AIC's 44th Annual Meeting

In recent years, major advances have been made in the technical documentation of art works and in the way that these data are made accessible. New on line archives have been created that significantly improve access to existing materials, for example on Cranach and Rembrandt. More innovative are the rapid developments in the fields of 3D scanning and printing; the standardization of documentation of art works; and the documentation of especially paintings and works of paper in extreme resolutions and in different modalities such as visible light, infrared, and X-radiography. These developments are increasingly impacting art history, technical art history, and art conservation, as well as museum practices and the art book publishing industry. It is also allowing specialists to create facsimiles of art works and other cultural heritage structures with unprecedented (and uncanny) precision. In this keynote presentation, I will discuss several aspects of these developments based on my involvement in recent and current projects such as Closer to Van Eyck and Even Closer to Van Eyck on the Ghent Altarpiece; Van Eyck Research in Open Access (VERONA); the Bosch Research and Conservation Project on Jheronimus Bosch; and The Hand of the Master on panels by Pieter Bruegel the Elder. Ron Spronk Queen’s University, Kingston, ON, Canada Radboud University, Nijmegen, the Netherlands

Reflectance Transformation Imaging (RTI) has become an important part of the documentation repertoire of many conservation laboratories. The ability to enhance details of surface shape and color helps in discerning surface information not otherwise easily visible. RTI is usually used to obtain qualitative data, such as reading difficult-to-see inscriptions and decorative details. We have been experimenting with combining RTI with image analysis for quantitative applications. Image analysis starts with algorithms that enhance visual separation of different features in an image and mark for analysis (in a process called ‘segmentation’) features of a specific color, contrast, size range, and/or morphology. Satisfactory segmentation is the core requirement for successful image analysis. Once this is achieved, a variety of quantitative data on those highlighted regions can be collected simultaneously. RTI plus image analysis is a natural coupling. Since quantitative analysis of surface features first requires the best possible segmentation, the enhanced surface detail produced by RTI is a clear advantage. One application we have been experimenting with is the use of RTI plus image analysis to obtain quantitative data on surface corrosion. The technique has been applied to coupons from Oddy tests, coated coupons artificially aged in a weatherometer, and metal sheets used for rapid corrosion tests. Oddy tests are used to assess compatibility of storage and display materials with metals found in collections. The test provides qualitative data as to whether a material is advisable for long-term use, for short-term exhibitions, or not at all. Reading the results of these exposure tests on coupon surfaces, however, can be tricky. For example, the British Museum has recommended that to reduce surface reflections from silver and copper coupons, a sheet of white paper should be held at an angle of approximately 60° to horizontal over the coupons while making assessments. Another difficulty is that control coupons themselves can change due to the elevated RH of the test. These changes have to be accounted for in making judgements about the degree of change in non-control coupons. RTI can improve the test by allowing qualitative assessments to be made under the best standardized viewing conditions. Adding image analysis allows surface effects on the controls to be subtracted from all other coupon images, and can add quantitative data on percentage of surface tarnish. We applied this process to weatherometer tests of coatings recommended for outdoor architectural brass. Image analysis gives the percentages of pitting and corrosion products present. However, using images obtained through RTI, rather than through typical photographic or scanning methods, provides more satisfactory results. We also used this approach to assess the results of rapid corrosion tests developed in industry to test the efficacy of corrosion inhibitors. Two indicators are important but cannot be assessed easily in one image: the percentage of surface area covered by corrosion products, and the degree of pitting attack, which has the effect of darkening the shiny, polished metal surface. Using the RTI viewer followed by image analysis these two indicators can be separated and quantified.

In this talk we will show how reflectance transformation imaging (RTI) can be used as a quantitative technique capable of visualizing and measuring the surface shape of works of art. RTI utilizes multiple images captured from a fixed camera position but lit from various different directions to create an interactive composite image that reveals textural characteristics of materials. While current RTI methods offer conservators a powerful exploratory tool, the many systematic approximations inherent to the technique limit its use to qualitative assessments of appearance. As one step towards quantitative surface estimations, we address a fundamental limitation of the RTI model, that the whole object is lit from the same illumination angle with the same illumination intensity across the entire field of view. This requirement is rarely met in real-life experimental conditions because the light would need to be placed infinitely far away from the object. The mismatch between the lighting model and real experimental conditions has been documented to produce erroneous surface normal estimations, a “potato-chip” shape estimation error when the surface normals are integrated, and non-uniform illumination effects in relighting that we call the ‘spot-light’ effect. Using our new algorithm and capture methods, we show how to correct for these errors and advance RTI making it a practical and repeatable method to digitally capture the surface texture of a work of art. As a practical example to demonstrate the effectiveness of this approach, we will show high-quality 3D reconstructions of RTI data captured from the Art Institute of Chicago’s collection of the graphic works of Paul Gauguin.

