The conservation team have been busy preparing 144 exquisite illuminated miniatures from a manuscript dating to c. 1443, for our next temporary exhibition ‘Miniature Masterpiece: The Coëtivy Hours’.
The Coëtivy Hours (CBL W 082) was made for the renowned book collector, Prigent de Coëtivy (1400-1450), who was Admiral of France at the time. The book was specifically commissioned to commemorate his marriage to Marie de Rais in Paris in 1444. Nearly 500 years later, the book was given to Chester Beatty by his wife, Edith, on the occasion of their wedding anniversary in 1919.
The tiny manuscript (14.2 x 11.3 x 4.2 cm) is bound in an intricately tooled early nineteenth-century binding. The 364 folios are skilfully painted, with highly decorative borders throughout the manuscript. However, 144 of the 148 three-quarter page miniatures were removed from the book by Beatty soon after it came into his collection, as he wanted people to be able to ‘look at them as closely as they want and study them properly’. They were therefore stored between glass to aid their preservation and display.
Although the book itself did not require conservation treatment, it was decided that the miniatures should be removed from the glass in order to facilitate their digitisation and enable safe handling by researchers in the future. When the glass sandwiches were opened, it became clear that each folio had been attached to the glass at the top and bottom of the spine edge with pressure-sensitive tape. Thankfully, the carrier of the tape was easily removed with a metal spatula. The rubber-based adhesive left dark residual staining, but it was decided that this would not be removed as in some cases the staining was in contact with the original media and solvent treatment would be too risky.
The parchment folios of the manuscript are very thin and have very few visible flaws, indicating that they were made from carefully selected and evenly prepared skins. Scientific analysis by the BioArCh team at the University of York revealed that both calf and goatskin were used in the Coëtivy Hours. Overall, the media was in excellent condition, and did not require consolidation. In some areas there were losses to the blue pigment and gold leaf, but the areas around these losses appeared to be stable and, when examined closely, there was no active flaking of the media.
After the folios were condition checked, the new Digital Department at the Chester Beatty Library took high quality images of every folio using a Phase One XF camera with an IQ380 attachment, capable of producing images with a resolution of 80 megapixels (look out for the new digitisation blog that is coming soon!). The opening of the nineteenth-century binding was somewhat restricted, allowing it to open to little more than 90 degrees, so the conservation team provided advice on handling and helped to ensure the manuscript was supported on a cradle throughout digitisation, whilst the pages were held in place with polyethylene straps from Benchmark.
When devising a mounting system for the individual parchment folios, it was important to choose a system that would be strong enough to hold the folios safely in place during display and handling, but allow the parchment to move with natural fluctuations in relative humidity and temperature. The mounting system also needed to take into account the unique contours of each folio. For this reason, a bespoke system of Japanese paper tabs was used to mount the folios within window mounts.
The majority of the folios were mounted in pairs, in a standard size mount made from acid-free, buffered Conservation Board (1650 micron), with a standardised aperture. Each folio was over mounted on the spine edge only, with the other three edges floated just a couple of millimetres inside the aperture. This partial float mounting system ensured that each folio was held in place securely, but also offered room for the parchment to expand and contract. Aesthetically, the mounting also reflects the character of the object and reminds the viewer that the miniatures are not only artworks in their own right, but are folios from a bound manuscript volume.
Two sizes of tabs were used on each folio – two 25mm tabs of Japanese sekishu paper were adhered to the spine edge and 3-5 smaller 15mm tabs of a lighter weight Japanese usumino paper were attached along the other three edges. For each tab, the edge in contact with the object was water-cut and then trimmed down with scissors.
The tabs were attached to the folios, with an overlap of less than 2mm, using wheat starch paste and left to dry underneath Bondina, blotting paper and small bag weights.
In terms of positioning, the two spine tabs were placed about 7mm from the bottom and top edges, to reduce the risk of the corners catching when the verso of each folio is viewed. In some cases, the position of these tabs needed to be shifted in order to avoid the red ruling lines.
The level of planar distortion varied from folio to folio, as the parchment not only had a memory of being in a bound volume but also the memory of being part of an animal skin! To account for this variation, the smaller tabs were positioned on a case-by-case basis, allowing each folio to lie as flat as possible whilst also allowing some movement. No more than 5 staggered paper tabs per folio were added, to reduce the risk of tensions arising and cockling.
Fig. 6. Folios 241 and 270 during treatment, showing the positions of the Japanese paper tabs.
Next, each pair of folios was positioned in their mount and the tabs on the spine edge were pasted to the back board of the mount. A Teflon folder was used to ensure a strong attachment.
Fig. 8. Folios 294 and 295 after mounting.
The final stage in preparing these folios for exhibition involved framing the mounted miniatures in bespoke gold frames and then hanging them in the midnight blue temporary gallery, so the beautiful illuminations sparkled.
Fig. 9. Framing the folios in the lab (left) and installing the exhibition (right).
Alice Derham, Conservation Intern
The Miniature Masterpiece: The Coëtivy Hours exhibition is on display from 9 March until 2 September 2018. We do hope you’ll come along to see it!
A lavishly illustrated catalogue by exhibition curator Dr Jill Unkel (Curator of the Western Collection), with contributions from Dr Laura Cleaver (Ussher Lecturer in Medieval Art at Trinity College Dublin), and our own Kristine Rose Beers (Senior Book Conservator), is available from the Library’s gift shop for anyone who wants to have an even closer look at the brilliance of this miniature masterpiece.