Conservation of Leather

Pattens and mules, two distinct types of historical overshoes, represent a unique group of archaeological footwear commonly found in Northern Europe. In Estonia, they are well represented within archaeological collections. These overshoes exhibit a variety of construction techniques: pattens range from simple wooden-soled types to complex, leathercovered examples, while mules may feature cork soles. Both types functioned mainly as protective overshoes, typically worn over leather shoes to protect them from wet or rough terrain. From a conservator's perspective, the composite structures of pattens and muleswhich may include metal, textile, wood or cork, and leather-pose significant preservation challenges. This paper discusses the technical features of pattens and mules, their representation in Estonian archaeological material, and the conservation approaches employed to stabilize and preserve them. Although pattens and mules may not be the single greatest challenge in archaeological conservation, they exemplify some of the most complex, multimaterial, and interpretation-sensitive tasks faced by conservators.

Many objects of culture heritage, comprised of leather, need to receive the right treatment to be restored and to elongate their lifespan. Determination of the degradation degree and even better the type of the degradation is a crucial knowledge for the way of subsequent conservation, exhibition and long-term storage. Collagen based materials are very sensitive to the deterioration and undergo, mainly hydrolysis and oxidation. Namely acid hydrolysis and photooxidation are the most often causes of the disintegration of leather. Contrary to the leather investigation, a few studies dedicated to parchment described some typical features of hydrolysis, oxidation and gelatinization observed applying Attenuated Total Reflection Fourier-Transform Infrared spectroscopy (ATR-FTIR) which is widely used in collagen degradation type research. Except of the collagen secondary structure, followed by IR spectroscopy, we determined the shrinkage temperature of the collagen substrate by Micro Hot Tab...

Parchment bindings located in the Sternkammern in the Prunksaal (State Hall) of the Austrian National Library were subject of an exemplary conservation treatment with minimal intervention. As part of a treatment plan for selected damaged parchment bindings, a comparative study of the most common infill materials for parchment of parchment bound volumes was carried out: This paper discusses well-known and widely used materials for filling in losses in parchment book covers including Japanese paper, parchment and reconstituted parchment. Their properties were examined and compared with regard to their dimensional changes and long-term stability in a non-climate controlled environment, taking aspects of efficiency and economy into consideration as well. The main findings of this comparative overview show that Japanese paper multilayer infills are superior with respect to their dimensional stability while parchment and reconstituted parchment infills excel with respect to aesthetics. Possible fields of application as well as limitations of the studied materials are discussed so that this study may provide a guideline for the decision process.

This work concerns a group of eight gilded panels dated to the 16th-17th century and preserved at the Correr Museum (inventory no. Cl. XXI, nos. 145, 145a, 145b, 145c, 145e, 145f, 145g, 145h), which acquired them from the painter Cesare Laurenti in 1906 for 450 lire.
In addition to the provenance of the pieces, this contribution identifies their graphic models, discusses their place of origin —so far not specified— and their dating, which is set in the 17th century.
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Il presente lavoro riguarda un gruppo di otto corami dorati datati al XVI- XVII secolo e conservati al Museo Correr (n. inv. Cl. XXI, nn. 145, 145a, 145b, 145c, 145e, 145f, 145g, 145h), che li acquistò dal pittore Cesare Laurenti nel 1906 per 450 lire.
Oltre alla provenienza dei pezzi, questo contributo ne individua i modelli grafici e ne discute il luogo di provenienza, sinora non specificato, e la datazione, fissata al XVII secolo.

