Parchment and vellum are both animal skins prepared as writing surfaces. Their great improvement over previous materials, such as papyrus, was that they could be folded into the book text blocks that we are familiar with today, making the manuscript much easier to store and read. Many of these early books were written in script and decorated with tiny painted elements and illustrations in the great medieval monasteries.
Great collections of these illuminated manuscripts have been collected and studied, such as the collection at Trinity College, Dublin. As conservators and restoration specialists study the great manuscripts, they often make discoveries that are shared with the conservation community at large, thus improving practice.
In the past, parchment was used to describe skins made from adult sheep, goat, and cow skins, and vellum to describe skins made from young animals. Vellum came to be associated with finer workmanship, and more delicate writing surfaces. But the term is not routinely used any longer by conservationists. With parchment manuscripts, it is often difficult or impossible many centuries later to identify the specific skin used. Value and worth are determined by historical significance and the state of repair, rather than the original materials. Most scientists working in the field now use parchment or animal membrane to describe any skin writing surface that is prepared in the traditional way for manuscripts.
Some of the challenges involved in conserving these great parchment manuscripts are the results of previous efforts at restoration. Conservationists also address issues of wear on the written and illustrated surface, wear on the parchment material itself, replacement of other parts of the book structure, such as linen binding threads and cover boards, and environmental threats, such as insects, humidity and light exposure.
The parchment, as an organic substance, changes over time. One common change is drying out of the skins, which cause sewing holes to widen as the skins dry, and the edges of the pages to become fragile and brittle. The edges crumbling were dealt with, in the past, by trimming the damaged sections away. We now try to conserve as much original material as possible.
In the recent past, the practice of repairing holes and tears in the parchment skin was done by re-wetting the skins, and then carefully sewing sections back together, or with replacement parchment inserted, with tiny stitches. As the skins softened, collagen from the surface was scraped over the stitches, allowing the protein matrix to dry and form a scar of sorts to help the repair remain strong. Conservationists have now developed several collagen-based products that can be used to join new pieces or repair small cracks or holes without having to insert new stitches into the surface. New understanding of appropriate storage for humidity control, and the use of high-resolution digital imaging of the original pages for scholar’s use, have kept the manuscripts from further deterioration from use and exposure.
The inks used for the lettering and for the illuminated illustrations were common mineral and metal colourants used at the time, and these pigments are still available today. Carbon black and iron gall, brown and yellow ochre, indigo and woad, red, white, and yellow leads, and malachite and ultramarine are all available as pure pigments for restoration of original paintings and text that have worn from the abrasion of the parchment surfaces. If part of a parchment text page has crumbled away, and the page is repaired with new parchment, an effort may be made to rewrite the original or redraw the lost illustrations, if an image or description is available. This will change the value of the original, and should only be undertaken with an understanding of the issues of value and worth, historical significance, and planned usage and display.
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