Earthenware is known as a type of clay bodies are only able to be burnt at a low temperature (900 ° C-1180 ° C) .Contoh ceramic products are made of clay bodies are earthenware Earthenware. Some examples of types of clay products Earthenware others are bricks, tiles and terracotta. Clay in the raw state obtained from the place of origin (deposit) has a variety of colors: beige, yellow-brown, red-brown, gray, and black, the color difference was much influenced by the comparison of the levels of content of clay materials include a mixture or dirt humus ( organic), iron oxide (Fe), manganese oxide (Mn), cupper oxide (Cu), cobalt oxide (Co), etc.
At the time of the combustion process that is both organic dirt will burn out, whereas chemically bonded materials will cause the clay to color. In general, most Earthenware clay contains iron oxide (Fe). The form of granules or particles that will provide a smooth and soft plastic bending properties or if it contains water that serves as a lubricant.
Earthenware clay plasticity high enough so that dry shrinkage and shrinkage fuel is also high, so the higher the plasticity of clay the higher the dry shrinkage and shrinkage fuel. Another trait is fairly high porosity after experiencing the combustion process and this is because this clay still contains a lot of sand.
Figure 46. One type of pottery products in Bayat Ceramics Center (Central Java)
Given the porous nature allows water forming out of the ceramic body during the drying process so that the ceramic objects are not easily broken or cracked. Changes in the structure of clay Earthenware from the combustion process:
1) The fuel temperature between 700 ° C-900 ° C easily broken
2) The temperature burn between 900 ° C-1050 ° C is safe
3) fuel temperature between 1050 ° C-1180 ° C maximum
4) The fuel temperature above 1180 ° C will burn even melt.
The following is an example of the development of the clay body Earthenware formulas developed by changing the composition of the material: