Many archives will have collections of documents written on parchment, particularly deeds and other legal records. When it comes to long-term preservation, parchment beats paper by a mile. Parchment is animal skin which has been specially prepared for writing. Historically parchment was made from sheep (and sometimes goat) skin, and vellum from calf skin. “Parchment” has come to be used as a catch-all word for animal skin as a medium for documents – possibly because only those rare people with specialist conservation training can tell the difference! Vellum, on the other hand, is still used only to refer to calf skin. Until this year all official Acts of Parliament for the United Kingdom were written on vellum, a tradition which has just been discontinued.
Parchment is extraordinarily resilient. Documents can remain in near perfect condition for hundreds of years, and when the ink is of good quality can almost look as though they were written yesterday. Parchment doesn’t tear easily, doesn’t degrade if kept in reasonable conditions, and doesn’t easily burn. The thing most likely to cause catastrophic damage to parchment is water. Get parchment wet and it remembers that it is organic matter and begins to decompose, letting off an overpowering odour of dead sheep. Rumour has it that, due to the appalling smell, a former conservator at our archive lost two stone in weight during the time it took him to deal with a collection of parchment rolls which had suffered extensive flood damage. On the other hand, parchment likes a degree of humidity, and dry air can lead to it becoming brittle. Another weak spot is that insects and rodents can find parchment tasty.
Parchment has a memory. Once left rolled or folded for some time, that is how it will want to stay. Weights are often essential to keep parchment documents open and flat when they are being used; the documents will do their best to ping back into their accustomed shape. Whereas folded paper can be flattened by putting it under a heavy weight for a while, parchment will need specialist treatment. Here a trainee conservator explains how she went about the time-consuming process of flattening folded parchment deeds. Even though it is no longer being used by Parliament, there are still many uses of parchment which continues to be made by hand by a tiny number of specialist firms like William Cowley. This BBC video shows how they made the marriage certificate for Prince William and Kate Middleton.