 Clay is a weathering product of rocks, which disintegrate due to the significant temperature differences between sun and frost. As it is transported by water, for example, a sorting process takes place; stones, gravel, sand, and clay. The clay further weathers due to the action of weak acids dissolved in water, such as humic acids or carbonic acid. During the sorting process, various organic (plant residues) and inorganic (metal oxides) impurities can enter the clay. The different colors of the clay are caused by the metal oxides. Metal oxides are toxic, so wash your hands well after modeling and do not eat during modeling. |
 The purest clay is Kaolin. Kaolin is the raw material for porcelain (porcelain clay). Washed kaolin consists of weathered granite and has very low plasticity.Sedimentary clay - which we mostly use - can have the following composition:
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| Clay is made up of clay platelets held together by an electrical force. Generally, water acts as a lubricant between these platelets (compare this to water between two glass plates). The better they are layered, the greater the cohesive force. This results in very plastic clay. This is referred to as long clay. Clay whose platelets are jumbled (for example, due to frost) needs to be made plastic again. We do this by kneading or simply letting the clay rest for a few months so the platelets settle back into place. Generally, fatty clay is very plastic. However, this clay dries slowly and unevenly, increasing the risk of cracks and splits. |
 There are different types of clay. Clay is usually delivered in so-called 10-kilo loaves. Some types include:Natural Clay This is clay that has been cleaned after extraction and can be used without additives. Red Earthenware Clay Also known as terracotta. It is usually an iron-rich secondary clay, red in color, fairly soft, with good plasticity and strength. Red earthenware clay is excellent for modeling, hand-building, and throwing. Pipe Clay This secondary clay is blue or black in color and shrinks significantly during drying and firing. Adding pipe clay to a clay loaf increases plasticity and strength. A "clay loaf" is a type of clay or a mixture of clay types. |
| Porcelain Clay or Kaolin Porcelain clay or kaolin is a primary clay. Washed kaolin consists of weathered granite and has very low plasticity. It is less glassy than pipe clay, shrinks little, and becomes white during firing. Porcelain clay is used to make the clay loaf workable and serves as a binder. In most clay loaves, it is the primary agent for achieving a white color. Additionally, it can be used as a glaze based on aluminum salts and silicates. Fire Clay Fire clay owes its name to its heat resistance. The properties vary from type to type; some are plastic, while others are coarse and grainy. Fire clays usually contain some iron and are found near coal seams. They are used for insulating bricks, refractory bricks, kiln interiors, and as an additive to stoneware clay to give it plasticity and high-temperature resistance. Stoneware Clay Smooth, plastic stoneware clays from sedimentary rock are resistant to high temperatures. They are usually pale yellow, gray, or light brown in color. Stoneware clay cannot be used without additives. Bentonite This extremely fine and plastic clay originates from volcanic ash. Bentonite is added to clay loaves to improve plasticity. One of the most used clay types is Chamotte. There are two types:
The advantage of these coarse grains is:
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 When working with clay, you don’t need much equipment or materials. Many tools can be found around the house. For example, a simple paring knife can go a long way, and a putty knife is also frequently used. Additionally, you can use apple corers for making holes and forks for carving patterns and edges. |
 A turntable can be very useful. You can, of course, buy the intended turntables in a specialty store, but if you’re just starting and want to see if you enjoy modeling, you can also buy a cheap turntable for the kitchen at IKEA. This works perfectly fine for beginners. You can build your piece on this turntable and easily view it from different angles while working. Small slats and a rolling pin for making clay slabs are also very handy. A clay cutter is essential as well, which you can easily make yourself by attaching a sturdy wire to two dowels to serve as handles. |
 A modeling stand is mainly needed when modeling from observation. You need to have your piece at about chest height to work comfortably. If you work at a table, you’re looking down on it, making it difficult to judge if all shapes and directions are correct. |
 You need some cheap household cloths to keep clay pieces or parts moist while modeling. Sponges can also be handy at times. |
 For smooth finishing of surfaces, use a rib. These come in various materials, including metal, wood, and plastic. Which material you prefer is very personal. Just try a few out. |
 Clay slip for attaching clay slabs can be easily made yourself. Since you’ll use this frequently, it’s convenient to always have a jar ready. Make sure to use the correct clay slip for your piece. So, use red-firing clay slip with red-firing clay. You can still see the color after firing. However, interesting effects can be achieved by doing this differently. You can apply the slip with a finger or a cheap brush. |
 From left to right, you see a long narrow metal spatula, useful for hard-to-reach places. Next, a scratching tool for scoring the clay before applying slip. You can also use it to carve patterns on the surface. Finally, there are three loop tools. These tools are used to scrape off parts of the clay to shape your piece. |
 Here are more spatulas and loop tools. There’s a wide range in price and shape. Start with a limited number because you won’t use them all. Over time, you’ll build your own set of tools. |
 Sometimes, I find tools not specifically meant for modeling but interesting to experiment with. They all end up in my clay tool drawer. |
| This overview is, of course, far from complete. Nothing has been mentioned about glazing or engobing. But it’s enough to start modeling. Although the article is written with chamotte in mind, most tools can also be used for other types of clay. |