AIC's 53rd Annual Meeting

The corrosion of historic organ pipes continues to be a major problem for older historic organs in Europe. This is particularly true in the pipe feet of the larger bass pipes which are made primarily of lead. Corrosion in the pipe foot reduces the load-carrying capacity of the pipes, and makes them more difficult, if not, impossible to tune as corrosion eats away at the pipe wall and eventually breaks through. A number of recent major research projects including the EU COLLAPSE project and a project in Bremen, Germany indicate that the cause is corrosion of lead by acetic and formic acids emitted from the wooden windchest. Several measures have been suggested for dealing with the problem including neutralizing or removing residual acid in the corrosion product, coating the insides of the pipe feet, or replacing the feet with lead-tin alloys. 

This research has been primarily chemical in nature. While it provides evidence for the cause of corrosion, the proposed measures have a number of logistical and conservation ethics problems. The production of the acids is continuous, which means that pipes have to be treated regularly with some kind of aggressive solution. Coatings must be regularly maintained and replaced. Given that the affected pipes are usually the large bass pipes in a complex organ structure, such treatments would be a difficult operation to carry out regularly. Furthermore, the proposed measures only treat the symptoms and not the source of the problem, the acid emission into the pipes. 

It was noted in the previously mentioned projects that corrosion tended to be worse in organs which were not played as often, and in silent pipes. This led to a multidisciplinary pilot study conducted by the Cultural Heritage Agency of the Netherlands (RCE) to investigate the possibility of venting the pipes when the organs are not played. A team including an organ expert, a Dutch organ builder, chemists and fluid mechanics experts is studying the airflow through pipes as they are played, to see if that correlates with the corrosion in the pipe feet. Three-dimensional (3D) computer modelling and high-speed smoke visualization techniques are being used to determine the airflow within a transparent organ pipe, and locate eventual “dead” zones where corrosive gas concentrations may be higher. Endoscopic techniques are being used to determine the location of the corrosion in pipe feet. A sensor is being developed to measure the acid concentrations in the air in pipe feet.

The results of the fluid mechanics studies and initial endoscopic work indicate that corrosion correlates with dead air zones in the pipe foot. Venting the pipes is possible, and would be best accomplished by reversing the air flow in the pipe, that is, in the opposite direction to playing. Further work is planned to determine how often venting is required, and the most efficient way of doing this using the existing blower, as well as dealing with the fact that the organ will be continuously producing tones while being vented.

Research into the Deathwatch Beetle infestation on HMS Victory led to a unique collaboration between The National Museum of the Royal Navy (NMRN), Cranfield University and The Zoological Society of London (ZSL): London Zoo. Deathwatch beetles are woodboring beetles that are pests to historic timber structures whose lifecycles can span anywhere between 1-13 years. Historic investigations into Deathwatch beetles made use of live cultures of the beetles for observation and experimentation. However, the cultures were never maintained beyond the course of each research period, much to the detriment of our understanding of the species.

A PhD research project was jointly funded by NMRN and Cranfield University to enhance understanding of the Deathwatch Beetle infestation on HMS Victory and explore methods of communicating complex conservation information to the public. During investigations into non-invasive methods of larval detection, it became clear that a live culture for study was sorely needed. There seemed little point, however, to starting a culture, only to have it die out once the research was concluded. The main issue is that the culture needs care and facilities to ensure it is maintained and monitored. Enter London Zoo.

London Zoo is equipped to maintain a culture long-term, and it fits within the normal remit and activities. The presence of specialist knowledge for the establishment and long-term development of the culture is essential. Having the culture in a central location with suitable resources and a vested interest in the long-term survival will enable the future research into Deathwatch Beetle activity and behaviour, but it can also serve as a means of public engagement with a wider audience. Remarkably little is known about the Deathwatch beetle, and knowledge gained from the culture would be useful for NMRN, but also other sites dealing with Deathwatch beetle infestations. Research and investigations could be conducted by students of Cranfield, strengthening existing, and establishing new, research ties. Displaying the culture, with explanations, to the public will bring heritage science research and HMS Victory to the attention of a wider audience that would not usually come across it.

For the Zoo, the use of a wood-boring beetle notorious for its cryptid nature to develop non-invasive means of detection, means that techniques and methods can be investigated and tested on a non-threatened species before being used to detect endangered species, like the Fregate Beetle. Wildlife and heritage conservation, and the science and research behind them, can greatly benefit each other.

Lead and lead contaminated materials can be a danger in art. It can be obvious or hidden, for example: lead-containing primers, pigments, sculpture substrates, corrosion products, pigments, or art that contains contaminated synthetics. Identifying lead-containing materials can significantly change the treatment strategy, require additional safety precautions, and increase costs. However, even with the commercial availability of highly sensitive spot testing kits, determining if the artwork poses a “real” risk is not a straightforward process. Conservators at Monumenta and MoMA recently found themselves in a confusing world of false positives, opaque and uncooperative technicians at testing laboratories, and misleading thresholds. It suddenly became hard to answer the simple question “does the sculpture contain an unsafe level of lead?” using readily available testing materials.

Lead spot-testing kits available for home use range widely in precision, accuracy, and sensitivity, and are marketed for a variety of use cases. Scant comprehensive research available on the efficacy and suitability of commercially available lead spot-testing kits for conservation purposes further exacerbates the challenge of parsing out the differences between tests, making it difficult for conservators to make informed testing decisions. Further uncertainty follows because many laboratory test results offer only "presence or absence" reporting; the identification of lead does not necessarily indicate unsafe levels of lead, only that lead exists in the sample. Additionally, Federal and State standards for the total amount of unsafe lead in parts per million are inconsistent and not well delineated compared to contamination from the environment or another source. Commercial environmental testing solutions also do not provide the interpretation of test results owing to liability concerns.

