AIC's 52nd Annual Meeting

The aim of the Greener Solvents Project, [https://www.siconserve.org/greener-solvents/] conceived by Sustainability in Conservation (SiC), is to create accessible resources for promoting and disseminating greener solvent research, and support conservators in their safe and appropriate implementation of greener solvent approaches. Whilst ‘green’ is a widely popular and often arbitrarily-used term, in accurate accordance with its origins in Green Chemistry, there is no such thing as a green solvent. Recognising the need for a clearer definition, our research and resources have aimed to highlight the comparative nature of solvent ‘greenness’, and the requirement to incorporate human health, environmental and professional considerations for solvent selections in conservation practice. Thus rooted in sustainability, with approaches based on hazard and life cycle assessment methods, we have worked to develop and disseminate a clearer definition and perspective of greener solvents in conservation, with a focus on application specificity, and correct, yet simplified procedures for solvent selection by conservators.

Since the project was launched in 2020 we have been actively creating such open access resources for the conservation field. Our handbook, titled "Greener Solvents in Conservation: An Introductory Guide," edited by G. R. Fife and published by Archetype Publications in 2021, is freely accessible on SiC's website. This provides valuable information on identifying the most harmful solvents, practical methods for identifying alternative solutions readily available in studios, and a step-by-step guide to implementing greener solvent practices immediately.

Privileged to be joined by an expert scientific review committee and receive sponsorship for the handbook publication, we have been continually honored by the inputs and support we have sought and received from institutional partners and individuals for their collaboration.

Acknowledging that solvent use in conservation must be changed to benefit the health and safety of the conservator and environment, a key further action point identified has been the need to survey the field to understand the current practices and solvent use within conservation. We are currently developing the survey with partners at the University of Delaware, with plans for its launch in early 2024.

We have also developed a solvent database in collaboration with the University of Delaware. This database offers conservators a comprehensive view of potential greener solvent alternatives based on the specific substrate and their environmental impact. The database includes twenty-four data inputs, categorized into four main sections: identification, solvent properties, health and safety information, and details on the solvent's application in conservation. Developing this database requires us to actively research greener solvent alternatives, which we are doing in partnership with industrial and academic research partners in the US and EU. Consistent with an aim from the beginning of the project - enable conservators to stop using their most harmful solvents - our current research focuses on substitute solvents for replacing toluene/xylene in varnish applications on paintings and coatings on metal using a variety of modeling tools.

Cultural heritage conservation commonly uses solvents for the application and removal of polymeric resins in object disciplines from wall paintings and stone to easel paintings, ceramics and glass, ethnographic objects, and others. Polymeric resins carried in solvent are applied in a variety of object treatment schema. The most common of which are: 1) consolidants, fixatives; 2) coatings, lacquers or varnishes; 3) adhesives; 4) binding media of paints and fillers used for restoration, and 5.) barrier layers on porous surfaces.

Conservators prefer solvents that minimally impact health and the environment, typically those with low/no odor. Thus, identification and selection of safer solvents with the required solvation and final film properties for resins of interest are of great importance to the field. This work is developing a repository of solvents that both meet specific GHS-defined safety criteria and readily solvate the specific resins of interest. Two bespoke computer assisted systems from Dow were used in the solvent identification and selection process: CHEMCOMP™ Service and a custom CAS Sci-FinderN portal. (CHEMCOMP Service is a series of computerized solvent modeling programs: Evaporation Rate Program, Solvent Blend Program, VOC Program, Flash Point Estimator, and Hansen Solubility Parameter Sphere Estimator.) This CHEMCOMP™ Service is built upon an internally developed database of solvents and polymeric resins supplemented with a few additional materials commonly used in cultural heritage conservation. The CHEMCOMP™ solvent database was analyzed using the CAS Sci-FinderN tool that identified those solvents that met physical, health and environmental GHS Hazard Phrase requirements outlined by the team. The Hansen Solubility Parameter Sphere Estimator functionality within CHEMCOMP Service then provided computational predictions for which safer solvents solvate the resins included in this pilot study. The solubility predictions of interest have and continue to be validated at the bench and in silico. Physical and mechanical properties of the resulting polymeric resin films cast from a sub-set of the safer solvents & solvent blends will be reviewed to provide an initial assessment of the functional performance of the polymers in use. The full solubility data will be disseminated once thoroughly developed and vetted by those appropriately skilled and qualified in art conservation practices.

The development and evaluation of pedagogy that is responsive to our changing environmental and social context is essential to providing the next generation of conservators with the skills and insights to preserve tangible and intangible cultural heritage for an uncertain future. The UCLA/Getty Interdepartmental Program in the Conservation of Cultural Heritage is engaged in multi-phased research to develop methods for embedding sustainability in conservation education. In the first phase of our research, we learned that barriers exist to integrating sustainability not only in teaching curricula, but in all forms of conservation practice. Although in hindsight this finding could have been anticipated, it came up so often in our interviews that we decided to add a second phase to more clearly understand the barriers that conservators face in practice and in educational settings. In this presentation we present the results of our research on these barriers as well as the measures people in the field take to address them. We reviewed the literature in conservation and adjacent disciplines, conducted a survey of the field, interviewed key educators and practitioners on the barriers they encounter in their work, and met with two focus groups comprised of geographically dispersed professionals at different stages of their careers and working in different types and sizes of institutions, including private practice. We also worked with a sustainability coach, educational evaluators, peer reviewers, and other advisors who assisted with our research to better understand these barriers and how to mitigate them. During this research we identified and formulated responses to root causes, including resistance, time constraints, and financial barriers to sustainable practices. We will present strategies for breaking down these barriers in both practice and teaching that prevent our sector from fully embracing a more thoughtful, balanced, safe, and ultimately carbon-neutral approach to conserving cultural heritage collections. In the next phase of our research, we will build on this understanding of barriers to integrating sustainable strategies in practice and education. Our ultimate aim is to develop and disseminate pedagogical models representing activities that embed environmental, social,
cultural, and economic sustainability in all its forms. These pedagogical models will be presented at a later date.The development and evaluation of pedagogy that is responsive to our changing environmental and social context is essential to providing the next generation of conservators with the skills and insights to preserve tangible and intangible cultural heritage for an uncertain future. The UCLA/Getty Interdepartmental Program in the Conservation of Cultural Heritage is engaged in multi-phased research to develop methods for embedding sustainability in conservation education. In the first phase of our research, we learned that barriers exist to integrating sustainability not only in teaching curricula, but in all forms of conservation practice. Although in hindsight this finding could have been anticipated, it came up so often in our interviews that we decided to add a second phase to more clearly understand the barriers that conservators face in practice and in educational settings. In this presentation we present the results of our research on these barriers as well as the measures people in the field take to address them. We reviewed the literature in conservation and adjacent disciplines, conducted a survey of the field, interviewed key educators and practitioners on the barriers they encounter in their work, and met with two focus groups comprised of geographically dispersed professionals at different stages of their careers and working in different types and sizes of institutions, including private practice. We also worked with a sustainability coach, educational evaluators, peer reviewers, and other advisors who assisted with our research to better understand these barriers and how to mitigate them. During this research we identified and formulated responses to root causes, including resistance, time constraints, and financial barriers to sustainable practices. We will present strategies for breaking down these barriers in both practice and teaching that prevent our sector from fully embracing a more thoughtful, balanced, safe, and ultimately carbon-neutral approach to conserving cultural heritage collections. In the next phase of our research, we will build on this understanding of barriers to integrating sustainable strategies in practice and education. Our ultimate aim is to develop and disseminate pedagogical models representing activities that embed environmental, social, cultural, and economic sustainability in all its forms. These pedagogical models will be presented at a later date.

