THE BRITISH LIBRARY

Collection Care blog

Behind the scenes with our conservators and scientists

Introduction

Discover how we care for the British Library’s Collections by following our expert team of conservators and scientists. We take you behind the scenes into the Centre for Conservation and the Scientific Research Lab to share some of the projects we are working on. Read more

10 August 2017

Everything you need to know about birch bark book conservation

From sawdust to gold dust: The conservation of a 16th century birch bark book

Shelfmark: OMS/Or 13300
Curator: Pasquale Manzo
Treatment Time: 113 hrs
Estimated time: 92 hrs

Introduction:
Late 2016 a black acidic shoe box with a note was transferred to the British Library Centre for Conservation for treatment. The note was dated from 1972, reading ‘object is extremely fragile - do not touch’. Inside the shoe box was a mass of tissue, which when carefully lifted out, had thousands of tiny entangled bark fragments entwined in its fibres. Beneath the tissue was the birch bark book.

The following blog is about how the manuscript was conserved so that it could once again be safely requested and handled by the general public.

The Manuscript:
The manuscript is part of the British Library Asian and African collection. It was originally made in Kashmir, is written in Śāradā script and dates to the 16-17th century. It includes three different texts: (A) Nirṇayāmṛta by Allāḍanātha, a work in 4 chapters concerning suitable times for various Hindu religious ceremonies. (B) Narasiṃhaparicayā by Kṛṣṇdāsa son of Rāmācārya, a text on Vaiṣṇava ritual and (C) a fragment of the Padmapurāṇa.

Binding Structure:
The manuscript was formed of 10 sections, each with 8 folios to the centre. The manuscript was sewn with a thick hemp chord in an unsupported Coptic-style. The sewing had a knotted incongruous double loop centrally on the 3rd section.

Spine edge of textblock

Figure 1: Spine edge of the text block showing the 2 central sewing stations and the headband tie-downs at head and tail.

Both the head and tail had headbands, similar perhaps in style to Monastic headbands. However the cores were made of a Mahogany-type wood dowel, looped several times over with chord, then wrapped in a layer of alum-tawed skin and finally a turned-in leather flap extending up from the cover. The headbands were attached to the text block via tie-downs on each section.

Wood-core headbandFigures 2-4: Wood-core headband with alum-tawed and leather wraps secured to text block with chord tie-downs.

The manuscript was covered in thick brown goat leather with an inner parchment wrapper. The limp leather case was attached to the text block by the headband tie-downs.

Limp goat leather

Figures 5 & 6: Limp goat leather cover with parchment wrapper below.

Dimensions: (L x W x H) 190 x 189 x 70 mm

The Text block:
The text block had 231 folios, foliated 27-258. The folios were transcribed with a carbon-based ink. The media was stable. The folios themselves were made from very fine layers of bark from the outer periderm of the deciduous birch tree. The cork cells of the birch bark are compacted in radial rows according to seasonal growth, and the periderm layers were adhered together by pectin as well as physical knots and streaks.

Birch bark

Figure 7 (Left): Tree anatomy diagram showing the periderm layer of the birch tree (Wojtech 2013). Figure 8 (Right): Peeling birch bark off a birch tree to use as a substrate. Image shows inherent knots and streaks (Wojtech 2011).

Condition:
Unfit: Significant risk of damage even under controlled display conditions due to existing damage or extreme sensitivity, inherent vice.

Principal Substrate

In response to fluctuating environmental parameters, the inherently weak pectin adhesive in the birch bark had failed, causing the periderm layers to delaminate. It appeared that each folio was made up of around 7 periderm layers. Each folio was in a different state of delamination. Similarly, as a result environmental fluctuation the natural resins in the birch bark had been drawn to the surface, causing a gentle white blooming on the majority of the birch bark folios.

Changes in the birch bark’s moisture equilibrium over time had caused dimensional changes, forcing tangential curling and making the bark stiff and extremely brittle. This had resulted in each folio having significant tears extending from the foredge. Some of the folios had even degenerated into piles of fragmentary leaves. There were vertical cracks on most folios towards the spine, due to the stress induced by turning the pages.

