Leather Research

Leather is frequently encountered in cultural artifacts, and conservators are working to increase their understanding of the material, its aging properties, and preservation options. This page is intended to collect and summarize research of interest to conservators on leather, both completed and ongoing. If the work is published, citations are available in the Bibliography. 
Other related pages in the AIC Wiki include BPG Animal Skin and Leather in the BPG Wiki, which describes the chemistry of skin and its tannage, Leather and Skin in the OSG Wiki, and a page on Stabilizing Wet Skin and Leather during emergency response, and BPG Use of Leather in Book Conservation in the BPG Wiki.
Wiki Compilers: Katharine Wagner and Kristi Wright
Wiki Contributors: Firstname Lastname, your name could be here
==Leather Research Initiatives==
===19th century leather research===
====Sulfur in gas lighting====
:Date: 1841 
:Location: London, England 
:Affiliation(s): Athenaeum Club 
:Participants: Michael Faraday, William Thomas Brande, Arthur Aikin, Robert(?) Brown, William Prout 
:Premise: Widespread decay in leather bookbindings was noted. In some libraries, bindings would deteriorate in just 2-3 years. Circulating books would not deteriorate as much as companion volumes left on the shelves.
:Summary: The sulfur in gas lighting theory focused on the assertion that gas lighting raised the sulfur content of interior air in libraries. The team postulated that moisture containing sulfuric acid was condensing on books, especially in the upper levels of the stacks, and depositing sulfuric acid on the bindings. As the acid accumulated it accelerated decay. Faraday attempted to solve the problem at the Athenaeum Club by collecting the gas lighting’s combustion products in glass cylinders and carrying them away in connected tubes so that the sulfuric acid would not accumulate in the room. 
:Impact: The theory was corroborated by similar observations from multiple libraries across the country and alternatives to gas lighting were explored.
====Sulfuric acid in tanning====
:Date: 1851 
:Location: Manchester, England
:Affiliation(s): Chetham Library 
:Participants: Frederick Crace Calvert 
:Premise: Sulfuric acid attributed to both atmospheric sources and the tanning process. 
:Summary: The Chetham library consulted with Frederick Crace Calvert to determine the cause of leather decay in their collection. Because the library did not use gas lamps, which were widely blamed for the decay, Calvert explored the possibility that leather decay was due to either atmospheric pollution from coal consumption or sulfuric acid used in the tanning process. 
:Impact: While tanning processes did use sulfuric acid at this time, Calvert's theory was overshadowed by a continued focus on sulfuric acid accumulation from gas lighting. 
====Sulfur in coal gas====
:Date: 1854 
:Location: London 
:Affiliation(s): The Commissioners of Sewers of the City of London 
:Participants: Henry Letheby
:Premise: Byproducts of coal consumption contribute to leather decay. 
:Summary: Letheby presented his Report on the Coal Gas Supplied to the City of London : with examples of the injury done to books, &c., by the products of its combustion to London sewer commissioners, highlighting its impurities and health risks. In addition to a reporting on the condition of books in multiple libraries, he collected gas products from the air and from the Athenaeum club's specially designed ventilation pipes, applying them to leather, paper, linen, and cotton to demonstrate the products' ability to decay the materials.
:Impact: Letheby's emphasis on the harmful effect of both London's atmosphere and interior gas lighting on library collections demonstrated the widespread nature of the issue.
====Changes to library architecture====
:Date: 1859
:Location: London, England
:Affiliation(s): Royal Society of Arts
:Participants: John Leighton 
:Premise: Changes to library architecture may help with book preservation.
:Summary: John Leighton contributed an essay titled "On the library, books, and binding particularly with regard to their restoration and preservation" in the 1859 edition of the Journal of the Society of Arts, which proposed an ideal library design, complete with lighting and architectural recommendations. 
