“1H NMR study and multivariate data analysis of reindeer skin tanning methods” by Zhu et al (2017)

Zhu, L.; Ilott, A. J.; Del Federico, E.; Kehlet, C.; Klokkernes, T.; Jerschow, A.; “1H NMR study and multivariate data analysis of reindeer skin tanning methods”, Magnetic Resonance in Chemistry 55(4) (2017) pp.312–317.
Doi:10.1002/mrc.4529 (Wiley Online Library, restricted access) 

Abstract:

Reindeer skin clothing has been an essential component in the lives of indigenous people of the arctic and sub-arctic regions, keeping them warm during harsh winters. However, the skin processing technology, which often conveys the history and tradition of the indigenous group, has not been well documented. In this study, NMR spectra and relaxation behaviors of reindeer skin samples treated with a variety of vegetable tannin extracts, oils and fatty substances are studied and compared. With the assistance of principal component analysis (PCA), one can recognize patterns and identify groupings of differently treated samples. These methods could be important aids in efforts to conserve museum leather artifacts with unknown treatment methods and in the analysis of reindeer skin tanning processes.

“Species identification of ancient leather objects by the use of the enzyme-linked immunosorbent assay” by Liu et al (2016)

Liu, Y.; Li, Y.; Chang, R.; Zheng, H.; Zhou, Y.; Li, M.; Zhiwen, H.; Wang, B.; “Species identification of ancient leather objects by the use of the enzyme-linked immunosorbent assay”, Analytical Methods 8(42) (2016) pp.7689–7695. 

Doi:10.1039/C6AY01816E (Royal Society of Chemistry, restricted access)

Abstract:

Leather is one of the indispensable necessities in human daily life. However, the identification of ancient leather, especially species identification, is a great challenge for archaeologists and conservation scientists. Fortunately, the non-competitive indirect enzyme-linked immunosorbent assay (ELISA) offers a particularly promising approach for the analysis of ancient leather because of its advantageous properties such as high efficiency, low-cost, and high sensitivity and specificity. This study focuses on the use of a non-competitive indirect ELISA method to identify the species of ancient leather. Three ancient leather samples, which were unearthed from the desert in the Xinjiang area, were characterized using an analytical Oxford ISIS energy dispersive spectrometer (EDS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and ELISA. Two independent indirect ELISAs were established, and the results from the two methods were used in the determination of animal species. It was shown that all the three ancient leather samples were recognized by both anti-collagen-I antibody (ab23446) and anti-collagen-I antibody (ab117119), which indicates that the species of these leathers belong to cow. This is the first study to use an immunological method for the characterization of ancient leather. It is concluded that the ELISA method has the potential to become a powerful analytical tool in the identification of ancient proteinous materials.

"Influence of metal cations on leather degradation" by Ohlídalová et al (2017)

Ohlídalová, M.; Kučerová, I.; Brezová, V.; Cílová, Z.; Michalcová, A., “Influence of metal cations on leather degradation”, Journal of Cultural Heritage 24 (2017) pp.86–92.

doi:/10.1016/j.culher.2016.10.013 (ScienceDirect, restricted access)

Abstract:
In the presence of ions of transition metals, mainly iron and copper, there occurs a heavy damage in historical leathers: loss of firmness, fragility and even powdering. Ions of transition metals are contained in pigments used for leather dying or they come from chemicals used for leather marbling or from direct contact of leather with metal clips etc. After accelerated ageing of samples the influence of transition metal cations was evaluated by determination of changes in mechanical properties, pH values and shrinkage temperatures. Structural changes in leather were examined by means of scanning electron microscope, SDS-PAGE electrophoresis and spectroscopy of electron paramagnetic resonance. In leather samples a semiquinone radical has been detected, which initiates their oxidation. Transition metal cations catalyse this oxidation process thus increasing the damage extent when compared to leathers not containing these ions.

