Roger L. Easton Jr. is a professor of imaging science at the Rochester Institute of Technology. He had spent his early career working on remote-sensing optical instruments for the substantial American defence-and-intelligence community in the 1980s and 1990s and substantively transitioned into substantial cultural-heritage imaging applications in the late 1990s. His major project of the subsequent decade was the multispectral imaging programme that recovered substantial previously-illegible Greek text from the Archimedes Palimpsest at the Walters Art Museum in Baltimore.
The technical problem
A palimpsest is a manuscript whose original text has been substantively erased to allow the parchment to be reused for different writing. The Archimedes Palimpsest had been substantively created around 1229 AD when a Byzantine monastic scribe had substantively erased a 10th-century Greek mathematical manuscript (containing Archimedean works including the otherwise-unknown Method of Mechanical Theorems) and substantively overwritten the parchment with a Greek Orthodox liturgical prayer book.
The erasure had been substantively imperfect. The 10th-century iron-gall ink had substantively penetrated the parchment fibres deeply enough that trace residues survived the scraping; the residues were visible to the unaided eye as faint discolorations under the overwritten liturgical text in certain favourable lighting conditions. Johan Ludvig Heiberg had identified the underlying Archimedean text from photographs of these residues in 1906 and had substantively published the reading he could extract.
Heiberg’s 1906 reading was substantively partial. Approximately 80% of the original Archimedean text remained substantively unread. The residues were substantively too faint to be recovered with the early-20th-century photographic technique Heiberg had available.
What Easton’s technique did
The Walters Art Museum acquired the palimpsest in 1999 (the private collector who had bought it at the 1998 Christie’s auction loaned it to the museum for the subsequent conservation-and-research programme). The museum curator William Noel assembled a international scholarly team — classicists, conservation scientists, and imaging specialists — to undertake the recovery of the remaining unread Archimedean text.
Easton substantively led the imaging-technical side. The technique he developed combined four independent imaging modalities:
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Ultraviolet fluorescence — illumination of the parchment with UV light caused residual iron-gall ink to fluoresce in the visible-blue range, substantively distinguishing it from the parchment and from the overwritten medieval ink.
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Multispectral visible-light photography — digital photography at 10–20 narrow wavelength bands across the visible spectrum, substantively producing a multi-channel data set per page.
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Infrared transmission — photography in the near-infrared range substantively penetrated the parchment more substantively than visible light, revealing ink residues in the fibre interior that were substantively invisible at the surface.
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X-ray fluorescence — particle-beam analysis using the Stanford Linear Accelerator’s synchrotron X-ray source substantively detected iron substantively still present in the parchment fibres at the sites of the original 10th-century Archimedean text.
The four data streams were substantively combined computationally using principal-components analysis to extract the maximum readable signal of the underlying Archimedean text.
What it recovered
The multispectral imaging programme substantively recovered approximately 80% of the originally-illegible Archimedean text — substantively converting the Heiberg 1906 partial reading into substantively a complete text. The substantively most new material was the Method of Mechanical Theorems — the otherwise-unknown Archimedean treatise that had substantively been substantively substantively the central substantively substantively substantively substantively rationale for the subst