As demonstrated by this illustration by Szirmai (Fig.4), in tight back structures (A), common until the early 19th century, the cover material is directly glued to the spine. In the alternate approach called hollow back (B), the cover material is not attached to the spine leaving a "hollow" between the textblock spine and the cover.

A typical issue of tight back bindings is that they expose the book spine to increased mechanical stress and limit the ability for the book to open flat. These issues are amplified by the size and weight of the volume and by the grammage of the textblock paper.

This was exactly the case of the History of the World. The structure made the book difficult to open, and over many years of usage, the huge tension it had been exposed to had damaged the spine leather.  Moreover, continued usage was very likely to create further structural damage, not only to the spine leather but also to the textblock itself.

How do I tackle this problem? This was not a straightforward decision, and I had to find an acceptable balance between the ethical tenets of "minimal intervention" and the practical requirements of "functional recovery."

Let me explain. Conservation theory and most professional guidelines tell us that treatment decisions should be guided by the concept of "minimal intervention". This concept is inherited from the world of "fine art" conservation and tells us to put the integrity of the original object first and to restrict treatments to the strict minimum necessary to protect it against damage. According to this guidance, a conservator should not attempt interventive "restoration" of an object by reconstructing missing areas or recovering damaged areas, but only to stabilise the material and limit further damage.

But books present a major challenge; they are very rarely art pieces solely for display, but functional objects that will need to be manipulated and read after treatment. This means that in many cases, limiting a book treatment to "minimal intervention" leads to a major loss of function: the book cannot be practically used and read, OR is exposed to high risks of damage if used. Because of this, book conservators often have to consider far more interventive "functional recovery" techniques, not only to repair existing damage but to protect the book for a future "active life".

The challenge, on a case by case basis, is to find the right balance of techniques to both protect the object as a historical artefact and as a functional object. The condition of the book, the priorities of the client, the relevant techniques and the budget available all participate in this complex decision process. In this case, as illustrated below (Fig.5), I had a wide range of options to choose from, ranging from a "do nothing" cop-out to a very aggressive and interventive complete rebinding of the book with new material.

The options at the "minimal" end were attractive because relatively simple and low risk, but they would require me to turn a blind eye on the damage the book would be exposed to in the future. I could not resolve myself to do this. At the other end, the more "interventive" options could be disrespectful of the object's historical integrity, not something I was happy with either! After consultation with the client, it was confirmed that future usability of the book was a key requirement, but that historical integrity should be respected as much as possible.

The techniques I knew provided no "obvious" way to both preserve the historical integrity of the book and ensure its usability…some research was needed! I first found references to techniques allowing the change of a book's structure from the tight back into the hollow back by inserting fake hollows made of stiff card between the cover and the spine. These techniques were unfortunately not suitable in this case. This book has a raised cord structure where the shape of the sewing cords shows through the cover leather. The insertion of smooth fake hollows would not be compatible with this structure.

After some additional research and discussion with tutors, I finally found a suitable but technically challenging solution: The "Honey Hollow" technique. This was developed by Mr. Andrew Honey, a book conservator at the Oxford Bodleian Library. [1] (Fig.6)

[1] Honey, A. (2003) 'The conservation of Annotationes in Libro Evangeliorum using a natural cloth hollow over a moulded Japanese paper spine former', The Paper Conservator, 27, pp. 5-11

In this technique, the structure of the book is converted from tight back to hollow back while keeping the book's original aspect and materials.

The technique requires five main steps:

• First, the original spine cover is lifted
• A cast is made of the now exposed original spine
• The cast is attached to a fabric substrate for insertion in the boards
• The original spine cover is attached to the cast
• The cast with fabric is inserted and attached to the boards

This Honey Hollow technique uses a "cast" of the original spine which is used to support the original spine as a hollow, and the fabric layer joins the cast with spine and boards. Again the technique is based on the alteration of the structure and can be considered as "invasive", but the client kindly agreed with my idea and enable me to do this challenging project!

The mechanical lifting of the spine leather was relatively easy. I then lined the "bare" spine with Japanese tissue and cling film to protect the book during the casting phase. (Fig. 7-10)

The cast was created by applying seven layers of thin Japanese paper strips pasted with wheat starch paste on the spine to match its exact shape. Precision was of the essence there. (Fig. 11 - 12)

The assembly was then left to dry overnight and lifted from the book with the cling film. (Fig. 13)

The cast needs to be fixed to a larger fabric substrate to act as "flaps" for attachment to the book boards. For this I prepared an aerocotton layer which had to be cut precisely to match the "raised cord" patterns on the cast. (Fig 14)

For aesthetics, colour matches was made with the original materials and acrylic coloured paper patches prepared. These were glued to disguise the aerocotton and to match holes in the original leather spine.(Fig 15-17)

Finally the original leather spine cover was pasted on the cast (Fig 18)

The coloured pattern nicely disguise the missing areas on the leather. (Fig 19)

From a structural perspective the book now has a functional hollow back structure and can open much easier than before with less stress on the structure. (Fig. 20)

However the book remains very heavy and should not be opened flat to avoid damaging the text block spine. Additionally I issued handling recommendations such as the use of supporting forms when consulting the volume.

This was a very challenging test not only of my technical skills but in "real life" risk assessment and decision making in book conservation. I feel privileged to have had this opportunity and so glad to have found and successfully applied a satisfying solution, for myself, for the client and for the book.