White blooming and delamination
Figure 9 (Left): White blooming from natural resins on the surface of the birch bark. Figure 10 (Right): Delaminating periderm layers of embrittled birch bark.

Binding Condition

The leather and the parchment wrapper beneath were stiff and distorted and subsequently did not effectively cover or protect the text block. The cover was only partially attached to the text block by the headband tie-downs at the head of the spine. As such, when fully opened some of the text block spine was exposed. The sewing had broken at multiple points, however disparately the sewing structure was relatively stable. The opening angle of the manuscript had been compromised by the brittle substrate, so could open to around 60 degrees in a section or 160 degrees between the sections. Two sections at the back of the manuscript had detached and four pages were sitting loose in the back cover.

Distorted leatherFigure 11: Distorted leather no longer covers and protects the text block.

Detached tie-downsFigure 12: Showing detached tie-downs, exposed spine and broken sewing at the spine tail.

Evidence of Previous Repairs:

Previous repairs were carried out in 1972. There appeared to be a white bloom on the surface of the leather cover, suggesting the possible previous use of wax or oil based leather coatings.

Two folios, f.211 and f.212, were coated on both sides with a texacryl 13-002 adhesive (at various strengths) and nylon tissue, with Japanese paper borders. This conservation process was discontinued as the result is visually distracting (sharp contrast in tone and light refraction) and had irreversibly changed the nature of the original birch bark.

The areas of loss, of around twenty of the most fragile folios at the front of the volume, had been infilled with hand-transcribed western paper. Similarly heavy-weight cream paper repairs had also been crudely adhered to multiple folios along edge tears.

Crude paper repairsFigure 13: Showing the crude paper repairs at the foredge of multiple folios

Fragmented sectionsFigure 14: Showing the crude texacryl-adhered nylon lining on 2 birch bark folios.

Texacryl-adhered nylon lining

Figure 15: The fragmented first two sections with annotated western paper infills.

Analytical Adhesive Testing

The decision was made to identify the adhesive used to adhere the paper patch repairs and the annotated infills. This would not only provide more information about the history of the object, but would inform the treatment decision-making process.

A microsample of adhesive residue was removed from beneath the distorted and lifting paper infills. The microsample was then analysed via use of FTIR-ATR to identify and characterise the present adhesive. The results suggested the adhesive used in previous repairs was a protein-based animal glue.

Subtraction spectrumFigure 16: Image of the subtraction spectrum suggesting the adhesive residue was a protein based animal glue.

Micro-sampling locationFigure 17: Adhesive residue visible on birch bark folio. Highlighted area shows micro-sampling location.

Conservation Treatment:

The choice of treatment for any object of historical or cultural significance must reflect its artifactual value, uniqueness and the accessibility of the information it holds. It was decided a minimally interventive treatment would be carried out with the aim of preserving the original and rare binding structure, whilst stabilising the folios for digitisation.

Repair Method Selection

Due to the laminar structure of the birch bark, it was decided that traditional paper-patch repairs would not suffice, as they would only encourage the delamination of the top layer. After experimentation, it was decided that thin strips of toned Japanese tissue, woven in between the stratified layers of each folio would act as an effective repair method.

Inter-woven toned Japanese tissue repair

Figure 18 & 19: An inter-woven toned Japanese tissue repair.

Paper and Adhesive Selection

Kozo 2 Japanese tissue was selected as the repair material. It was chosen as it was semi-opaque and thus not visually obstructive; weaker than the primary substrate; and had a degree of stiffness that enabled it to be inserted and woven between bark layers. The tissue strips were adhered with a low concentration of methylcellulose (2%) in water. Methylcellulose was chosen as adhesive firstly because of its cellulosic similarity to birch bark, secondly its refractive index was similar to birch bark, and lastly it had a greater water retention capacity and flexibility than wheat starch paste.

Tears and areas of delamination repaired

Figure 20 & 21: Tears and areas of delamination were repaired and reinforced with toned Kozo 2 tissue adhered with 2% methylcellulose.

Tissue Preparation

The Kozo 2 tissue was toned using an airbrush, with dilute burnt umber and raw sienna Golden heavy body acrylic paints. The tissue was toned in a colour-range of tones so that the repairs match the multi-tonal folios. The tissue was then cut into thin strips using a scalpel. The widths of the strips varied from about 3-6 mm.