In response to this need for a reliable lead-testing practice, Conservators aim to develop a lead-testing protocol that includes both interpretation of in-the-field spot testing followed by comprehensive (qualitative) analytical testing using environmental laboratories all to ascertain a creditable risk. This work includes evaluating commercially available spot testing kits for their usefulness, surveying state and federal thresholds for lead-containing coatings, cultivating relationships with toxicologists, and developing strategies to communicate with environmental testing laboratories that are reluctant to interpret data for liability reasons. A summary of research to date will be presented, which represents only the beginning of much-needed research on this crucially important safety topic.

Paper conservators working with different concentrations of agarose gels have observed that stain removal efficacy increases as the gelator concentration is increased. Although the exact process(es) contributing to this increase in efficacy have not been studied previously, many physical phenomena are thought to play a role, including diffusion and capillarity processes involved in the transport of solvent and solubilized components to and from a substrate placed into contact with a gel. We propose that the process of adsorption plays an important role in the sequestration of water-soluble products once they have migrated into the gel. The adsorption of solubilized components by the gel network essentially purifies the bulk solvent in the gel, increasing the uptake of more material and preventing redeposition. 

Adsorption measurements of solid agarose indicate that it could remove 90% of crystal violet (hexamethyl pararosaniline chloride, C25N3H30Cl) from an aqueous solution rapidly. Even when engaged in a gel network, agarose is capable of functioning as an adsorbent. Critically, a gelator can do more than act as a vehicle to deliver solvent: it can also trap solubilized components via adsorption onto its polymer chains. By adding a range of additional adsorbents, including microcrystalline cellulose powder and silica gel (200400 mesh), at 1 wt% into agarose gels, we have shown we can increase the adsorption rate and total cleaning capacity of these systems. One consequence is we can reduce the amount of gelator required for a treatment.

If the mechanisms at work within gels are better understood, it may be possible to design systems that amplify the effects of stain removal treatments while reducing the need for expensive and/or unsustainable materials. Agarose, a component of the algal extract agar, is costly due to the purification process involved in isolating the polymer and the limited availability of the algae from which it is derived.[1] However, agarose is often preferred for gel treatment of paper due to its minimal deposition of residue and the good aging properties of those potential residues.[2] This research offers an approach to decrease the quantities of this important resource needed to carry out a conservation treatment. The applicability of adsorbent-bulked agarose gels in hands-on conservation practice is being tested, and the effectiveness of specific adsorbents for certain applications is being investigated. Through the close collaboration between scientist and conservator, conservation practice informs scientific experimentation, and analytical results can impact treatment methodologies.

[1] Santos, R., Melo, R.A. Global shortage of technical agars: back to basics (resource management). J Appl Phycol 30, 2463–2473 (2018). https://doi.org/10.1007/s10811-018-1425-2

[2] Warda, J., Brückle, I., Bezúr, A., & Kushel, D. (2007). Analysis of Agarose, Carbopol, and Laponite Gel Poultices in Paper Conservation. Journal of the American Institute for Conservation, 46(3), 263–279. https://doi.org/10.1179/019713607806112260

In recent decades, conservators and conservation scientists have proposed additions and refinements to the conservation cleaning toolkit, drawing inspiration from allied fields and leveraging expertise from industrial chemists and soft matter scientists. As a result, the field has seen continued progress toward options with improved control and specificity while also favoring materials and techniques that are more sustainable and safer for the practitioner and the environment.

Inspired by conservators’ creative adaptations of rigid physical hydrogels and the working properties of chemical hydrogels adopted by the field in recent years, this paper describes the development of physical hydrogels that are thermoreversible, optically clear, cohesive, flexible, and conformable with surprising elasticity and gel strength. Drawing from food science, haute cuisine, and traditional foodways, the shared formulations are based on the synergistic binding of xanthan gum and konjac glucomannans modified with a second network of agar or agarose. These versatile, cost-effective gels are simple to produce and are compatible with typical aqueous preparations used in conservation cleaning. Additionally, these hydrogels provide options for delivery of small proportions of organic solvents and microemulsions capable of swelling and removing tenacious coatings and overpaints with minimal mechanical action. Analogous formulations substituting other glucomannans or galactomannans and selecting agar instead of agarose offer flexible decision-making favoring economic and environmental sustainability by sourcing materials native to many regions around the globe.

The development of xanthan-konjac/agar gels and their analogs has been informed by early tests in several cross-specialty professional workshops and academic courses, providing key insights into how this versatile addition to the cleaning toolkit complements our established range of rigid gels, viscous polymeric solutions and spreadable gels, viscoelastic gels, and chemical hydrogels. Case studies from collaborators will be shared in another proposed submission.

A unique partnership comprising focal points from academia, chemical industry, non-profit, and private practice was carefully curated with specific expertise, capabilities, and priorities to advance safer solvent identification and education for cultural heritage use. The work highlighted within is a continuation of the “Safer Solvent Selections for the Removal and Application of Synthetic Resins” paper presented at the 2024 RATS Specialty Session of the annual AIC meeting.  The work justification and vision is unchanged from last year: conservators seek solvents for the application and removal of polymeric resins that a) are no/low-odor, b) have minimal health and environmental impacts and c) achieve the necessary solvation and film properties.