Created in 1936, Meret Oppenheim's Object is perhaps the best known artwork from the artist’s oeuvre. The spectacle and absurdity of the fur-lined porcelain teacup, saucer, and metal spoon provoked immediate fascination, derision, and notoriety. Almost instantly, Object, became synonymous with the Surrealist movement and part of the art historical canon, entering the collection of the Museum of Modern Art (MoMA) shortly after its creation. Over time, the fascination with the artwork never waned, yet the exact nature of the materials used to create Object have not been fully understood for almost a century. Originally described by the artist as being made with the “pelt of a Chinese gazelle”, conflicting historical records, purposeful obfuscation by the artist, and a lack of concrete analysis have put this attribution into question in recent years. Accurate species attribution for objects that contain animal fur provides invaluable insight into the making and significance of the piece, the understanding of inherent degradation patterns, and conservation treatments. Beyond this, it dictates crucial implications for travelling and loans.




This investigation, undertaken by the David Booth Conservation Department at MoMA, revisits the species identification of the fur used to create Object by combining archival research with scientific analysis. The most common method for species identification in the field is polarized light microscopy. However, this technique relies heavily on accessible, robust data sets that outline the morphological and optical characteristics of hairs from different species so that accurate comparisons can be made. Restricted by a severe lack of comparative resources, especially for non-North American mammals, polarized light microscopy only identified the likely order of which the animal was classified. Upholding the longstanding tradition of borrowing from other fields, a collaboration with the Department of Science at John Jay College of Criminal Justice and Dr. Dan Kirby, conservation scientist, offered access to techniques not commonly used in conservation.




DNA analysis offered a more accurate method for identification by sequencing the genetic information from samples that can then be compared to libraries for identification. However, the age of the sample, prior treatments, and contamination from handling over its lifetime affected the efficacy of this technique. To mitigate these contamination factors, the less common technique of mitochondrial genetic sequencing was undertaken. Comparatively, MALDI-TOF peptide mass fingerprinting (PMF) was also conducted on hide samples taken from Object with the goal of obtaining species information through collagen analysis. PMF analyzes the specific mass of peptides from collagen samples, which are then compared to a database containing known protein sequences to achieve species identification. This technique has the benefit of being highly sensitive and the potential for overcoming contamination issues. However, it is again highly reliant on robust databases for comparison.




This presentation explores the advantages of combining these techniques, as well as their individual disadvantages, and argues for the benefit of using complementary analytical methods. Furthermore, this research demonstrates how the combination of traditional and modern analytical techniques with conservation and art historical practices can add a greater overall understanding of art objects.

A new method for non-invasive extraction of protein binders in plate paintings using high acyl (HA) gellan gum is proposed, which solves the limitations of previous non-invasive extraction methods that mainly target the shallow surface of cultural relics and are susceptible to environmental pollution. The extraction effects of different gums on protein binders in simulated panel paintings were compared and characterized in terms of extracted protein concentration, macroscopic and microscopic appearance, color difference, pH and contact angle. Then, Fourier transform infrared spectroscopy was performed to analyze the extraction mechanism. on this basis, the non-invasive extraction of plate paintings containing different types and concentrations of protein binders using HA gellan gum was explored. The results showed that neither HA nor LA gellan gum significantly affected the surface color, pH value, contact angle and visual appearance of the paint layer. The concentration of the protein solution extracted by HA gellan gum is 2.4 times higher than that of LA gellan gum, and the possibility of gel residue is less. In addition, HA gellan gum showed good extraction effects on different types and concentrations of protein binders. Therefore, it is expected to become an effective method for non-invasive extraction of proteins from painted cultural relics. HA gellan gum shows good extraction effects on different types and concentrations of protein binders. Therefore, it is expected to become an effective method for non-invasive extraction of proteins from painted cultural relics. HA gellan gum shows good extraction effects on different types and concentrations of protein binders. Therefore, it is expected to become an effective method for non-invasive extraction of proteins from painted cultural relics.