"Unilateral NMR and thermal microscopy studies of vegetable tanned leather exposed to dehydrothermal treatment and light irradiation" by Badea et al (2016)

Badea, E.; Şendrea, C.; Carşote, C.; Adams, A.; Blümich, B.; Iovu, H., “Unilateral NMR and thermal microscopy studies of vegetable tanned leather exposed to dehydrothermal treatment and light irradiation”, Microchemical Journal 129 (2016) pp.158–165.

doi:10.1016/j.microc.2016.06.013 (ScienceDirect, restricted access)

Abstract:

Unilateral nuclear magnetic resonance (NMR) and imaging thermal microscopy (imageMHT) were performed on newly obtained and artificially aged vegetable tanned leathers. Calf and sheep leathers tanned with vegetal extracts of mimosa bark, quebracho and chestnut wood were compared. Ageing was simulated by exposing the leather samples to heating at 70 °C in controlled atmosphere at 30% relative humidity and irradiating them with 4000 lx in the visible light region for 8, 16, 32 and 64 days. Proton spin-lattice relaxation times T₁ and effective spin-spin relaxation times T_2eff were measured at room temperature and their trend variation compared with the corresponding variations of shrinkage temperature T_s and total length of shrinkage interval measured by imageMHT. Newly obtained leather displayed different proton relaxation times and shrinkage temperatures depending on both the collagen origin and tannin type. Effective spin-spin relaxation values shown to be discriminative for collagen origin and sensitive to the cross-linking degree, whereas spin-lattice relaxation values were more sensitive to the tannin type. Both NMR relaxation times were sensitive to the changes in the water dynamics upon ageing due to the formation of collagen damaged intermediate states and shown a sudden change when the tannin matrix was depleted (e.g. de-tanning).

"The Characterization of Vegetable Tannins and Colouring Agents in Ancient Egyptian Leather from the Collection of the Metropolitan Museum of Art" by Elnaggar et al (2017)

Elnaggar, A.; Leona, M.; Nevin, A.; and Heywood, A., “The Characterization of Vegetable Tannins and Colouring Agents in Ancient Egyptian Leather from the Collection of the Metropolitan Museum of Art”, Archaeometry 59 (2017) 133–147.

doi:10.1111/arcm.12239 (Wiley Online Library, free access)

Abstract:

This work characterizes both tanning and colouring materials found in ancient Egyptian leather objects from the Metropolitan Museum of Art. The analytical investigations focused on assessing the development of the technology of ancient tanners using high-performance liquid chromatography (HPLC), surface-enhanced Raman spectroscopy (SERS), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FT–IR), X-ray radiography and a scanning electron microscope connected to an energy-dispersive X-ray detector (SEM–EDX). Reference leather samples and archaeological leather objects were investigated to identify the animal skin species and the early use of hydrolyzable vegetable tannins for leather tanning. Different methods were used to colour th leather, including madder dying and staining with hematite, or painting with Egyptian blue and Egyptian green.

"In the Flesh? Anthropodermic Bibliopegy Verification and Its Implications" by Gordon (2016)

Gordon, J.; "In the Flesh? Anthropodermic Bibliopegy Verification and Its Implications", RBM: A Journal of Rare Books, Manuscripts and Cultural Heritage 17(2) (2016) 118–33.

URL (rbm.acrl.org, open access)

Caractérisation des effets de la chaleur sur des cuirs de tannage végétal et développement d’une stratégie de restauration par voie enzymatique par Izquierdo (2015)

Izquierdo, Eléonore, Caractérisation des effets de la chaleur sur des cuirs de tannage végétal et développement d’une stratégie de restauration par voie enzymatique, PhD thesis, Université de Cergy Pontoise, 2015. 