Tonal variation
Figure 22: Tonal variation of different birch bark folios.

Repair

A strip was selected, woven through the delaminated layers using tweezers, adhesive applied with a paintbrush (size 001), and the joint gently pressed into place using a cotton swab. The swab also removed any excess adhesive. The repair was then pressed gently under weights. Pressure-light weights were used due to the brittle nature of the substrate. Large areas of delaminated layers were re-adhered to their folio similarly, using a thin application of methylcellulose and gentle pressure.

Delaminated corner repairs

Figure 23-25 (Left): Applying toned Kozo 2 to delaminated corner. Centre: applying methylcellulose with a fine brush. Right: Applying gentle pressure to the join using a cotton swab.

The folios were conserved systematically, one by one, starting from the back of the volume (as these were in better condition than those at the front). Each folio took around 15-20 minutes to repair depending on the extent of its damage.

The crude previous paper repairs and the annotated infills were lifted from the birch bark using tweezers, and the dry powdery adhesive carefully scraped off the surface of the folio using a scalpel. The repair’s locations were documented prior to removal.

The four loose pages at the back of the manuscript were stripped up with Japanese tissue and adhered into the two detached sections according to their foliation. The texacryl-coated pages were trimmed to remove the Japanese paper border, and likewise stripped up and attached into these sections.

The final repairs were made to the outer spine folds of the sections. These were carefully repaired in-situ using slightly wider strips of toned tissue.

Treated folios stripped up and sewn into their section
Figure 26: The trimmed texacryl 13-002 and nylon coated folios, stripped up and sewn into their section.

Re-sewing Loose Sections

The two detached sections at the back of the volume were attached at the head-edge sewing station via Coptic chain stitch. An extra Coptic stitch was attached to the 3rd section to reinforce the attachment. The decision to not attach the section at two sewing stations was due firstly to the fragmented state of the sewing on the tail-edge station, secondly because the minimal sewing sufficed, and lastly because the purpose of the attachment was solely to prevent loss and disassociation.

Repaired spine edge of textblock
Figure 27 & 28: Showing the repaired spine edge of the text block and the three chain stitches at the head of the volume.

Cover Decisions

SC6000 leather treatment was rubbed lightly into the leather cover to reduce the white blooming.

The sewing, despite being broken, was remarkably stable post treatment, . This is perhaps because the chords were consolidated in place by the Japanese tissue repairs. The relative stability of the binding enabled the decision to not interfere with the original sewing, and to leave the binding, as well as the cover, as it was. The object post treatment was stable enough to digitise and even stable enough to be handled and viewed by researchers.

It was noted also that by leaving the leather cover attached only at the head, it facilitated the viewing of the sewing structure and spine. As the rare binding style is as much of cultural value as the textual content of the object, the fact that it was left exposed was regarded positively.

Volume post treatment
Figure 29 & 30: Showing volume post treatment with limp leather cover left in its original state.

Re-housing Fragments

Adhesive labels and condition reportsFigure 31 & 32: Showing adhesive labels and previous condition reports re-housed in Melinex sheaths.

Annotated infills and birch fragmentsFigure 33 & 34: Showing annotated infills and birch bark fragments spot-welded into Melinex sheaths.

After treatment there was varied ephemera to re-house and to keep with the object:

1. The old adhesive labels on the old box
2. The previous condition reports
3. The annotated infills
4. Three unplaceable birch bark fragments.

The old adhesive labels and the condition reports were placed in independent inert polyester Melinex © sheaths. The top edges of the sheaths were left open so the items could be removed, unfolded and read in the future.

The annotated infills and the birch bark fragments were secured in place in their independent Melinex sheaths using an ultrasonic spot-welder. Both sets of sheaths were hole-punched and secured together in the top left hand corner using an archival snap-ring.

Re-housing the Manuscript

To impede the likelihood of potentially harmful physical or environmental damage, it was decided that a custom made drop-back box would be made. It was decided that a shelved compartment would be included in the design in which to store the sheathed ephemera. A four flap wrapper was also made for the volume from Kraft paper, to further impede the potential of damage and to facilitate future handling.

