This is called ceramic. Kaolinite is a soft, earthy clay mineral with white color. This compound is found in all clay types. The compound is flexible but inelastic. Kaolinite is a silicate compound. Smectite refers to clay minerals that contain varying amounts of alkali metals and alkaline earth metals. Clay minerals absorb water and are able to expand. Chlorite is a mineral compound containing iron, magnesium, manganese, zinc, lithium, calcium, and nickel.
The chemicals vary per mineral. Chlorite itself is no longer considered a clay compound, but it can be found in some clays as a mineral. Illite is a non-expanding clay material. It contains silicon, aluminum, iron, magnesium, and potassium.
It can also contain sodium and chromium. When it comes to using clay one clay does not fit all. There are many different clays for different skill levels and different uses. These are the 4 most common types of clays. Earthenware clays are the oldest clays used by potters and happen to be the most common today. It is very plastic and is beginner-friendly. The earthenware colors are mostly warm. The wet clay has a tone of Brown, red, orange, or grey.
After firing, earthenware shows brown, orange, red, grey, or white colors. Colors in pottery show after being fired. Terracotta is the most popular color you can yield. Earthenware can be easily decorated over with paints and glazes.
Earthenware is used for sculpting, hand-building, and wheel throwing. You can create sculptures, flowerpots, and other outdoor decorations. In comparison to other clay types, earthenware fires at the lowest temperatures with pottery achieving the desired hardness. This is due to the compound containing impurities like minerals. Once fired, earthenware is non-vitreous i. Even after being fired, earthenware is somewhat soft and can be scratched with a sharp object. Ball clays are the most plastic clays and contain very limited mineral impurities.
Ball clays occur naturally as sediments or deposits, containing very fine minerals. Materials like lignite can also be found in ball clays. Ball clays lose color on firing. At the greenware stage, ball clays have a grey color.
After firing, they obtain a light buff color. They produce a fine white color when fired right, making them popular among potters. Because of the high plastic and high binding quality, Ball clays are commonly used for floor tiles, toilet bowls, vases, kiln furniture, and tableware. Ball clay alone tends to be too fine and slippery for use. It can be used for wheel throwing but is mainly used in slip casting. It also depends on the sediment that it picks up on its journey.
Once a commercially produced clay body has been mined from the ground, it is processed in a plant. This usually involves, amongst other things, crushing, grinding, and screening 3. Other ingredients can be added to the clay as it is being processed to enhance its performance. Frit is a manufactured glass powder that melts at low temperatures 4.
By adding frit to the earthenware, its glass-forming potential is increased. Therefore, making it stronger and less porous. Earthenware clay has a reputation for being quite plastic. Also, plastic clay will keep its form when it has been shaped. Some clay has a tendency to slump or return back to its original shape when it is being used.
Plastic clay tends to be quite cooperative and will keep the shape it has been fashioned into. Because it is plastic, earthenware clay is a good clay for beginners.
I like working with earthenware clay, in particular, terracotta can feel very nice to throw on the wheel. Some clay has a mind of its own and takes a bit of persuasion to do what you want. However, I find terracotta quite cooperative, and generally does what I ask quite easily. If clay has added grog it will feel gritty. However, if it does not contain extra grog, terracotta can feel silky smooth on the wheel. One of the next types of clay for pottery that we are going to have a look at is stoneware.
Like the term earthenware, stoneware is an umbrella term that refers to a variety of different clay bodies. However, in general, stoneware, as its name suggests, is tough when it has been fired. Compared to earthenware clay it is denser, more resistant to breaks and chips, and less porous. Stoneware clay fires at higher temperatures than earthenware clay. Normally stoneware clays mature when fired in the mid to high fire range. In practice, this means that they are fired somewhere between F C.
Using the language of the cone system, this means stoneware is fired between cone 4 and cone The temperature that is used to fire stoneware depends on the clay body itself.
And the potters own preference. Normally manufacturers will state the temperature range that best suits a clay body on the packaging. And potters will choose a temperature that suits them within that range. The mid-range firing temperatures are usually thought of as cone And High firing temperatures are cone Here is a table to help clarify what temperatures are considered low, mid, and high fire.
And also, what cones are associated with each temperature range:. You will often hear potters talking about a cone 6 stoneware or a cone 10 stoneware. This refers to the temperature they fire at, but also the kind of stoneware they are using. The depth of color will vary from a pale grey to quite a deep grey color.
And a stoneware that is a darker grey in its wet workable state will be tan or beige when fired. However, you can also get black and brown stoneware. Stoneware used commercially is often made of quite refined particles. As a result, the fired product has a smooth consistent look. However, stoneware used by potters for making pottery by hand often has a speckled look. This is partly to do with impurities in the clay.
But it is also the result of grog that is added to the clay to improve its performance. Grog is clay that has been fired, and ground up into granules. This is then added back into a clay body.
Grog makes clay easier to work with and less likely to crack when it dries. The grog granules are made in different sizes. Larger granules will give clay a gritty grainy appearance. As stated above, clay contains glass-forming materials that melt when the clay is fired. Some clays contain more of these glass formers than others. And stoneware clay produces more glass when it is being fired than earthenware.
Therefore, provided stoneware clay has been fired to a high enough temperature, it will be more vitreous than earthenware. A vitreous substance is basically a glass-containing material. And materials can be more or less vitreous depending on how much glass they contain. The more vitreous a material is, the less porous it is, and the more waterproof the item becomes. Some fired stoneware clay is vitreous, and other stoneware is semi-vitreous, meaning it is semi-porous.
Either way, stoneware is less porous than earthenware and this makes it more suitable for functional use. Stoneware is a common choice of clay for dinnerware and water holding vessels like vases. This is partly to do with the fact that it is less porous than earthenware.