The non-invasive in-situ infrared analysis of art objects was first accomplished with single point portable analysis systems. A small FTIR spectrometer could be brought to the object of interest and a quick analysis performed. This allowed objects to be analyzed without the need of removal from the gallery or removal of small samples from the object. The analysis is accomplished by illuminating the sample with infrared light and collecting the signal reflected by the sample. A natural extension of this method would be the replacement of the single detector element with a many pixel array detector such as a Photovoltaic Mercury Cadmium Telluride (PV-MCT) focal-plane array (FPA). FPA’s have been used for many years in the remote sensing of airborne chemicals, hazardous material, and spilled liquids .2-5 The conventional remote sensing infrared spectrometer with a single detector records the spectrum from a single field of view in seconds, and in contrast imaging spectrometers acquire thousands of spectra per second. As the pixels from state-of-the-art FPA detectors are small, microscopic data can be collected at high magnification over small areas or larger areas can be analyzed with less resolution. Such analyses can be accomplished in passive or active modes of analysis. Spatial and spectral information may be combined in order to improve the determination of chemical distribution. Art objects present unique challenges to the remote measurement concept. The objects typically do not emit a signal strong enough for passive detection and the introduction of a high temperature source could potentially damage the object in question. Also, traditional SiC sources were designed to illuminate small areas and had too low a power output to be useful for large fields of interest. Objects can also be irregular in shape. A preliminary study of a variety of art objects has been performed to determine the feasibility of applying full-field middle infrared imaging to objects of interest. The large depth-of-field of a stand-off imaging system like the HI90 allows almost any object to be analyzed quickly and easily.

The utilization of non-invasive imaging techniques to capture preservation and heritage content information from a range of analog materials is becoming a common tool used in the preservation of cultural heritage. Spectral imaging expands the information that can be found outside the visible region, and by generating data-cubes of registered images, allows a range of image processing to reveal hidden content information from historic materials. While this at is of significant interest for historic materials such as paper and parchment documents, it is increasingly important for more modern materials that are considered restricted in being machine-readable or machine dependent for viewing. For example, a range of illumination modes has been used to capture high quality images from photographic materials such as negatives without any traditional processing. Faded information on hygrothermograph and United States Geological Survey charts with historical environmental data and fugitive inks can also be captured, providing more information about degradation processes of specific materials within different environments. This emphasizes the need for capture of analog materials of various materials requiring different illumination and imaging parameters, including z-plane imaging. Often the range of materials are diverse but supporting documentation for scientific studies. Two and three-dimensional imaging (2D, 3D) provides additional advantages for the capture of information from modern media carriers that are considered machine-dependent, but are easily damaged by the stylus, needle or other play component. In collaboration with Lawrence Berkeley National Laboratory the Library has been integral to the development of the IRENE system “Image Reconstruct Erase Noise Etc.” a non-contact imaging system using a laser to image the surface of lateral grooves of audio disc carriers of sound recordings. Further 3D confocal imaging captures the vertical grooved information on materials such as fragile wax cylinders and field recordings, materials that would be potentially damaged if attempts were made to capture using traditional methods. The imaging system has been modified to capture information from other historic sounds recordings such as dictabelts. For both imaging systems, spectral and IRENE a focus on standardized processing to expand the information captured has been critical. For spectral imaging, a range of software packages have been assessed and standard processing techniques compared to assure high quality and accurate data is being captured from these imaging systems. The standardization of image processing and assurance of accuracy without creation of artifacts is paramount to the utilization of imaging technologies and digital derivatives for heritage science.