:Impact: Leighton recommended glass cases to protect volumes prone to decay from atmospheric conditions and that libraries use oil lamps or natural light in lieu of gas. By the 1877 Conference of Librarians in London (see below) several librarians mentioned architectural considerations in light of preserving leather bindings.
====Conference of Librarians====
:Date: 1876, 1877
:Location: Philadelphia, Pennsylvania (1876) and London, England (1877)
:Affiliation(s): Conference of Librarians
:Participants: Librarians in America and Europe 
:Premise: Investigate the relationship between library architecture, gas lighting, and leather deterioration
:Summary: The effects of gas lighting, heat, and library architecture on leather bindings had been discussed at the 1876 conference in Philadelphia and the discussion continued at the 1877 London conference. These appear to be some of the first published international discussions regarding leather deterioration. Guillaume Depping, assistant librarian at the Bibliotheque Ste. Genevieve, Paris, requested that the Conference of Librarians create rules or principles for building libraries that would improve preservation.
:Impact: While the committee did form, the findings were not published. 
====Action of gas fumes====
:Date: 1880
:Location: Birmingham, England
:Affiliation(s): Birmingham Library
:Participants: C.J. Woodward 
:Premise: Assessment of the absorption of sulfuric acid into skins using gas fumes
:Summary: C.J. Woodward published one of the last studies to focus on gas lighting in 1888. Gas lighting was actively being replaced by electric lighting across the world, removing this source of sulfuric acid accumulation from public view 
:Impact: 
====Central School of Arts & Crafts discussions====
:Date: 1898
:Location: London, England
:Affiliation(s): Central School of Arts & Crafts, London; Herold's Institute, Bermondsey; Yorkshire University, Leeds
:Participants: T.J. Cobden-Sanderson, Doublas Cockerell, Cyril Davenport, James Gordon Parker, Henry Richardson Proctor 
:Premise: Bookbinders collaborate with scientists to find a long-lasting leather
:Summary: London bookbinders, some of which are listed above, felt that the overall quality of leather on the market was poor. Electric lighting was now common, and they asked Parker and Proctor to look into leather degradation. The group met periodically but ultimately decided the project was too large for them alone.
:Impact: Led to the formation of the Royal Society of Arts Committee on Leather for Bookbinding in 1900. 
===20th century leather research===
====Committee on Leather for Bookbinding====
:Date: 1900-1905
:Location: London, England
:Affiliation(s): Royal Society of Arts, Court of the Leathersellers Company
:Participants: 
::Bookbinders: T.J. Cobden-Sanderson, Douglas Cockerell, Cyril Davenport, Walter James Leighton, Sarah T. Prideaux, Joseph Zaehnsdorf
::Leather manufacturers: Siegmund Hermann Epstein, Ernest Fuller, A. Seymour-Jones
::Scientists: John Evans, Morris Charles Lamb, James Gordon Parker, William Henry Perkin, Henry Richardson Proctor
::Librarians: Edward Gordon Duff, Richard Garnett, Herbert Maxwell
::Others: William Abney (chairman), John Cavendish Lyttelton (chairman), Henry Trueman Wood (secretary) 
:Premise: 1.) Determine whether perceptions of leather decay were objective 2.) Determine chemical analysis of leathers and deterioration factors
:Summary: The RSA committee on leather for bookbinding directly addressed the declining quality of leather, assessing it from both internal (tanning) and external (environmental, treatment) sources. A preliminary report in 1901 proved that funded research was needed, subsequently provided by the Court of the Leathersellers Company. The committee documented the deteriorated state of library bindings, determining that the majority of the decay was in nineteenth century leather, evaluated problems in the tanning process, addressed library preferences, and assessed the relative fading of leather dyes. The report culimates with recommendations to tanners, bookbinders, and librarians regarding leather creation, selection and use.
:Impact: Tanners were asked to use approved tannins, sumac being one example, and to avoid sulfuric acid during tanning. Bookbinders were encouraged to user thicker skins rather than paring them excessively or having them shaved down. Librarians were given preservation and binding policy recommendations. 