But it is also to do with its strength. Vitrified pottery is stronger and denser than non-vitrified pottery. So, stoneware is less vulnerable to chips and breakage than earthenware pottery.
Like earthenware clay, stoneware is a secondary clay. It is then mined, processed, and prepared to be used for the production of pottery and ceramics.
Part of the production process involves refining and blending the ingredients of the clay. As already stated, there are lots of different types of stoneware.
However, broadly speaking stoneware is a mixture of feldspar, quartz, and ball clay. Feldspars are used as fluxes in clay and glazes.
Fluxes reduce the melting point of glass-forming ingredients in clay. Quartz is a mineral with a high content of silica.
And silica is one of the main glass-forming ingredients of clay. Ball clay is a very plastic type of clay that is often added to stoneware clay to make it more workable.
Also, fire clay is sometimes added to stoneware. This raises the temperature that it can be fired to, and is a common ingredient in high fire stoneware. Some stonewares do contain kaolin, which is the main ingredient in porcelain. Different types of stoneware vary in how they feel to use. However, stoneware has a reputation for being easy to use.
It is generally quite plastic, workable, and versatile. Some stoneware clay feels quite smooth and silky to use. However, if it has added grog or sand it can feel more coarse and gritty. I tend to think of stoneware as being like a reliable workhorse. That sounds unflattering, but what I mean by that is that it can be used for a wide range of techniques.
It is cooperative, and will usually do what you want it to do. And it is strong and durable. At the same time, it can look refined and delicate, without being as high maintenance as porcelain. One of the more refined types of clay for pottery is porcelain clay. Porcelain clay is sometimes referred to as kaolin clay. However, kaolin is a very pure kind of white clay also known as china clay. Kaolin is actually used as a primary ingredient in making a wider range of porcelain types of clay.
Normally porcelain clay bodies contain other ingredients too. Porcelain is a high fire type of clay, which means that it usually fires at temperatures from F C upwards. However, it is most often fired above F C , which is cone 9. Depending on the particular type of porcelain being used, it will mature between cone 6 and However, it can be mixed with other ingredients that bring its firing temperature down.
Once fired, porcelain is normally white and can have a translucent appearance. The particles that porcelain is made from are very fine. Because they are so fine, the number of clay particles in porcelain is higher than in stoneware and earthenware. For this reason, porcelain can be pulled and shaped into very thin delicate forms. As a result, it is good to have a good grasp of the different types of clays that are out there.
Oil-based clay is arguably the favorite of artisans who specialize in any of the expressive forms of art. This type of clay comprises various kinds of oils mixed into the clay till it is homogeneous. It is easy to manipulate, highly plastic, and can be reused. Due to the interaction between temperature and oil molecules, the molecular structure of oil-based clay can be affected by temperature. When exposed to high temperatures, oil-based clays melt and become runny, and when cooled, they harden.
It has often been described as waxy, except that it is also grouped with other such clays known as non-hardening clay. It is not recommended for use in making ceramics , for obvious reasons. Also referred to as Walter E. Disney clay WED clay, this type of clay is as malleable as oil-based clay. In the case of WED clay, the oil in oil-based clay is substituted for water. This type of clay is ideal for quick sculptures, wax-like figures, live models, etc. WED clay also falls under the category of non-hardening clay, and it requires enough moisture to remain soft and pliable.
When exposed to high temperatures, WED clay may explode in the kiln due to its high moisture content. When exposed to low temperatures, the water molecules may freeze, allowing them to become firm. However, when it melts, the structure changes and creates fissures in the pottery. When the water dries off, it may become flaky and may break, so keep it hydrated. This type of clay falls under the category of hardening clay.
It is more accommodating of high temperatures than oil-based and water-based clays. It is commonly used as decorative pieces, accessories for some sculptures, art projects, for making models of live objects, etc.
Although the polyvinyl chloride polymer content allows it to harden when fired, it also means that it loses its malleability. This temperature range is achievable with a kitchen oven, and it prevents the clay from shrinking. Although it is considered unsafe for consumption by some, it goes without saying that it should be kept away from babies.
It can be used and reused, and it is completely safe for children to play with. Some companies even make edible and inedible versions of the clay. This type of dough is the favorite of children and elementary school teachers.
It has also been recommended by psychiatrists for relieving stress and working through stressful situations. Dough clay can be made at home by combining flour, oil, water, cornstarch, and some salt. For a variety of colors, you could add food coloring and flavoring for the edible ones. It is not recommended for use in long-lasting objects, as it can crack and flake, so enjoy reusing them as you see fit. This helps it retain the firm, solid form that you desire. These are the different types of clays that are used in making pottery or ceramics.
There are many different types of ceramic clays out there, and finding the most suitable one can be a hassle. One neat thing about most ceramic clays is that they are ideal for use in very high temperatures. Earthenware clays are the most abundant and commonest type of clays. They are said to be among the oldest type of clay to have been used in pottery. This type of clay has the characteristic of being very sticky, and as such, it is extremely easy to work with.
Earthenware clay is also known as terra cotta clay, and it mostly naturally occurs as a red clay body. Terra cotta is very popular as an ingredient for making planters, some traditional sculptures, and figurines. Typically, earthenware clay produces porous wares when fired, which makes it ideal for use as planters. Knowing that earthenware clay produces porous wares, it is often used to make plant pots, terra cotta, figurines, and so on. Furthermore, earthenware clay can be glazed and baked so that it can hold moisture.
This type of earthenware, although less porous, is used to make bowls, pots, serving dishes, etc. Typically, earthenware has low silica content, so it does not easily lead to the formation of glass or become vitrified. This high firing temperature occurs as a result of the presence of mineral impurities in the clay. The last two points are optional and are for making potteries that are used to hold or retain water and other liquids.
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