Dry Shrinkage and Shrinkage Fuel

Clay in a plastic state still contains water that is formed into ceramic objects. Once dry the ceramic object will experience shrinkage. This happens because the evaporation of water, and water membrane forming on the surface of the body and ceramic objects, causing the granules of clay into meeting each other.

Figure 20. Changes in the size of the object raw, dry matter, biscuits objects, objects glaze

The clay will have twice the shrinkage, the shrinkage that occurs from the wet into the dry, so-called dry shrinkage and shrinkage which occur during the combustion process, called shrinkage fuel. The total percentage of shrinkage (dry shrinkage and shrinkage fuel) required should be between 5% -15% .Tanah clay has a variety of different shrinkage, the higher the plasticity of clay, the higher depreciation.

Clay too plastic typically has a percentage shrinkage of more than 15%, so that when the clay is formed will have a risk of cracking or rupture is high. Shrinkage of clay that is too high can be improved by reducing or adding ball clay fire clay or grog. The following are examples of clay shrinkage Singkawang (Kalimantan Barat) of plastic condition, dry, and biscuits (from left to right) as shown in the figure below.

Pictures 21.Tanah plastic clay, dried, and biscuits.

Shrinkage of the clay through a drying process and the combustion process can be seen as shown below.

Pictures 22.Tahap dry shrinkage of clay.