Characterization and digital restauration of XIV-XV centuries written parchments by means of non-destructive techniques. Three case studies

Parchment is the primary writing medium of the majority of documents with cultural importance. Unfortunately, this material suffers of several mechanisms of degradation that affect its chemical-physical structure and the readability of text. Due to the unique and delicate character of these objects, the use of nondestructive techniques is mandatory. In this work, three partially degraded handwritten parchments dating back to the XIV-XV centuries were analyzed by means of X-ray fluorescence spectroscopy, µ-ATR Fourier transform infrared spectroscopy, and reflectance and UV-induced fluorescence spectroscopy. 'e elemental and molecular results provided the identification of the inks, pigments, and superficial treatments. In particular, all manuscripts have been written with iron gall inks, while the capital letters have been realized with cinnabar and azurite. Furthermore, multispectral UV fluorescence imaging and multispectral VIS-NIR imaging proved to be a good approach for the digital restoration of manuscripts that suffer from the loss of inked areas or from the presence of brown spotting. Indeed, using ultraviolet radiation and collecting the images at different spectral ranges is possible to enhance the readability of the text, while by illuminating with visible light and by collecting the images at longer wavelengths, the hiding effect of brown spots can be attenuated

Characterization and digital restauration of XIV-XV centuries written parchments by means of non-destructive techniques. Three case studies

Parchment is the primary writing medium of the majority of documents with cultural importance. Unfortunately, this material suffers of several mechanisms of degradation that affect its chemical-physical structure and the readability of text. Due to the unique and delicate character of these objects, the use of nondestructive techniques is mandatory. In this work, three partially degraded handwritten parchments dating back to the XIV-XV centuries were analyzed by means of X-ray fluorescence spectroscopy, µ-ATR Fourier transform infrared spectroscopy, and reflectance and UV-induced fluorescence spectroscopy. 'e elemental and molecular results provided the identification of the inks, pigments, and superficial treatments. In particular, all manuscripts have been written with iron gall inks, while the capital letters have been realized with cinnabar and azurite. Furthermore, multispectral UV fluorescence imaging and multispectral VIS-NIR imaging proved to be a good approach for the digital restoration of manuscripts that suffer from the loss of inked areas or from the presence of brown spotting. Indeed, using ultraviolet radiation and collecting the images at different spectral ranges is possible to enhance the readability of the text, while by illuminating with visible light and by collecting the images at longer wavelengths, the hiding effect of brown spots can be attenuated

Understanding multispectral imaging of cultural heritage:Determining best practice in MSI analysis of historical artefacts

Although multispectral imaging (MSI) of cultural heritage, such as manuscripts, documents and artwork, is becoming more popular, a variety of approaches are taken and methods are often inconsistently documented. Furthermore, no overview of the process of MSI capture and analysis with current technology has previously been published. This research was undertaken to determine current best practice in the deployment of MSI, highlighting areas that need further research, whilst providing recommendations regarding approach and documentation. An Action Research methodology was used to characterise the current pipeline, including: literature review; unstructured interviews and discussion of results with practitioners; and reflective practice whilst undertaking MSI analysis. The pipeline and recommendations from this research will improve project management by increasing clarity of published outcomes, the reusability of data, and encouraging a more open discussion of process and application within the MSI community. The importance of thorough documentation is emphasised, which will encourage sharing of best practice and results, improving community deployment of the technique. The findings encourage efficient use and reporting of MSI, aiding access to historical analysis. We hope this research will be useful to digitisation professionals, curators and conservators, allowing them to compare and contrast current practices

New insight on south western iberian rock art by non-invasive analytical approaches: the cases of Ardales and Escoural Cave

