Image of Detail of CBL InE 1463 f.6.

Delaminating and fraying fibres: developing an advanced treatment approach for the conservation of a 12th century palm leaf manuscript

25 March, 2020

The Perfection of Wisdom Sutra in 25,000 verses (Panchavimshatisahasrika Prajnaparamita), CBL InE 1463, is an extremely rare Buddhist manuscript from West Bengal. This important sacred manuscript is dated to circa 1100 AD (1) and is written in Sanskrit. The Chester Beatty holds the largest portion of this manuscript with 59 leaves, although a total of approximately 140 surviving leaves are dispersed in collections around the world. The manuscript probably originally contained at least 560 leaves, making it a substantial object at the time of production.

Alongside two painted wooden covers, 17 of the Chester Beatty folios are delicately painted. They are illustrated with a sacred deity at the centre, and bands of bright geometric decorations and Stupas at either side of the leaf.  The pressing need to access this extremely fragile and significant manuscript has led to the need to address the manuscript’s long-term preservation.

Image of CBL InE 1463 f.32, detail of central panel (left); detail of decorative bands, including a stupa at the edge (right).
CBL InE 1463 f.32, detail of central panel (top); detail of decorative bands, including a stupa at the edge (bottom).

How palm leaf manuscripts were made:

Throughout South East Asia, palm leaf was commonly used as a writing material for centuries. Palm leaf manuscripts were made from two different types of palms: the palmyra and the talipot leaves. The palmyra leaf (Borassus flabellifer) is rather thick and inflexible with brittleness developing over time. The surface of the leaf has a pitted appearance. The talipot leaf (Corypha umbraculifera) is thinner and more flexible. Most of the earliest examples of palm leaf manuscripts from India are made using this type of leaf (2) while the palmyra was introduced much later. Indeed, CBL InE 1463, which has remained quite flexible over time, is most likely (3) made from talipot leaves.

Image of 2. The talipot palm (Corypha umbraculifera) growing by a lakeside in Ceylon. Coloured etching after W. Daniell, c. 1810. Credit: Wellcome Collection. Attribution 4.0 International (CC BY 4.0).
The talipot palm (Corypha umbraculifera) growing by a lakeside in Ceylon. Coloured etching after W. Daniell, c. 1810. Credit: Wellcome Collection. Attribution 4.0 International (CC BY 4.0).

Three areas are identifiable within the structure of the palm leaf: the epidermis, the mesophyll, and the veins. The outer surface, the epidermis, covers the lower and upper sides of the leaf and protects the two internal elements, the mesophyll and the veins.

Each side of the leaf epidermis is composed of cells protected by the waxy cuticle, which helps to prevent water loss. This gives the leaf surface a smooth finish with a natural surface sheen which has been desirable for writing on.

The inner core of the leaf, made of the mesophyll and the veins, tends to be soft and spongy, and gives the leaf its natural flexibility.

Image of there is a clear distinction in the palm leaf structure between the epidermis where the ink has been applied, and the mesophyll and veins underneath. Detail of a folio from CBL InE 1463.
There is a clear distinction in the palm leaf structure between the epidermis where the ink has been applied, and the mesophyll and veins underneath.

There are different ways palm leaves can be prepared for manuscript making, however there are no known instructions available from 12th century India.

Paper conservator Yana Van Dyke (4) identifies three processes of leaf preparation in India:

  1. The fresh leaves could be dried in the shade and rubbed with gingili oil to make them smooth.
  2. They could be hung and smoked, then the surface deposit wiped off, sometimes followed by rubbing with turmeric paste.
  3. They could be dried in the sun, buried in pond mud for ten to fifteen days, cleaned, dried, and rubbed with turmeric paste.

Once the leaf was prepared, it could be written on. In keeping with what is expected to be found on a 12th century Northern Indian manuscript, the black ink on CBL InE 1463 is carbon-based. It has been carefully used for calligraphy on the surface of the leaf.

Agrawal (5) identifies two main techniques for writing on palm leaf manuscripts:

  1. Writing with a thin brush and pigment directly on the leaf surface, often seen in Northern India.
  2. Writing by incision with a pointed metal stylus and rubbing soot into the incised areas. This technique is found all over South-East Asia (6).

Conservation:

Palm leaf is by nature fragile and prone to diverse types of degradation, making preservation particularly challenging. Degradation agents inherent to the palm leaf, such as the lignin content, lead to the palm’s tendency to become rigid and loose flexibility, therefore becoming prone to brittleness over time.

The mechanisms of physical degradation in CBL InE 1463, such as partial blocking between the leaves caused by significant water damage at some point in the manuscript’s life, along with poor handling, have resulted in localised delamination, fraying, breakage and large losses on many of the most damaged leaves.