Genomics can offer unique perspectives into the creation and history of cultural heritage objects. The possibility of learning more about the makers of objects through genomics is tantalizing: there are examples where an artisan’s intimate contact with the manufacturing of art materials suggest that genetic information may survive. Gofun, a calcium carbonate pigment commonly found in traditional Japanese paintings, is one of these examples, and this abstract describes our attempts to isolate the genetic information of the maker from a modern preparation. The paint is prepared from gofun powder, which is made by an intensive pulverization of air-dried oyster shells and kneaded by the artist or their assistant with an animal binding glue. A small amount of water is added before application to a textile or paper support. The paste is kneaded by hand for at least an hour, thus increasing the opportunity for cell-free DNA from the artisan’s hands, including the artisan’s own DNA, to become incorporated into the paint. This phenomenon sparks intriguing questions about what information genomic tools can provide about the history of a painting such as: Who prepared the paint? Could that correlate to the attribution? Does attribution require a combination of human and microorganism genetic information? What microorganisms and organic materials were the painting exposed to, and how might that impact conservation treatment?

This project, representing a novel collaboration between the Metropolitan Museum of Art and the Mason Laboratory of Weill Cornell Medicine, explores the extent to which these questions can be answered using the smallest paint sample possible. As sample size is the limiting factor for most art analysis, especially Asian art, which typically is painted in very thin layers, the following work describes what might be possible on milligram sample sizes with the hope that miniaturization could be achieved. A modern gofun paint mockup, prepared by a Met conservator, served as our paint source. A protocol optimized for highly-fragmented DNA from calcium-based sources was implemented on four samples, ranging between 0.5 - 2 mg of paint. We selected a protocol that was sensitive to small fragments of DNA as the paint source was exposed over time to light, water, and enzymes that digest DNA, all of which drive DNA degradation reactions. Moreover, calcium ions from the gofun interfere with extraction by tightly binding to DNA, so a protocol that sequesters calcium was essential for DNA recovery. As the extraction yield was too low for detection, we amplified the extracted DNA to reach the minimum concentration required for sequencing. Fluorometry and automated electrophoresis following amplification support the presence of DNA in the paint samples. Moreover, software tools for organism identification reveal the presence of human, bovine, and mollusk DNA, among other species, suggesting the power of genomic tools for material verification. Genomic isolation and analysis from smaller-sized samples of gofun may be possible; however, challenges remain. Repetitive amplification of the sample can create byproducts that interact with other samples run on the same instrument, leading to crosstalk between samples. This can result in the false identification of unexpected species found in other samples. Future studies will probe into better addressing these issues.

Art Bio Matters (ABM) stands as a dynamic alliance of enthusiastic and curious curators/cultural historians, scientists, and conservators. Together, we combine diverse research methodologies, unique perspectives, and ambitious objectives in our pursuit of unraveling the mysteries within biological materials found in cultural heritage collections.

Your perspective is invaluable to us, whether your aspirations align with advancing preservation techniques, conducting in-depth analyses, or contributing to the nuanced interpretation of cultural artifacts. At the heart of ABM are the core values of inclusive participation, curiosity, respect, candid debate, and collaboration between the core disciplines of science, curatorial/cultural history, and conservation, working seamlessly to safeguard our cultural heritage.

By supporting ABM, you not only endorse innovative research but also embrace a collaborative ethos. We extend a warm welcome to all participants in cultural heritage studies, recognizing that it is through collective efforts that we can make a lasting impact on the preservation and understanding of our shared cultural legacy. Join us in shaping a future where knowledge and appreciation of our cultural heritage flourish, thanks to your vital contribution.

In this presentation, we will share a novel method of acquiring the cross-sectional images of 35 sample papers using optical coherence tomography (OCT) and feeding the images through Deep Convolutional Neural Networks (AlexNet) to achieve highly accurate and non-destructive classification. Paper identification and analysis of morphological characteristics related to plant cultivation and craft tradition have long relied on interpretive observation and/or destructive fiber sampling techniques [1-3]. Optical coherence tomography (OCT) is a non-invasive technique used for medical imaging that has been applied to art conservation to capture both the surface and subsurface structure information of cultural heritage objects [4]. Thirty-five paper samples were sourced from a conservation vendor specializing in Japanese handmade papers. These were selected based on their known fiber content and production methods as well as use in book and paper conservation treatments for hinging, tear repairs, and loss compensations. Cross-sectional images of the samples produced by OCT reveal how light scatters in the paper substrate. The patterns of scattering light seem arbitrary to the human eye, however, AlexNet, first introduced in 2012 as a convolution neural network (CNN) for image classifications [5], can be used for deep learning to classify these papers. A total of 35,840 OCT cross-section images were generated, of which 3,500 images (~10% of the dataset) were used for training, 8,960 images (25% of the dataset) were used for validation, and 23,380 images (~65% of the dataset) were used for testing. The AlexNet achieved a test accuracy of 98.99%, with 23 out of 35 paper samples achieving 100% accuracy in the tests. This presentation will share information on this testing methodology and equipment, as well as a summary of the results which demonstrate that combining OCT with AlexNet can provide conservators with a highly accurate tool for classifying papers used in treatment repairs.







Reference

[1] Barbara Borghese, “Understanding Asian papers and their applications in paper conservation”: a workshop review by Laura Dellapiana,” The International Institute for Conservation of Historic and Artistic Works, 2017.

[2] P. Webber, “The use of Asian paper conservation techniques in Western collections.” [Online]. Available: https://icon.org.uk/node/4998

[3] H. Yonenobu, S. Tsuchikawa, and K. Sato, “Near-infrared spectroscopic analysis of aging degradation in antique washi paper using a deuterium exchange method,” Vib Spectrosc, vol. 51, no. 1, pp. 100–104, Sep. 2009, doi: 10.1016/j.vibspec.2008.11.001.

[4] X. Zhou et al., “A Note on Macroscopic Optical Coherence Tomography Imaging Enabled 3D Scanning for Museum and Cultural Heritage Applications,” Journal of the American Institute for Conservation, pp. 1–10, Oct. 2022, doi: 10.1080/01971360.2022.2093537.

[5] A. Krizhevsky, I. Sutskever, and G. E. Hinton, “ImageNet classification with deep convolutional neural networks,” Commun ACM, vol. 60, no. 6, pp. 84–90, May 2017, doi: 10.1145/3065386.

