Living Virtually: Creating and Interfacing Digital Surrogates of Textual Data Embedded (Hidden) in Cultural Heritage Artefacts

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Since the discovery of the carbonised papyri at Herculaneum in the 18th century, there has been a great deal of interest in accessing the content contained in the scrolls preserved by the intense heat from the eruption of Mount Vesuvius in 79 CE. The first attempts to open these scrolls were made by hand using a knife, but this caused them to break into fragmented chunks. Subsequently in 1756 a machine was invented to create a safer method of unrolling, which was more successfully applied to numerous scrolls. However, in many cases it was impossible to keep the different layers of papyrus from sticking to each other, and so substantial portions of text remained hidden in even successfully opened scrolls, while hundreds of scrolls remained too firmly carbonised to unroll at all. The content of these fully intact scrolls, together with that of text under the stuck-on layers remains a mystery. New technology offers a solution. In the early 21st century the application of non-invasive CT scanning, a concept already proved by project members, reveals new possibilities. The structure of a scroll can be rendered digitally in three dimensions, revealing the layers of the papyrus in the scroll's circumference. Computational methods for algorithmically separating, unrolling, and flattening these layers have been developed by project members over the past decade. The virtual unrolling method has been successfully applied to P. Herc. 375 and 495. Nevertheless, despite such an achievement, the ink does not appear with any significant clarity. And while faint traces of a handful of Greek letters have been transcribed, there is currently no means to verify and replicate such results.This project aims to address the problem of detecting ink in this non-invasive imaging and thus definitively solve the long-standing problem posed by the Herculaneum papyri. In 2016 project members successfully applied the virtual unrolling method to a carbonised Hebrew scroll from the site of Ein Gedi in Israel. The ink was immediately visible, but this was due to the fact that it was contaminated with heavy trace elements and thus naturally appeared in CT scanning. The carbon-based ink used in Herculaneum papyri cannot be visualised in the same way. However, we now know that the ink is weakly contaminated with lead. We thus propose a new method called Dark Field X-ray Imaging. This reveals ink by isolating and capturing trace elements, such as lead, in its composition. To enhance the resulting ink signal further we introduce a new neural network called Reference-Amplified Computed Tomography (RACT) to amplify both the ink's presence and the shapes of the Greek characters for improved legibility. This method will definitively solve the problem of reading the text hidden in the Herculaneum papyri. To add value, the project will make the data generated by this process accessible to researchers and the curators responsible for these artefacts, by developing a new digital platform, the Augmented Language Interface for Cultural Engagement (ALICE), ensuring that the data produced by the Dark Field X-ray Imaging and RACT processes is accessible, can be properly curated, and that the extracted text can be digitally edited. Moreover, ALICE includes the functionality for integrating 3D models of the original artefact and for recording the metadata that explains both how the text was created and from where in the object's geometry the text originates in the model generated along with its digital edition. This is necessary for scientifically verifying and replicating any subsequent analysis or publication of the data. Significantly, for other cultural heritage artefacts that contain hidden text, our new imaging techniques and digital platform will be built using open architecture standards; the source code will be easily adaptable for non-invasive reading of writing inside other intractable artefacts, such as burnt books, book-bindings, and mummy cartonnage.