In this study, sodium alginate (SA) was oxidized with potassium periodate to produce an alginate-based tanning agent. Using OSA as a biodegradable tanning agent and a nano-hydroxyapatite (nano-HAp) low concentration suspension to give flame retardancy to leather, eco-design concepts were applied to establish a chrome-, aldehyde-, and phenol-free tanning process. Micro-DSC, 1 H unilateral nuclear magnetic resonance (NMR), attenuated total reflection mode Fourier transform infrared spectroscopy (FTIR-ATR), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) were used to investigate the complex matrix collagen-OSA-nano-HAp. Micro-differential scanning calorimetry (micro-DSC) was used to assess OSA's ability to interact with collagen and stabilize the collagen-OSA matrix, while 1 H unilateral (NMR) was used to investigate the aqueous environment and its limitations around collagen molecules caused by their association with OSA and nano-HAp. Industrial standard tests were used to assess the mechanical properties and fire resistance of the new leather prototype. The findings reported here indicate that both OSA and nano-HAp are suitable alternatives for cleaner tanning technologies and more sustainable leather.

Tanning is among the most polluting industries in the world. Industrial-produced hides and skins are fully or pre-tanned with highly polluting chromium salts. The purpose of the study was to gain new knowledge about Iron Age tanning methods to clarify whether sustainable
tanning methods can be developed based on this. Fur skin capes, uncovered in Jutland bogs, from Baunsø Mose (20-220 AD), Borremose I (365-116 BC), Huldremose I (1-174 AD) and Vindum Mose (386-203 BC) were analysed by Attenuated Total Reflection-Fourier Transform
Infrared Spectroscopy (ATR-FTIR), Gas Chromatography-Mass Spectrometry (GC-MS) and morphological assessment of the skin fibres to identify tanning substances and material condition. Analyses were supplemented with source studies of previous visual assessment of the capes and measured shrinkage temperature of leather and skins excavated from bogs. Our results show that only the samples from Baunsø Mose, Borremose I and Huldremose I contain vegetable tannins. Furthermore, Baunsø Mose contains cow fat and Borremose I, Huldremose I and Vindum sheep fat. All contain indications of the presence of aluminum and iron compounds. The samples are decomposed to varying extents. Remnants from conservation were detected on Huldremose I, Baunsø Mose and Vindum Mose.

Lubricants and leather dressings are the most common treatments of dry and water logged historical leathers. Color change has a great importance during the time and treatment process, due to visual and aesthetic values of historic leather relics. Polyethylene glycol (PEG) and silicone oil (SiO) are frequently used leather dressings in the conservation procedures. Therefore, color stability of treated leathers with PEG and SiO were investigated before and after heat accelerated aging. Moreover, application of ascorbic acid was evaluated as an antioxidant additive for PEG (PEG+AA).Color change after treatment and aging were studied by colorimetry technique in the CIE *L*a*b system. Results indicated to severe color alteration in PEG treated and aged leathers with or without ascorbic acid. Whereas, SiO treated samples showed better stability and minimum color shift after aging. Silicone oil was characterized as the best dressing for historical leathers with compared to PEG and PEG+AA, ...

Since 2003, the ICPAL Laboratory for the Conservation of Library Materials in Rome has been developing a conservation method to carry out cleaning interventions on works of art on paper using rigid aqueous Gellan gels, a microbial exopolysaccharide that allows a constant and controlled release of water onto the paper. The adoption of this method, which has been modified by research carried out during cleaning interventions on moveable paintings, is a result of the need to find a technique that—in comparison to traditional ones—minimizes the effects of aqueous swelling, guaranteeing the maintenance of the codicological aspects of the artefact and which takes into account that, in this type of work, paper not only plays the role of support for graphical media but is an integral part of the image itself. The mechanism of exchange that is established between the paper and the gel during treatment allows the effective removal not only of surface deposits but also of a part of the substan...

