The highest quality parchment from the supple unsplit skins of stillborn calves (or lambs or goats) specially treated to form a fine writing surface on both sides. Valued for producing durable copies of important texts. Most biblical codices of the 4th- 6th c. CE are on top grade vellum. The increased demand for books after 600 CE led to the substitution of lower grade leathers from older animals.

Other On-line Resources:

• The History of Vellum and Parchment - detailed illustrated account of the use of skins in the production of books (Eden Workshops: A Bookbinders Resource).

• Vellum - brief dictionary article from Bookbinding & the Conservation of Books (archived by the American Institute for Conservation).

• Vellum - description of the processing of skins & production & conservation of mss. (Wikipedia).