Grandpas in the bookstack
How we preserve parchment books
22 September 2016
Deep within the depths of our book stacks is a room filled with every bibliophile’s dream—thousands and thousands of old books. The rare book stack contains a wonderfully diverse collection of Renaissance and Early Modern-era parchment bindings. As part of our founding collections these books are affectionately called our ‘Grandpa books’.
Some of our Grandpa books have fine historic bindings with parchment, leather, alum tawed, and paper covers. Examples of coloured parchment, such as the blue books in the image above, are particularly striking.
Parchment bindings are amongst the most at risk books in any library collection. The problem lays in the inherent nature of the skin, which is generally sheep, calf (vellum), or goat. Parchment is a hygroscopic material which means it absorbs moisture easily. It is held in a state of high tension due to the highly-skilled manufacturing process which is done entirely by hand. The process renders the animal-shaped pelt into a perfectly flat substrate suitable for writing on. This technique for producing parchment has not changed over several millennia.
Natural fluctuations in temperature and/or humidity can cause parchment to shrink or expand as it struggles to return to its original three-dimensional animal shape. Vellum can twist and distort even the thickest of book-boards, causing the books to tear themselves apart.
Parchment has always been a sturdy but expensive and time-consuming material to make. For this reason, parchment covers are found on books of considerable value. Parchment was also used as a covering material for blank stationary books which often contain important manuscript material.
The perpetual movement of vellum means there is a very high chance of the books sustaining severe structural damage. This means our preservation team have been busy developing suitable techniques for relaxing and flattening bindings with severely bowed boards.
The technique we use to relax the parchment is to gently introduce moisture back into the skin. We apply a sandwich of damp blotter and Goretex™ membrane to the boards. A ziplock bag is placed over the sandwich and sealed off to make a humidity chamber. The humidification process is a passive treatment which introduces moisture in a slow and controlled manner. On average, it can take between 4-6 hours for the parchment to become malleable enough to flatten.
We have come across some surprising finds during our treatment of the rare book collection. This 17th century binding contains a piece of medieval manuscript ‘waste’ dating from centuries earlier. A thrifty bookbinder has used the waste as reinforcement for the lovely green endband.
When the bowed boards have been flattened these precious books return to their original dimensions and can be properly stored. Storing the books in custom-made pressure boxes contributes enormously to their long term preservation by providing gentle pressure and a more stable microclimate.
The opportunity to help preserve our Grandpa books is a real joy. There are fine examples of parchment bindings on display in our Treasures Gallery—see what you can discover next time you visit!
Christopher Clarkson, ‘Rediscovering Parchment: The Nature of the Beast’ The Paper Conservator Vol. 16 1992, pp. 5-26, nla.cat-vn1561469