Parchment is commonly made from sheepskin or calfskin. It is usually treated with paste, flour, egg whites or milk to make it white.
Leather is also made from animal skins, but leather is tanned with acids to make it tougher and waterproof. Parchment is only treated with lime and alcohol. It can be ruined by water.
Parchment from a fresh animal skin is soaked in water for a day to clean it. The skin is then put in an alcohol or lime bath for up to a week to remove any hair or fur, and stretched over a frame to dry, and any remaining hair scraped off.
Throughout history parchment makers have used certain materials to make specialized forms of parchment. In medieval Europe, some parchment was made with the skins of unborn animals. Known as uterine parchment, this material was both thin and strong.
Parchment was historically a leading writing medium for nearly 2,000 years. It is still used today, but mostly for ceremonial or religious uses.