What is China clay or Kaolin?
China Clay is a hydrated Aluminium silicate, part of the group of industrial minerals, with the chemical composition Al2Si2O5(OH)4. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra. Rocks that are rich in Kaolinite are known as kaolin or china clay. Kaolinite has a low shrink–swell capacity and it is a soft, earthy, usually white mineral, produced by the chemical weathering of aluminium silicate minerals like feldspar.
In many parts of the world, it is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lighter concentrations yield white, yellow or light orange colors. Commercial grades of kaolin are supplied and transported as dry powder, semi-dry noodle or as liquid slurry. The largest use is in the production of paper, including ensuring the gloss on some grades of paper. It is also used in paint, rubber, detergents & textile industries.
China Clay / Kaolin is used (or was used in the past):
- In ceramics (it is generally the main component in porcelain)
- In toothpaste
- As a light diffusing material in white incandescent light bulbs
- In cosmetics
- As paint to extend titanium dioxide (TiO2) and modify gloss levels
- For its semi-reinforcing properties in rubber
- In adhesives to modify rheology
- In the production of common smoking pipes in Europe and Asia
- In organic farming, as a spray applied to crops to deter insect damage, and in the case of apples, to prevent sun scald
- As whitewash in traditional stone masonry homes in Nepal (the most common method is to paint the upper part with white kaolin clay and the middle with red clay; the red clay may extend to the bottom, or the bottom may be painted black)
- As a filler in Edison Diamond Discs
- As an indicator in radiological dating since kaolinite can contain very small traces of uranium and thorium
- To soothe an upset stomach, similar to the way parrots (and later, humans) in South America originally used it[18] (more recently, industrially-produced Kaolinite preparations were common for treatment of diarrhea
- For facial masks or soap
- As adsorbents in water and wastewater treatment.
Physical Properties
| Appearance | White fine powder |
| Sp. gravity | 2.5 - 2.7 |
| Oil absorption | 25 to 35 |
| PH of 10% aqueous solution | 7 to 8 |
| Water Soluble salts | max 1.0% |
| Volatile matter | max 1.0% |
| Loss on Ignition | 13 to 15% |
Typical Chemical Analysis
| Al2O3 | : 36.1% |
| SiO2 | : 42.5% |
| Fe2O3 | : 0.5% |
| MgO | : 1.0% |
| Na2O | : 0.5% |
| K2O | : 3.0% |
Industrial Applications
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Paints
It is used in various paints like distempers, cement primer, wood primer, texture paint, spray plaster, putties, fillers & undercoats. -
Plastic
It is used as a filler in combination with others to impart strength & smoothness in plastic Industry. -
Paper
It is used in variety of papers, cardboards, hard boards and others. -
Electrical Industry
It is used for Electrical insulation, High voltage insulation components, electrical wires, EPDN rubber and others. -
Cosmetic & Soap
China Clay is used in toothpaste, cosmetic and soap industry.
Our Suggested Grades
| Grade | Brightness | Particle Size | Top Cut | Oil Absorption | Application |
| Kaolin-05 | 84% | 2 - 5 micron | 20 | 38 | Paints, Paper, Electrical |
| Kaolin-10 | 82% | 10 micron | 40 | 36 | Paints, Paper, Cosmetics, Electrical |
| Kaolin-15 | 82% | 15 micron | 50 | 32 | Paper, Rubber, Soaps |
| Kaolin-20 | 80% | 20 micron | 50 | 32 | Rubber, Cosmetics & Soaps |
Apart from above grades we develop tailor made Kaolin to meet the specific requirement of our clients. Our R&D is also working on ultra-fine China Clay powders to develop many new products with exciting possibilities.