Knowing the different types of clay and how to use them effectively is the first hurdle you have to overcome as a new potter.
Although there are many different types of clay that you can use, in this article you’ll learn the four most common types.
What are the main types of clay?
There are many different types of clay available for crafting purposes, including earthenware clay, stoneware clay, porcelain clay, and ball clay. The type of clay used depends on the project being undertaken. The four most common types of clay are:
- Earthenware clay: ideal for making smaller vases and cups because it has a low firing temperature.
- Stoneware clay: works well for larger bowls and other dishes, but requires a higher firing temperature than earthenware.
- Porcelain clay: has a much higher firing temperature than either earthenware or stoneware and is ideal for any kind of pottery.
- Ball clay: works well in making highly sculptural pieces that require a lot of strength. Ball clay is a special kind of clay that is used in ceramics and pottery. For example, when someone says they’re working with ball clay, it means they’re working with the specific type of material used to create items such as plates, cups, and sculptures during the pottery-making process.
What is earthenware clay?
Earthenware clays are orange, red, grayish-white, or brown. Earthenware clay is mostly used to make pottery objects such as flower pots and bricks to build houses.
It can also be formed into tiles and oven-proof dishes to cook food in an oven safely. Furthermore, earthenware clay is commonly used for decoration by applying glaze on top of the object made from this kind of clay before it gets baked in the oven.
Earthenware clay is mainly composed of quartz, kaolin, and mica or feldspar. For pottery objects made from earthenware clay to be safe enough to be used in a household, they must be free of any lead.
A glaze should also be applied on top of the object before baking it in an oven to become more resistant to damage from water and soap.
For decoration purposes, you only need to apply a single coat of glaze on top before baking it. Using multiple coats will not change the color contrast between those objects and the already baked glaze. Applying too much glaze will ruin its design, so applying it sparingly is key.
The firing temperatures required for making earthenware items depend on which raw materials are in the clay and their ratio.
What is stoneware clay?
Stoneware clay is mainly used to make pottery and other forms of ceramic art. Stoneware clay is usually dark brown or black with speckles throughout depending on its composition, but can come in many colors to make certain pottery types.
Since stoneware clay already contains a mixture of 85% stoneware blend, there isn’t much to be added to produce this type of clay product. Only a small amount of water and plasticizer (liquid or powder) must be added to turn the dry stoneware blend into a wet slurry.
For the material to hold together well, it must be kept moist until ready for use by applying a protective covering such as plastic sheeting or waxed paper over the top. If it is not used within a few days, it should either be kept inside an airtight container or frozen. Otherwise, it can become too dry and crumble when worked with.
Although adding water will make the mixture easy to work with, once enough water has been added, any excess must be drained off if there is going to be a long wait before using the clay again.
However, stoneware clay can become very stiff if left too long without being re-wetted. To avoid this, it should only take about 20 minutes for the material to reach an adequate consistency for use after applying additional water.
Stoneware gets its name from how well it holds up outside in regards to wear and tear. So even though it is much stronger than regular clay, stoneware cannot withstand extreme heat without breaking or cracking.
However, when mixed with certain additives like grog, stoneware can be fired in a kiln up to 2300 F. Yet firing the material above 1800 F should only be done if necessary because of how much strength will be lost at that point.
What is porcelain clay?
Porcelain clay is a type of clay that has been fired to such high temperatures that all organic materials are burned off, and it becomes vitrified, which means it has become glassy in texture.
It can withstand a much higher firing temperature than regular earthenware, terra cotta, or stoneware clays without being destroyed by thermal shock.
It’s typically used for fine china dinnerware but also as structural bricks in kilns and furnaces. In addition, it can be mixed with alabaster powder to produce an extremely strong plaster compound.
Porcelain clay is a specific kind of material made from naturally occurring minerals that have been heated at very high temperatures until they become a ceramic material closely resembling glass.
It can be shaped for all sorts of uses, from dinnerware to fine art sculptures and kiln bricks.
What is ball clay?
Ball clay, also known as potter’s clay, fine china clay, or just plain white clay, is a type of plastic kaolinite that can create many different types of finished products.
It has many uses, but it is most commonly used in ceramic production and craft projects because it fires so well without cracking or shattering.
Ball clay sometimes contains other ingredients beyond kaolinite to give it its characteristic properties, which lend it to being transformed into objects like plates and figurines.
For instance, talc (magnesium silicate) is often added to shrink the fired china slightly and make it smoother, making glazing easier. Ball clay is also used as a substitute for other clays, such as porcelain and stoneware, to give them properties they would not normally have.
What kind of clay is used for pottery?
Depending on the style of pottery being made, a specific type of clay is used. The type of clay used for making pottery will depend heavily upon what area or region it came from and if it was prepared well.
The general belief within the industry is that there are two types of clays – plastic and non-plastic.
Plasticity refers to how easily a clay can be shaped and manipulated without cracking or breaking apart. Plastic clay is the more common type of clay used in making pottery.
When fired in the kiln, plastic clay shrinks less than non-plastic clay because it has absorbed the water evenly throughout the clay body. This type of clay is used often because it can easily be hand-built or thrown.
What kind of clay is used for ceramics?
Potter’s Clay, White Iron Clay, Red Clay, and China Clay are the most common types of clay used for ceramics.
Potter’s clay, also known as grog, refractory ceramic fiber (RCF), and fireclay, is high in silica and alumina oxide and other compounds that make it heat-resistant. This type of clay is ideal for making items used in ovens such as pots, plates, jars, etc. but not those made specifically for microwaves as they will explode due to thermal shock.
White iron clay can be found in most parts of the world and is used for making pottery, tiles, figurines, etc. It contains high amounts of kaolin which makes it very smooth and lustrous when calcined at high temperatures.
It also resists staining by water and oils. Red clay is heavy due to its mixed composition but is widely used because it can easily be molded into small and large items without breaking or cracking. However, it should be baked at low temperatures as higher ones will cause warping or fracturing. It is mostly suitable for household utensils like pots, plates, etc.
China clay has a very soft composition and is suitable for making ceramic wares like china and porcelain used on dining tables. This clay is also found in other parts of the world besides China, and it takes on a pinkish hue when fired at high temperatures, making it even more appealing as a material for ceramics.