AIC's 53rd Annual Meeting

Conservators have employed numerous techniques and chemicals to remove discoloration and staining from paper objects. While ammonium and sodium citrates have long been utilized as cleaning agents by other conservation specialties, they have been gaining traction in paper conservation. Citrates show particular promise for removing metallic impurities and staining while preserving the integrity of both media and cellulosic supports. However, additional
research and practical knowledge are needed to fully understand their safe application.

This panel brings together presentations that explore recently published analytical research, treatment case studies, and theoretical considerations regarding the use of citrates in the treatment of works on paper. Three short presentations will be followed by ample time for questions and discussion of emergent approaches to treatment using citrates. The collaborative dialogue will serve as a springboard for identifying critical gaps in current knowledge and generating innovative research directions to advance our understanding of citrate applications in paper conservation.

The effects of ammonium citrate on calcium and iron levels in a 19th century rag ledger paper
Crystal Maitland, Senior Conservator of Paper at the Winterthur Museum, Garden & Library, Affiliated Professor for the Winterthur/University of Delaware (WUDPAC) program
Theresa J. Smith, Associate Professor of Paper Conservation in the Patricia H. and Richard E. Garman Art Conservation Department at SUNY Buffalo State University
Maeve Moriarty, Senior Conservation Scientist, Canadian Conservation Institute
Ute Henniges, Academic Staff Member, Stuttgart State Academy of Art and Design
Irene Brückle, Professor and Head of the Program Conservation of Works of Art on Paper, Archival and Library Materials program at the Stuttgart State Academy of Art and Design

Highlighting the inorganic analysis of work recently published in JAIC,* this talk will examine data gathered into the effects of immersion treatments with solutions of ammonium citrate (pH 5.5; pH 8.5) and citric acid (pH 1.8) on the calcium and iron levels and distribution in a 19th century ledger paper, both with and without a secondary calcium bicarbonate deacidification step. As ammonium citrates are chelating agents capable of binding both calcium and iron ions we used X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray spectrometry (SEM-EDX), scanning X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) to examine how the distribution of calcium and iron changed with treatment. Despite the brightening effects measured in the paper, in our data we saw very little change in iron levels for any of the treatments tested. The three chelating solutions removed significantly more calcium than the other wash solutions; some calcium was reinstated by the calcium bicarbonate treatment step. There was no statistically significant variation in either the calcium or iron levels achieved by changing the pH of the citric acid or citrate solutions.
* Venus, Philine, Ute Henniges, Irene Brückle, Crystal Maitland, Theresa J. Smith, Maeve Moriarty, Kamila Bladek, Diogenes Vedoy, and Antje Potthast. 2025. “Testing Ammonium Citrates for Enhanced Washing of Paper.” Journal of the American Institute for Conservation, March, 1–20. doi:10.1080/01971360.2025.2464337.

A citrate retrospective
Madison Brockman, Paper Conservator, Los Angeles Art Conservation

Madison Brockman will present treatment case studies featuring citrates used with gels, in combination with oxidative and reductive bleaches, and citrates used in an overall aqueous treatment solution. Madison will present some successes and limitations when treating different kinds of discoloration on paper and media types, considerations when sourcing and disposing of citrates in private practice, and other tips and tricks for practical use. This presentation will also briefly touch on an accelerated aging study previously published in the WAAC newsletter and an informal exploration of the effects of citrates on friable media.

Why do citrates work?
Sarah Bertalan, Conservator of Works on Paper, New York NY

Citrate treatments succeed because they address the unstable inorganic content of modern papers. The additives in papers are well known, however, paper conservators tend not to consider them when discussing condition and treatment. The pigment and mineral additives in modern papers react when exposed to high or fluctuating humidity, daylight and changing pH. These reactions noticeably alter the appearance of works of art. This brief presentation focuses on the use of inorganic additives in modern paper manufacture and their behavior over time.

Books are kinetic objects that perform finely-engineered movements to reveal their contents. If a book’s structure is broken or compromised, its information cannot be experienced in the manner that its creator intended. Loss of mechanical function is particularly disruptive for manuscripts, artist’s books, photograph albums, and scrapbooks, in which unique, intimate narratives may be presented. In some ways, nineteenth century photograph albums present worst-case treatment scenarios to conservators; these albums tend to be both heavy and very fragile, due to inherent vice, yet these albums may be frequently requested by researchers. Furthermore, photographs are physically and chemically sensitive, and nineteenth century papers are often quite water sensitive, which limits treatment options. As heavy leaves and delicate hinges embrittle with age, a nineteenth century album may pull itself apart, posing many questions; is it possible to restore mechanical function to this album without frequent re-interventions? Which materials are best for reinforcing the connections between heavy leaves and delicate hinges? Do adhesive mixtures, such as 75% wheat starch paste and 25% methylcellulose, provide better flexibility when dry?

