Manufacture

Techniques

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Firing Techniques

       Firing is the best technique to produce ceramics that can withstand a large amount of stress. Firing usually occurs in an oxygen atmosphere and pieces usually have a characteristic reddish colour. The overall look of the piece is dependant on the temperature at firing, the time it is fired and hoe long the piece has been dried before firing. There are two principal methods of firing pottery. These are open firing and the use of kilns. Below is a piece that has been fired.

Open Firing

       Open firing is the most primitive of these methods but it does take a lot of skill to produce pottery this way. This method involves no building or maintaining of structures. With this method the fuel and vessels are set together and fired. This requires a very high temperature so some kind of insulation is needed. Also there can be some control over the firing rate by choosing certain types of fuel. For example dung burns slowly and uniformly while things like straw burn quickly and have rapid temperature increases. For this method to work one must make sure that the ceramics are dry or they well explode.

Kilns

       The use of kilns is not necessarily simpler then that of the open firing technique. There are two basic types of kilns that have been used. First off, there are those that have the fuel and vessel set together and the second involves the separation of these two. The problem of kilns is that it is difficult to reach the high temperatures that occur with open firing because much of the heat is absorbed by the kiln itself. With the kiln the one great advantage is that one can control the atmospheric conditions.

Black Ware

       With this atmospheric control one can produce pottery called black ware. This is the blacking of pottery by reducing the oxygen in the kiln. This occurs when the temperature is sufficient for sintering to occur. Sintering is when the outer surface of the clay becomes soft and molten. At this point additional fuel is added and the fire is covered with sand. This process produces smoke, depositing carbon on the surface of the vessel and giving it the characteristic black sheen. The piece below was fired using this method.