Potters work with different types of clay. Most pottery projects use natural clays that you fire in a kiln. There are also synthetic clays, which you would use for modeling and sculpting.
It can be confusing what to use for your first pottery project.
Ultimately, you need to work with the types of clay that’s best for the type of pottery you want to make.
What Are the Types of Clay Bodies?
Clay bodies are the actual mixtures of natural clay that you use for making pottery.
They are different from even the best modeling clays, which are used to create temporary models of the final product but will never be the final product.
There are three main types of clay bodies: earthenware, stoneware, and kaolin. Each one is different from the others in certain ways.
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Mineral content plays a huge role in classifying clay. It determines certain qualities, including the clay’s color, texture, and level of plasticity. The more elastic a clay body is, the more workable it gets.
Potters also classify clay bodies according to their firing temperature. This is the temperature they need to reach optimum hardness and durability.
How to Choose Clay for Pottery
To understand the types of clay you want to use, you need to know what clay is first.
Pottery clays comprise of fine rock particles eroded by wind, ice, and rain.
These particles are carried off by water and settle at the bottom of rivers and streams, where they come together into a single mass.
Clay tends to be sticky and moldable into any shape when moist. When dry, it can take on the consistency of cheddar or old chocolate.
Natural clay is the best air-dry clay, but its shape doesn’t become permanent until it’s heated to very high temperatures.
When choosing what types of clay you want to use, consider the following: mineral content, firing temperature, texture, color, and your skill level.
Types of clay bodies
The three main types of clay bodies are earthenware, stoneware, and kaolin.
Ball clays and fire clays are secondary types of clay. You add them to the main clay bodies to improve plasticity.
1. Earthenware clays
Among the different types of clay, earthenware is the most common.
Ancient potters used earthenware to sculpt everything from religious figurines to jars for storing wild cereals.
Potters prefer to use earthenware because it is the most forgiving among the types of clay.
It is very easy to work with, even for beginners. It’s suitable for both throwing on the potter’s wheel and hand-building. It’s also some of the best clay for sculpting.
Of all the types of clay, earthenware is the most porous.
Water easily passes through the clay, making it impossible for unglazed earthenware vessels to hold liquid. So, it’s not a suitable clay for making mugs, pitchers, and vases.
But that also means water can’t get trapped inside and freeze in the winter. Many artisans make bricks, tiles, and flowerpots with earthenware clay.
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Earthenware has a high iron oxide content. This gives it its signature reddish and orange colors. Terra cotta, which means “baked earth,” is one of the most common types of earthenware clay. Earthenware fires at lower temperatures, usually at 1,745 degrees to 2,012 degrees Fahrenheit.
When fired, it can become orange, brown, buff, medium gray, or even white.
It remains unvitrified, which means it doesn’t turn into glass.
2. Stoneware clays
Stoneware clay is just as forgiving as earthenware. It’s one of the easier types of clay to work with.
But it’s also more durable than earthenware.
Stoneware is a non-porous clay. It bonds well with glazes.
When matured to optimum hardness, stoneware doesn’t crack, chip, or break as easily as earthenware. It can also withstand the heat of baking ovens.
For this reason, stoneware makes a great material for dinnerware and drinking glasses.
When moist, stoneware can take on any shade of gray. It’s plastic and workable, making it great for throwing and hand-building.
Mid-fired stoneware matures anywhere between 2,150 degrees and 2,260 degrees Fahrenheit.
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High-fired stoneware needs to fire at higher temperatures, usually 2,345 degrees to 2,462 degrees Fahrenheit. Stoneware fired at higher temperatures is waterproof and more durable.
When fired, stoneware can go anywhere from brown to buff or different shades of gray to white.
3. Kaolin clays
Of all the types of clay, kaolin is the most regal. It’s also the most expensive.
Kaolin derives from fine, smooth silicate minerals. It is pure white in color and buttery smooth to the touch.
It comes from China, specifically the Kao-Ling hill in southeastern China. Kaolin is not one of the easiest types of clay to work with, especially for beginners.
Its low plasticity makes it difficult to mold with the hands or on the wheel. Working kaolin too much can also cause it to collapse. Once it does, it can be near impossible to get it back up.
Kaolin can also crack or dry during firing. It’s best to start with other types of clay before getting your hands on kaolin. By itself, kaolin fires at a very high temperature of 3,275 degrees Fahrenheit.
When mixed with other types of clay, kaolin becomes much more workable. This also lowers its firing temperature.
When fired to maturity, kaolin becomes a hard, smooth, and shiny material called porcelain. There is no need to glaze kaolin.
It has a range of colors but all are very light. Moist kaolin is typically light gray. When fired, it becomes anywhere from light gray to near-white and pure white.
You'll find kaolin clay often used for making delicate items, such as laboratory equipment.
4. Ball clays
Ball clays are highly plastic and easy to work with.