URL / PDF (HAL)

Resumé:

L'exposition à la chaleur, notamment lors d'incendies est particulièrement dévastatrice et dans le cas d'objets du patrimoine elle entraine la destruction de tout ou partie de ces témoins du passé. Notre étude porte sur les effets de la chaleur sur le cuir, matériau largement présent dans les collections patrimoniales. A ce jour, aucune méthode de restauration permettant d'inverser les effets de la chaleur n'a été développée. Le premier objectif de notre étude est d'évaluer les effets d'une exposition à une chaleur sèche par une caractérisation systématique d'échantillons avant et après exposition à la chaleur. Des échantillons modèles, issus d'une même peau de veau de tannage végétal connu, ont été utilisés et caractérisés à différentes échelles structurales par un large ensemble de techniques physico-chimiques et biochimiques avant et après chauffage.Au-delà du brunissement et de la rétraction visible du cuir, la chaleur induit de nombreuses altérations au niveau de la structure du matériau, notamment, une perte de masse, une fonte des structures cristallines, une augmentation de l'hydrophobie ainsi qu'une rigidification. Une partie de ces changements sont attribués à l'agrégation protéique mise en évidence par cette recherche.Le second objectif était de développer une méthode de restauration innovante basée sur l'utilisation de molécules biologiques afin de respecter la nature de l'objet. Des enzymes de type protéase, capables de rompre les agrégats protéiques ont été utilisées. Un des défis est d'apporter suffisamment d'eau, nécessaire pour l'activité de l'enzyme, sans mouiller le cuir pour éviter tout dommage supplémentaire. Plusieurs supports d'application de la protéase ont été testés. Avec une émulsion enzymatique les résultats obtenus ne mettent en évidence ni coloration, ni rétraction et dans certains cas un gain de souplesse est observé. Des résultats encourageants ont également été obtenus dans le cas d'un cuir de veau historique (XIXe siècle). Des mesures complémentaires ont fait attribuer ces propriétés principalement à l'émulsion elle-même, cependant des mesures à plus long terme semblent mettre en évidence un effet positif de l'enzyme sur le gain de souplesse. Sous réserve de nouvelles caractérisations à des temps plus longs, le traitement élaboré pourrait constituer un nouveau support de restauration par voie biologique.

“A shagreen walking stick" by Silverman (2015)

Catherine Silverman, “A shagreen walking stick", ICON news: the magazine of the Institute of Conservation 59 (2015), pp. 33-36. 

URL (Icon, free access) 

This conservation work was also presented in May of 2014 as a post of the West Dean College-School of Conservation Blog.

URL

A comparative study of Roman-period leather from northern Britain by Douglas (2015)

Douglas, Charlotte R., A comparative study of Roman-period leather from northern Britain, MPhil(R) Thesis, University of Glasgow, 2015.

URL (University of Glasgow Theses)

Abstract:

This thesis draws together all of the data on Roman-period leather from northern Britain and conducts a cohesive assessment of past research, current questions and future possibilities. The study area comprises Roman sites on or immediately to the south of Hadrian’s Wall and all sites to the north. Leather has been recovered from 52 Roman sites, totalling at least 14,215 finds comprising manufactured goods, waste leather from leatherworking and miscellaneous/unidentifiable material. This thesis explores how leather and leather goods were resourced, processed, manufactured and supplied across northern Britain. It considers the potential of inscriptions and stamps to provide insights into the leather trade. It also considers the contribution that the study of footwear might make to our understanding of the demography of Roman settlements, shedding light in particular on evidence which suggests that military communities may have been more diverse than previously thought, and that there were women and children living on the northern fringes of the empire long before the Antonine Wall and its civilian communities were established.

“Feasibility of ultrafast picosecond laser cleaning of soiling on historical leather buckles” by Elnaggar et al (2016)

Elnaggar, Abdelrazek; Fitzsimons, Paul; Lama, Anne; Fletcher, Yvette; Antunes, Paula; Watkins, K. G., “Feasibility of ultrafast picosecond laser cleaning of soiling on historical leather buckles”, Heritage Science 4 (2016) 30.