Multispectral imaging (MSI) has seen a rapid development within the field of conservation, thanks in part to its adaptation with digital imaging techniques. One recent advance in MSI is the use of visible-induced infrared luminescence (VIL) to map pigments that might otherwise be invisible to the naked eye. This technique, first published by Giovanni Verri (2009), involves the excitation of pigments on object surfaces with visible light, and the photographic capture of the resulting emission of infrared radiation. Specific pigments, including Egyptian blue, Han blue, Han purple, cadmium red and cadmium yellow, emit infrared radiation when excited in the visible range, creating visible-induced luminescence. The ways in which this phenomenon can be captured in an image involve a wide range of photographic equipment and associated techniques, which will be the focus of this paper. The authors will discuss their own experiences at the Metropolitan Museum of Art and the J. Paul Getty Museum Villa, where this technique has been used on a wide range of projects, including both in-lab and in-gallery imaging campaigns. Conservators have also tested the technique on archaeological excavations and have found that with the right equipment (battery-powered, durable) and the ability to limit ambient light, VIL can be successfully carried out in less controlled environments. This paper will provide a review of previous and current methodology, including a discussion of image capture and processing trade-offs, and also highlight areas for future development and experimentation.

With over 1,200 cultural institutions owning and operating portable X-ray fluorescence (XRF) analyzers, these instruments have become familiar tools for elemental analysis of collection objects. The X-ray source in these instruments can be repurposed for use in X-ray radiography. Successful trials demonstrate this imaging application and suggest the potential for its use on a variety of objects. This radiography method enables portable, small-scale imaging capability without traditional X-ray equipment or beta plates. Tests were carried out using a Bruker Tracer III-V handheld XRF analyzer. This instrument uses an X-ray tube and is capable of producing a voltage range of 0-45kV and an amperage range of 0-60μA. The XRF unit was mounted on a tripod and operated through a computer, allowing the energy levels to be adjusted and the operator to work at a distance from the X-ray beam. The X-ray beam is emitted at approximately 45° relative to the perpendicular of the face of the unit. The instrument was positioned to compensate for this angle, ensuring the object and film were within the beam. An intensifying screen, removed from a film cassette for medical radiography, was used to aid in placement. The intensifying screen is coated with phosphors that convert X-ray energy into visible light, permitting the beam spot size, shape, and location to be viewed in the dark. As with traditional X-ray radiography, the spot-size increases as the distance between X-ray source and target increases, also necessitating a longer exposure. The current in the portable unit is 1,000 times less than in traditional X-ray radiography equipment, and therefore longer exposures are required. Fugi Super HR-T and Kodak BioMax MR films were used and developed in an automatic processor. Recommended safety protocols were followed. X-ray images were successfully produced of paper to record the watermark and wood to evaluate the length of an embedded metal screw. At the following exposures, a working distance of 15 inches resulted in a usable image size of approximately 6 inches in diameter. A sheet of handmade paper with a thickness of 0.008 inches was exposed for 30 minutes at 15kV and 45μA. The resulting image of the watermark and laid lines had less contrast than a beta radiograph of the same sheet, but took less than half the time to produce. A ¾-inch thick block of balsa wood was exposed for 20 minutes at 45kV and 43μA. The wood grain was clearly visible in the X-ray image, as was the presence of an embedded metal screw. More information about the metal screw might be obtained with different operating parameters, but the capacity of the portable instrument may limit the ability to penetrate and record dense materials. Although not suited to all circumstances, this radiography method offers utility, flexibility, and relative ease. A watermark can be recorded without a beta plate; the presence of a pin, crack, join, etc. can be determined without a traditional X-ray imaging facility. The widespread availability of portable XRF units makes such exploratory radiography accessible for a variety of applications.

This presentation will explore ways to achieve effective and timely integration of conservation science into conservation practice. Two key elements for ensuring maximum impact for conservation science are research conducted in a collaborative and transdisciplinary way and proper dissemination of results. Conservation science is an integral and essential part of conservation. It provides a sound basis for informing conservation activities, by expanding our understanding of the composition, aging and deterioration of heritage materials to better care for collections, by developing improved techniques for conservation treatments or by advising on the choice of conservation materials through testing and research. Technology is constantly progressing and advances in other scientific fields are soon applied to conservation science. Techniques that were once considered sophisticated and expensive, such as Raman spectroscopy and laser cleaning, are now routinely used. The sophisticated methods of today that are not easily accessible because of scarcity or cost may become part of the arsenal of conservation scientists in a few years. However, conservation science remains expensive, especially if one wants to take a leadership role in this field. Considering the many issues that need attention, an efficient approach is to join forces in research to find practical solutions to key issues, and to ensure that work carried out for one single institution ultimately benefits the entire community through effective sharing of knowledge. Drawing from the author’s professional experience in the context of the Canadian Conservation Institute and her knowledge of the profession, examples of work carried out on different types of objects will be used to show how research projects are designed to maximise benefits so that conclusions are applicable to other objects or collections, and how projects undertaken to answer a specific question from a single museum can generate data that, once compiled, can provide a wealth of information to the broader museum community. The presentation will also discuss strategies to involve stakeholders in defining research objectives and methodologies and to ensure active collaboration with the communities using the research results.