This study focuses on the challenging task of identifying various species of mahogany, a prized wood sourced from the Caribbean in the 18th and early 19th centuries. Distinguishing between 'true mahogany' species and other tropical hardwoods, as well as North American woods mimicking mahogany, poses a significant challenge. Accurate wood identification is crucial for understanding the origins of raw materials, craftsmanship choices, and for effective conservation. Traditional methods involve microscopic examination by a wood anatomist, but obtaining suitable samples may not always be feasible or desirable. An alternative approach utilizes chemotaxonomy, leveraging variations in organic and inorganic chemical composition for wood differentiation.

In collaboration with Yale University Art Gallery, our ongoing project employs handheld laser-induced breakdown spectroscopy (LIBS) and pyrolysis gas chromatography-mass spectrometry (Py-GC/MS), complemented by machine learning (ML). Our goals are to distinguish mahogany from similar-looking woods and, ultimately, to differentiate between the three Swietenia mahogany species. Promising outcomes have emerged from the analysis of numerous samples, including those extracted from furniture. This presentation will highlight recent efforts to optimize data preprocessing steps, effectively deploy machine learning tools, and develop more robust classifiers. A collection of over 400 wood reference samples were studied with the two techniques, prior to examining approximately 200 areas on historic pieces of furniture employing the same approach.

Py-GC/MS is well-known among conservators for its efficacy in characterizing heritage materials. This method utilizes small samples of wood, either as tiny fragments or powdered material obtained with a hand drill. It takes about one hour to analyze a single sample in the laboratory. The resulting pyrograms show the presence of materials associated with cellulose, hemicellulose, and lignan, which are polymeric components common to all types of wood, as well as extractives, the non-structural, low molecular weight organic molecules that are the principal source of chemotaxonomic discrimination.

LIBS is a form of optical emission spectroscopy capable of simultaneously detecting all elements within a single laser pulse. Consequently, a broadband LIBS spectrum can be likened to a diagnostic fingerprint. With a commercially available handheld instrument, it is possible to analyze objects in situ in a matter of seconds. Notably, LIBS enables the detection of light elements, including both organic (e.g., C, H, O) and inorganic components (e.g., Li, Na, Mg, Al, Si, K, Ca, Ti, Fe, Zn, Sr).

Before applying machine learning tools, a preprocessing protocol was developed for the LIBS and Py-GC/MS data. This included baseline correction, alignment to ensure that the wavelength or retention time values were standardized across all data collections and were therefore directly comparable, and, in the case of LIBS, the removal of data with low signal-to-noise ratios (SNR) based on a spectral similarity analysis. Principal Component Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLSDA) was then applied to build classifiers. Iterative refinement of ML algorithms and preprocessing steps resulted in models with a high level of classification success. Software was then developed to allow chemometric processing of LIBS data to be carried out in real-time in a gallery space.

This poster summarizes the results of a short internship in 2023 focused on plastics identification at Cooper Hewitt, Smithsonian Design Museum in New York City. The goal of this research was to more accurately identify a selection of plastics in collections objects and deepen my understanding of the types of polymers typically found in design museum collections.

This project follows up on a year-long survey begun in 2012. In this survey, ca. 1,500 collections objects were assessed for condition, storage recommendations were made and implemented, and a handful of objects were analyzed using portable Raman and Fourier-transfer infrared (FTIR) spectroscopy by conservation scientists. My project focused on a small subset of the objects included in the earlier survey. Over four weeks, 37 collections objects and 58 reference samples were analyzed using Attenuated Total Reflection (ATR)-FTIR spectroscopy.

Cooper Hewitt’s remit is to collect and care for important and impactful design. As indelible materials of the 20th century design narrative, its Product Design and Decorative Arts curatorial department is filled with examples of natural (horn, tortoiseshell) and early plastics such as those made of cellulose derivatives and formaldehyde-based resins (i.e., Bakelite). Modern plastics like polyvinyl chloride (PVC) and polyurethane foams have consistently made their way into the collection over time. As today the museum collects a wide variety of objects, from one-of-a-kind works of art to disposable commodity items, an impressive range of plastics in varying conditions are present both on display and in museum storage.

It’s no secret that art and design museums face unique challenges when it comes to understanding plastics in their collections. Plastics are made from varying proportions and mixtures of polymers and additives and can be nearly impossible to distinguish from one another, even if their degradation phenomena and aesthetic qualities appear nearly identical. The complex composition of these objects challenges both identification and appropriate treatment and/or storage options. Complicating matters is the fact that many design objects exist as multiples or editions, calling into question long-held conventions in our field regarding authenticity, authorship, and ownership.

While many objects in our survey were identified with confidence, matches using FTIR were not always straightforward. Plasticizers and other additives can obscure spectra, rendering confident identification nearly impossible. Compounding the complexity of the task is the fact that many objects are made of composite materials. While ATR-FTIR is a very useful technique for bulk polymer identification, not all collections objects are suitable for this technique due to their size, shape, and/or condition, among other factors. It thus became vital to use a three-pronged approach: considering historical context along with sensory information and the use of scientific analysis to accurately determine polymers. The short but ambitious project provided the institution – and me – with a wealth of information about the complex plastics materials increasingly encountered by cultural heritage professionals, especially those working in modern and contemporary design collections.

Egyptian limestone objects are known to be sensitive to unstable conditions in storage. Exposure to fluctuating humidity can cause the soluble salts inherent in these objects to dissolve, migrate, and recrystallize leading to delamination, flaking, and general loss of structural stability. The Walters Art Museum found three such objects in their collection in need of stabilization through desalination. These Egyptian limestone works were determined to be too fragile to be treated through the traditional desalination approach of submersion in a water bath. The conservators sought an alternative approach to desalination with agarose hydrogel poultice, which desalinates the stone through the formation of a concentration gradient. Prior to treatment, the surface will be secured with B-72 consolidant to preserve its structural integrity.

This research explores the effect of consolidation on the rate of desalination and the efficacy of the treatment using an NMR-MOUSE spectrometer, a non-invasive analytical technique that measures the transverse relaxation time (T2) of the protons in limestone-bound water. As such, T2* rates measured over the course of the treatment allows direct observation of the salt changes in the stone. Preliminary data suggests that the non-consolidated stone reached full desalination after 5 days compared to the consolidated stone which took 11 days. The data suggests that use of an agarose hydrogel treatment is feasible even after the application of the B-72 consolidant.

