This is a guest post by John Bertonaschi, Senior Rare Book Conservator in the Conservation Division.
In part two, I acquainted you with the history and condition of our 13th century Law Library manuscript, Decretum Gratiani. I told you that, as part of a restoration in the late 19th or early 20th century, the spine was coated with liquid hide glue, which caused the parchment text block to distort and the spine to become rigid. The book could not be opened fully, making the script on the inner margins inaccessible. Now, I will write about our efforts to alleviate these problems and repair some of the wear and tear suffered by the manuscript over the past 700 years.
Together with Senior Rare Book Conservator Katherine Kelly, we first had to remove the cover from the book. The sewing supports, heavy thongs of alum-tawed skin, had long since broken or been cut off at the joints. Individual slips of thread had been looped around the ends of the supports and pasted to the boards. These were cut and the leather detached from the spine. The hide glue was quite brittle and broke away easily. Next, we had to cut the sewing thread in order to separate the individual quires. This manuscript retained its original sewing, so this was not a step we took lightly, but keeping the sewing intact would have meant keeping the supports, which would never be flexible enough to allow the book to open sufficiently. We worked our way through the book, carefully pushing the quires open to gain access to the center fold and snip the sewing thread. During this process, we discovered many quire tackets, small loops of thread used to keep the pages in order while the scribe copied the text.
When all the quires had been separated and could fully open, the next step was to try to reduce some of the distortion in the parchment. This was done with gentle humidification, but we first had to make sure the media would not be affected by the moisture used for this process. Katherine tested all the various inks and pigments in the manuscript with de-ionized water, painstakingly blotting tiny drops with pieces of paper to see if any softened or soluble media would offset. Most of the media did not react to moisture, with the exception of some heavily applied black ink and the blue pigment in the large initials and glossing, but we were confident that, by limiting the amount of moisture used, we could humidify safely.
We decided to concentrate on the distortion around the center folds of the bifolia caused by the application of hide glue to the spine, leaving alone the undulations at the fore edge which, to us, seemed like the form the parchment had comfortably adopted over the course of its life. We did not want pages which looked as though they had been pressed completely flat. We worked out a simple procedure which involved covering the center of a bifolium with Gore-tex®, a permeable membrane which allows moisture to pass through in the form of vapor. On top of this, we placed blotter which had been misted with water, then shrouded everything with plastic sheeting. After 20 minutes, the parchment, which is extremely sensitive to humidity, had relaxed enough to allow us to apply weight to the spine fold, moving the weights up from the center towards head and tail to create a gentle stretching action. When dry, the problematic distortions in the center were significantly reduced. Since we had to do over 130 bifolia, we spread the work out by opening the project up for the rest of the Conservation Division staff to participate. Not only was the task completed more quickly, but it gave some of our colleagues their first chance to work with old parchment.
After the humidification and drying steps were completed, we reassembled the bifolia back into quires. Our intention was to leave the manuscript between felts with weight on top for a few months, to let it rest in its new, more planar state, but life had other ideas. In March 2020, the Library and all other Federal offices closed due to the COVID-19 pandemic. A few months became a few years and it wasn’t until late summer of 2022 that Katherine and I were able turn our attention once again to Decretum Gratiani.
To us, this manuscript is a beautiful object. A Library catalog notes that the parchment is of “mediocre quality” and that is no doubt true. We find many thin spots and holes which were made during processing. Sometimes, the skins used were a bit too small for the format, resulting in irregular edges that could not be cut straight. The scribes worked with what they had, and this is part of the book’s charm.
A conservator can become rather intimate with an object while working on it as they learn more about it. This is especially true of books, which have all kinds of things accidentally or purposely left in them. In our Decretum we found insects (very common to see), a hair embedded in the pigment of an initial, and some tiny flowers which found their way deep into the gutter margin.
Our examination of the manuscript showed that there was not too much mending to be done. We determined to keep our intervention to a minimum and repair tears around the edges, and holes and weak spots in high-stress areas such as near the center fold. Many old patches were left in place if they were not causing distortion and were not covering any of the script.
For centuries, parchment has been repaired with parchment, but we have a few more alternatives available to us today. Katherine and I considered several materials for mending, but, from the beginning, we were leaning towards the use of paper as our repair material. As book conservators, we work almost exclusively with paper for mending, and have a high level of comfort with it. Again, we did not want to use a lot of moisture during the mending process, which could cause cockling. To avoid this, we coat the repair paper with adhesive ahead of time and let it dry. We then apply just enough moisture to reactivate the adhesive and get the repair to stick. After experimenting with various combinations, we settled on RK-0, a relatively strong but very thin Japanese kozo tissue. Coated with a mixture of starch paste and methyl cellulose, it is used to mend tears and reinforce weak areas. We intend to use the original sewing holes when we rebind the manuscript, but some of them have attained an unacceptably large diameter. For these, we use a thicker kozo paper, one heavy enough to sew through, pre-coated with a 5% gelatin solution.
Once all the repairs are done, the Decretum will be returned to the Law Library for scanning, the initial motive for it coming to the Conservation Division in the pre-pandemic years. Scanning will be easier before the manuscript is rebound.
In Part 4 of this series, I’ll tell a little about Romanesque books and our task to resew the quires of Decretum Gratiani.
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