Finally the shelfmark of the item was gold tooled onto the spine of the box.

Drop-back box
Figure 35 & 36: Showing Kraft paper 4 flap folder and buckram-covered drop-back box with shelf compartment.

Gold tooling

Figure 37 & 38: Gold tooling the manuscript shelfmark onto the box.

Before and After Treatment Photographs:

Before and after treatmentBefore and after treatment 2Before and after treatment 3

By Daisy Todd

Image References

Wojtech, M 2013, The Language of Bark, American Forests, article: http://www.americanforests.org/magazine/article/the-language-of-bark

Wojtech, M 2011, Getting to know bark, Northern Woodlands, article: http://northernwoodlands.org/articles/article/getting-to-know-bark

Further Reading

Agrawal, OP & Bhatia, SK 1981, Investigations for preservation of birch bark manuscripts, ICOM committee for conservation, 6th triennial meeting, Ottawa, September, pp. 21 – 25.

Batton, S 2000, Seperation Anxiety: The Conservation of a 5th Century Buddhist Gandharan Manuscript, WAAC Newsletter, Vol. 2, No.2

Florian, ML, Kronkright, DP, Norton, RE 1991, The Conservation of Artifacts Made from Plant Materials, Getty Trust Publications, Getty Conservation Institute.

Gilberg, MR 1986, Plasticization and forming of misshapen birch-bark artifacts using solvent vapours, Studies in conservation, Vol. 31, No. 4, pp. 177-184.

Gilroy, N 2008, The Stein birch-bark collection in Oxford: Thirty years of developing treatment options for our most fragile manuscripts, ICOM Committee for Conservation:15th triennial meeting, New Delhi, 22-26 September, Delhi: Allied Publishers, Vol. 1, pp. 264-269.

Suryawanshi, DG, 2000, An ancient writing material: Birch-bark and its need of conservation, Restaurator: International journal for the preservation of library and archival material, Vol. 21, No. 1, pp. 1-8.

24 July 2017

Do more together than we can ourselves: The unique partnership between curator and conservator

Zoë Miller and Peter Toth

curator, n. Traditionally, a curator or keeper of a cultural heritage institution (e.g. gallery, museum, library, or archive) is a content specialist charged with an institution's collections and involved with the interpretation of heritage material.

conservator, n. A person employed in the conservation of artefacts or sites of archaeological, historical, or cultural significance. Cf. conservation n. 1f.

The British Library is the custodian of thousands of manuscript treasures and it is a shared duty of its curators and conservators to care for and interpret them. I’m inviting you to share this meeting of minds and how it brings our collection to life through the rediscovery of a unique fourteenth century manuscript; Egerton MS 2516.

Once part of the library of bibliophile friar Leonardo Mansueti of Perugia (d.1480), this fragile selection of writings from Cicero and the famous African magician and philosopher Apuleius was brought to our conservation studio by curator Peter Toth for assessment and treatment advice.  

Ownership note

Ownership note by Leonardo Mansueti in Egerton MS 2516, f. 162r.

The volume had been rebound in the nineteenth century in a style and design typical of the collection of Francis Henry Egerton. The very small script was written in iron gall ink on thin parchment to save money, and decoration was kept to a minimum. This book was destined to be a scholarly study text and it is an early and important manuscript of the works of the second-century Apuleius.

Original spineTight opening

Original spine and tight opening in Egerton MS 2516.

Peter is able to read and interpret the ancient text and marginalia and to provide this crucial contextual and historical narrative. When he presented us with this book we could immediately see the problem. Its materials had aged so much that it couldn’t be opened beyond forty five degrees! It was so tight that we could not see the text in the gutter. The pages were fragmented, mutilated and corroded by the chemical action typical of this ink. Like leaf skeletons they were incredibly fragile and impossible to turn.

Damaged foliosCut marks

Damaged folios and cut marks in Egerton MS 2516.

As conservators, our first sight and handling of an object can play like a movie of its life. We experience the ageing character and material signs of use and damage known so well of leather, parchment, threads and paper. Even the smells and stains, the cuts, marks and tears of a hundred scholars thumbing the pages are brought to life as we hold it in our hands. There were mysterious cuts to the tail of many folios, which suggested a purposeful extraction. Could this have been to remove mould, mistakes or secret text? Perhaps the parchment was stolen for love notes by a fifteenth century student? 