In addition to NMR relaxometry measurements, ICP-MS, SEM-EDX, and a series of microchemical tests were employed to analyze the salt composition of powder which had delaminated from the three Egyptian limestone objects found in the Walters Art Museum’s collection. Quantitative evidence of Na+, K+, and Mg2+ cations were found in each sample in addition to the likely presence of phosphates, sulfates, and chlorides. This project advances the understanding of the use of agarose hydrogel for the desalination efforts of fragile objects. The NMR-MOUSE and other laboratory instruments can be applied to the cultural heritage field to better understand the treatment approaches already in use and to assist the development of new processes. This collaborative effort between the scientific research and art conservation fields exemplifies the knowledge that can be gained through interdisciplinary work.

This research was performed as part of the Baltimore SCIART Program, which is supported by the Andrew W. Mellon Foundation under Award 41500634.

Arsenic sulfide pigments, broadly ranging in color from red to yellow, have been used since prehistoric times in their natural, mineral form.1 The most widely known of these arsenic sulfides are orpiment (As2S3), realgar (α-As4S4), and the light-induced alteration product of realgar known as pararealgar (γ-As4S4). The poisonous quality and reactivity of such pigments has been known for centuries, with Cennino Cennini warning that “there is no keeping company with [the arsenic sulfides]” and to “look out for yourself” when working with them. Although arsenic sulfides lost popularity and became commonly replaced by less-toxic yellow colorants over time, they are heavily used in works of art dated prior to the 19th century. Much research has been carried out on understanding the alteration of realgar into pararealgar, both from an atomic-level perspective2 and from a museum perspective.3 Nevertheless, there are many other mineralogical arsenic-bearing phases that have scarcely been identified in works of art, including dimorphite (As4S3), bonazziite (β-As4S4, which is the high-temperature counterpart of α-As4S4), and alacranite (As8S9).4 As a result, the light-stability of these pigments has not been fully assessed from a conservation viewpoint. Recently, as part of Harvard University’s Mapping Color in History project, an arsenic sulfide pigment identified as β-As4S4 was collected from the workshop of the traditional Indian painter, Mr. Babulal Marotia, based in Jaipur, Rajasthan. It is known that β-As4S4 can be obtained from realgar by heat-treating the mineral at temperatures approximating 250 ºC.5 Considering that naturally occurring bonazziite is particularly rare, the identification of this arsenic sulfide phase suggests that the pigment was procured by roasting natural realgar. In the current study, the lightfastness of the Indian pigment will be evaluated and compared to paint outs of natural realgar, orpiment, pararealgar, and artificial realgar from the Forbes Pigment Collection housed at the Harvard Art Museums. The limitations of using a microfading tester on realgar-type pigments will be explained and compared to results from fading experiments carried out in natural lighting conditions. The light-induced alteration of the Indian pigment will be further assessed in-situ using a combination of Raman spectroscopy and photocrystallography. Insights on the photochemical reactions taking place will be evaluated against the natural light fading colorimetry measurements, providing a thorough review on the light-induced degradation pathways of the roasted pigment, and its implications for art conservation.

References

(1) Daniels, V.; Leach, B. The Occurrence and Alteration of Realgar on Ancient Egyptian Papyri. Stud. Conserv. 2004, 49, 73–84.

(2) Bonazzi, P.; Menchetti, S.; Pratesi, G. The Crystal Structure of Pararealgar, As4S4. Am. Mineral. 1995, 80 (3–4), 400–403. https://doi.org/10.2138/am-1995-3-422.

(3) Trentelman, K.; Stodulski, L.; Pavlosky, M. Characterization of Pararealgar and Other Light-Induced Transformation Products from Realgar by Raman Microspectroscopy. Anal. Chem. 1996, 68 (10), 1755–1761. https://doi.org/10.1021/ac951097o.

(4) Gliozzo, E.; Burgio, L. Pigments—Arsenic-Based Yellows and Reds. Archaeol. Anthropol. Sci. 2022, 14 (1), 4. https://doi.org/10.1007/s12520-021-01431-z.

(5) Bonazzi, P.; Menchetti, S.; Pratesi, G.; Muniz-Miranda, M.; Sbrana, G. Light-Induced Variations in Realgar and beta-As4S4: X-Ray Diffraction and Raman Studies.

(6) Zheng, S.-L.; Wang, Y.; Yu, Z.; Lin, Q.; Coppens, P. Direct observation of a photoinduced nonstabilized nitrile imine structure in the solid state J. Am. Chem. Soc. 2009, 131 (50), 18036–18037. https://doi.org/10.1021/ja9094523

Relevance and background

Preserving the integrity of historical artifacts remains a paramount concern for cultural heritage. However, stewards of heritage grapple with the material degradation over time catalyzed by environmental conditions, such as air quality, humidity, and light. Light can cause photochemical damage when directed onto light-sensitive artwork like textiles, paper-based works, or oil paintings, resulting in color fading, varnish yellowing, or undesirable color shifts.

While light is an imperative medium for human visual perception, the dichotomy it presents—between enhancing visibility and inducing damage—is at the crux of conservation endeavors, exerting a critical influence on art display within museums. The "visibility-damage dilemma" shapes the lifetime of artworks, governed by the antagonistic relationship between prolonged exposure and longevity. While prevailing museum lighting guidelines underscore the importance of curbing light exposure, it is important to acknowledge that stringent light reduction measures, while mitigating damage, may not uniformly cater to human visual perception. Under dim lighting (often 50 lux or lower), paintings may lose their inherent vibrancy, owing to the decreased sensitivity of the human visual system. Such conditions can render objects visually muted, prompting the re-evaluation of universally adopting reduced light levels as a catch-all solution for both conservation and visual appeal.