They have very few mineral impurities and mature to hardness at about 2,340 degrees Fahrenheit. Unfortunately, ball clays cannot be used by themselves because of excessive shrinkage after firing.
Ball clays work best when combined with other types of clay, such as kaolin clay. They increase the plasticity of the clay body to make it easier to work with.
Ball clays also decrease the firing temperature of kaolin.
5. Fire clays
Different fire clays have different characteristics.
The one thing they all share is their very high firing temperatures.
Most fire clays fire to maturity at 2,912 degrees Fahrenheit and above.
They’re often mixed with other types of clay, such as stoneware, to increase the firing temperature. Fire clays also give stoneware clay a bit of roughness.
Although fire clays are mostly pure, they sometimes have bits of iron, which gives them a speckled look when hardened.
When choosing what types of clay to work with, you want to know if it has a good amount of grog. Grog comes from hardened clay particles crushed to a fine sand.
Adding grog to a clay body makes it stronger and more workable at the same time. Grog also reduces shrinkage and cracking during firing.
A hand-building clay must have anywhere from 5 percent to 30 percent of grog. This allows the clay to stay firm during construction.
It also prevents the clay body from slumping, stretching, or sagging while you sculpt it into different shapes.
The more complex shapes you’re making, the higher the amount of grog you need to add. Grog also quickens drying time and cuts the risk of cracking during drying.
If you’re throwing on the wheel, you need types of clay bodies that won’t fall apart but won’t hurt your hands either.
You also need a plastic, workable clay that you can easily mold into different shapes.
Keep in mind, though, that more plastic clays have greater potential to shrink and warp while drying. They must also have enough grog to keep them upright while throwing.
A grog ratio of 7 percent to 9 percent is ideal for throwing. To test if you have the right amount of grog, roll your clay into a string and wrap it around your finger.
If it cracks or breaks, you may have added too much grog. If it remains smooth, you have a good clay on your hands.
Firing is a critical step in pottery. It doesn’t require as much creativity as it does technical knowledge.
Synthetic clays, such as air-dry clay, don’t need to mature in a kiln.
Natural clays, however, need to be fired at specific temperature ranges. So do the different types of glaze. It’s important to fire the types of clay bodies and glazes at the right temperatures. Otherwise, you won’t be happy with the results.
Fire clay at too high temperatures, and it can warp or melt. Fire it too low, and it will stay rough, dry, and unsolidified.
There are three temperature ranges for firing clay. There are slight variations for each type, but they mostly fall into the following:
Low-fired types of clay reach maturity at 1,745 degrees to 2,012 degrees Fahrenheit.
Historically, low firing temperatures are the most common because of the limitations in kiln technology.
These temperatures are best for earthenware clays. If you want to add colorants to your clay, it’s best to use low-fired clays. At higher temperatures, the additives can burn or become unstable.
Low-fired clays are vitrified. They remain porous and less durable.
If you’re using colored glazes, the color will look brighter but can also be too harsh.
Mid-fired clays mature at 2,124 degrees to 2,264 degrees Fahrenheit.
The result is more durable than low-fired clay but still not as hard as high-fired clay. Mid-fired glazes do not appear as harsh as low-fire glazes but look just as vibrant.
High firing temperatures turn clay into a strong, non-absorbent, highly durable material.
These temperatures range from 2,282 degrees to 2,462 degrees Fahrenheit. High-fired clay doesn’t need to be glazed.
There are many colors of clay to choose from just as there are many types of clay.
If you want the colors of your glaze to pop, choose a white clay. The glaze will look more vibrant on the clean surface. Plus, it will be easier to clean your workspace because white clay doesn’t stain.
Light clay colors such as sand and buff also cause their colored glazes to pop. Although they look dark when moist, sand and buff clays are light enough when fired.
If you want to work with darker colors, such as the deep, rich reds of earthenware or a stunning black, keep in mind that darker clays stain.
They can be hard to clean off your hands, clothes, and the floor. But the end result can look gorgeous with the perfect stain.
Red clays work well with clear, matte, or glossy glazes. Darker colors like black can be decorated with light underglaze or just clear glaze.
If you want to create artificial colors, you can use powdered colorants for your clay. You can also mix different colored clays of the same type to create a marbled effect.
Always keep different colors and types of clay in different bins. Do not use the same wedging board for dark and light clays to prevent the colors from bleeding into each other.
What Types of Clay Should You Use?
Knowing the types of clay helps you choose the right clay to work with. In general, you can choose from earthenware, stoneware, and kaolin clays. You can also mix these clays with ball clays and fire clays to improve their workability.
For simple beginner’s projects, start with earthenware or stoneware. When you start to feel more comfortable, experiment with kaolin and ball clay combinations.
You can work with any type of clay, as long as you know how to use them well.
What pottery project are you working on? Share it with us in the comments below.
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