The existing book boards with a gold crest and inscriptions are part of the unique provenance of this object, and yet the re-binding destroyed evidence of the manuscript’s original shape and sewing. Peter explained that its hard work as an academic ‘set text’ contributed to the patterns of deterioration we see today. We therefore tailored our treatments to preserve evidence of this damage and limit our repairs and intervention to safeguard the narrative. We created a new binding from calfskin replicating the Egerton tradition to respect this significant part of its history.

Removing sewing

Removing sewing from Egerton MS 2516.

The old leather, glues and overcast sewing threads were painstakingly removed by parchment specialist intern Camille Thuet. Once the delicate folios had been released, medieval manuscript cataloguer Laure Miolo was able to access and identify hidden marginal notes. She found fifteenth and sixteenth century comments and a Greek quotation from Euripides which had been added by early readers of the text and reveal how it was used and interpreted. 

Quotation

Quotation from Euripides in the lower margin of Egerton MS 2516, f. 123v.

With the help of conservation imaging scientist Christina Duffy, Camille analysed dark stains across areas of script which were speculated to be early attempts at revealing hidden text. Multi-spectral imaging was also useful in enhancing faded marginalia.

Chemical damage

Historical chemical damage on Egerton MS 2516 f. 4r in an attempt to improve legibility of corroded iron gall ink.

Multi-spectral imaging

Multi-spectral imaging of Egerton MS 2516, f. 116r.

The treatment proposal had two clear aims: 

Enabling access and digitisation through repair of the delicate and damaged folios to ensure they continue to exist for future generations

Preserving and protecting historical evidence so that as much of the past is accessible to the future reader.

A new guard book structure means that the original parchment text block is protected from adhesive and the necessary mechanics of the binding’s spine. This allows every part of it to be viewed, and no part to be constricted. Parchment likes to breathe!

New guard structure

New guard structure.

New flat opening

New flat opening.

New binding

New binding.

Gold finishing

Gold finishing on Egerton MS 2516.

The books in our rich collection inspire both for the intellectual information they carry and as artefacts of craft. We were able to make complex conservation decisions to preserve this manuscript through collaboration with curators. We must together protect what our collection will represent in the future where respect for such treasured objects only grows in this changing digital age.

Thanks to Camille Thuet for her observant eye and parchment knowledge, and to Peter Toth, Andrea Clarke, and Laure Miolo for their historical expertise. The manuscript has now been restored and completely digitised and is available at the Library’s Digitised Manuscripts site here.

03 July 2017

Vacancy: Collection Care North Manager

Description

Full Time, Permanent

We wish to appoint a Collection Care Manager to manage collection care activities on our Boston Spa site. The post-holder will be the primary collection care contact on site and will work with colleagues and stakeholders to identify and manage risks to physical collections in storage, transit and use. The post-holder will line manage the Collection Care North team who box, shrink wrap and process collection items for an external binding contract.

Collection Care North

Working in close collaboration with the Preventive Conservation and Conservation teams in St. Pancras the post-holder will develop and manage a yearly work programme which balances the needs of the collections with changing user and business needs. The initial focus will be to review activities and further develop the team to ensure it meets the future needs of the site and collections stored there to ensure a consistent approach to collection care across both sites.

You need to have a degree in book or paper conservation or equivalent experience, recent experience managing preventive conservation/preservation activities and an understanding of digitisation processes and workflows. In addition you will have a broad knowledge of preventive and conservation treatments within library collections together with the ability to diagnose conservation problems and to develop and evaluate options for solutions. You will work with minimal supervision and have the skills and knowledge to plan and manage your work to ensure that deadlines are met. You must be able to communicate effectively with people at all levels, and be able to keep clear, detailed and accurate records of all treatments undertaken. You will have previous experience managing staff, interns or volunteers and delivering coaching or training.

Closing Date: 23 July 2017

Interview Date: Week Commencing 7 August 2017

For more information and to apply see the main recruitment page here.