Kaolin is a non-metallic mineral, a kind of clay and clay rock dominated by kaolinite clay minerals. Because it is white and delicate, it is also called white cloud soil. It is named after Gaoling Village, Jingde Town, Jiangxi Province.

Its pure kaolin is white, delicate and soft clay-like, and has good physical and chemical properties such as plasticity and fire resistance. Its mineral composition is mainly composed of kaolinite, halloysite, hydromica, illite, montmorillonite, quartz, feldspar and other minerals. Kaolin has a wide range of uses, mainly used in papermaking, ceramics and refractory materials, followed by coatings, rubber fillers, enamel glazes and white cement raw materials, and a small amount used in plastics, paints, pigments, grinding wheels, pencils, daily cosmetics, soap, Pesticide, medicine, textile, petroleum, chemical, building materials, national defense and other industrial sectors.
Folded Whiteness Brightness
Whiteness is one of the main parameters of kaolin’s technological performance, and kaolin with high purity is white. The whiteness of kaolin is divided into natural whiteness and whiteness after calcination. For ceramic raw materials, the whiteness after calcination is more important, and the higher the calcination whiteness, the better the quality. The ceramic technology stipulates that drying at 105°C is the grading standard for natural whiteness, and calcining at 1300°C is the grading standard for calcining whiteness. Whiteness can be measured with a whiteness meter. A whiteness meter is a device that measures the reflectance of light with a wavelength of 3800-7000Å (ie Angstrom, 1 Angstrom = 0.1 nm). In the whiteness meter, compare the reflectance of the sample to be tested with the standard sample (such as BaSO4, MgO, etc.), that is, the whiteness value (for example, the whiteness 90 means 90% of the reflectance of the standard sample).

Brightness is a process property similar to whiteness, which is equivalent to whiteness under 4570Å (Angstrom) wavelength light irradiation.

The color of kaolin is mainly related to the metal oxides or organic matter it contains. Generally, it contains Fe2O3, which is rose red and brownish yellow; contains Fe2+, which is pale blue and pale green; contains MnO2, which is pale brown; contains organic matter, which is pale yellow, gray, blue, and black. The presence of these impurities reduces the natural whiteness of kaolin, and iron and titanium minerals also affect the calcined whiteness, causing stains or scarring in porcelain.