Find China Clay Definition,Processing ,Properties & uses here.China Clay is also known as kaolin & white clay.Can used to make required shape when it is wet.
What is china clay?
China Clay is also known as kaolin & white clay. Primary clay formed by natural kaolinisation process. it is formed by decomposition of some part of feldspar mineral.White in color , Used in ceramic slip casting process, Pressing processes and forming process as a body former and filler. China clay
Chemical formula of China clay is Al2Si2O5(OH)4.
Formation of China Clay:
Many theories are put for the Formation of China clay , some of them are accepted widely. we will see some of the theories in details: 1) The igneous emanation theory. 2) The surface weathering theory. 3) The bog or moor water theory.
The igneous emanation theory:
As per Igneous emanation theory igneous gases from the center of the earth and superheated steam, carbon dioxide , fluorine compounds and boron are the active agents to decompose some part of feldspar. Clay formed by this theory will be in deep depth from the Surface. Clays Found in china supports this theory.
The Surface Weathering Theory:
Clayes formed by this Surface weathering theory found near to the surface. this theory explains that feldspar is decomposed by water containing carbon dioxide. Clay found in france are formed by this theory.
The bog or moor Water theory:
Clay Formed by this theory found near to the lignite beds.This theory explains that water from bogs are active agents for kaolinization as it contains ammoniacal salts and organic acids. German clays are formed by this theory.
Processing of China Clay:
Processing of china clay difference from place to place but the basic step are same. i)Excavating china clay. ii) Sieving process. iii) Settling process. iv) Filter press process. v) Drying process. vi) Packing and Transporting.
Excavation of china clay:
China clay is extracted from the deposits by mixing with water using jet water splashier. Forced water is sprayed on clay and mixed with water, this water plus clay slurry is pumped to ground level. In this slurry clay content is very low normally below 10 percentage. then this slurry is sent to net process.
The slurry mix from deposit is passed through series of sieves. Normally 40 Mesh , 100 mesh and 200 mesh are kept in series to remove all other materials from the slurry. In this process small stones to sand materials are removed by sieves.sieved slurry will be sent to settling process.
Then this slurry is sent to series of settling tanks. Clay particles are allowed to settle in settling tanks. In this process clay percentage in the slurry is increased upto 50 to 60 percentage. The settling tank is designed in zig zag way as you can see in the below picture. It is to make the clay particles to settle easily by Restricting the flow.
Filter press process:
Then the clay slurry is sent to fitter press by pump. After the fitter press process the clay will have around 15% to 20% of moisture content. Cake like material is taken out from the filter press.
This Cake form clay is dried naturally to remove moisture from it. Once dried the moisture contact will be around 5%.
Packing & Transporting:
Dried china clay will be broken to small pieces and packed in 50kgs bags. And then it is transported to required location. Find the tests are carried out in Clay here and for sanitary ware product.
Properties of China Clay:
China clay is Primary clay and normally found in white colour. 1. Casting Rate : High casting rate in slip casting compared to ball clay. 2. Particle size: Large particles when compared to Ball clay. 3. Green MOR: Modulus of rupture is low compared to ball clay. 4. Plasticity: Low plasticity compared to ball clay. 5. Refractoriness: High Refractoriness.
Uses of China Clay:
China clay is used in all Kind of ceramic product production and other products for its properties. Following are the major uses of the china clay, 1. Used In Sanitaryware industry 2. Used in tiles Production industry. 3. Used in Refractory production. 4. Used in Paper industry as a filler. 5. Used in Rubber industry as a raw material. 6. Used in textiles industries. 7. Used in Dinnerware production process as a raw material. 8. Used in pottery works and Etc... Comment below if you think I need to add anything more to this article. Find about Ball clay here.
Venkat Mani is a Ceramic Engineering Graduate from India, working in Sanitaryware production line for 10 years. He shares Meaningful content related to sanitaryware professionals that others find useful.