The nature of the clay axis is the water absorption properties of ceramic objects by weight or density can be said after the burned body of ceramic objects. The nature of porosity is very important because the presence of these properties would allow water evaporation and water membrane forming during the process of drying out and burning. In pengglasiran poses these properties also affect the absorption of the glaze on ceramic objects that will have the sticking power before the glaze firing process implemented.
Greatly influenced by the nature of porosity and smooth rough clay particles that form the ceramic body. Containing clay particles and forming soil consisting of fine particles and coarse particles. Comparison of large grains in the soil and affect the nature of the soil.
Plastic clays generally contain finer particles that dry shrinkage and high shrinkage grilled and this will also affect the porosity, clay plastic properties tend to have low porosity, clay sebailknya less plastic shrinkage and shrinkage grilled dry low that porosity high
Must be sufficiently porous clay, in order:
- plastic water (water-forming) ie amount of water added to clay to be formed) can easily evaporate during the drying process, resulting in dry shrinkage.
- chemical water (water that is chemically bound) water that is contained in the natural clay can easily come out at the beginning of the combustion process and so avoid eruptions of steam and cracked. various gases arising from the combustion process of organic substances present in the soil can come out, when the combustion process occurs again called shrinkage shrinkage fuel.
Combustion temperature affects the porosity and also the strength of fired clay, but when the combustion temperature is raised there will be a continued process penggelasan on clay and strength to be reduced. This is as shown in the following figure.
Figure 6:15. Effect of fuel temperature on the porosity and strength of clay