Kaolin is a non-metallic mineral, which is a clay and clay rock mainly composed of kaolinite group clay minerals. Due to its white and delicate appearance, it is also known as Baiyun soil. It is named after Gaoling Village in Jingdezhen, Jiangxi Province.

Its pure kaolin is white, delicate, and soft in texture, with good physical and chemical properties such as plasticity and fire resistance. Its mineral composition is mainly composed of minerals such as kaolinite, halloysite, hydromica, illite, montmorillonite, as well as quartz and feldspar. Kaolin is widely used in papermaking, ceramics, and refractory materials, followed by coatings, rubber fillers, enamel glazes, and white cement raw materials. A small amount is used in plastic, paint, pigments, grinding wheels, pencils, daily cosmetics, soap, pesticides, pharmaceuticals, textiles, petroleum, chemical, building materials, national defense, and other industrial sectors.

The minerals contained in kaolin in nature are mainly divided into clay minerals and non clay minerals. Clay minerals mainly include kaolinite group minerals and a small amount of montmorillonite, mica, and chlorite; Non clay minerals mainly include feldspar, quartz, and hydrates, as well as some iron minerals such as hematite, siderite, limonite, titanium minerals such as rutile, and organic matter such as plant fibers. The main factor determining the performance of kaolin is clay minerals.

Kaolin has become an essential mineral raw material for dozens of industries such as papermaking, ceramics, rubber, chemical engineering, coatings, pharmaceuticals, and national defense.

The ceramic industry is the earliest and most widely used industry for the application of kaolin. The general dosage is 20% to 30% of the formula. The role of kaolin in ceramics is to introduce Al2O3, which is beneficial for the formation of mullite, improving its chemical stability and sintering strength. During sintering, kaolin decomposes to form mullite, forming the main framework for the strength of the body. This can prevent deformation of the product, widen the firing temperature, and also give the body a certain degree of whiteness. At the same time, kaolin has a certain degree of plasticity, adhesion, suspension, and bonding ability, endowing porcelain mud and glaze with good formability, making the ceramic mud body beneficial for vehicle body and grouting, making it easy to form. If used in wires, it can increase insulation and reduce dielectric loss.

Ceramics not only have strict requirements for the plasticity, adhesion, drying shrinkage, drying strength, sintering shrinkage, sintering properties, fire resistance, and post firing whiteness of kaolin, but also involve chemical properties, especially the presence of chromogenic elements such as iron, titanium, copper, chromium, and manganese, which reduce the post firing whiteness and produce spots.

The requirement for the particle size of kaolin is generally that the finer the better, so that the porcelain mud has good plasticity and drying strength. However, for casting processes that require rapid casting, accelerated grouting speed, and dehydration speed, it is necessary to increase the particle size of the ingredients. In addition, the difference in the crystallinity of kaolinite in kaolin will also significantly affect the process performance of porcelain billets. If the crystallinity is good, the plasticity and bonding ability are low, the drying shrinkage is small, the sintering temperature is high, and the impurity content is also reduced; On the contrary, its plasticity is higher, drying shrinkage is greater, sintering temperature is lower, and corresponding impurity content is also higher.