Purpose and hypothesis

A promising novel application is the optimization of light using projection mapping techniques, which can improve the viewing experience while simultaneously reducing degradation caused by light. Previous studies show that light source spectra can be spectrally optimized to reduce light absorbed by materials, only emitting light that is reflected off of surfaces. We hypothesize that light projection systems can be used to go beyond visual enhancement, embracing the mitigation of photodegradation-induced color desaturation or compensating for low light levels.

Methods and outcomes

Our research started with computational simulations aimed at quantifying reduced damages. Linear optimization methods gauged the appearance of 15 color samples under different illuminants, yielding energy savings up to 71% without perceptible color shifts. Extending this exploration into heritage conservation, we used a seven-channel LED system targeting the preservation of monochromatic oil paintings, demonstrating the feasibility of halving damage and energy consumption without inducing discernible color shifts. In a follow up study, an absorption-reducing light projection prototype was tailored for Joaquín Sorolla's painting "Walk on the beach". This RGB projector-based system utilized point-by-point light projection to curtail damage by up to 49% compared to daylight, and up to 67% compared to incandescent illumination, all the while preserving color fidelity. Finally, we conducted a vision experiment to test the appearance of artwork under light projection to test user acceptance.

These advancements herald the path toward spatially and spectrally precise light optimization, culminating in prototypes attuned to the spatial complexities of multi-colored artworks. This comprehensive exploration not only underscores the intricate interplay between light, preservation, and visual aesthetics but also supports evidence for the potential of light projection systems as transformative tools within the realms of conservation.

Siloxane has been used for the protection of metal artefacts from corrosion in the form of transparent barrier coating films because of their good adhesion to the metal substrate. The effect of oxygen plasma pre-treatment on the adhesion properties of the siloxane thin film on the silver-copper alloy substrate was investigated. Radiofrequency plasma-enhanced chemical vapour deposition (RF-PECVD) was used for the deposition process. Surface identification and characterization of the deposited films were carried out using Scanning Electron Microscopy coupled with energy dispersive X-ray (SEM-EDX) and Fourier-transform infrared spectroscopy (FT-IR). Surface topography and roughness were investigated by atomic force microscopy (AFM). The hydrophobic characteristic was measured by water contact angle measurement (WCA). The film thickness was evaluated using a spectroscopic ellipsometer (SE). Colorimetric measurement (CM) was used to evaluate changes in the appearance of the surface following the PECVD deposition of the SiO2 protective layer. The corrosion protection ability of siloxane films for metal substrates as a function of RF power and gas feed composition was examined by the electrochemical impedance spectroscopy (EIS) technique. It was found that the deposited film improved the protective efficiency for samples from 55.29% to 92.93%. Besides, after the oxygen plasma pretreatment step, the film showed better corrosion resistance of the tested samples.

This session will discuss the findings from the 2022 survey on “Vibratory Impacts of Music and Transport on Museum Collections”, which indicated a noticeable variation in knowledge of shock and vibration issues and mitigation practices across institutions. We will also summarize the general findings from the May 21 Towards Art in Transit 2.0 pre-session symposium and discuss possible next steps for the field.

The theme of “Crate Performance and Sustainability” was touched upon in several presentations and a panel during the May 21 Towards Art in Transit 2.0 pre-session symposium. This session will continue the panel discussion among practitioners on topics such as crate design, the prediction of crate performance, assessing existing packing methods, and possible reductions in the environmental footprint of travel. Panelists will include Dale Kronkright (moderator, Georgia O’Keeffe Museum), Julia Latané (LACMA), Bill Wei (formerly of RCE), and Merv Richard (formerly of the National Gallery of Art).

The theme of “Transit Logistics” was a focus of several presentations and a panel during the May 21 Towards Art in Transit 2.0 pre-session symposium. This session will continue the panel discussion among practitioners on topics such as risk assessments for travel, new approaches to monitoring and couriering, loan agreements, and their impact in developing sustainable transit practice. Panelists will include Cayetana Castillo (moderator, Art Institute of Chicago), Samantha Springer (Art Solutions Lab), Scott Pustai (Total Fine Arts), and Lisa Swedberg (The Kiruna Centre).

Non-invasive micro-scale analysis are bringing a revolution to the scholarly understanding of the texts and images of medieval manuscripts, unlocking new information about their current condition, original making, and meaning. A dramatic example of this was recently found in a diminutive devotional miscellany manuscript written circa. 1518 in the Upper Rhine region, currently part of the Library of Congress’s Lessing J. Rosenwald Collection.

Rosenwald Ms 13, Betrachtungen des Leidens Christi und Gebete für Klosterfrauen (Contemplations of the Passion of Christ and prayers for nuns) is a particularly interesting example of a manuscript crafted for devotional purposes, used and re-used over several centuries within the context of a female religious community in Germany. The hand-written text is decorated with red initials and highlights throughout, and small hand-colored woodcuts pasted into the book. These vary considerably in style, format, and palette, suggesting that they derive from multiple sources and may have been purchased already painted. One image stands out as exceptional: the Holy Face on folio 58v, which presents the face of Christ in shades of dark gray and black.

Technical study of the woodblock was conducted to learn whether the present appearance of the Holy Face is intentionally black due to deliberate material choices, or due to deterioration of the materials used. Synergistic application of x-ray fluorescence spectroscopy, reflectance spectroscopy, and multispectral imaging revealed that the present appearance is a combination of alterations and intent. Quite unexpectedly, the small painted image includes uncommon and novel material uses to render the unexpected palette. Identifying its present appearance as (largely) intentional fundamentally alters the meaning of the image, linking it not just to private devotional practice centered in the text on the page, but to the practices of pilgrimage, spiritual pilgrimage, and exchanges of relics and devotional images in the intellectual, social and spiritual lives of cloistered women of the era.

