Pages or book covering made from a prepared animal skin. Parchment describes any animal skin used for books, while vellum is a specific form of parchment made exclusively from calf skin. Parchment is one of the oldest methods of creating book pages, predated, of course, by stone or clay tablets, paprys, tree bark among others. Parchment dates as early as 2000BC, and lasted as a primary method of book printing in the Western world for thousands of years, and is still used today to a much lesser extent. The popularity of parchment was in part due to the durability. Tough, supple and resistent to decay with age, the main disadvantages to parchment are its susceptibility to humidity that can cause warping in textblocks, and it's cost of production. Another advantage to parchment was its ability to be "erased" for reuse by scraping the surface. A reused parchment is called a palimpsest.