Previous work identified solvent blends that met rigorous GHS-defined safety criteria and demonstrated ranges of solvency for Laropal A81, PARALOID™ B72, and PARALOID™ B44. This presentation will provide the next stage of research with advanced solvent blend considerations, characterization of polymeric films properties casts from select blends, and Greener Solvents project partner feedback on test evaluations.  A dialogue with the AIC community is critical to bring this research into practice over time. We look forward to productive discussion that moves the field towards safer solvent alternatives that work.

The Cooper Hewitt, Smithsonian Design Museum has a collection of approximately 300 sketches by Jan van der Straet (called Stradanus) a 16th century court artist to the Medici in Italy. A group of these drawings may have important information on the verso written with black chalk, but unfortunately, have been lined with paper. The presence of inscriptions/drawings on the verso has been detected using transmitted visible light when the media is ink but not for chalk. To minimize carrying out interventive conservation treatment to remove the linings from the fragile drawings, transmitted IR imaging was investigated to determine whether the technique could be used to detect chalk drawings on the verso without removing the linings from the drawings.

This initial imaging investigation involved four Stradanus drawings. Reflected and transmitted visible light and IR images were acquired of the recto and verso of the drawings. The investigation started with the three drawings that had the paper linings removed and had known verso chalk drawings. The first step involved testing whether transmitted IR imaging of the recto could resolve the verso chalk drawing which could be verified with reflectance images of the verso. Preliminary processing, during the image acquisition, indicated that transmitted IR and image processing could detect the verso drawing, so the next step involved imaging one of the unlined drawings with a paper support placed behind the object to mimic the lining. The final step involved the imaging of a fourth drawing that had not had the paper lining removed and it was unknown whether there was a verso chalk drawing. 

Transmitted IR images on their own did not provide much information, but image processing, both false color and image subtraction, was essential for further analysis. The false color image processing involved combinations of reflected and transmitted visible light and IR images including newer techniques that have only been introduced and used on paintings. The image subtraction processing was the difference between the reflected and transmitted IR images. The most promising methods were the image subtraction and the false color processing using transmitted visible and IR images. The image subtraction was able to fully resolve the verso chalk drawing for one of the drawings (both with and without a tertiary support), but the same processing was less conclusive for a verso chalk drawing that did not have identifiable features. When the difference mode was less conclusive, some of the false color processing seemed to be able to reveal some features that do not correspond with the recto ink drawing and could suggest that there might be verso chalk drawings.

The imaging of four Stradanus sketches suggests that transmitted IR imaging and additional processing is promising for detecting verso chalk drawings without removing the paper lining, but the results were not always definitive. Additional testing with a larger subset of drawings is needed to further investigate the potential of transmitted IR imaging and image processing.

Colorant Detectives: An Interactive Dichotomous Key for Multiband Imaging

L. M. Ramsey, The Metropolitan Museum of Art

The Colorant Field Guide is an online, interactive tool designed to aid in the visual interpretation of colorants on paper based on their responses to visible (VIS 380-650nm), ultraviolet induced fluorescence (UVF 420-650nm), ultraviolet reflected (UVR 320-400nm), and reflected infrared radiation (IR 780-1100nm [850 peak]). By employing standardized vocabularies and metrics like CIELAB and Munsell color systems, the guide ensures rigorous, reproducible, and communicable results.

Rather than relying on static research papers, black-box algorithms or automated false color post-processing systems to locate and provide results, users must navigate through a decision tree that exposes them to the various factors that influence sample behavior, including light absorption, fluorescence, and reflectance. This process demystifies colorant response by breaking it down into manageable steps, helping users to build a strong foundation of knowledge that can be applied in real-world conservation scenarios.

Transparency in documenting light/radiation sources, filters, and post-processing techniques is emphasized to achieve consistency and comparability across institutions. This approach fosters collaboration and enhances the collective knowledge base in conservation while addressing the inherent uncertainties in multispectral imaging and dichotomous identification methods.

Building a dynamic dichotomous key involves both a logical framework and technical implementation to ensure usability and functionality. I designed it to be simple and effective using basic HTML, CSS and JavaScript languages to make the key interactive, process user input, and display results dynamically. To translate the flow chart to an interactive framework, it was important to list each colorant and their responses in a standardized order. This order helps build a logical, hierarchical flow. At each decision point, users are guided either to the next question or to a result, allowing for the possibility of future expansion.

In addition to the key, I am developing a pictorial atlas of colorants recorded under these imaging techniques to serve as a visual reference. This project is intended to be publicly accessible and expandable, allowing users to submit data that meets established criteria. These submissions will be clearly credited, promoting transparency and collaboration. By encouraging contributions, this tool fosters a cooperative research environment, enriching the field of cultural heritage preservation and providing a shared resource for the broader academic community.

Dichotomous keys have long been valued in education, particularly for teaching critical thinking, systematic problem-solving, and observation skills. As multiband imaging becomes a standard practice in more institutions, this accessible tool will help ensure visual literacy in the conservation field remains strong.

Both multiband and multispectral imaging can provide a wealth of information about material characteristics and condition—with insights derived from qualitative and quantitative comparisons of images captured at different wavelengths and with different excitation sources. Workflows for these types of imaging often require costly additions to existing setups: IR-modified and/or monochrome cameras, filter sets, apochromatic lenses, and even licenses for proprietary image processing software, the sum of which can present a significant cost barrier. Certain equipment is essential, such as modified UV-VIS-IR full spectrum color or monochrome cameras. However, it is possible to perform multiband and multispectral imaging without the added cost of an apochromatic lens—one which produces a single focal plane across all wavelengths. The main challenge, however, with using a regular (achromatic) lens is the need to re-focus for each filter band, leading to registration issues across the entire set of images captured. This misalignment must be corrected post-capture not only to remove visual inconsistencies in false-color images but also to carry out any further computational analysis, such as Principal Component Analysis or Spectral Angle Mapping. 