Three basalt sculptures by the South Korean Artist Byong Hoon Choi called “Scholar’s Way” were installed in a pool of water, outside the new Kinder building for Modern and Contemporary art, at the Museum of Fine Arts, Houston in 2020. The sculptures are carved from naturally occurring columns of basalt sourced from Indonesia, with most of the surface being highly polished to a black mirror-like finish. Parts of the sculptures around the bases and at projecting elbows of the abstract forms retain a weathering crust. Before the installation, conservation had concerns about what effect the surrounding environment and the addition of chemicals, to control the water quality, would have on the sculptures. In a short time, the polished surface had dulled and granules of the crust were falling off. Although the artist has worked with this material for 40 years, only a few of his sculptures are installed outside in water. Despite his assurance about the material durability we obviously had a problem whose mechanisms needed to be more fully understood. Conservation collaborated with students and faculty at Rice University to determine the geochemistry of the basalt and weathering crust, as well as to analyze the water quality and its chemical composition. Surface measurements of the columns with near infra-red, energy dispersive spectroscopy (EDS) and electron probe microanalysis (EPMA) showed that the base rock that was used was already in a highly altered condition before installation. The degree of alteration on the surface was accelerated by weathering in humid conditions. The weathering crust is largely made up of clay and some remnant basaltic igneous minerals. The EPMA showed that the basalt contains orthopyroxene, Ti-augite, plagioclase, and Ti-magnetite and is thus an iron-titanium basalt. Secondary minerals are widespread and make up more than 90% of the crust. These minerals are mainly clays such as ferripyrophyllite, ferrisepiolite, and kaolinite. The presence of these minerals proves that the rock was altered by hydrothermal processes prior to human intervention. The effect of weathering in humid conditions affects the surface of the rock. The porous clay aggregate readily absorbs water and the other remnant minerals are somewhat soluble in the chemically treated water. The civil ordinance governing water features which had been used to justify the use of harsh chloride containing bleach and acid in the water was deemed inapplicable to this non-interactive feature. The clay minerals occur over the entire surface of the sculpture including previously polished portions, consistent with recent weathering in addition to the original weathering crust. This study is ongoing. A protective wax has been applied to the polished areas. We have not decided on whether a consolidation treatment can be applied to the weathering crust as this may cause greater damage. We are removing the additive acid/alkali mix from the water and are investigating replacement with a copper salt to prevent algae growth.

The revenues from the salt trade were of great significance to the Bavarian electors until the late 18th century. The 'white gold' was transported by waterway from Hallein and Berchtesgaden to Stadtamhof near Regensburg, with so-called 'salt ship trains' being used on the Danube. These were convoys of ships specially designed for transporting salt, which were pulled upstream with the help of horses, a process known as 'towing'. The only known sculptural representation of a Palatinate salt ship convoy is housed in the Bavarian National Museum (BNM) in Munich. The group of objects has so far been dated to the second half of the 18th century. As an object, it is culturally a piece of regional historical significance.

This representation of a salt ship convoy is made of glazed ceramics, leather, metal, and wood. Initial investigations revealed a notable pattern of damage on all figures and ships: sporadically growing "needles" from the surface. Initially, it seemed likely that these could be salt efflorescences, but a closer examination held a surprise. The white material always had its origin in a metallic core. Knowledge of the exhibition conditions during recent years led to the assumption that the white material is indeed lead corrosion, which was confirmed by SEM-EDX and X-ray diffraction. The lead had reacted with formic and acetic acid emissions from display cases to form lead hydroxycarbonate (lead white) and lead formate. The question of the origin of the lead accumulations was investigated through CT scans. It became evident that the lead did not originate from impurities in the body but was formed from the lead glaze during firing.

The restoration of the salt ship convoy involved dealing with various options for treating active lead corrosion and discussing their applicability to an object made of mixed materials. The decision was made to mechanically remove the lead corrosion products and apply a protective coating to the lead accumulations. Aspects of preventive conservation were also considered because the new display case is made again of wooden materials that can lead to an accumulation of acetic acid. Therefore, options for retrofitting an existing display case to reduce emissions are also being discussed.

Encounters with an unusual black paint during treatment of Bwa masks in 2000 and 2022 inspired this black paint investigation focusing on Bwa and Mossi masks. This heavy-bodied black paint is used for raised linear designs on tri-color (red, black and white) wood masks depicting hybrid creatures or animals made by multiple cultural groups in the region of Burkina Faso. Several masks in our study were collected directly by the eminent University of Iowa scholar and art history professor Christopher Roy (1947-2019), who worked in Burkina Faso over four decades. In 25 years of treating African objects, one author has encountered various black substances, yet none to-date has resembled the unusual Bwa paint she first noted in 2000 at the Smithsonian’s National Museum of African Art. In personal correspondence with Roy about this and in his publications, Roy explained that laborious processing of Acacia nilotica seed pods produced the paint. Later object treatments undertaken in 2022 for the inauguration of the UI Stanley Museum of Art’s (SMA) new building afforded access to the Burkinabè masks collected by Roy and an increased exposure to his scholarship. The distinctive appearance and Roy’s intriguing description of the paint’s derivation led to our collaborative effort to corroborate Roy’s field observations with scientific analysis.

Following Roy’s descriptions, the processing of Acacia nilotica seed pods was recreated in the lab, and the newly created samples compared with paint from the objects. Multiple analytical techniques, including FTIR, py GC-MS, and SEM-EDS, were applied to elucidate the nature and composition of the paint samples and reference material to confirm Roy’s field description. While an array of substances is used to produce the important color black throughout the African continent, the use of Acacia nilotica seed pods for black paint appears to be localized to the Burkinabè. The study of the compelling biographies and materiality of the masks sheds light on a long cultural tradition in Africa’s Western Sudan region.

Historical objects are key to understanding the context that led to their creation – cultural, social, and technological. The growing interest in studying overlooked collections has aided in shedding light on certain periods and places, such as the transition from New Spain to (independent) Mexico. This is the case of a painting donated in 2022 to the Winterthur Museum, Garden & Library, an institution known for their American decorative arts collection. Originally referred to as a “Mexican Retablo”, the object depicts 10 figures commonly associated to the Catholic religion. This term was used despite lacking provenance, bibliographic information, or a thorough description.