The acceptable pollutant concentration limits for sensitive artwork are generally at or below the few ppb regime: this is only ~1% of the permissible exposure limits (NIOSH PEL) required for humans. Monitoring such pollutants at such low levels is an exceptional scientific challenge, especially to do so in a cost effective fashion for a large number of locations and microenvironments (e.g., every display case in a museum). To meet this challenge, we have extended with new sensor array chemistry our already extremely sensitive and portable “optoelectronic nose” [1-4] and developed cumulative colorimetric sensor arrays. The resulting disposable sensor arrays are inexpensive, cross-reactive sensors using a wide range of chemical interactions with analytes (i.e., not just physical adsorption): an optical analog of mammalian olfaction. By digitally monitoring the change in color of each spot in the easily printed array, one has a quantitative measure of the composite response to volatiles. The use of a disposable array permits the use of stronger chemical interactions, which dramatically improves both sensitivity and specificity compared to any prior enose technology. Importantly the sensor array has been specifically engineering to be insensitive to humidity changes. A new and highly compact reader (the size of a deck of cards) for these arrays based on the color contact image sensor (CIS, used for portable business card and paper scanners) was used for these studies. We have broadened these studies by the use of cell phone camera imaging and made trial experiments in the monitoring of artwork from the Disney Animation Research Library exhibition in Beijing and Shanghai in order to monitor pollutant exposure both during shipping and during exhibition. This exhibition, "Drawn from Life: the Art of Disney Animation Studios" features animation drawings, story sketches, layouts, backgrounds, and concept art spanning the 90 years of the Walt Disney Animation Studio's history. Sensor arrays were used to monitor both exterior and interior environments of passepartout frames at the exhibition and inside the shipping crates during transport. 1. Rakow, N. A.; Suslick, K. S. "A Colorimetric Sensor Array for Odor Visualization" Nature, 2000, 406, 710-714. 2. Suslick, K. S. “Synesthesia in Science and Technology: More than Making the Unseen Visible” Current Opin. Chem. Bio. 2012, 16, 557-563. 3. Lim, S. H.; Feng, L.; Kemling, J. W.; Musto, C. J.; Suslick, K. S. “An Optoelectronic Nose for Detection of Toxic Gases” Nature Chemistry, 2009, 1, 562-567. 4. Askim, J. R.; Mahmoudi, M.; Suslick, K. S. "Optical sensor arrays for chemical sensing: the optoelectronic nose" Chem. Soc. Rev. 2013, 42, 8649 - 8682.

This presentation will describe the scientific investigation of fogging on glass display cases at the Royal Ontario Museum (ROM). This is a serious problem, affecting many museums around the world with post-2000 display cases. At the ROM, most of the glass panels that exhibited fogging were from display cases installed in 2005-2008 as part of a major renovation at the museum. In some instances, panels showing the heaviest fogging were situated next to panels showing very little or no fogging, and on some panels the fogging revealed conveyor belt and suction cup patterns. Initial efforts to clean the fogging from the glass using commercial cleaning products were temporarily successful, but were unable to remove persistent greasy residues on the glass. The fogging returned within a year, even after multiple cleaning treatments. The fogging occurred on both the inner and outer surfaces of glass panels, in cases with and without climate control, and in cases containing all types of artifact materials. In 2012, a project was developed and initiated by the ROM and the CCI whereby 21 panels from 16 display cases in 10 galleries were sampled on both inner and outer surfaces. Additionally, three panels exhibiting varying degrees of fogging were removed from display cases for testing. Analysis at the CCI was undertaken using several analytical techniques, including: pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS). The composition of the glass panels was determined to be normal for soda lime glass. The fogging residues were found to be composed mainly of sodium salts of organic compounds (such as sodium lactate and sodium salts of fatty acids) and other sodium salts (such as sodium sulfate and sodium chloride). The source of the sodium in the residues was likely the glass itself. Off-gassing experiments with paints and a floor finish used at the museum determined that those products were not likely contributing to the fogging. Rather, it was concluded that the organic acids and inorganic anions that formed the salts likely originated from normal volatile organic compounds (VOCs) and particulate matter in the air. The formation of the fogging patterns on the display cases was greatly exacerbated by the presence of greasy material on the surface of the glass. This consisted predominantly of hydrocarbon lubricants that were transferred from machinery used in the manufacture of the glass and were not successfully removed before the installation of the display cases. Because of the variation in surface cleanliness, panels with a relatively high abundance of greasy material appeared to be heavily fogged while others with a lower abundance appeared to be unfogged. A cleaning protocol using Synperonic A-7 surfactant was tested on the three glass panels that were removed. SEM imaging of the panels before and after cleaning showed that a 200:1 solution of water and surfactant was sufficient to remove all traces of fogging, cleaning and manufacturing residues from the surfaces of the glass.