In continuation of part IV, this part deals with the colour tests, free sugars and phenolic agtycones of 28 plants (Lauraceae to Meliaceae). A detailed discussion of each plant is given, dealing with the results obtained by us and those given in literature. The present study is a continuation of the previous reports searching for plants containing tannins and flavonoids (1, 2). It covers those plants belonging to the families Lauraceae to Meliaceae. Emphesis was also made on tests specific for tannins and flavonoids as well as paper chromatographic analysis of the free sugars and phenolic agtycones. This study contains the well known family Legurninosae which is rich in tanniniferous plants. Among the barks of the plants of this family belong mimosa (Acacia mearnsii), babul (A. arabica) and avaram (Cassia auriculata), the woods of some plants are also well known tanning materials e.g. catechu or Burma cutch {Acacia catechu} and chestnut (Castanea sativa); moreover the pods may be a rich source for tannins in this family as those of divi-divi (Caesalpinia coriaria), algorobilla (C brevifolia), tara {C spinosa) and sant {Acacia arabica); the Egyptian species are known as A. nilotica (3). Besides, other plants belonging to the same family are recorded as containing over 10% tannins (4); among these are a number of Acacia, Albizzia, Bauhinia, Cassia, Piptadenia, Pterocarpus and others. In this study 28 plants are studied and each plant shall be discussed in details hereafter. RESULTS AND DISCUSSION Cinnamomum gtanduli f enLm { Lauraceae } The leaves and bark of this plant were found to contain condensed tannins. Protocatechuic acid was detected in both the leaves and bark, while caffeic acid was only identified in the bark. This plant has not been recorded to contain tannins.

In the past two decades, worldwide interest in the natural dyes obtained from plants has rapidly increased, and a diversity of health and environmental benefits were found or argued for the practice. Cloves are the aromatic flower buds of a tree in the family Myrtaceae, Syzygium aromaticum, which their chemical compounds makes them suitable for the application in dyeing process. The important essential chemical constituents of clove include acetyl eugenol, beta-caryophyllene, vanillin, crategolic acid, gallotannic acid, and methyl salicylate. In this study, clove as the plant-derived dyestuff was used for dyeing the wool yarns to be investigated the effects of the different dyeing parameters including dyeing methods, acid and mordant type, and concentration and dyeing temperature in the yielded dyeing. The dyeing capability of the samples at different concentrations and temperatures was investigated using the spectrophotometer method and Beer–Lambert law. The results show that apply...

Many objects of culture heritage, comprised of leather, need to receive the right treatment to be restored and to elongate their lifespan. Determination of the degradation degree and even better the type of the degradation is a crucial knowledge for the way of subsequent conservation, exhibition and long-term storage. Collagen based materials are very sensitive to the deterioration and undergo, mainly hydrolysis and oxidation. Namely acid hydrolysis and photooxidation are the most often causes of the disintegration of leather. Contrary to the leather investigation, a few studies dedicated to parchment described some typical features of hydrolysis, oxidation and gelatinization observed applying Attenuated Total Reflection Fourier-Transform Infrared spectroscopy (ATR-FTIR) which is widely used in collagen degradation type research. Except of the collagen secondary structure, followed by IR spectroscopy, we determined the shrinkage temperature of the collagen substrate by Micro Hot Table method (MHT) to reach the degradation level. In this paper, artificially degraded leather samples as a theoretical representative of cultural heritage objects were examined. We discuss the use of both techniques (IR and MHT) as potential methods for fast assessment of oxidation and hydrolysis of vegetable tanned leathers and degradation level. New samples of leather tanned by various vegetable tannins were artificially degraded under controlled conditions. We simulated the photooxidation by means of the Xenon arc lamp exposure, oxidation using the soaking in hydrogen peroxide, acid hydrolysis by the soaking in hydrochloric acid and alkaline hydrolysis using the soaking in natrium hydroxide. ATR-FTIR spectra of reference and tested samples were compared. Oxidation causes increase of the distance between amide I (A I) and amide II (A II) wavenumbers (Δν) above 100 cm −1 and the intensity ratio between A I and A II bands (A I /A II) above 1.6. The A I / A II ratio depends on the type of hydrolysis. The increase above 1.8 proves acid hydrolysis while the decrease under 1 demonstrate alkaline hydrolysis. MHT results are not so obvious. Generally, mainly the hydrolysis causes the decrease of the temperatures. We have found out that knowledge of the whole shrinkage interval is important and provides more appropriate information about the leather disintegration.

