These days, ceramics are used for pottery or tiles production and used in much more sophisticated displays, such as insulators, conductors, electronics, household appliances, etc. Thus, ceramics production has received more demand from various sectors in recent years. Generally, there are two types of ceramic; traditional and industrial. Traditional ceramics typically consist of glassware and household utensils, while Industrial ceramics are used as components for a specific production, such as utensils and electronics.
High quality kaolin is a fine raw material that functions to add flexibility and strength during the manufacturing process of porcelain or ceramic. It can be used both as filler or the main body compositions of white ceramics production. The white color is formed mainly from the natural property of kaolinite. Kaolin characteristics are similar to residual or primary clay that has coarse-grained properties. The mineral is a bit more stiff compared to other sedimentary clays, so it isn’t easy to form as it is. In addition, it is suitable as a whitening agent because of its low iron content.
Kaolin or kaolinite is a primary clay (residue) produced from weathering of feldspathic rocks by endogenous forces that do not move from its origin layer. Since the sediment does not move, it is purer than the secondary clay beneath the coating. The formation of this mineral is hugely affected by hydropower and hot steam from the earth’s core.
Since water currents are not affecting the mineral in any way, the high quality kaolin is not mixed with any organic materials, such as hummus or rotten leaves. As a result, the clay will have whiter color than any other sediment. Aside from kaolin, minerals found in the higher layer of the ground are also called “primary clay.” Some of these minerals are bentonite, feldspathic, quartz, and dolomite.
In general, the characteristics of primary clay are:
- Bright white color
- Coarser texture
- Small shrinkage
- Fire resistant
When dry, the primary clay texture is so brittle. This is because the particle size formed is not symmetrical and angular, unlike secondary clay particles, which are included in parallel slabs.
Furthermore, quartz and alumina cannot be found in the same layer as other primary minerals. However, both are classified as types of primary clay because they are a by-product of kaolinite clay formed from weathering of feldspathic rocks.
Ceramic Production with Kaolin
Ceramic that contains kaolin is heated, molded, and dried at a temperature of 1000 °C or more. Depending on the additional element put into the mixture, manufacturers can produce various ceramics with this method.
Moreover, kaolin has several unique properties compared to other materials. Those properties are:
- Rough texture and coarse-grained
- More brittle in its raw form. That being said, kaolin adds strength and durability to ceramics once it is processed and altered.
- Less flexible when compared to other sedimentary clays. In other words, it is more difficult to form without additional components.
- Its low iron content causes a prominent white color.
High quality kaolin has the same properties as the standard kaolin you can find in the current market. However, minerals with better purity levels are claimed to be more effective in reducing the degree of shrinkage and adding strength to ceramic compounds. Therefore, this clay cannot be used alone but must be mixed and combined with other materials.
Combining Kaolin with Other Materials
Several other materials can be combined with kaolin in the commercial-scale ceramic production process to achieve the best result. These materials are:
1. Stoneware Clay
This material is a type of raw ceramic that does not fall into any earthenware categories or pottery that absorbs water. Stoneware is classified as sedimentary clay, and there are various kinds of stoneware which contain sufficient feldspar, which is vital for commercial ceramic production.
Stoneware clay is very flexible and easy to dry. This material is widely used alongside acid and alkali-resistant materials in tiles, art ceramics, and pipes. In Indonesia, this clay is widely available in West Java.
2. Earthenware Clay
Earthenware clay is an ordinary clay used for producing building bricks, striped pots, and other kinds of pottery. It contains a lot of iron oxide. Some earthenware has a flexible texture, while others are a bit brittle because of its high content of sand.
This clay appears yellow, orange, red, brown, or black during the burning process. The color depends on the high combustion temperature and the amount of iron oxide within the mineral. Naturally, earthenware clay has red-brownish, greenish or gray color.
This material is essential to reduce cracks during the drying process. It also reduces burn time as well as improves the overall product quality. In addition, silica has the most prominent role as the core material in the combustion process since it can superbly retain heat needed to alter the chemical compound.
Another form of silica used in ceramic production is flint. This mineral has a fine texture and a high level of purity. Flint typically is added during the glazing process to reduce cracking.
4. Feldspar, Lime, and Magnesite
When the raw materials for ceramic production are burned, the fieldfare melts and forms a glass which causes the clay particles and other materials to stick together. Meanwhile, lime and magnesite, mainly consisting of the carbonate form of the metals calcium and magnesium, are used in small amounts as a fusing agent in glassware production. Manufacturers may combine this material with high-quality kaolin to enhance the result.
5. Alumina and Talc
Alumina or aluminum oxide cannot be found in a pure form. Instead, this mineral can only be formed using a specific chemical process. Meanwhile, talc is a reasonably common mineral that contains a lot of magnesium. It is widely used as a filler and covering material in various industries. Still, almost a quarter of the talc production is used in the ceramic industry, both traditional or commercial.
Ultimately, the role of high quality kaolin in ceramic production is vital, especially for commercial purposes. Moreover, aside from using its properties to strengthen the ceramic, kaolin can also reduce production costs while increasing production volume.