Gustave Caillebotte’s 1877 masterpiece “Paris Street; Rainy Day,” a centerpiece of the Art Institute of Chicago’s collection, was treated in 2013-14 and, along with its related preparatory drawing “Study for ‘Paris Street; Rainy Day’,” was given an in-depth examination as part of the Online Scholarly Catalogue “Caillebotte Paintings and Drawings at the Art Institute of Chicago.” These systematic examinations included infrared reflectography (multi-spectral, 960 to 2500 nm, and hyper-spectral, 967 to 1680 nm, 3.4 nm sampling); ultraviolet and transmitted visible and infrared photography; and photomicrography. The painting was also x-rayed and thread-counted, and the ground and pigments analyzed. These investigations led to major discoveries about the artist’s working process, from his initial sketch on the sidewalk of the Rue de Turin in Paris to the execution and finishing of the monumental painting. First, the combined information from the multi and hyperspectral imaging allowed visualization of the stages of underdrawing and painted pentimenti. Most notably, the technical images exposed major changes to the right side of the composition including movement of the far right building and nearby compositional edge, and the addition of the large, rear-facing figure. But that was only part of the story. To begin, the drawn sketch, that first phase of the preparatory drawing, is so accurate in its depiction of the Parisian intersection that scholars have long speculated that Caillebotte employed an optical device. Researching the likely candidates led to collaboration and recreation of this initial step at the original site in Paris, still largely unchanged in its architecture. The most likely culprit proved to be the camera lucida, a small, lightweight drawing aid in use since its development at the turn of the 19th century. Once back at the studio, Caillebotte then clarified the perspective via a set of ruled and re-angled lines, resulting in a regularized architectural skeleton. Comparing careful measurements of the drawing and painting and overlaying high-resolution, scaled images, it is clear that the first stage of underdrawing in the painting is a direct enlargement of the preparatory drawing by a factor of approximately seven. With this answer came another question: how did he do it? There was no discernable grid or obvious method of enlargement. Microscopic indentations in the drawing, and small pinholes in the painting revealed via a high-resolution infrared capture at 2100 to 2500 nm, illuminated a possible method of transfer. A drafting tool such as calipers was used to carefully measure distances on the drawing, leaving small, almost invisible indentations. With a full-size canvas tacked to a studio wall, the enlargement process was recreated, and small tacks, placed along the horizon at strategic points, easily braced a straight edge to enable execution of the major architectural lines in linear perspective as made visible by false color hyperspectral infrared reflectograpy. After the setting was established, Caillebotte populated the scene with figures taken from a number of preparatory drawings and began to paint, constantly adjusting the composition, scraping, covering, rethinking, and repainting, until he reached the dynamic and familiar artistic conclusion.