====Sound Leather Committee====
:Date: 1904-1905
:Location: London, England
:Affiliation(s): Library Association
:Participants: Cyril Davenport, J.P. Edmond, J. Gordon Parker, E. Wyndham Hulme
:Premise: Determine whether council members would accept a common standard for bookbinding leather.
:Summary: Following up on the RSA Committee recommendations, the Sound Leather Committee explored the possibility of formalizing a standard. Parker was appointed to analyze leather sent by consumers and started publishing advertisements for this analysis, alongside his schedule of fees, in journals. Their findings were published in the 1905 report, Leather for Libraries. 
:Impact: Standards were not officialy adopted, but the United Kingdom did insert a clause into their government binding contracts that required leather meet certain minimum qualifications. Leathermakers started stamping their leather 'free of all injurious acids' in order to assure buyers of its quality. Though this and the RSA Committee were both London-based, their declarations had international impact. 
====British Leather Manufacturers Research Association (BLMRA)====
====United States Department of Agriculture (USDA)====
:Date: 1920s-1950s 
:Location:United States
:Affiliation(s):United States Department of Agriculture
:Participants:C. William Beebe, Ralph Wylie Frey, Jerome Stanley Rogers, Fletcher Pearre Veitch
:Premise:The USDA undertook leather research in the mid 20th century in order to assist with the development of better tanning methods, materials, and treatments. The USDA's involvement was related to the importance of hide and skin usage to the US livestock industry.
:Summary: USDA chemists examined leather bookbindings in US libraries and found them to be in various stages of decay. They reasoned that both tannages and treatment of the bindings may have contributed to the decay. 
:Impact: The research resulted in multiple publications, some aimed at tanneries and others aimed at libraries. Several publications encouraged the use of leather dressings in order to replace oils or greases lost in use (not to protect against decay, which was atrributed to the tannage). 
::Frey, R.W. and F.P. Veitch. 1930. Preservation of Leather Bookbindings. USDA Leaflet No. 69
::Rogers, J.S. and C.W. Beebe. 1956. Leather bookbindings : how to preserve them. USDA Leaflet No. 398
====FAIR Project====
====BS 7451:1991====
====STEP Leather Project====
:Date: 1991-1994 
:Location: Europe 
:Affiliation(s): 
::European Commission, the General Directorate XII for Science, Research, and Development
::School of Conservation (SC), The Royal Danish Academy of Fine Arts, Copenhagen, Denmark 
::Centre de Recherches sur la Conservation des Documents Graphiques (C.R.C.D.G.) Paris, France 
::Central Research LAboratory for Objects of Art and Science (CRL), Amsterdam, Holland 
::The Leather Conservation Centre (LCC), Northampton, England 
::Department of Library Research, Royal Library, The Hague, Holland 
::Royal Institute for Cultural Heritage, Brussels, Belgium 
::Department of Protein Chemistry, University of Copenhagen, Denmark 
::Chemistry Department B, The Technical University of Denmark, Lyngby, Denmark 
::Department of Chemistry, University of Sheffield, Sheffield, England 
:Participants: 
::René Larsen, Coordinator
::Sylvette Bonnassies, Christopher Calnan, Clair Chahine, Serge Copy, Daniel Floreal, Pieter B. Hallebeek, Edwin Haslam, Arne L. Jensen, Tony Lochmuller, Kurt Nielsen, Sophia Pauk, Henk Porck, Pascale Richardin, Christine Rottier, Frederic Saltron, Roy Thomson, Marie Vest, Leon-Bavi Vilmont, Jan Wouters. 
:Premise: 
::The STEP Leather project used comparative analysis of naturally deteriorated historic leather and artificially aged leathers to evaluate leathers considering the following objectives:
:::* Studying the changes in historic leather due to environmental exposures such as pollutants. 
