Pottery has a rich and varied history on the African continent, beginning almost 10,000 years ago and continuing on today. Clay pots were and still are being used to cook food, store water and for various other functions related to food preparation. In most cases, pottery was made by women, who worked entirely by hand or poured it into moulds. After drying, the pots are put in a pile and covered with wood, bark or dried cow dung and baked outdoors in an open fire; however in certain areas such as Nigeria and Mali, pots are baked in higher-heating kilns. After baking, the pots are then decorated. Polishing pots was and still is a common practice among various African tribes, especially those from the central region whose pots have a deep lustrous finish normally achieved by the firing process. Sometimes, plant dyes were randomly splashed on after the firing process for coloring. Additional decorative elements include engraved abstract or geometric patterns carved into the surface of the body. Human and/or animal figures also embellish certain works, sometimes as appliqués added to the wet surface before firing. Other materials were also added to the pots for functionality or ornamental purposes, such as the basketwork covers that are fitted over pots, making them more functional and also more elegant.