This is not only because pottery shards persist in the soil long after other traces of civilization disintegrate, but also because pottery remains reveal much about a culture's organization, its sophistication, and its aesthetic values. When molded clay is heated to a high temperature, its clay particles fuse with one another. When the molded object cools, it hardens and keeps its shape and, depending on the temperature it has been fired at and the nature of the clay it is composed of, it will be partially or entirely impervious to the passage of liquids. The simplest kind of pottery, one baked at relatively low temperatures, can be called unglazed earthenware. This is nothing more than moist clay baked until it is hard.
Unglazed pottery is rough to the touch.
Mar a simply placed her clay creations inside a stack of firewood, set fire to the heap, and hoped for the best. With such uncontrolled firing, probably it was inevitable that many of her pieces cracked as they were baking. Bricks and terra cotta are forms of unglazed earthenware. If earthenware is baked with such high temperatures that the clay on its exterior acquires a slight glaze, it can be called lustrous ware. If ordinary clay is coated with a truly glassy coating, then it is glazed ware .