With this issue in mind, this project has focused on developing a low-cost, open-source method for automating the registration of image sets generated from multiband and multispectral imaging workflows. Drawing on research beyond the field of art conservation, we have adapted Python code from a recent publication on vision-based robotics grasping in order to identify the specific feature-based pixel coordinates necessary for image registration. Specifically, the code utilizes an Open Source Computer Vision Library (OpenCV) tool called template matching as an alternative to feature-point detection algorithms or more complex object-detection models. In total, this method requires the addition of only a few printed paper targets and is designed to be integrated easily into existing multiband and multispectral imaging workflows. The current iteration of our adapted Python code can be executed directly from a computer’s command line, and we are hoping to create an ImageJ/FIJI plugin to make the script more readily available and user-friendly.

Northwestern University Libraries (NUL) is home to over 3,000 Arabic script materials from West Africa. Part of the Herskovits Library of African Studies, these manuscripts come primarily from northern Nigeria and cover subjects including history, theology and astronomy. Most are Arabic, but some are Ajami – non-Arabic languages written in Arabic script. The size, scope and uniqueness of these underrepresented collections, along with increasing global scholarly interest, make them a priority for conservation and digitization. In collaboration with curatorial, cataloging, and digitization staff, the NUL Preservation Department has established standardized protocols to survey, house, treat, and – using a VSC®80 forensic questioned document examination workstation – capture a range of multispectral images (MSI) that are integrated into the digital repository, adding a degree of materiality to the imaged West African manuscripts.  

Paden 417 (مختصر في فروع المالكية), a copy of the “Mukhtasar” of Khalil b. Ishaq b. Musa al-Jundi, a fourteenth-century handbook of Maliki legal principles, is one of the oldest, largest and most complex manuscripts we have worked on and serves as a case study. It is comprised of 230 individual leaves of handmade paper contained in a later leather wrapper. The primary text is written in neatly ruled lines using brown and red inks, with commentaries and annotations filling virtually all other areas of the paper in brown and black inks. The paper is brittle and discolored, with extensive losses along the edges. In preparation for imaging, the manuscript received over 300 hours of treatment from ten different current and former staff members. Our collaborative approach is not unique to this object, but it was critical for addressing the challenges presented by Paden 417, which would have been daunting and laborious for a solo conservator.  

Many of the Arabic manuscripts lack colophons or other means cataloguers use to establish clear provenance, so to understand their history and production, we must rely on the physical objects. NUL purchased a VSC®80, which allows us to quickly and consistently capture and annotate a wide range of MSI of watermarks, inks, ruling lines, and other materiality of the manuscripts.  

As one exciting example of how MSI may be used, portions of Paden 417, along with a selection of MSI files, were recently examined by scholars at the Centre for the Study of Manuscript Cultures in Hamburg, Germany. Although they had actual manuscript pages, the enhanced images of the watermarks allowed them to date the manuscript to the mid-16th century, making this one of the earliest written examples of Hausa Ajami.  

As of this writing, Paden 417 has been treated, housed, and VSC®80 images of select pages have been captured.  Digitization is underway and collation of this fragile object will follow. We anticipate that the manuscript and associated MSI will be publicly available in the digital repository by early 2025. Incorporating MSI into our digital repository augments the standard digital images, opens the door to scholarship worldwide and presents future opportunities for collaboration on machine learning and generative AI initiatives.

Collaborations among scientists, conservators, and curators have been fundamental for understanding and conserving objects like from fine and modern arts. Those collaborations have been successful in many cases, but in others, have been limited especially due to challenges associated with team dynamics. Professionals from different fields may use different terminologies and have different understandings of how cultural items should be used, conserved, and studied. The challenges are intensified when considering the engagement with non-academics, who have other terminologies and may be personally and culturally attached to the cultural items. For example, collaboration with local non-academic Indigenous people may be vital when scientifically investigating cultural items of communities still practicing their traditions. But when, why, and how scientists can or should cooperate with them?

In my research group, we are investigating a still unknown blue colorant among technical art historians and conservation scientists (https://doi.org/10.3390/heritage7090222). Such colorant has been prepared by the Tikuna/Magüta people, who live in the Amazon Forest near the borders of Brazil, Peru, and Colombia. The ethnologist and anthropologist Curt Nimuendajú described in his book, published in the 1950s, that "the juice of one fleshy fruit (T., na’inku) furnishes a dark violet which, upon contact with iron, changes into a clear blue." To investigate materials like this, scientists usually select cultural items from museums for analytical investigation, try to make the colorant using the historical recipe, or get a sample of the colorant directly from the community. All those options consider the publication of the results in scientific journals, which are usually investigator-driven and academically centered strategies that generate benefits mainly for the researchers and their scholarly fields. However, the Tikuna/Magüta people are a living culture, still producing colorants from natural sources, and it is vital to consider their collaboration in the research for mutual benefits.

Among the different approaches for community-engaged research, we have been exploring community-based participatory research (CBPR). CBPR has social justice and empowerment at its foundation and considers community members' participation from formulating research questions to developing methods and collecting, interpreting, and using data. It considers power-sharing with the community members, is based on the community's strengths and resources, promotes reciprocity and mutual learning, considers the outcomes' sustainability, and disseminates results for all interested parties and partners. In these kinds of research, Indigenous members can participate as collaborators instead of subjects or sources of materials.

