a) Silica
Silica is a material widely used to make ceramics, glazes, glass, etc. This material has the properties so that when the plastic is not used to make the ceramic body will reduce the level of plasticity and depreciation. Silica in the ceramic body is used to add capabilities to shape and hardener, while the glaze serves as penggelas. Silica melting point is 1710ºC.
Quartz is another form of silica which has a purity of 100%. Silica or quartz is found in oxide material called silicates such as kaolin / china clay, feldspar, nepheline syenite, lepidolite, petalite, spodumene, pyrophylite, ball clay etc. Other forms of silica are flint. This material is widely used to make ceramics and has a high purity. Precipitated silica found in nature is usually mixed with various ingredients impurity (impurities) which will affect its properties either in the raw state or after combustion.
Usefulness silica:
(1) reduce plasticity.
(2) reduces shrinkage.
(3) reduces cracks in the drying process.
(4) increase the ability of shapes and hardener.
(5) an order during combustion.
(6) reduces cracks (crazing) in the glaze.
Silica (quartz) contained in West Java, Aceh, North Sumatra, South Sumatra, Jambi, Bengkulu, Riau, Central Java, East Java, West Kalimantan, South Kalimantan, East Kalimantan, South Sulawesi, and Papua.
b) Feldspar
Feldspar resulting from weathering of granite and lava rocks (igneous) where clay was terbentuk.Feldspar including alumina silicate compounds containing one or more elements such as: K, Na, and Ca. As a material which is not plastic, feldspar is very important in the ceramic industry because it can serve to reduce shrinkage during the drying process and combustion in addition serves also as a flux (melting) at a temperature above 1200 ° C.
Melting point between 1170 ° C-1290 ° C.Feldspar very useful in the manufacture of ceramics glassware, stoneware, porcelain, as well as materials to make the glaze. Feldspar is composed of various types, including:
(1) Potashfeldspar (K2O.Al2O3.6SiO2)
(2) Sodiumfeldspar (Na2O. Al2O3.6SiO2)
Judging from the elements, feldspar containing alumina (Al2O3), silica (SiO2), and fluxes (K2O or Na2O) .Feldpar containing potassium (K2O) is usually used for making fine ceramic body because it is very active dissolve quartz, shaping the glass very thick, and as a good melting in the ceramic body so fine that becomes solid ceramic body without changing shape (deformation).
While feldspar which contains sodium (Na2O) is used to make a glaze. Feldspar contains all the ingredients necessary to form a glaze so that the so-called natural glaze, but in order to better satisfy the glaze should be added to other materials such as flint, whiting or kaolin. In Indonesia feldspar can be found in West Java, Central Java, Aceh, North Sumatra, Riau, West Sumatra, South Sumatra, Lampung, East Java, West Kalimantan, North Sulawesi, Central Sulawesi, South Sulawesi, and Papua.
Picture 42. Mining feldspar
c) Calcium carbonate (CaCO3)
Whiting serves as fluxpada high temperatures very important, that the material serves to lower the temperature bakar.Meskipun in limited use, the element Ca (calcium) contained in whiting used for ceramic body in small amounts because it can lower the melting point, providing white color , preventing lengkungdan reduce porosity ceramic body. With zinc in the glaze will form the matt surface (doff), due to crystallization. Dolomite is a material combination of calcium carbonate with magnesium carbonate which serves as a flux or lowering the temperature in a mixture of clay, these materials include materials that are not plastic.
d) Aluminum (Al2O3)
The element aluminum oxide (alumina) is not found in its pure form, but in combination with other elements, especially in the kaolin, ball clay, and feldspar.Alumina is a highly refractory material and the material is very stable both physically and chemically. In aluminum glaze serves to control and compensate for melting and give strength to the ceramic body and glaze, while the ceramic body to increase the viscosity, the melting point to prevent crystallization and stabilize the mass of glass. In the plastic mass of ceramic, kaolin element will provide Al2O3 but not pure enough whereas plastic ball clay will provide Al2O3 but not pure plastic.
e) Talc
Talc is a mixture of magnesium silicate has the chemical formula 3MgO.4SiO2.H2O hidroksidayang, serves as a flux (fusing) to low and add burnt glaze adhesion to ceramic body and prevent the emergence of cracks in the glaze. Talc is widely used as a filler material (filler) and cover material in some kind ceramic industry (particularly for walls and porcelain China), this is because the ceramic body containing talc to be highly resistant to temperature changes suddenly is widely used for the manufacture of power tools , cooking ware, kapsel, aids combustion (refractory), also in ceramic art and ceramic body burnt low.
Picture 43. Mineral talc
f) nepheline syenite (KNaO.Al2O3.4SiO2)
Nepheline syenite is a ceramic mineral that can be used as a substitute feldspar.Nephelinesyenite containing silica (SiO2) less and alumina (Al2O3) is higher than feldspar. This material can be used in glazes Earthenware or stoneware and glass-making materials as a source of Al2O3.
g) Grog
Grog is a clay material that has been burned biscuits and then finely milled with a level of refinement that is adapted to penggunaan.Grog widely used to make ceramic body measuring besar.Grog primarily serves to reduce the plasticity and shrinkage that can protect the body against deformation. With the grog cause the body to become more porous ceramic objects, but with this condition allows evaporation, also prevents the occurrence of cracks in the drying process and combustion, resistant to sudden changes in temperature, as well as provide a rough surface texture.
Picture 44.Bahan-ceramic material is not plastic