This thesis focuses on Escoural Cave, in southwestern Iberia, known as the only cave within Portugal to contain Palaeolithic rock art. Estimated to be roughly 20,000 years old, the paintings and engravings found inside the hypogeal environment face possible degradation due to natural and anthropogenic factors. Although previously well documented, the importance of continuous monitoring and documentation of at-risk cultural heritage, specifically rock art, is important for its survival and for the implementation of future conservation efforts. One aim of this thesis was to use non-invasive techniques and methods to document and analyze the rock art at Escoural Cave. Various imaging techniques were used to further reveal parts of the hidden rock art found within Escoural Cave while also documenting the current state of preservation of the eight most well-known paintings. The work completed for this thesis also investigated the effectiveness and reliability of Vis-NIR FORS and hyperspectral imaging in their usefulness and applicability for non-invasive rock art research. The Vis-NIR FORS and hyperspectral camera were determined to be periodically useful for the work completed at Escoural Cave; many factors from, lighting, location of the rock art, and extensive amounts of calcite coverage over the paintings created non-ideal conditions within the cave for the complete effectiveness of these approaches. These methods were useful for non-invasive pigment identification and proved less reliable for the interpretation of possible organic binders. Lastly, the eight locations sampled throughout Escoural Cave for microbial growth showed - through the use of culture-dependent and the culture-independent method of NGS - that the majority of microorganisms in Escoural Cave are naturally found within karstic systems. However, the presence of some strains of Enterobacter sp. raises concerns as it can be pathogenic to visitors with compromised immune systems; additionally, the presence of lampenflora is of concern for the protection of the rock art and is a contender for future preventive conservation efforts through its removal; Resumo: Um novo olhar sobre a arte rupestre ibérica do sudoeste por adordagens analíticas não invasivas – os casos das grutas de Ardales e Escoural Esta tese centra-se na gruta do Escoural, no sudoeste da península Ibérica, conhecida como a única com arte rupestre Paleolítica, em Portugal. Estima-se que tenham cerca de 20.000 anos de idade, as pinturas e gravuras encontradas na gruta e enfrentam uma possível degradação devido a fatores naturais e antropogénicos. Embora previamente bem documentada, a importância do acompanhamento contínuo e da documentação do património cultural em risco, especificamente a arte rupestre, é importante para a sua sobrevivência e para a implementação de futuros esforços de conservação. Um dos objetivos desta tese foi usar técnicas e métodos não invasivos para documentar e analisar a arte rupestre da gruta do Escoural. Usaram-se várias técnicas de imagem para revelar ainda mais partes da arte escondida na rocha, no interior da gruta, permitindo também documentar o estado atual de preservação das oito pinturas mais conhecidas. Este trabalho também permitiu avaliar a eficácia e a aplicabilidade de FORS Vis-NIR e imagem híper-espectral como metodologias não invasiva em arte rupestre, revelando-se metodologias úteis para o trabalho desenvolvido nesta gruta; muitos fatores, iluminação, localização da arte rochosa, e extensas quantidades de cobertura de calcite sobre as pinturas criaram condições não-ideais dentro da gruta para a completa eficácia destas abordagens. Estes métodos foram úteis para a identificação não invasiva de pigmentos e revelaram-se menos eficazes para a interpretação de possíveis aglutinantes orgânicos. Finalmente, os oito locais amostrados para o crescimento microbiano mostraram-através do uso de cultura-dependente e do método cultura - independente de NGS-que a maioria do microrgnismos na gruta Escoural são naturalmente encontrados em ambientes hipogénicos. No entanto, a presença de algumas estirpes, por exemplo de Enterobacter sp. podem apresentar patogenicidade para os visitantes com sistemas imunológicos comprometidos; além disso, a presença de lampenflora é uma preocupação para a proteção da arte rupestre e é um candidato para futuros esforços de conservação preventiva através de sua remoção

Identification of pictorial materials by means of optimized multispectral reflectance image processing

Image spectroscopy may allow identifying the materials present on a painting surface in a non-invasive way. The proposed method aims at optimizing, and thus reducing, the number of filters employed, while still providing a robust method, that achieves similar performances as traditional ones, which in turn employ a large number of filters. Moreover, we targeted the identification of the pigments present on the outer layer of a painting independently from their thickness, the underlying background or support, the binder employed, their aging and acquisition set-up. In order to achieve this objective, a relevant number of swatches have been prepared, on different supports and with different thicknesses and binding mediums. Spectral reflectance curves of such chemically known pictorial layers have been recorded by means of a spectrometer and a spectrophotometer. A novel Principal Component Analysis (PCA) based approach has been devised to select the most relevant wavebands, i.e. those that allow the most effective discrimination among (quasi)metameric colours, which are thus not to be distinguished with the naked eye or with an RGB camera. Comparisons of results using the 13 filters available on the filter wheel and of a selection of only 3 and 4 filters, support the idea of the simplified version investigated in this paper being a viable alternativ

Identification of pictorial materials by means of optimized multispectral reflectance image processing

Image spectroscopy may allow identifying the materials present on a painting surface in a non-invasive way. The proposed method aims at optimizing, and thus reducing, the number of filters employed, while still providing a robust method, that achieves similar performances as traditional ones, which in turn employ a large number of filters. Moreover, we targeted the identification of the pigments present on the outer layer of a painting independently from their thickness, the underlying background or support, the binder employed, their aging and acquisition set-up. In order to achieve this objective, a relevant number of swatches have been prepared, on different supports and with different thicknesses and binding mediums. Spectral reflectance curves of such chemically known pictorial layers have been recorded by means of a spectrometer and a spectrophotometer. A novel Principal Component Analysis (PCA) based approach has been devised to select the most relevant wavebands, i.e. those that allow the most effective discrimination among (quasi)metameric colours, which are thus not to be distinguished with the naked eye or with an RGB camera. Comparisons of results using the 13 filters available on the filter wheel and of a selection of only 3 and 4 filters, support the idea of the simplified version investigated in this paper being a viable alternative