CBPR has been employed in fields like healthcare, archaeology, and education. Still, it has yet to be explicitly and systematically explored in technical art history and conservation science. In this presentation, I will address the challenges and benefits of CBPR in the context of technical art history and conservation science, based on our case study of the Tikuna/Magüta blue colorant and experiences of CBPR in other fields from different authors. With our work and this presentation, I also aim to stimulate discussions about how we can promote more socially responsible and inclusive practices in technical art history and conservation science.

Historically, museums are perceived as repositories for definitive knowledge on the objects they exhibit. As a result, artworks that conservators and curators have the most questions about often remain in storage and out of public view. At the Walters Art Museum (WAM), a shift towards showcasing objects with unresolved histories has fostered engagement and curiosity from visitors.

The unexpected results of a recent technical study of a Chinese lacquer screen prompted a reassessment of whether and how it could be displayed. Inscribed with the date 1681, the four-panel screen depicts the hermitage of fourth-century scholar Xie An. This type of lacquerware was popularized during the Kangxi period of the Qing Dynasty (1661-1722). Kuan cai, meaning “incised colors,” refers to the technique in which compositions are carved into a smooth lacquer surface and filled with colored paints. Kuan cai screens were first produced for the domestic market in Southern China in the seventeenth century. They are commonly known in the West as “Coromandel screens” or “Bantam work,” referring to two popular European-run trading ports in Southeast India and Indonesia from which they were first exported. 

Kuan cai screens are made from a complex layered system of wood, clay-based grounds, fabric and paper preparatory layers, lacquer, and oil-based paints. Due to their composite nature, damage from fluctuating environments, mechanical forces, and light is common. The WAM screen entered the collection in 2012 but has never been exhibited. Prior to acquisition, it underwent multiple restoration campaigns which now partially disguise the original surface. The goal of this technical study was to determine the composition of the screen’s original and restoration materials to draw inferences on dating and historic context. Multiband imaging, microscopy, radiography, fiber optics reflectance spectroscopy (FORS), x-ray fluorescence spectroscopy (XRF), scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS), pyrolysis gas chromatography/mass spectrometry using tetramethylammonium hydroxide (THM-Py-GC/MS), and cross section analysis were completed.

While the screen was initially attributed to the seventeenth century, our results support the hypothesis that it was created during a later period. Radiography revealed an atypical construction with numerous nails attaching six horizontal cross bars on the verso. XRF showed the presence of zinc white in areas of white polychromy, while barium was detected in several passages of the screen in a variety of colors. Barium-based pigments were not available until the eighteenth century, raising questions about the screen’s dating and the extension of restoration. The absence of vermilion, orpiment, copper-based, and other commonly reported pigments was curious. 

WAM has established a precedent for displaying objects with pending questions. In the 2024 exhibition “Objects of Curiosity: What Will We Discover?,” visitors engaged in an ongoing conservation and curatorial investigation of artworks whose origin, authenticity, or utility were unknown. Taking inspiration from this exhibition, to tell the story of the lacquer screen we are developing didactic materials that reveal its layered history of use and repair. This approach to telling the stories of artworks situates visitors as active participants, rather than passive receivers of resolute information.

Recent discoveries of Patent yellow (also known as Turner’s yellow) a brilliant yellow lead-based pigment, in collection objects from The Colonial Williamsburg Foundation initiated research into the history and use of this under-researched colorant and an exploration of the most suitable analytical methods for its identification. Patent yellow’s precise introduction date and narrow window of use (1781 – ca. 1830) make it an important benchmark for dating and contextualizing objects, while recent documentary research shows it was an important and widely used inorganic yellow that may have been produced in the United States as early as 1783. However, it is little-known and rarely reported in conservation or art historical literature, possibly because lead (in the form of lead white) is ubiquitous on most historical painted surfaces, and chlorine, especially in the presence of lead, can be challenging to detect with techniques common to most conservation science laboratories such as XRF and SEM-EDS. Efforts to find and obtain reference samples of this pigment were fruitless, and attempts to synthesize it have, to date, been unsuccessful. These and other conditions can make this yellow frustratingly elusive to confirm. 

Collaborative analyses carried out at Colonial Williamsburg using cross-section and polarized light microscopy, XRF, and SEM-EDS, with further analysis using XRD and Raman spectroscopy at the Smithsonian Natural Museum of Natural History and the University of Delaware Microscopy and Microanalysis Laboratory have contributed to a better understanding of this pigment and challenges to its identification. Findings indicate its chief component is lead oxychloride (Pb7O6Cl2), consistent with Lorettoite, a (now-discredited) lead mineral, although other lead-oxide-chloride phases may be present. Raman and new XRD data for Patent Yellow have been obtained through this research, which has not previously been reported elsewhere in heritage science literature.  Photomicrographs of Patent yellow paint dispersions collected from case studies illustrate some previously unreported optical and morphological properties and demonstrate the effectiveness of polarized light microscopy in identifying this pigment, as it exhibits unique microscopic characteristics compared to other yellows, making optical microscopy a critical, simple, and effective first step in identification. Patent yellow case studies include varied decorative and fine art objects such as a painted coffeepot, a drum, a chair fragment, an easel painting by a Baltimore portraitist, and, most recently, a period room at the Museum of Early Southern Decorative Arts. This research suggests that Patent yellow/lead oxychlorides may be more common in painted surfaces than previously documented. It is hoped these findings can facilitate the identification of this pigment in other collections to better understand its broader use, properties, and role in late-eighteenth and early-nineteenth-century painted cultural heritage.

The Victoria and Albert Museum (V&A) has recently implemented a novel lighting policy (discussed in detail in VanSnick & Gaspar, 2024) - seeking to strike a balance between the display of light-sensitive objects and their long-term preservation. This work offers an evaluation of the practical rollout of the policy, refinement of process, and stakeholder uptake.