Our interest in this work is multifaceted, both professionally, and personally. The objectives were (1) giving a more informed attribution and significance; and (2) adding technical information on Mexican artists, outside those once endorsed by the Spanish Monarchy. Being Spanish the native language of most authors, who in addition were raised into Catholic traditions in a predominantly Catholic country played a central role in this study. For example, it was possible to rapidly identify most of the religious figures portrayed, later confirmed through iconographic cross-referencing. As well, we realized that it was incorrectly described as a “retablo” but instead it was a “devocionario”. Devocionarios are painted collections of Catholic icons that emulate retablos, which are comprised of both sculptures and paintings. In addition, as Spanish speakers, we could access primary sources, catalogs, and existing published studies in this language. Instrumental analyses included X-ray fluorescence (XRF), Raman, and fiber optic reflectance (FORS) spectroscopies; cross-section polarized light (PLM) and scanning electron microscopy (SEM) with elemental mapping (energy dispersive X-ray spectroscopy, EDS). This technical examination revealed the work’s relative simplicity (e.g., no preparatory drawing), and limited pigment palette (e.g., white lead, ochres, etc.). of particular interest was the presence of arsenic and sulfur suggesting orpiment, a pigment traditionally used in Mexico. This study contributes to the limited knowledge of painting traditions in present-day Latin America, as it evolved from being of European influence to finding its own identity by incorporating local materials and practices and owning its iconographic style.

Sometimes things are not what they appear to be. A thorough investigation of ‘Young Man at His Window’ by Gustave Caillebotte using broadband UV, visible light, infrared, and X-ray imaging showed that the painting had multiple varnish layers applied over significant losses to the original paint and ground which had been extensively overpainted. However, the unexpected happened during what was anticipated to be a relatively straightforward treatment: newspaper print and gauze were discovered along one of the edges of the painting when a small window was opened in the paper tape. Was this evidence of a transfer? A closer visual examination supported by a full technical investigation into the composition of the previously applied conservation materials using scanning macro X-ray fluorescence spectroscopy (MA-XRF), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FTIR) spectroscopy and gas chromatography- mass spectrometry (GC-MS) confirmed that the painting was, in fact, a transfer!

Painted in 1876 on a finely woven canvas, the work likely suffered significant damage from shrinking after exposure to water. Presumably, the damage to the original canvas was sufficiently great to warrant transferring the painted image to a new support. The materials used in the ensuing structural treatments, as well as their sequence of application, were deduced from the material evidence still present on the painting. First, the damaged painting was faced using newspaper and stiff cardboard. The original canvas was then removed from the paint and ground layers. A new priming layer - composed of barium sulfate, zinc white, and gypsum bound in linseed oil - was then applied to the exposed ground. Next, gauze was laid over the dried priming layer. The newly transferred painting was then lined, using starch and animal glue to affix it to an auxiliary canvas support, and re-stretched. The final step in the transfer process would have been to remove the temporary facing. Small islands of paint affixed upside down and rotated with respect to the surrounding weave suggest that additional damage occurred during this step, necessitating further conservation treatment. Large areas of the painting were covered using a chalk-based filler and overpainted using pigments bound in modern resins. Multiple varnish layers containing pine resin, dammar, bleached shellac, drying oil, and a UV-absorber were identified on the surface of the painting.

The results were contextualized through archival research and studying textual sources [1]. The materials associated with the transfer and lining coupled with their order of application are a close match with published Parisian recipes and documented workshop practices. In this case study, the materials used in the previous treatments functioned to hide the complete extent of damages, rendering many losses invisible using standard broadband imaging techniques. This treatment and scientific examination serve as a reminder that we should expect the unexpected in every work of art.

Bibliography

[1] Rostain Emile. 1981. Rentoilage Et Transposition Des Tableaux. Puteaux France: Erec.

In 1991, the Nevada Museum of Art presented an exhibition of shopping bags belonging to the private collection of J. Scott Patnode. The exhibition, titled It's On The Bag, aimed to bridge the gap between “functional” and “fine” art by celebrating the shopping bag as a ubiquitous and accessible reflection of consumerism and pop culture at the close of the 20th century, and many of the bags on display were commercially printed with reproduced or commissioned imagery made by popular artists. One such artist represented in the exhibition was the American painter, printmaker, and sculptor Frank Stella. Commissioned by the now-closed chain of Dayton’s department stores to promote the 1984 expansion of the Walker Art Center in Minneapolis, MN, Stella’s bag was titled Tyler Graphics Bag for the purposes of the exhibition.

Tyler Graphics Bag is named for the Tyler Graphics Studio, where the bag was produced. Under master printer Kenneth Tyler, the studio collaborated with numerous other artistic luminaries of the 1970s and 1980s, including David Hockney, Helen Frankenthaler, Ellsworth Kelly, and Roy Lichenstein, and was actively exploring new technologies for digital printing. Stella’s Tyler Graphics Bag is printed on all five sides, with compositions by Stella on the two largest panels and promotional information about the Walker Art Center’s new galleries written on the smaller side panels. Prints from the same edition are described inconsistently in the market and in institutional collections, contributing to lack of clarity around the media of the original design and the methods of production.

Two of the Dayton’s Stella bags are in the collection of The Conservation Center of the Institute of Fine Arts, New York University, where, in partnership with the Museum of Modern Art, technical analysis of the bags was carried out to characterize the colorants and printing techniques employed in their manufacture. The bags were analyzed using multiband imaging, portable Raman spectroscopy, and reflectance Fourier-transform infrared spectroscopy (rFTIR) to characterize the media and colorants used in their production. Microfading testing (MFT) was also used to classify the light sensitivity of the identified colorants to establish possible display recommendations. The manufacturing processes were explored through microscopic examination, which revealed evidence that the images on the shopping bags were created using offset printmaking techniques to mimic diagnostic characteristics of other printing methods; there is a faux woodgrain in the background of the printed composition, while the overlapping marks in the center suggest stone lithography and screenprinting techniques, all of which are ersatz, produced instead with halftones of combined gray spot color and CMYK color separation. This research sheds new light on printing techniques during a transitional period in printing and digital technology, and on collaborations between one of the foremost American artists and printing studios of the 1980s.