Clay secondary or sedimentary clay is a type of rock weathering clay results feldspatik that moves away from its parent rock due to exogenous force that causes the granules of clay loose and settles in low areas such as river valleys, wetlands, marine land, and the land of lakes. In the course caused by water and wind, clay mixed with organic materials and inorganic.
It is mengakibatkanperubahan chemical properties and physical properties of the clay. The size of the soil particles became finer and secondary clay plastis.Jumlah more than primary clay. Water transport has a specific influence on clay, one of which is the movement of water flow tends to erode the clay minerals so that the particles become smaller. By the time the flow velocity slows, heavier particles will settle and leave the fine particles in the solution.
At the current moment is quiet, like in a lake or in the ocean, fine particles will settle to the bottom. Transferred clay usually formed of several types of clay and come from several sources. In each river, sediment clay of some sites tend to mix together. The presence of various metal oxides such as iron, nickel, titan, manganese and so on, from the point of ceramic science regarded as a pollutant.
Organic material such as humus and leaf rot is also a clay impurities. Because the formation through a long process and mixed with impurities, the clay has the properties: a fine-grained, beige / gray / brown / pink / yellow, and maturation temperatures between 900 ° C-1400 ° C.
Figure 14. Making the stone from the ground Earthenware
In general, secondary clay is more plastic and have a higher shrinkage power than the primary clay. The higher the fuel temperature, makakekerasan increases and porosity decreases, so that ceramic objects become watertight. Compared with the primary clay, clay has characteristics not purely secondary, the color darker, finer grained and has a melting point that is relatively lower. Once burned clay are usually secondary beige, light gray to light brown to dark. In general, secondary clay has characteristics:
(A) less pure,
(B) tend to be fine-grained,
(D) the color beige / gray / brown / pink / yellow, light yellow, yellow, brown, red, black
(E) high shrinkage power,
(F) combustion temperature 1200 ° C-1300 ° C, there were up to 1400 ° C (fireclay, stoneware, ballclay), and
(G) a low combustion temperature of 900 ° C-1180 ° C, even up to 1200 ° C (Earthenware).
Figure 15.Seorang mother burn in the center of ceramic pottery products Kasongan.Tanah Earthenware clay (pottery) is one of the secondary clay.
Natural earth colors occurs because of the element iron oxides and organic elements, which will usually burn tawny colored, brown, red, rust color, or dark brown, depending on the amount of iron oxides and impurities contained. Usually the iron oxide content ranges between 2% -5% and will result in soil tend Iebih dark colored (red or brown). Secondary clay will usually mature at lower temperatures due to the influence of a mixture of metal oxides that function to lower the temperature. According to its melting point, secondary clay can be divided into five major groups, namely: clay refractory (fireclay), stoneware clay, ball clay, red clay (Earthenware clay), and clay type monmorilinit.
Figure 16.Fireclay to make refractory bricks.