A great part of the history of pottery is prehistoric, part of past pre-literate cultures. Therefore, much of this history can only be found among the artifacts of archeology. Because pottery is so durable, pottery and sherds from pottery survive from millennia at archeological sites. The earliest forms of pottery were made from clays that were fired at low temperatures in pit-fires or in open bonfires. They were hand formed and undecorated. Because the biscuit form of earthenware is porous, it has limited utility for storage of liquids. However, earthenware has a continuous history from the Neolithic period to today. It can be made from a wide variety of clays. The development of ceramic glaze which makes it impermeable makes it a popular and practical form of pottery making. The addition of decoration has evolved throughout its history. Image taken from page 301 of "Primitive Man" by Louis Figuier. Revised translation from the French by Edward Burnet Tylor. Illustrated with scenes of primitive life, 1870.