DOI:10.1186/s40494-016-0104-3 (SpringerOpen, open access)

Abstract:

The aim of the research is to present a system recently developed and used for automated cleaning of artworks and to examine the suitability of using this ultrafast and precise computed-scanning picosecond laser (1064 nm) with a repetition rate of 10 kHz and a temporal pulse length of 10 ps for the removal of soiling from leather buckles without damaging the leather substrate. Preliminary tests will be performed with the model artificially aged vegetable tanned samples to determine the leather damage threshold fluence and the soiling ablation threshold fluence before using a laser for the removal of the soiling from a historical leather buckle. As laser cleaning requires a physical parameterization for optimization of cleaning accompanied with an assessment of the morphological and chemical changes of leather, an investigations were performed to determine the leather damage and ablation threshold fluences of artificially aged and historical vegetable tanned leather using a number of analytical techniques including differential scanning calorimetry, optical microscopy, scanning electronic microscope with energy dispersive X-ray analysis, colorimetry and Fourier transform infrared spectroscopy have been used. Following optimization trials of the picosecond laser cleaning parameters on model leather samples, satisfactory removal of the soiling over the historical leather surface is achieved.

“Study of the effect of tannins and animal species on the thermal stability of vegetable leather by differential scanning calorimetry” by Carşote et al (2016)

Carşote, Cristina; Badea, Elena; Miu, Lucretia; Gatta, Giuseppe Della, “Study of the effect of tannins and animal species on the thermal stability of vegetable leather by differential scanning calorimetry”, Journal of Thermal Analysis and Calorimetry 124(3) (2016) pp. 1255–1266.

DOI:10.1007/s10973-016-5344-7 (SpringerLink, restricted access)

Abstract:

Micro-differential scanning calorimetry was used to reveal the deterioration patterns of collagen in vegetable-tanned leather. The influence of both the tannin type, i.e. hydrolysable or condensed, and collagen animal species, i.e. calf and sheep, was investigated. Comparison with the behaviour of unmodified collagen in parchment was made to explain the thermal destabilisation and denaturation of the chemically modified collagen in leather. Both leather and parchment were subjected to accelerate ageing by heating at 70 °C in controlled atmosphere at 30 % RH. The synergistic effect of the daylight exposure was studied by irradiating the samples in the visible domain with 4000 lx. The destabilisation effect induced by the hydrothermal ageing treatment was evident since the 8th day and reached a critical level after 32-day ageing time. The formation of damaged intermediate states with progressively lower thermal stability was the main feature of the deterioration pattern independent of the tannin type and collagen species. Quebracho-tanned calf leather was the most resistant against ageing, whereas chestnut-tanned sheep leather underwent de-tanning after a 32-day ageing period. Exposure to visible light irradiation induced an evident thermal stabilisation due to cross-link formation. The balance between thermal stabilisation and destabilisation processes in leather during visible light exposure was influenced by the tannin type.

"Caring for leather, skin and fur" by Carole Dignard and Janet Mason (2016)

"Caring for Leather, Skin and Fur" is a web resource of the Canadian Conservation Institute which presents key aspects of managing the care of leather, skin and fur objects in heritage collections based on the principles of preventive conservation and risk management. It outlines the different qualities and characteristics of leather, skin and fur and the causes of damage to these objects. It also provides examples of preventive conservation practice.

URL 1 / URL 2 (French version)

 

“An Improved Method of Tanning Leather” by Macbride (1778)

Macbride, David, “An Improved Method of Tanning Leather”, Philosophical Transactions of the Royal Society of London 68 (1778) pp. 111–130.

DOI:10.1098/rstl.1778.0008 (The Royal Society Publishing or JSTOR, free access)

“Nanomaterials for the cleaning and pH adjustment of vegetable-tanned leather” by Baglioni et al (2016)

Baglioni, Michele; Bartoletti, Angelica; Bozec, Laurent; Chelazzi, David; Giorgi, Rodorico; Odlyha, Marianne; et al., “Nanomaterials for the cleaning and pH adjustment of vegetable-tanned leather”, Applied Physics A 122(2) (2016) pp. 1–11.

