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Posters

  1. The Conservation Treatment of Robert Rauschenberg’s Untitled (Venetian), 1973
    Christine Frohnert, Cranmer Art Group; and Julia Sybalsky, Masters Candidate, New York University, Institute of Fine Arts, Conservation Center
  2. The conservation of Robert Rauschenberg’s Untitled (Venetian) from 1973 necessitated an innovative approach due to the fragile condition of its non-traditional media. The artwork consists of a weathered tree branch, four cardboard boxes, and a lace curtain. The cardboard boxes are pierced by the branch, and the four elements maintain their relative positions by means of their physical engagement without the use of hardware or adhesive. Over time, gravity and mechanical action involved in the installation and exhibition ofUntitled (Venetian) have enlarged the holes in the cardboard so that the boxes no longer support themselves in their original positions on the branch.

    This poster describes how the worn and/or torn holes and disconnected parts of the cardboard boxes were consolidated, stabilized, repaired, and reinforced by inserting inert, lightweight, resin fiber rods (Garolite 11, a phenolic resin, and nylon) into the internal channels of the corrugated cardboard. Where necessary, losses and gaps in the cardboard were filled and toned with toasted cellulose fibers and colored pencils. In addition, armatures were individually fabricated to fit inside of each box, securing it to the branch. Their correct location and orientation were re-established according to archival photography provided by the artist’s estate. Each armature was fabricated from rigid Alucobond (pre-finished aluminum-polyethylene composite panel) attached to an adjustable band that clamps around the branch. It was padded with Volara foam and covered with brown paper to imitate the appearance of the boxes.

    The treatment was designed to meet the goal of using a non-invasive, completely reversible approach that prioritizes the integrity of the work with the highest respect.

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  3. Order From Chaos: Analyzing Quantitative Hyperspectral Imaging Data of Historical Documents
    M.E. Klein, B.J. Aalderink, Art Innovation BV, Oldenzaal, The Netherlands; R. Padoan, G. de Bruin, and Th. A.G. Steemers, 
    Nationaal Archief, The Hague, The Netherlands

    Quantitative hyperspectral imaging (QHSI) is a non-destructive optical technique that provides accurate spectral measurements with high spatial resolution from virtually any surface. The high reproducibility of the calibrated measurements makes the QHSI technique also ideally suited for comparing different objects. By taking repeated measurements of the same object it can be used to detect changes, such as those caused by aging or conservation treatment.

    The Nationaal Archief (National Archives of the Netherlands, The Hague) in cooperation with Art Innovation has been investigating the potential of QHSI for the analysis of archival documents. This poster discusses the workflows and processing techniques developed to enable an efficient analysis of the huge amount of data provided by hyperspectral measurements.

    The SEPIA QHSI system in use at the Nationaal Archief measures 4 million calibrated spectral reflectance curves using 70 wavelength bands, in the 365-1100 nm range, covering a document area of 125 × 125 mm (5 × 5 in.). By covering this significant portion of the electromagnetic spectrum, from the near-ultraviolet to the near-infrared, it is possible to reveal features invisible to the naked eye, such as underdrawings, erased inscriptions, and media differences. The recorded reflectance curves are stored as pixel values in 70 grayscale images. Each image contains the reflectance of a document area at the corresponding wavelength band. This set of grayscale images creates what is known as the hyperspectral data cube of a QHSI measurement, which is over half a gigabyte of data.

    The different data processing steps of the analysis workflows can make use of both the image and the spectral aspect of the hyperspectral data cube to extract and visualize the required information. For example, the readability of a palimpsest may be improved considerably by simply selecting a suitable near-UV or near-infrared spectral image. However, spectral data processing is typically required to achieve maximum readability or to map and quantify the amount of spectral changes such as discoloration of substrates and media caused by aging process.

    For many applications it is important to distinguish among different classes of areas on the measured document (for example, to differentiate between media or to detect spectral variations caused by previous restoration). In order to generate a map from a hyperspectral data cube illustrating the locations of two different media, several analysis steps are required. During some analyses, it was found that applying a principal component analysis (PCA) to the spectral measurement data is a very effective first step in a workflow of vector calculus. The PCA method exploits statistical correlations within the hyperspectral data cube to condense all significant information into a much smaller set of images. Subsequent analysis steps, such as the comparison of the spectral features of different media and mapping of their distributions on the document, can then be carried out on this reduced image set. This speeds up the data processing considerably without sacrificing the accuracy or objectivity of the QHSI technique.

