What kind of soil can be fires into porcelain

Ceramics is the art of Earth and fire. Earth is the origin of all life on Earth and the resource on which human beings depend. Fire is the photon brought by the burning of matter, energy and heat radiation.​With these two elements, plus water, earth is like alchemy, from one substance to another completely different substance.

Soil, the technical term is clay (clay) or clay, that is, viscous soil, generally refers to particles less than 2 microns, strong plastic, containing a variety of water aluminum silicate salt mineral mixture​​​Can all the earth be turned into ceramics if there is fire (high temperature)? The answer is: NO! Why is that? Today, Make Small takes you to explore the “earth” that can be fired into ceramics.

Origin of Clay
Apart from water, air, plants and animals, the most abundant materials on Earth are rocks and clay.From a technical point of view, almost all rocks and clays are raw materials for making ceramics. Their main components are the combined materials of alumina, silica and water. Therefore, the ceramic industry is also known as silicates. Add iron, potassium, sodium, magnesium, calcium, titanium and other mineral substances, these eight elements accounted for 97.13% of the total earth’s crust, ceramic production is the main raw materials.​​​​​​

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Part of the original ceramic ore exists in rock state.Another part of the rock after tens of millions of years of geological movement, differentiated into powder particles, accumulated into clay.The clay deposited on site is called primitive soil.​​Over the years, the wind and Rain Water from the primeval Earth Cover alluvial flat areas of the mountains, settling on the ground, river beds, and seabed.Alluvial soil has been further differentiated, and mixed with some organic matter, more delicate and more plastic than the original soil.​

Clay is almost everywhere.In general, the surface soil of 0.07 meters to 0.33 meters containing a large amount of organic matter covered by plants is called soil.​​​​In areas with dry climates and little human activity, the clay may also be exposed.Soil mixed with plant roots and animal, insect carcasses, feces, soil is usually not suitable for direct use as ceramic materials. Pure clay or rock at a depth of more than one meter above the earth’s surface is the main raw material for ceramics.​

Excavated unprocessed soil is called raw soil. AncientMost low-temperature pottery and low-temperature tiles are made from raw soil, as are indigenous pottery around the world today.

>> Classification of clay

Clay commonly used in the production of ceramics can generally be divided into five categories (foreign divided into six categories): clay, ball clay, fireclay, porcelain clay, air-dried clay and stoneware clay (commonly used by foreign artists).​​​​​Different types of clay have different mineral substances and different firing temprature (depending on the process).​

1.porcelain clay:
Porcelain clay is the most primitive first layer of clay, almost no impurities.The color after firing is the whitest, most heat-resistant and least plastic, which we call kaolin or porcelain clay.Those “primordial” or “primordial” clays that have not migrated from the place where they were formed are also called primordial kaolin, which is the least abundant clay on the surface.​

After the original kaolin is taken away by the natural force, it is polluted by impurities, the plasticity is improved in this process, and the firing color will also be a little beige white, this kind of kaolin is called “secondary clay” or “secondary clay.”​Secondary kaolin is not rare and has greater plasticity than primary porcelain clay.When these two types of porcelain clay are fired at a high temperature of 1280-1400 ° C, they become hard and dense, and show a glassy texture.Porcelain clay is found in Asia, Britain, Germany and the southeastern United States.

2. Ball clay
Ball clay is second only to china clay in purity and is the most plastic of all clays. Most of them are secondary clays and usually migrate with water.Due to the characteristics of fine grain size, water migration and rock grinding, the spherical clay will have a large shrinkage rate after drying and firing, and the color is similar to that of porcelain clay, showing white.It becomes very dense between 1200 ° C and 1370 ° C.Kaolin and ball clay are two common raw materials for making porcelain.

3. Fireclay
Refractory clay is found in the mountains and desert areas, is one of the main raw materials for porcelain production.​Because of its different formation of different coarse particle size is not the same, the shape of the particles flat or round.​In addition to clay, it is also rich in displaced silica.After firing, it may appear beige, tawny, gold, red, brown, and most will become dense between 1205 and 1260 ° C and will also be vitrified.

Potters like this type of clay because of its high toughness and strength, and its ability to stand upright, making it suitable for sculptural works. It is used industrially to make refractory bricks, chimney liners, blast furnaces and heavy clay products.​

4. Rough earthenware
​Coarse clay, or clay, is probably the most common type of clay, and has been used by potters throughout the history of pottery making, and is probably the earliest type of clay used. The clay is very sticky, dry, malleable and easy to operate and use.​This clay is mainly composed of iron and some other mineral impurities, which is precisely what accounts for the clay’s unique properties.

The firing temperature of clay is generally between 950 and 1100 ° C.​​It is porous after firing at high temperature, and can also be glazed before firing to increase sealing. This type of clay is highly malleable, meaning it does not sink or collapse when made into pottery.Clay contains iron and some other mineral impurities that give it its unique effect.

5. Surface Clay
​The most common clay on Earth, is everywhere beneath our feet. Surface clays contain a lot of impurities and have undergone natural migration over millions of years, making them very plastic, and generally without the addition of any melting agent, they can make a “brick” on their own, often used to make functional containers, statues, bricks, and water pipes.​

​Unlike other clays, surface clay, when mixed with water, forms a plastic billet that can be made into any shape and remains unchanged.After drying, the volume is reduced by 10% and again during the firing process.Fired at a high temperature of about 700 ° C, all natural clays become hard and durable, but are not suitable for holding liquids, which is the earliest pottery.​

​6, stoneware clay
Stoneware clay contains mineral impurities such as silica, feldspar, ball clay and quartz. When mixed with ball-clay and fire-clay, the heat resistance to heating is greatly enhanced.Generally, the firing temperature of stoneware clay is much higher than that of pottery clay, between 1000 and 1380 ° C.Once fired, the clay becomes very strong, so it can be made into durable ceramics.

There is also a type of clay that does not need to be fired: air-dried clay.

This is a clay that naturally dries and hardens in the air, without the need to bake or fire in a kiln. A convenient and accessible option for artists, craftsmen and students who do not have access to professional equipment. Air-dried clay is usually softer and more ductile than traditional ceramic clay. Making it possible to shape, sculpt and mold with simple tools. Suitable for products including small sculptures, jewelry, flower pots and decorative ceramic tiles.