The above questions inspired this study, in which the author, a book conservator, collaborated with paper conservators, photograph conservators, and conservation scientists at the Metropolitan Museum of Art. This presentation will discuss the methodology and results of the study, in which the relative folding endurances of Jin Shofu wheat starch paste, photo-grade gelatin, and six cellulose ethers were evaluated, before and after artificial aging. Additionally, 3:1 mixtures of wheat starch paste, methylcellulose, and/or photo-grade gelatin were studied, to observe the mechanical performances of these mixtures, once dry. To inform the methodology of this study, a self selecting survey of seventy-five AIC Book and Paper Group members was conducted. Survey participants were asked to indicate their adhesive preferences for certain treatment scenarios, and whether they are in the habit of combining two or more adhesives to alter their wet and/or dry properties. In this study, all adhesives were prepared at concentrations that would normally be used by book, paper, and photograph conservators, or at viscosities that would allow a conservator to reline the spine of a book or repair its hinges. Strips of naturally aged chromatography paper (pure cotton linters, manufactured in 1959) were impregnated with these adhesives and were evaluated with a Tinius Olsen folding endurance machine. Although folding endurance machines do not perfectly replicate a book’s normal range of motion, these machines offer insight into the effects that adhesives and sizing agents may have on the mechanical strength of a standard paper.

The surprising results of this study indicate that wheat starch paste has a much lower folding endurance than cellulose ethers with comparable bonding strengths, and that mixing two adhesives together significantly impacts the folding endurance of a standard paper, both before and after artificial aging. The author hopes that the results of this study may assist book, paper, and photograph conservators when selecting resizing agents and when repairing the flexible components of books and moveable paper objects.

The selection of appropriate repair materials is a primary factor in the long-term success of interventive treatment. This is particularly challenging for parchment repairs in which we must find a material that is comparable in rigidity, color, and weight as well as compatible with the hygroscopic nature of the original parchment. When parchment repairs are needed in bound materials, these repairs must also be able to withstand repeated flexing from use. Following a 2019 cross disciplinary workshop hosted by the Folger Shakespeare Library, “Biocodicology: The Parchment Record and the Biology of the Book”, conservators at the Folger became interested in recreating an historic preparation of tawed parchment for use as a repair material. It was immediately apparent that this project would require extensive collaboration. The outline for the project included processing the skins, making sample repairs, and carrying out a suite of analytical and ageing tests. 

As a small independent research library, the Folger does not have the analytical capabilities necessary to evaluate the skins, nor do we have a scientist to help guide testing and interpret results, so we began reaching out to other institutions for assistance. The Folger collaborated with Jesse Mayer at Pergamena to prepare twelve skins of varying thicknesses using an historic recipe. Once the skins were prepared, conservators at the Folger worked with William Minter and the Penn State University Libraries to begin accelerated ageing tests on samples from the skins. The Preservation Research and Testing Division (PRTD) at the Library of Congress has an extensive array of analytical equipment and a staff of highly trained conservation scientists. In the spring of 2024 conservators at the Folger began working with Dr. Gwen dePolo at PRTD to analyze the tawed skins. With the specific use case of the repair material in mind, the analytical testing has focused on the mechanical properties, physical properties, thermal stability, and investigating the source of a residue exuding from the skins. Dr. dePolo and Kathryn Kenney have had regular meetings about the skins, types of tests to perform, and how the results impact the usability of the alum tawed parchment as a repair material. The collaboration between the Folger Library and PRTD has proved mutually beneficial as the methods applied to analyzing the alum-tawed skins will also be used in other parchment-related research projects that will be pursued at the Library of Congress. 

This talk will discuss the benefits and challenges of a large collaborative project. We will discuss how we defined the scope and scale at an institutional level and have been able to draw on the strengths and expertise of all the participants at an individual level. Specifically, we will focus on how we used our different, but complimentary knowledge to evaluate a potential new repair material considering usability and long-term stability.

This study investigates characteristics of three cellulose ethers in the search for a stronger solvent based adhesive to add to the options available to paper conservators. Cellulose ethers are available in various polymer chain lengths (corresponding to strength), can be water and/or solvent soluble, and often have desirable aging properties. Two of the most widely used cellulose ethers in paper conservation are methylcellulose (Methocel) and hydroxypropyl cellulose (Klucel). This research compares commonly used Methocel A4M (water soluble, long polymer chain) and Klucel G (water/solvent soluble, short polymer chain), with overlooked Klucel M (water/solvent soluble, long polymer chain). Klucel M has the potential to be a crucial tool in the toolbox of paper conservators, as it has a similar polymer chain length and adhesive strength to Methocel A4M, but has the advantage of being soluble in solvent, like the much shorter length and weaker adhesive Klucel G. While older research indicated that Klucel M is inappropriate for long term use with collections, more recent research has indicated that it could be an acceptable option. Using analytical techniques including accelerated aging, colorimetry and UV-vis-NIR spectroscopy, size-exclusion chromatography, Oddy testing, and PAT testing, this study compares the adhesives Methocel A4M, Klucel G, and Klucel M and offers case studies for the use of Klucel M.