This study aims to determine the efficiency of Polyamide 6 in consolidating fragile vegetable-tanned leather artifacts. Through two proposed interaction strategies, molecular modeling calculations demonstrated how the proposed polyamide 6 structure can protect vegetable-tanned leather from deteriorating environmental conditions. The total dipole moment was calculated as a potential descriptor of structure reactivity, and all of PA6 and the two proposed interaction models reveal poor reactive behavior when compared to pristine structures, confirming its capabilities as a protective layer. Furthermore, electrostatic potential maps were created to enhance PA6 s ability to safeguard leather artifacts and transform them into neutral, non-reactive substances. It was also created new vegetable-tanned leather prototypes. Polyamide 6 was produced in various concentrations and impregnated into the aged untreated samples. The evaluation process used some physical qualities (digital and scanning electron microscopes, color change, water absorption, and water vapor permeability). All examinations and investigations revealed that 2% and 3% concentrations produced the best results, while the concentration of 5% produced the worst. As a result, this study suggests employing 2% and 3% concentrations to treat historical and archaeologically fragile vegetable-tanned leather objects.

The first millennium BCE was pivotal for the environment and for human societies in Central and Eastern Eurasia because transformations accelerated and altered natural and cultural landscapes to hitherto unknown dimensions. Among the major driving forces was the increasing use of horse riding, which extended range of movement significantly and led to the development of cavalry units as a part of large armies. Empires with enormous outreach and gravitational pull formed and disintegrated in close dependence. The wide spread of military technologies demonstrates their bonds, though mostly in the form of metal objects due to the inherent survivability of their materials. Equipment and protective clothing of organic material, albeit produced in large numbers and thus an economic and environmental factor, are rarely preserved. In Yanghai cemetery site, Turfan, the remains of one leather scale armour were discovered. In this study, the results of the AMS radiocarbon dating as well as the construction details of the Yanghai find are presented and compared with a contemporary armour of unknown origin in the Metropolitan Museum of Art New York (MET) and with finds and depictions from the Near East, the adjacent northern steppe areas and the territory of China. The armour, datable to 786-543 cal BCE (95% probability), was originally made of about 5444 smaller scales and 140 larger scales, which, together with leather laces and lining, had a total weight of ca. 4-5 kg. Our reconstruction demonstrates that it can be donned quickly and without the help of another person by wrapping the left part around the back, tying it to the right part under the right arm and fastening with thongs crosswise over the back to laces at the opposite hip parts. Fitting different statures, it is a light and highly efficient defensive garment. In age, construction details and aesthetic appearance it resembles the MET armour. The stylistic similarities but constructional differences suggest that the two armours were intended as outfits for distinct units of the same army, i.e. light cavalry and heavy infantry, respectively. As such a high level of standardization of military equipment during the 7th century BCE is only known for the Neo-Assyrian military forces, we suggest that the place of manufacture of both armours was the Neo-Assyrian Empire. If this supposition is correct, then the Yanghai armour is one of the rare actual proofs of West-East technology transfer across the Eurasian continent during the first half of the first millennium BCE, when social and economic transformation accelerated.

In this study, woolen pile used in hand-knotted carpet was modified through biocompatible chitosan derivative, namely, chitosan-polypropylene imine dendrimer (CS-PPI) hybrid, and then its dyeability and color fastness using weld natural dye were investigated. The impact of CS-PPI, dyeing pH and dye concentration on the dyeability of the substrates were then studied. According to the results, as the CS-PPI amount increased, the dyeability and color depth was considerably enhanced. In the case of modified wool, the amount of dye exhausted at pH 7 was markedly higher than that at pH 4 while no appreciable difference was observed for pristine wool dyeability with pH changes. Color strength (K/S) data were in the following order of the CS-PPI modified wool>Aluminium-mordanted wool>pristine wool. Modification of wool had no adverse impact on color fastness and even in some cases resulted in minor improvement in fastness properties. Overall, it was concluded that mordant and acid could be eliminated from natural dyeing through wool modification with biocompatible CS-PPI that is of great importance from ecological point of view.

