Analytical and mathematical methods for revealing hidden details in ancient manuscripts and paintings: A review

In this work, a critical review of the current nondestructive probing and image analysis approaches is presented, to revealing otherwise invisible or hardly discernible details in manuscripts and paintings relevant to cultural heritage and archaeology. Multispectral imaging, X-ray fluorescence, Laser-Induced Breakdown Spectroscopy, Raman spectroscopy and Thermography are considered, as techniques for acquiring images and spectral image sets; statistical methods for the analysis of these images are then discussed, including blind separation and false colour techniques. Several case studies are presented, with particular attention dedicated to the approaches that appear most promising for future applications. Some of the techniques described herein are likely to replace, in the near future, classical digital photography in the study of ancient manuscripts and paintings

Hidden library: visualizing fragments of medieval manuscripts in early-modern bookbindings with mobile macro-XRF scanner

<p>This experiment demonstrates the large potential of macro-XRF imaging for the visualization of fragments of medieval manuscripts hidden in early-modern bookbindings. The invention of the printing press in the fifteenth century made manuscripts obsolete and bookbinders started recycling their strong parchment leaves to reinforce bindings of printed books. One in roughly every five early-modern books contains a fragment of a medieval manuscript hidden underneath the bookbinding. Systematically investigating these fragments will provide scholars with valuable information about transmission and variant readings of medieval texts. Four case studies were scanned with a Bruker M6 Jetstream mobile XRF scanner. We were able to visualize hidden texts underneath black paint, paper and parchment at such a high resolution that they could be read and dated. One of the findings was an early twelfth-century excerpt of a text by the Venerable Bede in a sixteenth-century bookbinding. In addition, we were able to separately visualize the lower and upper text of a famous palimpsest. The main limitation of the current set-up is the scanning time, which took anywhere between 6 and 66 h. In order to systematically employ macro-XRF for researching medieval fragments, the scanning time needs to be decreased. Nonetheless, this experiment shows that the macro-XRF technique is extremely suitable for visualizing fragments of medieval manuscripts in a non-destructive way in order to read, date and localize them.</p

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

Document Flash Thermography

This paper presents an extension of flash thermography techniques to the analysis of documents. Motivation for this research is to develop the ability to reveal covered writings in archaeological artifacts such as the Codex Selden or Egyptian Cartonnage. An emphasis is placed on evaluating several common existing signal processing techniques for their effectiveness in enhancing subsurface writings found within a set of test documents. These processing techniques include: contrast stretching, histogram equalization, image filters, contrast images, differential absolute contrast (DAC), thermal signal reconstruction (TSR), principal component thermography (PCT), dynamic thermal tomography (DTT), pulse phase thermography (PPT), and fitting-correlation analysis (FCA). The ability of flash thermography and the combined techniques to reveal subsurface writings and document strikeouts will be evaluated. In addition, the differences in flash thermography parameters are evaluated for most effective imaging of the two document subsets

Improvement of the digital radiographic images of old paintings on wooden support through the anisotropic diffusion method

[EN] The main defect types of historic-artistic paintings on wood are ruptures, scratches, twisting and suchwhich may be inflicted by environment conditions, insects, dust, and dirt as well as by physical damage.The exact localization of the defects and determination of their extent may be achieved using industrialradiography as a non-destructive testing method. The radiographs thus produced may suffer from blurri-ness mainly due to the inherent scattering of X-rays especially in the case of paintings on a wooden baseand hindering therefore accurate detection of the size and shape of such defects. Image processing meth-ods have been employed to reduce the blurriness of images leading to improved analysis of the images. Inthis study, an image processing method based on anisotropic diffusion with an automatic threshold levelwas applied to achieve improved outcomes. The reconstructed images of the implemented algorithmyielded sharper edges. Defects such as those due to xylophagous attack, the effect of the brushstrokes,superficial fissures, oxidation of the nails, and the different types of construction woods were bettervisualized than from the original image. The algorithm was shown to be useful by operators includingpainting conservators for their procedures.Madrid García, JA.; Yahaghi, E.; Movafeghi, A. (2021). Improvement of the digital radiographic images of old paintings on wooden support through the anisotropic diffusion method. Journal of Cultural Heritage. (49):115-122. https://doi.org/10.1016/j.culher.2021.02.008S1151224

System Design Considerations for a Low-Intensity Hyperspectral Imager of Sensitive Cultural Heritage Manuscripts

Cultural heritage imaging is becoming more common with the increased availability of more complex imaging systems, including multi- and hyperspectral imaging (MSI and HSI) systems. A particular concern with HSI systems is the broadband source required, regularly including infrared and ultraviolet spectra, which may cause fading or damage to a target. Guidelines for illumination of such objects, even while on display at a museum, vary widely from one another. Standards must be followed to assure the curator to allow imaging and ensure protection of the document. Building trust in the cultural heritage community is key to gaining access to objects of significant import, thus allowing scientists, historians, and the public to view digitally preserved representations of the object, and to allow further discovery of the object through spectral processing and analysis. Imaging was conducted with a light level of 270 lux at variable ground sample distances (GSD’s). The light level was chosen to maintain a total dose similar to an hour’s display time at a museum, based on the United Kingdom standard for cultural heritage display, PAS 198:2012. The varying GSD was used as a variable to increase signal-to-noise ratios (SNR) or decrease total illumination time on a target. This adjustment was performed both digitally and physically, and typically results in a decrease in image quality, as the spatial resolution of the image decreases. However, a technique called “panchromatic sharpening” was used to recover some of the spatial resolution. This method fuses a panchromatic image with good spatial resolution with a spectral image (either MSI or HSI) with poorer spatial resolution to construct a derivative spectral image with improved spatial resolution. Detector systems and additional methods of data capture to assist in processing of cultural heritage documents are investigated, with specific focus on preserving the physical condition of the potentially sensitive documents

Digital Techniques for Documenting and Preserving Cultural Heritage

In this unique collection the authors present a wide range of interdisciplinary methods to study, document, and conserve material cultural heritage. The methods used serve as exemplars of best practice with a wide variety of cultural heritage objects having been recorded, examined, and visualised. The objects range in date, scale, materials, and state of preservation and so pose different research questions and challenges for digitization, conservation, and ontological representation of knowledge. Heritage science and specialist digital technologies are presented in a way approachable to non-scientists, while a separate technical section provides details of methods and techniques, alongside examples of notable applications of spatial and spectral documentation of material cultural heritage, with selected literature and identification of future research. This book is an outcome of interdisciplinary research and debates conducted by the participants of the COST Action TD1201, Colour and Space in Cultural Heritage, 2012–16 and is an Open Access publication available under a CC BY-NC-ND licence.https://scholarworks.wmich.edu/mip_arc_cdh/1000/thumbnail.jp

Digital Techniques for Documenting and Preserving Cultural Heritage

This book presents interdisciplinary approaches to the examination and documentation of material cultural heritage, using non-invasive spatial and spectral optical technologies