), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), and microchemical testing. This paper endeavors to place the information gathered within the larger context of Kuba scholarship, by highlighting the common aspects between the masks as well as their variability. Examination of this collection of Kuba masks contributes to further understanding of the masks’ construction, adaptation, and use, thereby promoting a deeper and fuller understanding of the objects as historic artifacts as well as aid in determining proper methods of handling, storage, display, and conservation.

 
Posters
Treatment of eagle and northern flicker feathers on a Native American shield cover
Tessa de Alarcon

Stabilization of eagle and Northern flicker feathers (Colaptes aurates) was undertaken on a Plains shield cover in the collection of the University of Pennsylvania Museum of Archaeology and Anthropology. Material testing for vane repair and loss compensation was conducted on damaged turkey feathers. Vane repair testing included bridges of hair silk adhered with 5% methyl cellulose as well as linings of light weight Japanese tissue, Hollytex (spunbonded polyester), and silk Crepeline each adhered with 2% methyl cellulose, Lascaux 360, Lascaux 498, or AYAF (polyvinyl acetate resin). Both of the Lascaux adhesives and the AYAF were painted onto the supports and reactivated with heat or solvents. Methyl cellulose performed better than the other adhesives and the hair silk bridges were the least visually intrusive and provided the best support. Loss compensation methods tested included two weights of Japanese tissue (light weight and heavy weight), as well as Hollytex adhered with 2% methyl cellulose. Since methyl cellulose performed better than the other adhesives, it was the only one tested. The lightweight Japanese tissue adhered best in the loss compensation tests. Hair silk and Japanese tissue adhered with methyl cellulose were used on the shield cover feathers with good results.

 
The Significance of Surface in Central African Masks: Pigment Identification of Polychrome Wood masks from the Congo
Geneva Griswold, Casey Mallinckrodt, Brittany Dolph

The treatment of surfaces in African masking traditions reflects the adaptation of materials for cultural ritual and use. This poster presents a study of surfaces using micro-analytic techniques, whose results provoke questions regarding the masks’ methods of manufacture, material adaptation, and provenance. The colors of different chemical composition and microstructure were sampled from a suite of eight polychrome wood masks from the Kuba region of the Democratic Republic of Congo. Dispersion and cross-section samples of the wood and pigments were analyzed using polarized light microscopy (PLM) and scanning electron microscopy (SEM) in order to ascertain their chemistry and composition. PLM enabled direct observation of optical characteristics relating to particle size, habit, relief, and color under plane polarized light, as well as crossed polarized light observation of birefringence and interference colors, when present. Such characteristics successfully identified the pigments applied on each mask, and facilitated the comparison of manufacturing techniques and materials within the suite. As well, PLM and SEM analyses corroborated evidence attained from XRF, XRD, UV/Vis/NIR, and SEM/EDX investigations. This investigation contributes to our understanding of Kuba mask materials and production, as well as highlights the role of microscopy and microanalysis in the study of African masking traditions.

 
Tunable Light Sources and Modified Cameras: Utilizing Imaging Techniques to Better Understand Ancient Art at the J. Paul Getty Museum
Dawn Lohnas

Two relatively new imaging techniques, used by both the UCLA/Getty Conservation Program and the Getty Villa antiquities conservation laboratory, have recently been adopted to assist with the non-invasive analysis and documentation of artifacts. The UCLA/Getty Program utilizes a modified camera with an “alternate light source (ALS)” (Mini-CrimeScope®400), which is traditionally used in forensic science. Providing light at narrow band wavelengths using a series of filters, this equipment allows for easy analysis over a broad spectral range. Faintly painted figural outlines on a recently acquired lekythos in the Getty Villa collection were successfully photographed using this technique, and are now included on the object label in the museum’s galleries, illustrating how the vase once looked in antiquity. In addition to the ALS, scientists, conservators and students at the Getty make use of a modified camera system for capturing Visible-induced infrared luminescence of Egyptian blue. It can be used in-situ to confirm the identification of Egyptian blue without sampling, and has helped to identify areas of restoration, and areas of paint decoration that are difficult if not impossible to identify under normal lighting conditions. Several case studies involving these imaging techniques will be discussed.

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.