Treatment was carried out to ensure the Antiphonal's survival today and in the future.

Initially the book had to be "taken down" or dismantled. Dirt, including dust, insects and flaking black pigment, were carefully cleaned away from the folds in the leaves.

Due to the rigidity of the stitched vellum repairs along the backfolds, many of the folios could not open out fully. Apart from a few that were left as an historic record, these repairs were removed, revealing thick layers of animal glue. Cleaning this adhesive away left the vellum noticeably more flexible. Other rigid and unsuitable repairs were removed also.

A fascinating aspect of treating a 13th century book in the late 20th century is the mix of technologies that are used. The consolidation of the flaking text provided one of the most striking contrasts between the very very old and the ultra modern in one treatment operation.

After extensive testing of a range of consolidants - from modern synthetic adhesives to more traditional materials - we found that the best consolidant was the size or adhesive made by boiling up parchment scraps in water. This produced a thin easily applied solution with enough tack to hold the flaking ink, enough flexibility to move with the pages as they were turned and it caused very little or no darkening of the inks to which it was applied.

To apply the size to the precise areas requiring treatment, the State Library's conservators used the most modern of technologies - a stereo-microscope linked up to a video camera which produces digitized images on a computer. Using this equipment they could accurately place the size by either looking at the video screen or by looking down the microscope. They were also able to make a permanent record of this treatment step using the video.

Once the very labour-intensive consolidation was complete, work commenced on the repair of the vellum leaves. The first step was to examine every leaf in the Antiphonal and identify the areas to be treated and the type of treatment required. Wherever possible proteinaceous materials such as vellum, parchment, collagen sausage skin and/or fish skin were used as the repair materials. Vellum and parchment were ideal for filling areas missing from the original document while thin films such as sausage skin and fish skin were used to support other repairs and to hold small tears and cut together.

The outer folios of most sections were very badly damaged along the backfolds. To provide the flexibility and strength required, and to avoid extra bulk, Japanese paper was used with sausage skin or fish skin to repair these outer folios.

Humidification and flattening were considered for many of the leaves, in order to remove cockling and distortion. As the treatment progressed this step was largely abandoned. Vellum is said to have a "memory", i.e. it has a tendency to return to any shape it has held for a long time. Humidification and flattening was working against this very strong "memory" and in some cases created new distortions that would have affected adjacent leaves. This was not desirable.

The final treatment stages - sewing and binding - were the subject of many discussions between conservators and curators. The decisions made at this stage determined how well the Antiphonal would perform structurally and how it would look at the end of the treatment project.

The evidence of previous sewing structures was revised. It was agreed that the book had been sewn a number of times, but there was no conclusive evidence to indicate which were the earliest sewing stations, especially since the backfolds had been badly damaged by insects. It was agreed that the clearest and strongest evidence was from the most recent sewing and therefore these sewing stations were re-used.

It was agreed appropriate to sew the book on double cords, using a herringbone stitch, as research indicated that this closely resembles what would have been the original style. This sewing style also has structural advantages: it provides adequate support for such a large book with heavy wooden boards and limits the movement of leaves against leaves, thus reducing the risk of abrasion of the text.

A non-original element was added to the book. A concertina guard was incorporated in the sewing, thus allowing the spine of the textblock to be lined without applying adhesive directly to the vellum. The spine was lined with layer of strong, flexible Japanese paper. Lining the spine supports the sewing structure as it flexes when the book is used.

Headbands were provided to help to prevent movement of the textblock that could lead to abrasion. The current headbands have been sewn in a separate operation to the book sewing. This was done deliberately so that any damage to the headbands does not mean that the whole book has to be re-sewn. These headbands have a cord core and are sewn with linen thread.

The cords were laced into the boards. This, along with the leather spine covering and the endpaper pastedowns provides a very strong method of attachment for such heavy boards. This is most likely to have been the original method of attachment of the boards in the 13th century.

Finally a new leather spine was prepared and toned to closely match the leather that had been left on the oak boards.

Using a mix of traditional and modern techniques, the conservation team has not only conserved the Antiphonal itself, but has also preserved vital information about the history of past restorations and bindings.