Excavations carried out at the Yenikapı quarter of Istanbul under the Directorate of the Istanbul Archeological Museum between 2004-2013 and have brought the historical importance of the port to light. During the salvage excavations in Yenikapı, hundreds of leather sandals and leather objects from the Byzantine period have been uncovered. The aim of this study is to determine both tanning and coloring materials of eight leather objects belonging to the Byzantine period and physicochemical characterize the leather structure. A complementary analytical approach has been used to characterize leather objects. The ATR-FTIR analysis revealed that the leather objects were tanned with vegetable tannins (gallotanins, condensed tannins and hydrolyzable tannins). By HPLC-DAD analysis, it is known that tannin dye plants were used to color the leather (Quercus infectoria or Quercus ithaburensis). The EDS analysis result showed the possible use of cupric sulfate (CuSO 4) for preliminary preparation before tanning leathers during the Byzantine period. In addition, SEM was used for visual assessment of the degree of deterioration of leathers. Based on the EDX analysis, biological deterioration factors and changes in the element ratio have shown that the leather objects deteriorate. In addition, pH, moisture content and CIE* Lab values show that there is a deterioration in the structure of leathers under the sea. The study will sheds light to leather conservation studies.

The inks used in Arabic manuscripts written between the 11th and 17th centuries and belonging to the archive of the Sacromonte Abbey in Granada, Spain, were studied. The constituent materials were determined with DRX, SEM/EDX, FTIR, HPLC and EC analytical methods. The results obtained coincide with the components described in a considerable number of Islamic recipes and treatises from the period. In all cases gum arabic was identifi ed as the binding agent. Iron gall inks and carbon blacks were used for black inks. Vermillion and minium were the most used for red inks; verdigris, malachite and lead and tin yellows for green inks; natural ultramarine blue (lapis lazuli), azurite and smalte in blue inks; and, fi nally, gold and some silver for gold inks. Chlorine was detected in a large number of the samples for reasons that cannot be fully explained. Calcium and magnesium were present, presumably as in their carbonate form, as an additive in the pulp.

In this study six different commercial vegetable tannins were analysed by ultraviolet spectroscopy and multivariate analysis. In addition, also it was determinated a specific absorptivity and quantified the total polyphenols and tannin content of each extract by filter and Folin Ciocalteu methods, respectively. The lowest values of specific absorptivity were for extracts of condensed tannins and the highest for the hydrolysable tannins. At analysis of total polyphenols, the condensed tannins showed the highest percentage, 90% and 80% for the quebracho and mimosa, respectively. Hydrolysable tannins were in the range 60-67%. In the evaluation of tanning percentage, the quebracho, chestnut and mimosa presented a percentage around 80%, followed by valonea, tara and myrobalan, 74, 56 and 41%, respectively. At multivariate analysis, a well-defined separation can be seen through both principal component analysis (PCA) and hierarchical cluster analysis (HCA), between condensed (quebracho and mimosa) and hydrolysable (valonea, chestnut, myrobalan, and tara) tannins. In hydrolysable tannins, it was also possible to observe the formation of two different subgroups between samples of chestnut and valonea and between samples of tara and myrobalan. Of all samples analysed, the chestnut and valonea showed the greatest similarity, indicating that these extracts contain equivalent chemical compositions and structure and, therefore, have similar properties.

This study aimed to identify and classify the type of plants used for tanning historical leathers using cost-effective Fourier transform infrared (FTIR) spectroscopy. The investigation was carried out on five plants (oak bark, sumac, valonia, tara, and gallnut) and four historical leather samples from book bindings dating back to the Qajar period. Tannin extraction from both plants and leathers was performed using acetone–water solvent, and the samples were then subjected to FTIR spectroscopy. Pre-processing of the spectra included baseline correction, smoothing, and normalization. Principal component analysis (PCA) was used to identify the source of tannins based on FTIR results. FTIR was found to provide a good separation of condensed tannins from hydrolysable ones. However, PCA analysis allowed for the separation and identification of the type of plant used for tannin extraction. The examination of historical leather samples revealed that the primary classification based on the t...

