Rebinding Dimma

As discussed in a previous post, the decision was taken to remove the modern Roger Powell binding from the Book of Dimma, in order to accommodate digital imaging without undue stress to the brittle vellum and to carry out essential additional repairs to damaged backfolds of several bifolia.

Repairs to the calfskin vellum were successfully executed by bridging splits and areas of loss in the folds using a collagen based material called cecum, the source of which is a pouch connected to the large intestine of mammals. Once processed and degreased this membrane makes an excellent strong and flexible support to the areas of damage without adding bulk. The cecum is profiled to the correct shape and adhered with 11% isinglass, a fish gelatin adhesive.

Cecum repairs to a backfold.
Cecum repairs to a backfold.

With all repairs complete the six quires and two new vellum flyleaves the manuscript is now ready for resewing. This is a carefully considered operation as the thickness of the vellum, the number of bifolia in each quire, and the dimensions of the manuscript all play a role in determining the weight of both the sewing supports and sewing thread chosen for the job. All the sewing supports have been created in the conservation department using an unbleached linen thread twisted together mechanically to produce the desired product. The position of the sewing supports on the spine will be dictated by the existing holes in the backfolds of the quires, and no new holes will be made in the vellum. The book will be resewn on five flexible double supports which will be laced into the new binding boards, making for a strong mechanical structure. In effect the method used to sew the manuscript will result in a single length of thread running back and forward in the centre of each quire from the front flyleaf to the back flyleaf. This method of sewing mirrors that of the early medieval craftsman at the time when the Book of Dimma was produced in the eighth century.

Linen sewing support and alum tawed leather.
Linen sewing support and alum tawed leather.

The binding boards, traditionally constructed from a hardwood such as oak or beech will in this case be made from a very dense fibreboard laminate made from 100% cotton. This very stable material ensures there is no risk of contamination while being in close contact with the manuscript.

A ‘slotted spine’ of thin vellum will be fitted without adhesive to the back of the sewn manuscript and endbands sewn at the head and tail, with the core of the endbands laced into the new binding boards.

Cotton blue jean board being profiled to fit the manuscript.
Cotton blue jean board being profiled to fit the manuscript.

The manuscript will be covered in alum tawed leather, which strictly speaking is not a true leather being prepared in an aqueous solution of aluminum and potassium sulphates. The end result is a white skin that is very durable, although difficult to work. The process is of great antiquity and many examples can be found still adorning medieval books in libraries around the world.

The binding process will not require the legendary forty days and forty nights it took to write the manuscript but will be carried out in individual stages until complete, the last stage of which will be a new protective box. This approach to the rebinding and choice of materials employed will allow the Book of Dimma to be studied and displayed safely for both scholars and public alike.

John Gillis, Preservation and Conservation Department