:::* Determining an appropriate artificial ageing method. 
:::* Establishing standard tests for evaluating leather after artificial ageing and / or conservation.
:Summary: The project report contains multiple chapters describing analytical methods, materials, and trials, chemical characteristics of the leathers' studied, analysis of tannins and materials, and a summary and discussion of the results. 
:Impact: The STEP project participants concluded that the deterioration of leather occurs via both hydrylytic and oxidative breakdown. In general, the hydrolytic breakdown was attributed to acidic pollutant exposure while the oxidative breakdown was attributed to other environmental factors such as heat, light, and oxidative pollutants. Detailed analysis is available in the final report.
:Publications: STEP Leather Project: Evaluation of the Correlation between Natural and Artificial Ageing of Vegetable Tanned Leather and Determination of Parameters for Standardization of an Artificial Ageing Method
====ENVIRONMENT Leather Project====
===21st century Leather research===
====Craft Project BE-S2-3432 - "Development of Archival Quality Leather"====
:Date: 1999-2001 
:Location: Pan-European (UK, Germany, Italy, Greece)
:Affiliation(s): The CRAFT project was a pan-European project made up of tanners, bookbinders and research bodies from the UK, Germany, Italy and Greece
:Participants: J. Hewit & Sons, Ltd. and others 
:Premise: The CRAFT project emerged after the leather produced by the 1991 British Standard, BS 7451:1991, fell short of bookbinders' expectations. The project evaluated European bookbinding leathers used at that time with the goals of developing an objective leather quality testing scheme that could be understood by both tanners and binders. The participants aimed to optimize semi-metal tannages, with the goal of producing a leather with a longer life expectancy than normal vegetable tanned leathers in polluted environments. They also aimed to re-evaluate metal-free processes and their applicability in the creation of archival leather.
:Summary: A detailed project summary can be found in the Autumn 2001 (Volume 12) Skin Deep report by Roger Barlee: The Development of Archival Quality Leather
:Impact: The CRAFT project developed several tests and modified the British Standard specifications for bookbinding leather. These are published in the report's appendices.
===Ongoing Leather Research===
====Institute for Creative Leather Technologies (ICLT)====
:About:
:The Institute for Creative Leather Technologies is based at the University of Northampton in Northhampton, UK.
:Summary
:The Institute for Creative Leather Technologies (ICLT) is a research and education center. Their research responds to the scientific and technological needs of the automotive, fashion, footwear and allied leather industries. The ICLT works in partnership with external organizations such as the Leathersellers' Company, the National Leather Collection, and the Leather Conservation Centre
:Publications
:The ICLT maintains a research page containing ways to access their publications.
====Leather Discussion Group====
:About: 
:The Leather Discussion Group was formed in 2016 by four book conservators:
:* Holly Herro, Senior Conservator, National Institutes of Health, National Library of Medicine
:* William Minter, Senior Book Conservator, The Pennsylvania State University Libraries
:* Katie Wagner, Senior Book Conservator, Smithsonian Libraries and Archives
:* Kristi Wright, Contract Book Conservator, National Institutes of Health, National Library of Medicine
:Summary
:The Leather Discussion Group aims to acquire a better understanding of leather and the leather dyes traditionally used in conservation. The initial goals were to determine the best products available to meet the needs of conservation, to make those needs more apparent to leather manufacturers, and to identify effective methods to evaluate a skin’s quality and longevity. Since that time regular, leather-focused, meetings have furthered these goals. <Br>
:Ongoing conversations with and survey results from leather chemists, tanners, and conservators in multiple disciplines continues to provide valuable feedback. The group gave a panel presentation at AIC’s 2018 pre-conference symposium entitled “The Current Use of Leather in Conservation” covering changes to the tanning process, previous leather research, and the group’s current activities and goals. 
::Research topics include: 
::* The beginning of the leather process – the quality of the raw skin - with an exploration of changes in North American animal husbandry from the colonial era to the modern day. 