The application of leather dressing and lubricants is one of the important challenges in conservation of historic dry leathers, due to their effects on structural and visual properties and stability of leathers. This study aimed to investigate influence and stability of silicone oil and polyethylene glycol (PEG) on treated dry leathers, and application assessment of ascorbic acid (AA) as an antioxidant additive for PEG. The polymers, untreated and treated leather samples were submitted to heat accelerated ageing process. FTIR spectroscopy, colorimetry, pH measurements, investigation of mechanical properties and shrinkage temperature (Ts) were used to explain effect of treatments. Also, the oxidation of polymers during ageing process was monitored by FTIR spectroscopy. Results showed that silicone oil has better stability against thermal oxidation with compared to PEG. Ascorbic acid inhibited the PEG oxidation. Moreover, results revealed that the silicone oil has a better performance...

Organic materials, due to their vulnerable structure, are considered as rare archeological materials. Therefore, the number of research and literature about these materials is limited. In this project, four leather artifacts found in Chehrabad Salt Mine of Zanjan belonging to Achaemenid period have been studied in three sections: first, identifying the type of animal whose skin has been used in producing these artifacts; second, identifying the tanning materials; and third, identifying the materials used in fat liquor processing. For identifying the animal species, cross section of leather samples were studied using optical microscopy method. Results showed that sample no. 1 is of cow skin, sample no. 2 of goat, and sample no. 3 and 4 are of sheep skin. These results can prove the hypotheses related to animal species. For identifying tanning material, presence of plant tanning agents was studied using ferric chemical test. The results revealed the absence of any tanning agents and this disproves the hypotheses related to tanning material. For studying the existence of mineral tanning material, SEM-EDS elemental analysis technique was used and the results showed the absence of those mineral material; concluding that no tanning material used in the samples. For identifying the materials used in lubricating process, GC-MS technique was used. Separating organic compounds in samples, this technique also proved the absence of vegetable tanning materials in the process of manufacturing these artifacts and this confirmed the results of ferric chemical test. Comparing the compounds identified by GC with MS library, some fatty acids were recognized. Linoleic acid and stearic acid were identified in sample 1 which shows the presence of sunflower oil. Oleic acid and capric acid (decanoic acid) were identified in sample 2, but no material could be found with these two fatty acids. Probably two materials have been used in lubricating process of this sample. In sample no. 3, only oleic acid was found. For sample 4, no fatty acid could be found, proving the absence of oil and fat in this artifact. Finally for ensuring the results of GC-MS, FT-IR technique was used. In this regard, two important absorbance bands of fatty acids i.e. O-H and C=O bonds were considered. All samples, except sample no. 4, showed absorption in mentioned areas. Thus FT-IR confirmed the result of GC-MS analysis. These results support the hypotheses given about the materials used in lubricating process of the samples.

Lubricants and leather dressings are the most common treatments of dry and water logged historical leathers. Color change has a great importance during the time and treatment process, due to visual and aesthetic values of historic leather relics. Polyethylene glycol (PEG) and silicone oil (SiO) are frequently used leather dressings in the conservation procedures. Therefore, color stability of treated leathers with PEG and SiO were investigated before and after heat accelerated aging. Moreover, application of ascorbic acid was evaluated as an antioxidant additive for PEG (PEG+AA).Color change after treatment and aging were studied by colorimetry technique in the CIE *L*a*b system. Results indicated to severe color alteration in PEG treated and aged leathers with or without ascorbic acid. Whereas, SiO treated samples showed better stability and minimum color shift after aging. Silicone oil was characterized as the best dressing for historical leathers with compared to PEG and PEG+AA, ...