The dry climate of Egypt has preserved thousands of handwritten documents and books, from the Old Kingdom to the Middle Ages, that can provide insight into our understanding of ancient cultures. Unfortunately, in most cases the dates of these manuscripts are unknown, although several document types bear precise dates, often to the day. For the undated manuscripts, the only current scientific method of estimating the date of writing is radiocarbon dating, but these measurements are destructive and cannot be practically used to date the media as separate from the support. In contrast, micro-Raman spectroscopy, a non-destructive light scattering technique, can be used to distinguish physical and chemical properties of materials. We have discovered that, for a study of well-dated ancient Egyptian papyri covering the date range from 300 BCE to 900 CE, the Raman spectra (25 to 40 measurements on each manuscript) of black ink all show the characteristic spectrum of carbon black materials. The spectrum of carbon black is characterized by two broad features, the G and D bands. The G band at 1585 cm-1 is a Raman allowed transition that arises from the E2g in-plane vibration of sp2 bonded carbon. The D band is a forbidden Raman transition that occurs when the lattice symmetry is broken. The D band at approximately 1350 cm-1 is associated with disorder, vacancies, crystalline edges, etc. The broad spectroscopic features are indicative of crystalline and amorphous carbon. We observed the carbon black spectra exhibit systematic change as a function of manuscript date. This observation is unexpected given the dates of these papyri cover a 1,200-year time span and the fact that each manuscript has a unique provenance, archeological, and storage history. We conclude that, over this time-period, black ink pigments in Egypt were manufactured using similar processes. We attribute the systematic change we observe in the Raman spectrum to two concurrent oxidation processes: slow oxidation of the crystalline carbon and faster oxidation of the amorphous carbon. The changes we observed are well characterized by models for carbon black Raman spectra that relate the relative intensity of the D to the G peak to defect density in accordance with oxidation. Oxidative degradation must proceed relatively uniformly over time to alter the Raman response of the material, providing a direct experimental indicator for manuscript age. Using this technique, we have been able to distinguish between the Raman spectra of different carbon-based manuscript inks on ancient Egyptian documents. Most importantly, this research establishes the basis for a simple, rapid, non-destructive method for dating ancient manuscripts from Egypt as well as the ability to differentiating between modern forgeries and authentically ancient manuscripts.

This presentation will offer an overview of the challenges facing those seeking to use ED-XRF for quantitative analysis of cultural heritage copper alloys, and will describe a proposed method for maximizing the reproducibility of measurements between laboratories. By maximizing inter-laboratory reproducibility, this method should facilitate collaboration among researchers and allow the rigorous use of shared data and databases. Recently, interlaboratory reproducibility has been shown to be quite poor. The results of a 2010 round robin study will be discussed and possible explanations for the difficulties encountered will be described. The proposed method for improving reproducibility, nicknamed CHARMed PyMca, calls for the use of free, open source, fundamental parameters software called PyMca. PyMca allows for a consistent and transparent application of the fundamental parameters approach independent of the ED-XRF instrumentation used. In order to further improve reproducibility, the proposed method calls for the calibration of standardless PyMca results against a set of high-quality certified reference materials designed specifically for use with heritage copper alloys, the so-called copper CHARM set. Finally, this method calls for the calibration-to-standards to be carried out following a consistent strategy, including error modeling and the incorporation of a validation procedure. The results of a second round robin reproducibility study will be presented which demonstrate the efficacy of the method.

In conjunction with the upcoming exhibition Everywhen: The eternal present in Indigenous art from Australia, the Straus Center for Conservation and Technical Studies, Harvard Art Museums has conducted a major survey of the pigments and binders used in traditional Aboriginal bark paintings from Arnhem Land, Groote Eylandt, the Kimberley and the Tiwi Islands. Paints were analyzed for: 1. binding media using Fourier transform infrared spectrometry and pyrolysis gas chromatography mass spectrometry and 2. pigments by laser ablation-inductively coupled plasma-mass spectrometry to determine if an elemental fingerprint could be identified. Approximately two hundred samples from fifty paintings were analyzed from: Museum Victoria; Ian Potter Museum of Art, University of Melbourne; National Gallery of Australia; Art Gallery of New South Wales; Australian Museum; National Gallery of Victoria; Macleay Museum, University of Sydney; Peabody Museum of Archaeology and Ethnology, Harvard University. The following art centers provided standard pigments and binders: Buku Larrnggay Mulka, Yirrkala, NT; Tiwi Design, Bathurst Island, NT; Warringarri, Kununurra, WA. Binders were present in 77% of the samples we analyzed. No proteins, waxes, fats or blood were detected as a binder. The presence of nitrocellulose on Groote Eylandt paintings was connected to records from the 1948 expedition linking the condition of the paintings to an application of Duco to consolidate them. Orchid juice was chemically identified as a binder in a painting for the first time and was identified in the oldest bark paintings dating to pre-1878. The use of a variety of blacks from Groote Eylandt was identified as originating from natural manganese ore, dry cell batteries and charcoal. The differences in elemental fingerprints between ochres of the same location, as well as from painting samples indicates that more studies are required on a local level to determine the source and movement of ochres.