::* The influence of bookbinders' and conservators' choices when selecting and using leather
:Survey
:Do you have an interest in leather usage and longevity? Please contribute to the Leather Discussion Group's conversation by participating in this Leather Survey! 
:Presentations and Publications
:"Changes in North American Animal Husbandry from the 17th Century to the Present" 
:"Leather selection and use: a panel discussion on the impact of conservators’ choices"
:"The Evolution of Bookbinding Leather: Past, Present, and Future." In Suave Mechanicals: Essays on the History of Bookbinding Volume 7
:"Understanding the Material Properties of All Leathers, Both Old and New" BPG Use of Leather in Book Conservation
====Romanian and Hungarian Leather Research====
:About:
:Affiliations: Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Budapest, Hungary
:Advanced Research for Cultural Heritage (ARCH) Group, National Research and Development Institute for Textile and Leather INCDTP, ICPI Division, Bucharest, Romania
:University of Craiova, Department of Chemistry, Craiova, Romania
:National Museum of Romanian History, Bucharest, Romania 
:Summary
:One of the goals of these collaborations is assessing the state of degradation, materials and investigation / maintenance procedures for conservation (active and preventive) and restoration of historical and cultural heritage objects made of leather, parchment and textiles.
:Publications
: This team has published multiple papers on leather degradation and the effects of conservation treatments on leather longevity. Here are several:
::Sebestyén, Zoltán & Badea, Elena & Carsote, Cristina & Czégény, Zsuzsanna & Szabó, Tímea & Babinszki, Bence & Bozi, János & Jakab, Emma. (2022). "Characterization of historical leather bookbindings by various thermal methods (TG/MS, Py-GC/MS, and micro-DSC) and FTIR-ATR spectroscopy." Journal of Analytical and Applied Pyrolysis. 162. 105428. 10.1016/j.jaap.2021.105428. 
::Niculescu, Olga & Gaidau, Carmen & Badea, Elena & Miu, Lucretia & Gurau, Dana & Simion, Demetra. (2020). "Special effect finish for bookbinding leather." The 8th International Conference on Advanced Materials and Systems 231-236. 10.24264/icams-2020.II.21. 
====Sulfur-Free Calf Project====
:About: 
:Steven Siegel, Siegel Leather, North Carolina, United States 
:René Larsen, Copenhagen, Denmark
:Eric Themmen, Gruppo Biokimica, Santa Croce sull'Arno PI, Italy
:Summary: 
: The Sulfur-Free Calf team is actively producing and testing leather made with metal-free methods with the goal of creating an archival, fully vegetable tanned leather.
:Publications: 
:Larsen, et al. 2021. "Preliminary Report on the Development of a Sulfur Free Full Vegetable Tanned Archival Calf" in ICOM-CC Leather and Related Materials Working Group Newsletter. International Council of Museums – Committee for Conservation (ICOM-CC). 6-7.
==Quality Tests for Leather==
===Determination of Hydrothermal Stability (Shrinkage Temperature)===
:Summary: The hydrothermal stability, or shrinkage temperature, of a leather is a valuable indicator regarding the physical strength present in the collagen fibers. There are several methods available to assess shrinkage temperature. 
=====Micro Hot Table Method=====
:Application: Micro Hot Table (MHT) testing uses a small (1-2 mg) sample, a micro hot table, and a thermometer or thermoelement. The test is performed under magnification. Methodology for MHT testing is described in the resources linked below.
:Resources:
::Carsote, Cristina et. al. 2019. "Micro differential scanning calorimetry and micro hot table method for quantifying deterioration of historical leather" Heritage Science Vol 7. No. 48.
::Larsen, René et al. 1993. "Determination of Hydrothermal Stability (Shrinkage Temperature) of Historical Leather by the Micro Hot Table Technique." Journal of the Society of Leather Technologists and Chemists Vol. 77 p. 151-156.
