25 June 2015
A CT Scan of the St Cuthbert Gospel
A CT scan of the St Cuthbert Gospel – the earliest intact European book dating to the early eight century - has been published in a ground-breaking new book launched this week: The St Cuthbert Gospel: Studies on the Insular Manuscript of the Gospel of John, edited by Claire Breay, Head of Ancient, Medieval and Early Modern Manuscripts at the British Library, and Bernard Meehan, Head of Research Collections and Keeper of Manuscripts at Trinity College, Dublin. Colleagues from Collection Care and Medieval Manuscripts took the pocket gospel to the Natural History Museum for CT analysis to understand the structure of the ancient gospel, which was found inside the coffin of St Cuthbert in 1104.
Figure 1: The British Library project team at the Natural History Museum. From left to right: Claire Breay, Flavio Marzo and Christina Duffy.
X-ray computed tomography (CT) is a non-destructive technique which creates 2-D cross-sectional images from 3-D structures. The St Cuthbert Gospel was scanned using a Metris X-Tek HMX ST 225 CT scanner with an operating voltage of 225 kV at the Natural History Museum.
To protect the gospel during scanning it was placed inside a custom-made phase box and then secured upright in a bespoke piece of polyethylene foam.
Figure 2: The St Cuthbert Gospel was placed in a phase box which was secured in a piece of foam.
A facsimile of the gospel produced by Jim Bloxam and Kristine Rose was generously made available to the team during the CT scan. This enabled a direct comparison of materials known to be used in the facsimile with those unknown in the original St Cuthbert Gospel. Both volumes were placed inside the CT chamber on a precision rotation stage between an X-ray source and a detector.
Figure 3: The two copies were placed side-by-side in the CT chamber.
As the volumes rotated on the stage through 360⁰ a conical beam of X-rays took digital projections in 0.5⁰ increments. The CT image pixels are displayed in terms of their relative radiodensity allowing us to scroll through the image slices revealing the materials underneath the leather binding.
Figure 4: The results were poured over in the lab. From left to right; Christina Duffy, Claire Breay, Nicholas Pickwoad and Dan Sykes.
The results were initially examined by the British Library team and Professor Nicholas Pickwoad, whose chapter in the new publication draws on the CT scan results and discusses how the central motif on the binding appears to have been made using a clay-like material, rather than gesso or cord as previously thought.
Figure 5: The St Cuthbert Gospel with raised plant-motif decoration examined under high magnification.
Figure 6: Analysis of the internal structure of the binding.
CT datasets contain vast amounts of information and samples can be visualised in many ways using various software tools. Drishti, which stands for vision or insight in Sanskrit, is an open source volume exploration and presentation tool. It allows volumetric data sets to be both explored and used for presentation of results.
Figure 7: A screen shot showing the St Cuthbert Gospel as visualised in Drishti.
CT scanning can provide tremendous amounts of information on the condition and construction of books and their bindings. This level of detail is unavailable through visual examination and can often lead to speculation. More information about the project can be found over on the Medieval Manuscripts blog. The new publication, The St Cuthbert Gospel: Studies on the Insular Manuscript of the Gospel of John, can be bought in the British Library shop or ordered online.
Christina Duffy (@DuffyChristina)