Parchment

 Parchment

Parchment replaced papyrus as the most common writing material during the early Middle Ages in Europe. Parchment is made from animal skins, generally sheep, goats and calves. It  has considerable strength and durability, but it is sensitive to humidity (or lack of humidity). Sometimes the term vellum is used instead of parchment, but vellum (from the Old French word for calfskin, "velin") refers specifically to the skin of calves, used mainly as a covering material.

Parchment-making is a lengthy process. The hair and flesh are removed with the aid of lime (a strong alkali), then the skin is stretched on a frame where it is scraped, wet, and stretched again until the fibers become aligned.

Leather  and parchment differ in that leather has been tanned, a process in which animal skin has been chemically altered to resist rot, whereas parchment has not been tanned.

Parchment rolls were once very common, but the chief value of parchment is its ability to be stitched together in large gatherings to form durable and flexible volumes. The sewing to produce the parchment codices was notably Coptic [add to glossary]in style until the fifth to eighth centuries, when it became common to sew the parchment signatures onto thongs or cords with heavy wooden boards to stabilize the shape of the text.

Identification

The characteristic features of parchment, which confirm its animal origin, can usually be recognized under close examination with a hand lens (30x) or a microscope. These features include the hair follicle pattern, veining, natural scars and bruises and in certain skins, fat deposits. The follicle pattern may be most pronounced across bony areas of the animal, such as the ribs or spine. Raking, transmitted, and ultraviolet light often help to make these features more prominent.

Analytical testing is also possible. Since, it involves destructive testing of a small sample taken from the parchment, it should be done only under the supervision of professional conservators. Cross-sections of parchment can be examined under the light microscope and with scanning electron microscopy. During visual examination it can be difficult to distinguish between certain types of parchment (usually thin flesh splits from the 19th and early 20th centuries, sometimes called "forrel") and highly calendared papers, often called "parchment" paper or "vellum" paper. Imitation parchment made from vegetable matter or paperlike material usually is easily recognizable because the surface characteristics are too even and do not bear the marks of an animal skin.

Condition Concerns

Parchment is hygroscopic (absorbs moisture) and, while chemically stable, is dimensionally unstable and reactive to changes in the moisture level. Because parchment was created by stretching the fibers under strain, moisture will allow the fibers to change shape and cause distortion and wrinkles. Parchment documents need to be kept under some pressure constraint, and bindings in parchment should be boxed.

Relevant readings

Bell, L. A. 1992. Papyrus, Tapa, Amate, and Rice Paper. McMinnville, Ore.: Liliaceae Press.

Kenyon, Frederick. 1951. Books and Readers in Ancient Greece and Rome. London: Oxford University Press.

Reed, R. 1972. Ancient Skins, Parchments and Leather. London: Seminar Press.