Image of delamination of the epidermis and breakage parallel to the edges of the leaf. Details of CBL InE 1463.
Delamination of the epidermis and breakage parallel to the edges of the leaf.

The high cellulose content of the palm leaves in association with different chemical compounds and the leaves’ physical characteristics, such as a smooth outer layer and a soft and spongy inner layer, makes using traditional paper conservation techniques possible, with small changes in the approach to achieve the best results.

Using two different adhesives and different application methods on the different areas of the leaf has allowed me to conserve the palm leaf manuscript with success.

Following Yana Van Dyke’s research, I decided to use Isinglass remoistenable tissue when working on the outer layers of the palm. Isinglass is a strong adhesive which holds onto the extremely smooth and waxy layer of the leaf. Whereas wheat starch or Methyl Cellulose would have failed rapidly and indeed possibly not adhered at all, isinglass provided a strong bond to secure the leaf.

I used thin strips of the prepared tissue to support frayed edges and repair broken areas. Remoistenable tissue was particularly helpful to support larger brittle areas, such as the edges of the palm which had tended to fray and break lengthwise. To minimise the introduction of moisture to this extremely dry material, I used a combination of pre-humidification of the repair tissue, by laying it adhesive-up on a wet cotton pad, and a wet brush application directly on the object. Initial tests using pre-humidification alone were sometimes unsuccessful and the tissue would partially or totally lift off the leaf when dry. Using a controlled amount of moisture from a carrier such as a thin brush allowed me to introduce the extra moisture needed to reactivate the adhesive layer as well as applying a gentle pressure to the repair material to encourage it to dry in place. Whereas I would usually only use one or the other method, I found that using a combination of rehydration techniques worked very well in this case.

Image of Remoistenable tissue prepared with Isinglass, applied using a small damp brush (left); Epidermis fibres encouraged to lay flat using small brass weights. Details of CBL InE 1463.
Remoistenable tissue prepared with Isinglass, applied using a small damp brush (left); Epidermis fibres encouraged to lay flat using small brass weights.

For the areas of delamination, where the waxy outer layer of the leaf (epidermis) was lifted and the spongy area underneath (mesophyll and the veins) was exposed, I used dry wheat starch paste in small quantities. This was applied primarily to the spongy area, to reattach the epidermis to the mesophyll, without disturbing the fibre layer or the moisture sensitive black ink. The moisture of the adhesive was sufficient to relax the dry fibres of the epidermis, and using tweezers and small weights, comparable to weights used in papyrus conservation, I was able to realign and re-adhere the fibres to the leaf substrate.

Image of before and after conservation of a small damaged area using the combination of methods. Detail of CBL InE 1463.
Before and after conservation of a small damaged area using the combination of methods.

The development of this new conservation methodology for palm leaf manuscript materials stems directly from the case study of CBL InE 1463. Having used Yana van Dyke’s research as an initial starting point, I realised that the damage observed on the Chester Beatty manuscript necessitated a different approach for the re-alignment of the lifting epidermis layer. The methodology using two adhesives to repair the different damaged areas has proved successful, if not a little time consuming. However, the fragility and significance of this object warranted such a minute treatment to be undertaken. The manuscript remains fragile as the material is inherently friable and brittle with age. However, through research and reflection, this conservation treatment has allowed an extremely delicate manuscript to be made accessible to scholars and the wider public through display and digitisation.

Julia Poirier, Book and Paper Conservator

Image of CBL InE 1483, f.15, after treatment. Broken and weak areas have been supported and infilled as necessary.
CBL InE 1483 f.15, after treatment. Broken and weak areas have been supported and infilled as necessary.

Footnotes

(1) The manuscript is dated to the eighth regnal year of Harivarman (c.1100 AD), ruler of Southern Bengal, for a donor named Ramadeva.

(2) Diringer, D. The book before printing, Dover, Mineola. (1982): P.358

(3) No test was carried out. This conclusion stems from visual observation and physical behavior alone.

(4) Van Dyke, Yana. “Sacred Leaves: The Conservation and Exhibition of Early Buddhist Manuscripts on Palm Leaves.” In The Book and Paper Group Annual 28 (2009), 83–97.

(5) Agrawal, Om Prakesh, Conservation of Manuscripts and Paintings of South-East Asia, Butterworth-Heinemann, London (1984), 31.

(6) Udaya D, Kumar GV, Sreekumar U, Athvankar A: Traditional Writing System in Southern India – Palm Leaf Manuscripts. Southern India: Palm leaf manuscripts; (2009).

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