Miniature Masterpiece: Repair Work Revealed

Earlier this year 144 fifteenth-century medieval miniatures from one of the Chester Beatty’s most treasured works, The Coëtivy Hours (CBL W 082), were re-mounted by the conservation team in preparation for the temporary exhibition, Miniature Masterpiece: The Coëtivy Hours (9th March – 2nd September 2018).

In general, the miniatures were in good condition and did not require any treatment prior to re-mounting, but one particular miniature, CBL W 082 f.295, required rather more care and attention.

An unsympathetic historic repair along the spine edge of the folio had caused the parchment to deteriorate and it was decided that conservation treatment would be beneficial, in order to improve the physical and chemical stability of the folio before it was mounted. For more information on the mounting process do take a look at our previous blog post here.

Fig 1

CBL W 082 f.295 before conservation.

Fig 2

CBL W 082 f.295 in transmitted light.

Four distinct areas of damage were visible along the spine edge of folio 295. It is likely that the losses may have occurred when the folio was removed from its binding, and could possibly correspond with the sewing stations of this previous structure.  Unfortunately, when the damaged areas were repaired, the infill paper that was used was thicker, more yellow and several shades lighter than the original parchment, immediately detracting from the delicate illumination. When viewing the folio in transmitted light, it could be seen that the repair paper overlapped the parchment on both the recto and verso by 1-5mm. This overlap was not only visually displeasing, but also increased the risk of tensions occurring if the folio were to expand and contract in response to changes in relative humidity. In addition, the parchment along the repair edge had darkened and become embrittled, possibly due to aging of the adhesive with which the repair was applied.

For these reasons, it was decided that the historic repair and any residual adhesive should be removed, in order to prevent any further deterioration of the parchment support. Since parchment is very sensitive to moisture, mechanical removal of the repair was attempted in the first instance, but this was not successful. Instead, a small damp brush was used to introduce just enough moisture to swell the adhesive so that the repairs and adhesive could be carefully removed with a small dental tool.

Fig 3

Removing the historic repairs from CBL W 082 f.295.

Fig 4

CBL W 082 f.259 after the historic repairs had been removed.

As often occurs during conservation treatments, there was a stage where the object looked a lot worse than before the treatment began! As well as revealing the true extent of loss to the spine edge, removing the old repair revealed two small tears in the parchment. These were repaired on the verso of the folio using RK2 remoistenable tissue, prepared using isinglass (a proteinaceous adhesive derived from the swim bladder of sturgeon fish). Isinglass was chosen for its excellent ageing properties as well as its strong adhesion at low concentrations. It is also a collagen-based material, just like parchment. The prepared remoistenable tissue was cut to the desired shape and peeled off its Melinex backing. Then the repair paper was carefully positioned over the tear, activated with a damp brush and left to dry under a small weight. When dry, the two tear repairs were trimmed down and the folio was ready to be infilled.

Fig 5

Details showing the torn areas on CBL W 082 f.295 before (left) and after (right) repairing with remoistenable tissue.

The paper chosen for the infills was a Japanese sekishu paper (20 gsm), dyed with yasha (click here for more information on how this was prepared). The paper was thinner and lighter than the parchment, to ensure that it would work in harmony with the folio and avoid incurring any tensions between the two materials.

Fig 6

Tools used for infilling.

Fig 7

Infilling losses using sekishu paper.

The folio was placed over a light box and a layer of Melinex was used as a barrier between the folio and the repair paper above. This allowed the shape of the first damaged area to be traced onto the repair paper with a water pen. A bamboo spatula was used to score along the same line and to tease away the remaining paper, revealing a feathered edge. Next, the edge of each infill was trimmed down with scissors and pasted with wheat starch paste. Over the light box, each infill was carefully positioned (with a 1mm overlap between the repair and the folio) and left to dry under light pressure. After treatment, the folio was mounted in the same way as the other miniatures and is currently on display in the Miniature Masterpiece: The Coëtivy Hours exhibition.

Fig 8

CBL W 082 f.295 after treatment.

As an intern, this small project was a fantastic opportunity to learn more about parchment conservation. Discussing treatment options with the conservation team here at the Chester Beatty Library was an invaluable experience and I look forward to applying what I have learnt to new parchment projects in the future.

Alice Derham, Conservation Intern

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.

 

 

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Miniature Masterpiece: The Coëtivy Hours

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.

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Fig. 1. The Coëtivy Book of Hours (left) and miniatures housed between glass (right), before conservation.

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.

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Fig. 2. Removing folio 291 from glass.

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.

Fig. 3
Fig. 3. Digitisation of the Coëtivy Book of Hours.

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.

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Fig. 4. Tabs of Japanese paper, with trimmed water-cut edges, for hinging the folios to the mounts.

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.

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Fig. 5. Attaching the Japanese paper tabs to the verso of each folio using wheat starch paste.

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.

2018_Composite_ImagesFig. 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.

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Fig. 7. Attaching the tabbed folios to the mounts using wheat starch paste.

Fig. 8

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.

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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.