These are the general terms for the refined and flattened membrane of sheep or goat skin. Parchment is firm and cream in colour, generally made of sheepskin and used for manuscripts or printing. Vellum is softer and flexible, off-white in colour, made of calf or goatskin and is used for bookbinding and writing.
If parchment is allowed to become damp or wet it can cause the smooth flat appearance to distort by ‘moving’ back to the shape of the animal it once was.
This will generally result in mould growth, that migrates into the surface and will eventually destroy the legibility of the manuscript. This, accompanied by an evil rotting odour is a good reason to keep parchment at the right humidity, between 50-60%.
When it becomes very dry the distortions become like the hills and vales of Devon, and would need expert treatment to be flattened again. In the worst cases it can become like an Indian Poppadum in appearance and brittleness, when it has dried out. This is particularly unattractive if it has only affected a corner or one side of a document. The ideal temperature for parchment is 13-18C.
The ink on parchment also behaves differently to ink on paper, in that it rests on the surface of the skin and does not ‘soak in’ to any real depth. The consequence of this, is that the ink has a tendency to flake off, if the parchment is flexed or treated roughly. When unfolding a parchment document, you can observe dust, ink and sand, loose in the folds. Some lose is unavoidable, If the script is just a hazy blur, it can sometimes be read with an ultra-violet lamp.
Large documents that have been folded into a compressed package or tightly rolled are at best very springy to unfold and at worst will crack and break when you attempt to open them to their full extent. If this seems to be happening, -stop- and seek the advice of a qualified conservator. There are methods of flattening parchment best left to the professionals. If they will unfold easily, use weights to hold down the corners.
The mounting and framing of parchment is also more problematic than paper. Once flat, the mounts and frame must be of the correct type to maintain this state. A knowledgeable framer or a conservator will help you. Be cautious of enthusiastic amateurs; ask for evidence of insurance and qualifications.
These must also be considered. They should not simply hang from the document. They are subject to being brittle and can easily be broken if knocked or dropped. Folding or rolling of the document can damage applied seals. A protective barrier in the form of a padded calico bag or acid-free tissue around the seal will provide a shock absorber and keep the seal clean. If your seal is broken, a padded bag around it will stop the pieces from being lost.
In the case of framing, a depression made in the mount will secure the seal, often without further need for fixings.
Light, delicate cleaning with a dry cotton bud is all that is required in most cases.
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