Multispectral Imaging of Insular Manuscripts

Dr Christina Duffy

The British Library is using multispectral imaging to recover erased passages, obscured corrections, faded annotations, hidden inscriptions, indecipherable glosses, under-text and underdrawings across a vast array of collection items. The remarkable results are enabling new and ground-breaking scholarship on material once thought fully-understood. Some collections have even been re-dated through the discovery of intricate details in illuminations which have lost clarity over the centuries.

Multispectral scanner

The British Library uses a Megavision Cultural Heritage EV Imaging System with a monochrome E7 50-megapixel back. Iron gall ink is found in many insular manuscripts and responds best under LED illumination in the near-ultra-violet (365 nm).

Narrow-band LED illumination subjects the manuscripts to only the required light energy to expose the sensitive unfiltered monochrome sensor. Images are captured over fourteen spectral bands from the near ultra-violet (UV, 365 nm) to the near infra-red (IR, 1050 nm). Data captured can be processed using statistical methods such as Principal Component Analysis to further extract and enhance areas of illegibility. The technology has been used on some of the Library’s most significant Treasures and has enabled discovery of a fugitive figure on a folio of Leonardo da Vinci’s notebook, as well as recovering text on a burnt copy of Magna Carta.

Fire-damage causing illegibility of text has proven to be a significant challenge to scholars of the famous collection of manuscripts assembled by Sir Robert Cotton held at the British Library. On 23 October 1731, a fire broke out where the collection was being stored at Ashburnham House, Westminster, destroying and damaging many of the manuscripts. A conservation effort in the 18th and 19th centuries oversaw gathering of what remained of these precious manuscripts and loose fragments were bound into volumes. Many of these volumes contain unique texts or their earliest known copies.

In 2017, the British Library conducted a Fragmentarium case study to explore the possibilities for improving access to burnt fragments of Anglo-Saxon manuscripts from the Cotton Collection. One of the worst affected collection of manuscripts were those in the Cotton Otho press. Early catalogues show that in the 17th century the manuscript contained four distinct texts written some time during the second half of the 8th century.

Multispectral imaging of Cotton MS. Otho A. I and subsequent processing of the data has revealed far more details from the surviving fragments than are otherwise visible. This work has improved comparison studies to other portions of the manuscript held at Bodleian Library, Oxford, and helped to preserve the present state of these vulnerable fragments, which are often too fragile to be issued in the reading room.

Left: A fragment of Cotton MS Otho A. I (folio 1v) as seen under normal visible light showing severe darkening and illegibility due to fire damage. Right: The fragment as processed following multispectral imaging.

Results from multispectral imaging can reveal the primitive version of texts by seeing through corrections and providing scholars with a greater understanding of the thought-process of their authors. High-resolution images enable better comparison of scribal hands and give a clear indication of where ink is changed or replenished.

Conversations between scholars and scientists will help to improve the impact of this developing technique to the study of insular manuscripts by targeting specific challenges unique to this research area. Through collaboration we can look forward to some exciting revelations that are currently hiding in our collections, patiently awaiting discovery.

Dr Christina Duffy
The British Library
June 2018

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