Dorte Sommer - Academia.edu (original) (raw)

Papers by Dorte Sommer

Zeitschrift fuer Kunsttechnologie und Konservierung, 2009

Tierhäute gelten seit langem als wesentliche Elemente in der Herstellung von eisen- und wikingerz... more Tierhäute gelten seit langem als wesentliche Elemente in der Herstellung von eisen- und wikingerzeitlichen Schilden Nordeuropas. Trotz vieler gut erhaltener Funde blieben diverse grundsätzliche Fragen bezüglich der Beschaffenheit dieser Produkte bisher jedoch weitgehend unbeantwortet. Wie wurden beispielsweise die Tierhäute behandelt bevor sie auf die Schilde aufgezogen wurden und welche Tierarten wurden bevorzugt? Beide Aspekte sind sehr wichtige Faktoren in der Interpretation prähistorischer Schilde und deren Widerstandsfähigkeit sowie der damit verbundenen Kampftechniken und taktischen Überlegungen. Das Ziel des in diesem Beitrag vorgestellten Projekts war es, diesen Fragestellungen mittels Mikro- sowie sogenannten ZooMS-Analysen an Tierhautproben von vier gut erhaltenen eisen- bzw. wikingerzeitlichen Schildfunden nachzugehen. Die Untersuchung brachte neue Erkenntnisse zur Schildkonstruktion in Nordeuropa. Zudem ist es nun zum ersten Mal gelungen, die Beschaffenheit der Tierhautp...

General rights Copyright and moral rights for the publications made accessible in the public port... more General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Reports on the result of the condition assessment of the Vinland Map (VM). The damage assessment ... more Reports on the result of the condition assessment of the Vinland Map (VM). The damage assessment was based on visual and simple non-destructive methods observing characteristics at the macroscopic and microscopic level, mainly relating to the surface of the parchment including the ink. Additional damage assessment was performed on selected parchment sheets bound in the Tartar Relation (TR) and the Speculum Historiale (SH). The bindings of the TR and the SH were subjected to a technical examination of the book structure and a simple non destructive damage assessment of the leather. The condition of the parchment and ink of the VM, SH and TR as well as the book bindings are reported. Also discussed are the authenticity of the VM, dating of the rebinding of the SH and TR, and the relations between the three objects.

Journal of Cultural Heritage, 2019

In this paper, two species identification methods are compared and discussed based on a case stud... more In this paper, two species identification methods are compared and discussed based on a case study of medieval archaeological leather shoe parts from the Danish cities of Ribe, Viborg and Odense. The species identifications are performed by both morphological grain pattern analysis using stereomicroscopy and zooarchaeology by mass spectrometry (ZooMS), which identifies species based on small structural differences in collagen type I, creating unique fingerprints of genera and in some cases species. Of the 105 shoe parts analysed and sampled, only 37 shoe parts were found to have preserved grain patterns. Grain pattern analysis was in some cases complicated by the lack of hair holes, degraded grain and the presence of soil particles. The varying morphological appearance and condition of the grain patterns are demonstrated through a series of stereomicroscope colour photos at 10x enlargement. The microscope photos reveal considerable complexity and variety in the morphological appearance of the decayed archaeological leather in comparison with well-preserved modern leather. The colour photo examples of the grain pattern and ZooMS-identified leather may help to improve the grain pattern analysis of archaeological leather in future. Where grain patterns were preserved, a good correlation between the two methods was observed. ZooMS had a high overall success rate and has a large potential for species identification of archaeological leather. In the cases where grain pattern analysis was problematic, ZooMS was found superior for species identification. Even though grain pattern analysis had a lower success rate, in a few cases it did produce results at a higher taxonomic level than ZooMS identification. Moreover, grain pattern analysis provided additional contextual information. In conclusion, an interdisciplinary approach is recommended for conservators, archaeologists and other researchers of cultural heritage wishing to find the most potential way to identify different species. The identification method used should be tailored to suit each given archaeological leather assemblage depending on the degree of preservation, object type and context of the material in question, as well as the available expertise, time and budget.