DOI:10.1007/s00339-015-9553-x (SpringerLink, restricted access)

Abstract:

Leather artifacts in historical collections and archives are often contaminated by physical changes such as soiling, which alter their appearance and readability, and by chemical changes which occur on aging and give rise to excessive proportion of acids that promote hydrolysis of collagen, eventually leading to gelatinization and loss of mechanical properties. However, both cleaning and pH adjustment of vegetable-tanned leather pose a great challenge for conservators, owing to the sensitivity of these materials to the action of solvents, especially water-based formulations and alkaline chemicals. In this study, the cleaning of historical leather samples was optimized by confining an oil-in-water nanostructured fluid in a highly retentive chemical hydrogel, which allows the controlled release of the cleaning fluid on sensitive surfaces. The chemical gel exhibits optimal viscoelasticity, which facilitates its removal after the application without leaving residues on the object. Nanoparticles of calcium hydroxide and lactate, dispersed in 2-propanol, were used to adjust the pH up to the natural value of leather, preventing too high alkalinity which causes swelling of fibers and denaturation of the collagen. The treated samples were characterized using scanning electron microscopy, controlled environment dynamic mechanical analysis, and infrared spectroscopy. The analytical assessment validated the use of tools derived from colloid and materials science for the preservation of collagen-based artifacts.

“The Chester leather industry, 1558-1625” by Woodward (1967)

Woodward, D. M., “The Chester leather industry, 1558-1625”, Transactions of the Historical Society of Lancashire and Cheshire 119 (1967) pp. 65–111.
PDF (The Historic Society of Lancashire & Cheshire)

La dorure sur cuir: reliure, ciselure et gaufrure en Allemagne par Stockbauer et Maul (1888)

Stockbauer, Jacob; Maul, Johannes; La dorure sur cuir: reliure, ciselure et gaufrure en Allemagne, 2 vol., Paris, B. Rouveyre (1888).

URL (Gallica)

Trunk covered with Russia leather, 1689-1702, Victoria & Albert Museum

“Use of aluminium alkoxide and oxazolidine II to treat acid-deteriorated historic leather” by Lama et al (2015)

Lama, Anne; Antunes, A. Paula M.; Covington, Anthony D.; Guthrie-Strachan, Jeffry; Fletcher, Yvette;“Use of aluminium alkoxide and oxazolidine II to treat acid-deteriorated historic leather”, Journal of the Institute of Conservation 38(2) (2015) 172–187.

DOI:10.1080/19455224.2015.1071713 (Taylor& Francis Online, restricted access)

Abstract:

This study was undertaken to develop a product that will potentially delay the progress of deterioration of acid-deteriorated historic leather. Acid-deteriorated leather samples were treated with a new formulation consisting of aluminium di(isopropoxide) acetoacetate ester chelate (aluminium alkoxide) and 5-ethyl-1-aza-3,7-dioxabicyclo[3.3.0]octane (oxazolidine II). The leather samples were also treated with oxazolidine II and aluminium alkoxide separately to compare the effectiveness of these reagents against the new formulation. Untreated leather samples were used as a negative control. Acid-deteriorated leather samples treated with Cellugel®, aluminium alkoxide and the new formulation along with corresponding untreated leather samples were also subjected to accelerated ageing in order to investigate the longevity of the treated leather. The impact of the treatments and accelerated ageing was determined by measuring the hydrothermal stability of the leather and pH of the aqueous extract. The formulation showed a potential to provide the acid-deteriorated historic leather with long-term protection against an artificially-created acidic environment.