=====Differential scanning calorimetry & micro differential scanning calorimetery=====
===Fiber Coherence===
===Printing Industries Research Association (PIRA) Test===
==Other Resources for Leather Researchers==
====European Research Centre for Book and Paper Conservation-Restoration (ERC)====
:About:
:The ERC is affiliated with the University for Continuing Education, Krems.
:Summary
:The ERC aims to initiate, execute and support research in the field of book and paper conservation-restoration, to provide tools for research and practical conservation in the field of book and paper conservation-restoration, and to communicate and disseminate research results to those who can apply them to the conservation of cultural heritage.
:Resources
:The ERC created MuLiBiNe, a multilingual bibliography database developed to assist conservators in bridging language barriers during literature searches.
:The ERC publishes Conservation Update, an open-source, international, double-blind peer reviewed journal. 
==Glossary of Leather Terminology==
==Bibliography==
Athenaeum Club, London. 1842. “Report of the Committee” in “Addenda to Rules and Regulations for the Government of the Athenaeum." London: W Clowes and Sons. Accessed March 24, 2021.
Conference of Librarians, London. 1877. Transactions and Proceedings of the Conference of Librarians Held in London. London: Chiswick Press. Accessed March 23, 2021.
Dana, John Cotton. 1910. "Leather, General Notes." Notes on Bookbinding for Libraries. Newark, NJ: Free Public Library. 93-100. Accessed March 24, 2021.
Dewey, Melvil, ed. 1876. "The Library Journal." Journal of the American Library Association 1. Accessed March 23, 2021.
European Commission. 1994. STEP Leather Project: Evaluation of the Correlation between Natural and Artificial Ageing of Vegetable Tanned Leather and Determination of Parameters for Standardization of an Artificial Ageing Method; Research Report No. 1. Ed. Rene Larsen, Marie Vest et al. Copenhagen, Den.: Bjarnholt Repro.
Frey, R.W. et al. 1930. Preservation of leather bookbindings. USDA Leaflet No. 69. Washington, D.C.: U.S. Dept of Agriculture. Accessed January 18, 2022.
Hulme, E. Wyndham, et al. 1905. Leather for Libraries. London: The Library Supply Co. Accessed March 24, 2021.
Leighton, John. 1859. "On the library, books, and binding, particularly with regard to their restoration and preservation." The Journal of the Society of Arts. 327. 207-222. Accessed March 23, 2021.
Letheby, Henry. 1854. Report on the coal gas supplied to the City of London : with examples of the injury done to books, &c., by the products of its combustion. . London: C. Dawson. Accessed March 23, 2021.
Minter et al. 2020. "Changes in North American Animal Husbandry from the 17th Century to the Present". In Proceedings of the 11th interim meeting of the ICOM-CC Leather and Related Materials Working Group. Paris: International Council of Museums – Committee for Conservation (ICOM-CC) and Centre de Recherche sur la Conservation. 179-182.
Rogers, J.S. et al. 1956. Leather bookbindings : how to preserve them. USDA Leaflet No. 398. Washington, D.C.: U.S. Dept of Agriculture. Accessed January 18, 2022.
Society of Arts, The. 1905. Report of the Committee on Leather for Bookbinding. London: George Bell & sons. Accessed March 24, 2021.
Wagner et al. 2021. "Leather selection and use: a panel discussion on the impact of conservators’ choices". Presented at AIC's 50th Annual Meeting: Reflecting on the Past, Imagining the Future. May 5, 2021
Wright et al. 2022. "The Evolution of Bookbinding Leather: Past, Present, and Future." Suave Mechanicals: Essays on the History of Bookbinding (7). 200-294. Ann Arbor, Michigan: The Legacy Press.
==History of This Page==
This page was created in 2019 within the BPG Wiki, but the compilers intend for it to become a more general topic page across specialty groups
.
Category:Materials and TreatmentCategory:Book & PaperCategory:Leather