This policy works by whittling down collection on display to those objects that have the most pressing light vulnerabilities, looking experimentally at those objects, and using that new information to inform how we select vulnerable objects in the future. The first step is determining light vulnerability on a broad material level, flagging objects on display made from materials academically known to be highly light sensitive. These broad strokes are of huge benefit as it ensures that the first action of this policy will target those objects with the potential to be currently undergoing massive light damage. The second phase invites curatorial colleagues to assign a relative value each object in the group of highly light sensitive objects, allowing resources to be targeted in on the most exemplar objects which are materially assumed to be highly light sensitive. Where possible, objects that are highly light sensitive will be rotated out of display in a time period dependent on their rating value. Where rotation is not possible objects are examined experimentally using Microfademetery Testing (MFT).

Objects are unique in their vulnerabilities and these vulnerabilities are not as linear, consistent and predictable as one might expect. Experimentally analysing objects using MFT has the potential to bring their actual current light vulnerability into sharper focus. Given the vast size of the V&A’s collection, it is truly unfeasible to experimentally analyse every object - however this policy allows precise targeting of experimental resources to the places in the collection where they are most immediately needed. The lessons learnt about discrepancies between the assumed light sensitivity and the current experimental reality found are fed back into the initial stages of this process, allowing us to redirect resources to more vulnerable objects. For example, MFT conducted on Chinese, Japanese, and Korean lacquerware as part of this process has found this material to generally be drastically less sensitive to fading in practice than was academically thought. Not only does this mean that these objects can have far greater lifespans on display, improving access and ensuring we are focussing on the collections that need us most. 

This is not a static system - it is a cyclical process that edits and allows a more accurate picture of the collection’s sensitivities to coalesce in each iteration. It allows us to learn about our collection today and to react as the composition and the needs of our collection evolves over time.

The light sensitivity of works on paper is an important issue for any paper-based collection with regular exhibition cycles. The main concern is to protect the media from light-induced color changes, and MFT is a proven in-situ method for predicting these changes. As a substrate, however, white paper and especially rag paper is generally considered to be quite stable, with the exception of wood-containing and colored paper, which are considered light-sensitive according to the lighting guidelines. However, within the broadly defined class of white papers – which have been the most widespread worldwide since their emergence – there are also lignin-free white papers that are affected by moderate exposure to light. Our research group – three conservation scientists and five paper conservators collaborating from a print and drawing collection, a conservation science research laboratory, and two universities – studied typical light sensitivities related to compositions of paper and the ability of MFT to predict light-induced change in a broad range of the most typical white paper compositions.

We prepared nine sets of 37 papers divided into four compositional groups that represent papers across time. Three sets were aged in UV-filtered museum and commercial gallery exhibition-simulated settings (LED, mixed fluorescent/daylight, up to ca. 2.5 Mlxh), four underwent cyclic light-dark aging with or without pre-aging, and two sets were micro-faded by two commercially available MFT devices, one with a xenon source, the other a LED source. Using this test setup, we evaluated the influence of paper components on the color development of the papers during these different natural and accelerated aging conditions and compared them with the MFT results. The color change data of all exposures are given in Blue Wool Scale (BWS) by comparison to co-exposed Blue Wool Standards. 

Most white papers in exhibition simulation fell into the relatively stable BWS 2.5–4, but aged rag papers and papers containing ligneous and OBA papers ranged at BWS 1.–2.5. The predominant color change tended to be fading, but highly optically brightened (OBA) papers of low quality darkened. Groundwood and other high-lignin papers changed to yellowing after initial fading. Iron-contaminated papers without a significant alkaline reserve also tendentially darkened. Previous light-dark aging cycles had an effect on the type of color changes caused by light. Both MFT types and the cyclic light-dark aging predicted the papers’ sensitivity adequately compared to the simulated exhibition exposures and identified the most light-sensitive gelatin-sized rag papers and lignin-containing papers. However, predicting the color change of OBA-containing papers proved to be much less reliable. The color change of the papers that were exposed to LED in the exhibition-simulation was better reproduced by LED-MFT than by xenon-MFT or cyclic light-dark aging.  

We hope that the research results of the recently completed project will provide a clearer idea of the role of white paper in predicting the light sensitivity of artworks on paper using MFT. 

Our collaborative project was funded by the Germany Research Foundation 2021–2024.

Preservation Programs at the National Archives and Records Administration (NARA) investigated the characteristics of iron gall ink (IGI) in low or no-oxygen environments. NARA has vast holdings of 18th,19th, and early 20th century documents with iron gall ink. With the 250th anniversary of the Declaration of Independence, conservators and scientists seek to understand more about long-term display of sensitive IGI documents. In the past, NARA has used sealed anoxic encasements for some permanently-displayed iron gall ink documents. However, recent research into IGI behavior in anoxia [1] as well as material and structural differences between the majority of paper-based documents in NARA's holdings and other treasured national records on parchment meant that the use of a low oxygen display environment needed to be examined. 

