Kaolin, named after Gaoling village in Jingdezhen, Jiangxi, is the “soul material” of ceramics. Its main component is kaolinite (chemical formula Al₂[(OH)₄/Si₂O₅]), formed by the weathering of feldspar and other silicate minerals. It has a fine, pure texture with both plasticity and refractory properties. From ancient ceramics to modern applications in paper-making, chemicals, and aerospace, kaolin remains an “invisible champion” in industry.
Six core technological characteristics of kaolin
Whiteness and brightness: the “purity” that determines quality
Natural whiteness: Whiteness after drying at 105°C. Impurities (such as Fe₂O₃, MnO₂) will make it appear yellow, brown, etc.
Calcination whiteness: The whiteness after calcination at 1300℃ directly affects the glossiness of ceramics and coatings. The whiteness of high-quality kaolin after calcination can reach more than 90%.
Brightness: Reflectivity under 4570Å wavelength light, which is particularly important in the papermaking industry.
Particle size distribution: the “gold standard” for industrial applications
The finer the particles (e.g. less than 2μm), the stronger the plasticity and suspension. For example, the United States requires that more than 90% of the kaolin particles used in coatings be less than 2μm.
Particle size control technology (such as water-petroleum pulverization and magnetic separation for iron removal) is the key to increasing added value.
Plasticity: The “magic” of ceramic forming
The plasticity index (the difference between liquid limit and plastic limit moisture content) and the indicator (deformation resistance) are core parameters. Highly plastic kaolin (index >15) enables easy shaping and resists cracking.
Bonding and Adhesion: Adhesives for Industrial Formulations
Binding property refers to the strength after mixing with non-plastic materials (such as quartz sand). The higher the amount of sand, the stronger the binding property.
Viscosity affects the fluidity of mud. Papermaking coatings require a viscosity as low as 0.5Pa·s (low-speed coating).
Drying and sintering properties: the transformation from clay to porcelain
Drying shrinkage: Linear shrinkage rate is 3%-10%. Excessive shrinkage can easily cause cracking of the ceramic body.
Refractoriness: The refractoriness of pure kaolin reaches 1700℃, and impurities will significantly reduce its high temperature resistance.
Adsorption and insulation
Kaolin has weak ion adsorption ability, but after modification, it can be used in environmental protection fields (such as wastewater treatment).
It has excellent electrical insulation and is an important material for manufacturing high-voltage electrical porcelain and radio components.
The main uses of kaolin
- Ceramic industry (accounting for about 40%)：Daily ceramics, building ceramics, and electrical porcelain all rely on the forming and high-temperature resistance properties of kaolin.
- Papermaking and coatings (accounting for about 30%)：As a filler and coating, kaolin enhances the gloss and smoothness of paper.
- Refractory Materials：Refractory bricks, crucibles, etc. need to withstand high temperatures above 1600℃, and kaolin is the core raw material.
- New materials field: Modified kaolin is used for rubber reinforcement and plastic filling, while nano kaolin is used in biomedicine.
- Environmental protection and energy: Tailings comprehensive utilization technology reduces resource waste.
Conclusion
From the “binary formula” of ancient kilns in Jingdezhen to modern nanotechnology, the value of kaolin has been continually redefined. Moreover with stricter environmental policies and growing demand for new materials, deep processing and recycling of kaolin will become a new direction for the industry. EPIC powder is dedicated to ultra-fine grinding of various minerals. Help you solve various problems, if you need, please contact us
English 
العربية 
Español 
Português 
Français 
Türkçe 
Tiếng Việt 
Русский