Resumé:

Cette étude a été menée afin de développer un produit pouvant potentiellement retarder la progression de la détérioration du cuir ancien devenu acide. Des échantillons de cuirs acides ont été traités avec une nouvelle formule composée de chélate d'aluminium d'acétoacétate de di-isopropoxyde (alcoolate d'aluminium) et de 5-éthyl-1-aza-3,7-dioxabicyclo [3.3.0] octane (oxazolidine II). Les échantillons de cuir ont également été traités avec, séparément, de l'oxazolidine II et de l'alcoolate d'aluminium pour comparer l'efficacité de ces réactifs par rapport à la nouvelle formule. Des échantillons de cuirs non traités ont été utilisés comme témoin négatif. Des échantillons de cuirs dégradés par l'acidité traités avec du Cellugel®, de l'alcoolate d'aluminium et la nouvelle formule ainsi que des échantillons correspondant aux mêmes cuirs non traités ont été également soumis au vieillissement accéléré afin d'étudier la longévité du cuir traité. L'impact des traitements et le vieillissement accéléré ont été évalués par une mesure de la résistance du cuir à la chaleur et du pH de l'extrait aqueux. La formule a montré une capacité à fournir au cuir ancien acide une protection de long terme face à un environnement acide artificiel.

“Thermal characterization of new, artificially aged and historical leather and parchment” by Sebestyén et al (2015)

Sebestyén, Zoltán; Czégény, Zsuzsanna; Badea, Elena; Carsote, Cristina; Şendrea, Claudiu; Barta-Rajnai, Eszter; Bozi, János; Miu, Lucretia; Jakab, Emma; “Thermal characterization of new, artificially aged and historical leather and parchment”, Journal of Analytical and Applied Pyrolysis 115 (2015) pp.419–427.
DOI:10.1016/j.jaap.2015.08.022 (ScienceDirect, restricted access)

Abstract:

The aging mechanism of leather and parchment was studied by thermoanalytical methods to understand the effect of the environment on the historical manuscripts and the heritage of libraries and archives. Alkaline and acidic treatments followed by thermal dehydration were applied to achieve chemical changes in the structure of new leather and parchment similar to the slow natural aging of historical samples. Chemical and structural changes during both natural and artificial aging processes were characterized by thermoanalytical techniques. The thermal stability and the evolution profile of the decomposition products under slow heating were studied by thermogravimetry/mass spectrometry (TG/MS). The distribution of the decomposition products of these collagen-based materials under fast pyrolysis was characterized by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). It was found that the maximal rate of the thermal decomposition (DTGmax) significantly decreases by aging in case of both leather and parchment samples indicating the degree of deterioration. Py-GC/MS has been found to be a suitable technique to sensitively monitor the degradation of the polyphenolic components of the vegetable tannins under natural or artificial aging. It was established that the tannin content of leather is more significantly affected by natural aging and alkaline treatment than the main structure of the polypeptide chains. Principal component analysis (PCA) has been used to find statistical correlations between the experimental data for leather samples. The results of the PCA confirmed that the alkaline treatment and the natural aging processes similarly modify the tannin content of the vegetable tanned leather.

“Thermal analysis on historical leather bookbinding treated with PEG and hydroxyapatite nanoparticles” by Ershad-Langroudi and Mirmontahai (2015)

Ershad-Langroudi, Amir; Mirmontahai, Akram, “Thermal analysis on historical leather bookbinding treated with PEG and hydroxyapatite nanoparticles”, Journal of Thermal Analysis and Calorimetry 120(2) (2015) 1119–1127.

DOI:10.1007/s10973-015-4461-z (SpringerLink, restricted access)

Abstract:

Thermal analysis approaches give the opportunity to investigate structural changes in historical leather like as dehydration, crystallization, and melting process. An historical leather sample from nineteenth century was considered in this study. The leather samples were treated with a suspension of nano-hydroxyapatite and polyethylene glycol 400 (PEG 400) in an aqueous solution. The treatment effects on the structural changes in historical leather were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). DSC technique has been employed to study the thermal-associated changes in historical leather to an artificial aging and the conservation of nanocomposite treatment. Moreover, thermogravimetric analysis and differential thermal gravimetry (TG–DTG) are used as useful methods for the investigation of the mass losses of the treated and untreated samples at the progressive heating in N2 gas flow. Furthermore, scanning electron microscopy studies indicated the collagen fibril changes in treated sample in comparison with those of untreated sample and after accelerated aging test.