Scientist Bruce Ford previously demonstrated that fading of iron gall ink is somewhat reversible in the dark but that anoxia diminished this reversion potential. His experiments exposed ink to light levels equal to several decades of display exposure, followed by a period of darkness that allowed ink to revert overnight. We sought to conduct a similar experiment, but with a closer match between typical exposure and rest periods to exhibit conditions. Additionally, we wanted to know if IGI reversion potential could ever be exhausted or would change with past treatment history. Subsequently, we designed experiments using an automated LED MFT (2700K white LED, ~3.1Mlux) in an atypical manner. We repeatedly exposed 19th century, post U.S. Civil War era, non-record samples and paused for reversion periods in the dark on the same spot. We tracked incremental and overall change in color (ΔE00) and L*a*b* color space parameters. We also tracked and controlled temperature and humidity as much as possible to prevent movement during test periods (up to 1.5 weeks) and kept the dose for each exposure as low as possible (0.04-0.4 Mlux-hrs.), only inducing enough change required for reasonable signal to noise ratios. We performed mock de-silking and delamination treatments on historic samples to mimic the condition of many NARA holdings. Treated ink required higher dosages of light to induce the same amount of change as non-treated IGI. We conducted multiple cycles of low-dose MFT both in air and anoxia and were able to reproduce Ford’s result showing reversion in air, and significantly reduced reversion in anoxia. We investigated the nuances of reversion in each of L*, a* and b* under each condition. After several tests in anoxia, we reintroduced oxygen up to 2% concentration which showed a returned ability to revert. MFT results were also compared to an experiment with 2 klux LED lamps (up to 4.5Mlx-hrs) where no visible change was observed. This indicated reciprocal failure, however these results still have important implications for display design options for iron gall ink records.

Works Cited

1. Ford, B. 2014. “The accelerated light fading of iron gall inks in air, hypoxia and near-anoxia.” In ICOM-CC 17th Triennial Conference Preprints, Melbourne, 15–19 September 2014.

Joe Overstreet (1933-2018) was an innovative artist who defied easy categorization. Interested in art from a young age he studied in California at different institutions but by 1958 he felt he had outgrown the West Coast and moved to New York where he became friends with many of the abstract expressionists and color field painters working there. Always politically motivated, many of his works from the 1960s directly referenced the civil rights movement, some such as The New Jemima(1964) are overtly figurative whereas others, such as 16th Street Birmingham (1963) and Strange Fruit (1965), are more abstract. In the late 1960s, urged by Frank Stella and Sam Gilliam, Overstreet began to create shaped, unprimed canvases painted in acrylic with bold geometric patterns that referenced his African and Shoshone heritage. These works, exemplified by North Star(1968) and Justice, Faith, Hope and Peace, presaged his growing interest in the sculptural possibilities of paintings. In his next, perhaps best-known series of works Overstreet freed himself from the stretcher altogether. His mandala paintings, such as Hoo Doo Mandala(1970), retain the geometric patterns of the shaped canvases but are stretched onto the surface of the wall. His slightly later flight patterns incorporate the soak-stain approaches of Gilliam and Frankenthaler and are held in taut geometric shapes through ropes attached to the walls, floors, and ceiling. Overstreet indicated that his use of ropes referenced both construction techniques used by Ancient Egyptians, and the ropes used in lynchings, while his desire to create easily transportable works was an homage to his nomadic ancestors who survived with our art by rolling it up and moving it all over."The founders of the Menil Collection, John and Dominique de Menil had a long association with Overstreet, purchasing The New Jemimaand several flight patterns. Through this connection he was invited by Larry Rivers to participate in the 1971 Some American Historyexhibition and in 1972 Dominique organized a solo show of Overstreets works at the Rice Institute for Arts. In 2025 the Menil Collection will open Joe Overstreet: Taking Flight,which brings together shaped canvases, mandalas, flight patterns and his seminal late series of oil paintings made after visiting Senegal in 1992. This exhibition, and access to Overstreets artworks and studio materials provided by the Eric Firestone Gallery and Corrine Jennings, Overstreets partner, provided an unparalleled opportunity to begin to examine Overstreets materials and methods. Overstreet said that My work has changed every picture I've ever made, because I'm searching for the unknown truth, but how did his materials and methods change over time? Non-destructive analysis by XRF and limited sampling revealed a shift in pigments, and an increasingly complicated painting process as he moved from shaped canvases to mandalas to flight patterns while his Senegal series marks a return to the use of oils, particularly those of the New Holland line. This is the first in-depth study of this seminal artists practice and helps reveal the various ways he sought to express his truth.

Beginning with his Nocturnes, Whistler began diluting his oil paint with a secondary medium he referred to as his “sauce.” Such a fluid medium allowed the artist to work wet-in-wet, and facilitated scraping, rubbing, and scumbling. While there are primary source references to copal being used in his “sauce,” there have been no technical studies that have identified copal as an ingredient that Whistler employed. In the 1980s and 1990s, Stephen Hackney and Joyce Townsend collaborated on a series of technical studies on paintings by Whistler in the Tate, National Gallery of Art, and Hunterian Art Gallery, among others. Their research did not find any evidence of copal, instead determined that turpentine and mastic varnish were added to the oil paint to create the sauce.

The four Nocturnes in the Harvard Art Museums’ collection (1943.171, 1943.172, 1943.173 and 1943.176) were completed over the course of the 1870s. The paintings are significantly understudied, largely due to their inclusion in the Winthrop collection, which stipulates their continuous display in the galleries and prevents their travel. The closure of the museum during the pandemic provided a rare opportunity to study the paintings. This research aimed to contribute up-to-date material analysis to compare with primary sources and build on the work of both Hackney and Townsend.

