When the Library received the Prato Haggadah it was bound in an inappropriate modern twentieth-century leather binding that was causing damage to the codex. The quires of medieval codices were traditionally sewn with strong flax or hemp thread, and no adhesive was applied to the spine before a protective cover was added to the book bloc. In the course of several rebindings over the centuries, the haggadah's spine was covered with layers of glue that were impeding the opening of the pages, distorting the parchment and were a factor in the flaking away of ink and loss of pigment.
The entire manuscript has now been treated. The main steps involved: disbinding, dry cleaning of blank areas with a chemical sponge, removal of paper strips (guards) and adhesives from the spine folds, consolidation of text, consolidation of illuminations, repair with alum-tawed cow caecum (steer appendix), re-assembling the quires, and gentle flattening between felts.
The folios were cleaned of surface dust and grime with extreme caution, so that no patina was removed. Thick coatings of animal glue and PVA, a modern synthetic adhesive, were removed from the spine folds allowing the bifolia to relax and open more easily.
Loose particles of pigment were carefully reattached to the parchment substrate under a stereomicroscope. This is a labor-intensive procedure, in which alcohol is applied with a very fine sable brush immediately followed by an application of dilute gelatin. The alcohol draws the gelatin into the substrate, and the gelatin binds the loose pigment to the parchment underneath. Flaking text and areas abutting lost pigment were consolidated in a similar manner. Losses and ragged edges of parchment were reinforced with cow caecum, using gelatin as an adhesive. Finally, the manuscript was flattened between felts.
Upon completion of the project, the manuscript will be rebound
in a manner sympathetic to its age and place of origin.