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  4. Replicating Missing “Lanthorn” Panes: Another Use for the Versatile Melinex®
    Ellen Promise, graduate fellow Winterthur/University of Delaware Program in Art Conservation; and Bruno Pouliot, Winterthur Museum Objects Conservator and University of Delaware Adjunct Assistant Professor

    For centuries before the mid 19th century, window-panes in lanterns were commonly made of horn. Though it transmitted less light than glass, horn was durable, abundant and much less expensive. To achieve the desired level of translucency, panes were crafted from light colored horns and most often obtained from flattened sheets of horn that were delaminated into two or more layers after prolonged soaking in water. This process resulted in considerable variation in thickness, direction of grain and tint amongst different horn panes.

    Horn-paned lanterns that have survived in museum or private collections often have one or more damaged or missing windows. For a conservator, replacing these panes with true horn is usually not practical, as it is difficult to obtain or process horn in the traditional way of the hornsmith. The use of real horn may also be undesirable, as it does not create a clear distinction with original panes, or because other components of the lantern may be too damaged to accommodate an entirely new and strong horn pane. Therefore an adaptable method for mimicking horn panes becomes a great tool for conservators.

    A method for imitating horn panes was initially devised in 2003 by Bruno Pouliot and employed on a lantern missing all three of its original panes. This method was then used by graduate fellow Ellen Promise in the fall of 2010 on a different lantern to create one pane in imitation of two horn windows that remained in place. The technique was used to great effect in two different scenarios, demonstrating that it is controllable and can be adjusted to fit individual treatment goals and imitate horn of different thicknesses.

    The approach utilizes Mylar and a 1:1 solution of Agateen Lacquer #27: Thinner #5 which has been appropriately tinted using Orasol dyes and acrylic paints. To match the grain of horn and increase opacity, the Mylar is sanded using fine grit sandpaper and micromesh. After the initial coloration has been applied to the Mylar with brush coats of tinted Agateen, further adjustments can be made using acrylic paints. The Mylar panes can be distressed to imitate aged horn by creating bends or making strategic cuts with a scalpel blade. The method is easily accomplished, and the panes can be quickly inserted without any stress to the original lanterns, while being barely distinguishable from real horn panes.

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  5. An Investigation of a Curious Discoloration on Exhibit Case Fabric
    Carmen E. Hazim, Student Intern and Renee A. Stein, Conservator, M.C. Carlos Museum, Emory University

    A curious discoloration was observed on the fabric beneath individual ceramic objects displayed in the Greek and Roman galleries at the Michael C. Carlos Museum of Emory University in Atlanta, Georgia. The discoloration was first noted several years ago when certain shards were repositioned, revealing the pinkish orange spots beneath points of contact with the case fabric. This discoloration was not seen beneath all ceramics, and the objects associated with discolored areas did not share ancient provenance or recent collection history. Treatment of the ceramics before they entered the Carlos Museum collection seemed a probable cause for the discoloration, but treatment records were not available. Spot tests with several cleaning agents used in recent decades by collectors, archaeologists, dealers, restorers, and conservators indicated that a similar discoloration of the fabric could be produced with hydrochloric acid. This preliminary observation suggested that the discoloration was due to the presence of residual chloride ions from prior treatment with hydrochloric acid. An ancient shard associated with the discolored case fabric was soaked in distilled water, and the bath tested positive for chloride ions through a reaction with silver nitrate. In an effort to replicate the discoloration, samples of case fabric were also exposed at elevated temperature and relative humidity to volatile hydrochloric acid from solvent solutions and from fragments of treated ceramics. This experimental design was modeled upon a version of the Oddy Test. This series of tests illustrates that hydrochloric acid used in treatment may not be completely removed from porous substrates. It is not known whether the previously treated ceramic shards were rinsed, as is often described in procedural descriptions, or if the cleaning agent was expected to volatilize, as is sometimes suggested. Exhibition and storage materials such as fabric, wood, carpet, paint, and plastic are routinely tested for the threat they may pose toward objects, yet in this example it is the collection objects themselves that provide a source for potentially damaging compounds.

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