Pit firing the oldest known method for the firing of pottery. Examples have been dated as early as 29,000–25,000 BCE. Unfired pots are nestled together in a pit in the ground and are then covered with combustible materials such as wood shavings, leaves, metal oxides, salts, sawdust and dried manure. The top of the pit may be protected with moist clay, shards, larger pieces of wood or metal baffles. The filled pit is then set on fire and carefully tended until most of the inner fuel has been consumed. At around 1,100°C (2,000°F) the maximum temperatures are moderate compared to other techniques used for pottery. After cooling, pots are removed and cleaned to reveal patterns and colours left by ash and salt deposits.