A small set of samples were taken from each painting and were either prepared as a cross-section or analyzed by thermally assisted hydrolysis and methylation pyrolysis-gas chromatography mass spectrometry. A comparison of the data has revealed some insight into Whistler’s painting materials and technique for this set of paintings. In darker compositions (1943.171 and 1943.173) multiple layers of media rich paint, some of which were unpigmented and all varying in thickness, were applied. This is in contrast to lighter compositions (or areas, 1943.172 and 1943.176) where single, relatively thick, pigment rich layers were applied. In these layers the addition of organic media was observed, in patches or waves, suggesting incomplete mixing. Pinaceae resin, may at the very least be suggested to be part of Whistler’s ‘sauce’ based on the analysis conducted here. Using written accounts as a guide the use of turpentine could be suggested, which would result in a more fluid paint medium which is a characteristic of Whistler’s paint. Analysis also suggests the recipe for Whistler’s sauce was not fixed, with evidence found for the incorporation of bleached shellac (1943.171) and perhaps mastic (1943.172) into the paint in some but not all of the nocturnes.

The Courtauld Gallery’s version of Edouard Manet’s iconic painting Le Déjeuner sur l’Herbe is perplexing. It has long been thought to be a copy created after the iconic large-scale French masterpiece of the same title; a work described as a founding moment of modern art by the last great old master. The Courtauld’s smaller work, painted “in a curiously harsh and hasty style” (Wilson-Bareau, 1986), and the large Musee d’Orsay canvas has long been a subject of scholarly debate. The Courtauld canvas has indeed been considered to be a preparatory sketch, a later replica of the d’Orsay version, or even a copy by a later hand

This Courtauld “sketch” was purported to have been commissioned by a close friend of Manet, Commandant Hippolyte Lejosne. However, according to the Gallery archival records the Courtauld painting was understood to be a gift from the artist to his friend. Following the Commandant’s death, the Lejosne family (of Maison-Lafitte) approached the Galerie Duret, one of Manet’s key dealers in Paris, who took the work on commission. In June 1928, the small sketch was brought to the attention of Samuel Courtauld by his principal art advisor and top London art dealer, Percy Moore Turner. Mr. Courtauld purchased the painting, and later, in 1932, bequeathed it to the newly formed Courtauld Gallery

Although signed by Manet in the lower left, scholarly debate has also extended beyond the painting function and onto questions over attribution. Much has been written about the narrative and symbolic meaning behind the making Le Déjeuner sur l’Herbe but the ambiguous status of the Courtauld work is in no small part due to the fact that the painting had not the focus of a materials investigation, nor had it been painting treated in the Courtauld Conservation studio for over four decades. Now, after an in-depth material investigation and the full conservation treatment this paper endeavours to explore the relationship of the Courtuald’s painting to the largescale signature work housed in the collection of the Musee d’Orsay.

This paper is a typical collaborative story between art history, science and conservation. Working closely with the curator, the conservator and the conservation scientist considered the painting materials and artistic working practice in an attempt to shed new light on the meaning behind the making of Courtauld’s version of Manet’s iconic work. Using new techniques, such as macro-XRF scanning and steadfast archival research methods, it hopes to propose a possible chronology by looking at the notions of the artist’s sketches, working as well as later copies and finally look at the possibility of replicating by another hand.

Red-figure pottery is a type of ancient Greek ceramic that originated in Athens in the later 6th century B.C. It typically features decoration in diluted clay slip that turns black after firing and is painted on a clay body that appears reddish orange. This kind of ware was used in daily life, dedicated in sanctuaries, and placed in tombs. The “red” areas contain hematite (Fe2O3), and the black background contains magnetite (Fe3O4) and hercynite (FeAl2O4). The red and black designs of Attic pottery have been shown to result from a complex firing process involving cycles of oxidation, reduction, and reoxidation. Initially, fine-grained red hematite is reduced to a dense, vitrified layer of black magnetite and hercynite, which resists reoxidation. In the final oxidation step, only the coarse-grained, porous ceramic body reoxidizes to red hematite, creating a sharp contrast between the red figures and the glossy black background (1–3).  

The Harvard Art Museums house an impressive collection of Athenian red-figure pottery. This includes the focus of this study, the so-called Bouzyges krater (1960.345), a 5th century B.C. mixing bowl for wine and water, named after the protagonist of the mythological scene depicted on its front. Although there are areas of well-preserved red-figure decoration on the krater, other areas display various levels of discoloration. The pronounced differences between adjacent sherds suggest that some alterations occurred after the vessel was broken, likely due to its involvement in a cremation burial. In such burials, ceramic vessels, often used as grave goods, were likely thrown onto the pyre and then swept into the burial, leading to the discoloration seen on the krater. Funeral pyres can reach temperatures up to 1000 ⁰C, creating a partly reducing environment due to the evolution of carbon monoxide and dioxide from burning bodies (4). It is to be expected that the temperature and oxidation/reducing environment will vary across the pyre, causing the broken fragments to display different degrees of discoloration. On some fragments, the red ceramic is altered into grey due to the reduction of hematite. On others, the black gloss is partially altered into red, suggesting high-temperature oxidation of the iron oxides occurred in areas of the fire where oxygen was more abundant.  

The disassembly of this vessel as part of its conservation treatment provides an ideal opportunity to study the krater, shedding light on the high-temperature material changes observed from the surface of the slip to the bulk of the ceramic. Using techniques such as SEM-EDS, X-ray diffraction, Raman, and FTIR spectroscopy, this material study will be important for the conservation of similar ceremonial vessels, furthering our understanding of their involvement in ritualistic practices. 

References 

1. R. Jones, Adv. Archaeomaterials. 2, 67–127 (2021). 

2. M. Walton et al., J. Am. Ceram. Soc. 96, 2031–2035 (2013). 

3. S. Balachandran, Arts. 8, 70 (2019). 

4. M. S. Walton, M. Svoboda, A. Mehta, S. Webb, K. Trentelman, J. Archaeol. Sci. 37, 936–940 (2010).