Heritage Science, 2018

This article presents a collaborative study to determine the condition within volumes of the Grea... more This article presents a collaborative study to determine the condition within volumes of the Great and Little Domesday Book, held in The National Archives, UK. Advances in technology in both biochemical and biophysical analysis have allowed for the first time undetectable sub milligram sampling of the five-volume Great and Little Domesday Books at nine sites in total. Visual analysis was followed by microscopic fibre assessment, hydrothermal stability (shrinkage activity), amino acid analysis and microfocus X-ray diffraction. Based on the visual examination of 887 leaves in all five volumes of the Domesday Book, 587 leaves or 66% of the leaves exhibit a degree of surface gelatinisation due in part to humidification and pressing practices carried out as part of the many re-binding campaigns carried out over the centuries. Microfibre assessment indicated the percentage of damaged fibres detected varies from 56 to 100% in the samples taken, a correlation between the sum of oxidative sensitive amino acids and the observed damage of fibres was obtained. More than 1000 X-ray diffraction patterns collected showed a significant variation in amount of visible fibrillar collagen within each sample scan. Micro analysis performed here on corium collagen, means the results represent an average of the cross section of the structure of which the surface constitutes the smallest part. As the major part of damage is on the surface of the parchment leaves, the condition is likely to be worse than that reflected by the analytical results shown here. This evidence therefore prompted a rethink of the preservation protocols required to extend the usable life of the Domesday Book volumes. To this end, the preservation environment for the volumes is maintained at 40-45% relative humidity (RH) significantly lower than the recommended parameter of 55% RH.

Archaeometry, 2016

A sample of the Vinland Map remaining from the radiocarbon dating was analysed with the purpose o... more A sample of the Vinland Map remaining from the radiocarbon dating was analysed with the purpose of identifying the post-1950 contaminant and establishing other evidence on the material composition, identity and condition. The analyses revealed that the parchment originates from a bovid and contains hair remnants. The fibre structure was in poor condition, with fragmented collagen fibres and a low hydrothermal stability. Greenish and reddish particles were observed on the parchment. The greenish particles were identified as basic copper(II) chloride, most probably atacamite, and the reddish particles as rust; that is, various iron(III) oxides. The extracted modern contaminant was identified as being naturally produced glycerol monostearate.

In order to ensure the best possible methods for preserving our cultural leather and parchment he... more In order to ensure the best possible methods for preserving our cultural leather and parchment heritage in archives and libraries, a scientific approach that includes systematic assessment, evaluation and diagnosis in the professional praxis of conservation-restoration is necessary. The present paper is a review of our research towards the development of simple micro and non-destructive analysis and diagnosis for use in the practical conservation of vegetable tanned bookbinding leathers and parchment manuscripts. A review of the chemical deterioration of the materials and its characteristic appearance as well as examples of how simple analytical and diagnostic methods can reveal the effects of moisture, humidity and humid treatment on vegetable tanned leather and parchment, respectively, are given. The most severe effect is dissolution and gelatinization of the fibre structure from exposure to moisture and water at elevated or room temperature. Observations made by the naked eye, by...

The main constituent in leather and parchment is the fibrous protein collagen type I. Experiments... more The main constituent in leather and parchment is the fibrous protein collagen type I. Experiments and studies have shown that the chemical mechanisms causing deterioration of the collagen structure in these materials are acid hydrolysis and oxidation and that these can be correlated to the hydrothermal stability of the material. For parchment and leather tanned with condensed types of vegetable tannins stored under acid conditions, the chemical deterioration may lead to a transformation of the collagen into a gelatine-like substance that may dissolve in water even at ambient temperature. This process follows certain typical denaturising patterns that can be observed as characteristic morphological transformations of the collagen fibre structure at the microscopic level. Moreover, this transformation process has shown to be the same as that taking place during measurement of the hydrothermal stability of fibres heating in water. Eight major characteristic morphological breakdown feat...

Studies in Conservation, 2016

This paper examines the impact of heat-induced oxidation for new and historical parchment with th... more This paper examines the impact of heat-induced oxidation for new and historical parchment with the purpose of improving diagnostic tools for use in practical parchment conservation. Oxidation was generated by heat aging at 120°C in a dry oven for 24, 48, and 96 hours, respectively. The degradation was assessed on all samples at macrolevel by measuring color changes, at microlevel by measuring the shrinkage temperature as well as by performing a visual assessment of the fibers' morphology and determining the amount of damaged fibers, and finally, at molecular level where amino acid analysis was used to reveal changes in the oxidized collagen. The study shows that the heat-induced oxidation leads to significant color changes, decrease in hydrothermal stability, as well as changes in the amino acid composition. Surprisingly, the results show that the historical parchment is more sensitive towards dry heat oxidation on a molecular level than is the new parchment. Furthermore, for the first time, we can show that physical damage reflected in the morphological characteristics of fibers can be attributed to oxidation by dry heat.

Journal of Cultural Heritage, 2012

This paper reports the first systematic study of the dimensions of morphological changed microsco... more This paper reports the first systematic study of the dimensions of morphological changed microscopic collagen fibres in historical and new reference parchments with the aim to improve the knowledge on deterioration and the diagnosis of their damage in connection with conservation activities. The dimensions of fibres from the parchments were measured before and during shrinkage, with special emphasis on fibres with degradation characteristics designated as "pearls on a string" and "butterflies". In addition, measurements of the total shrinkage of the length of fibres and pieces of parchment were also carried out. The observations support the assumption that in vivo transformation of the fibre structure by natural ageing is similar to that taking place when heating parchment and fibres in water. Based on statistical cluster analysis, four subpopulations of pearls representing different stages of deterioration are found. Moreover, the dimensional changes in the specific structures observed at room temperature can be related to specific temperatures in the interval of shrinkage suggesting that the hydrothermal stability of the fibres may be predicted on the basis of the ratio between length and width of the so-called pearls (P l /P w). The total shrinkage measured is drastic, in average around 56% for fibres and 43 to 48% for pieces of parchment depending on the direction of the skin. The total shrinkage of fibres corresponds to a mean change in the ratio P l /P w from around 10 to around 2.3. Finally, relations between the measured dimensions at the microscopic level with those of collagen at nanoscopic and molecular levels including known and potential chemical splitting points strongly indicate that the formation of the butterfly-like fragments formed by cleavage of two adjacent pearls in the fibre can be ascribed to chemical modification of specific tripeptides in the collagen molecule.

1. Department of Chemistry, Faculty of Sciences, University of Craiova, Calea Bucuresti 107 I, 20... more 1. Department of Chemistry, Faculty of Sciences, University of Craiova, Calea Bucuresti 107 I, 200512 Craiova, Romania 2. Division Leather and Footwear, National Research and Development Institute for Textile and Leather (INCDTPICPI), Ion Minulescu Str. 93, 031215 Bucharest, Romania 3. School of Conservation, Royal Danish Academy of Fine Arts, Esplanaden 34, 1263 Copenhagen C, Denmark 4. Department of Inorganic Chemistry, Ivanovo State Chemistry & Technology University, F. Engels prosp. 7, 153000 Ivanovo, Russia 5. Department of Chemistry, University of Turin, Via P. Giuria 9, 10125 Turin, Italy

The microscopic assessment of collagen fibres structure and measurement of their shrinkage activi... more The microscopic assessment of collagen fibres structure and measurement of their shrinkage activity were used to provide a quantification of the deterioration at microscopic level for two groups of historical parchments from the Royal Library of Copenhagen and the State Archives of Florence. The micro differential scanning calorimetry (micro DSC) was used to quantitatively assess the deterioration at mesoscopic level through the analysis of fibrillar collagen thermal denaturation. The results enabled us to classify the historical parchments in four categories, i.e. not damaged, displaying minor, medium and major damage. The measurement protocols, deterioration parameters and criteria for assigning a parchment to one of the four categories are reported. Such a comprehensive deterioration profiling can support improved preventive care and conservation treatment of collections.

Analytical and Bioanalytical Chemistry, 2014

Suitable analytical markers to assess the degree of degradation of historic silk textiles at mole... more Suitable analytical markers to assess the degree of degradation of historic silk textiles at molecular and macroscopic levels have been identified and compared with silk textiles aged artificially in different environments, namely (i) ultraviolet (UV) exposure, (ii) thermo-oxidation, (iii) controlled humidity and (iv) pH. The changes at the molecular level in the amino acid composition, the formation of oxidative moieties, crystallinity and molecular weight correlate well with the changes in the macroscopic properties such as brightness, pH and mechanical properties. These analytical markers are useful to understand the degradation mechanisms that silk textiles undergo under different degradation environments, involving oxidation processes, hydrolysis, chain scission and physical arrangements. Thermo-oxidation at high temperatures proves to be the accelerated ageing procedure producing silk samples that most resembled the degree of degradation of early seventeenth-century silk. These analytical markers will be valuable to support the textile conservation tasks currently being performed in museums to preserve our heritage.

The present paper evaluates the micro hot table technique used for measuring the hydrothermal sta... more The present paper evaluates the micro hot table technique used for measuring the hydrothermal stability of leather and parchment. It deals with the consequences of using a higher heating rate than the standard 2°C/minute. Measurements using heating rates at 1, 2, 4, 8 and 16°C/min were performed. The results show that an increased heating rate leads to an increased shrinkage temperature, but also that the shrinkage intervals increase drastically when increasing the heating rate. Furthermore, as the B1-interval in some cases seems so short that it can be questioned whether its presence is statically significant, the validity of the B1-interval was investigated. However, the statistical analysis shows that the B1-interval still remains valid.