The types of pottery clay and what they are used for
Pottery has a lot of terminology, and it can sometimes feel a tad overwhelming... including when it comes to the most basic ingredient of all - the very clay you use! But there are not as many clay types as you might think.
This is a quick guide to the main clay types and their uses. As always, we welcome your questions!
The three main pottery clay types
Earthenware clay
Earthenware is glazed or unglazed non-vitreous pottery that has normally been fired below 1,200 °C (2,190 °F).
Basic earthenware, often called terracotta, absorbs liquids such as water. However, earthenware can be made impervious to liquids by coating it with a ceramic glaze.
Earthenware is a popular choice for beginner potters because earthenware clay is generally easier for potters to work with and is more forgiving. However, it’s also less versatile and more fragile than other types of pottery once it's fired.
Uses: Earthenware is used for sculpting, hand-building, and wheel throwing. You can create sculptures, flowerpots, and other outdoor decorations.
Porcelain or china ceramics are incredibly popular, especially for dinnerware. They are mostly pure mineral kaolin, otherwise known as “China Clay.” and other materials.
There are three types of porcelain ceramics: hard-paste, soft-paste, and bone china.
Hard-paste or “true” porcelain is the most common type. “True” porcelain is fired at very high temperatures such as cone 10 (2345℉ or 1285℃) and yields sturdier objects. It contains added minerals to the kaolin, usually feldspar or mica.
Soft-paste porcelain is the least common type. Europeans invented it and fired it at lower temperatures, about cone 5 (about 2167℉ or 1186℃) Cone 5. Soft paste porcelain is considered weak porcelain. It doesn’t need a fixed mineral to be created. Kaolin is mixed with bone ash, quartz, glass, and soapstone to yield this type, with ball clay often added into the mix.
Bone china has mostly replaced true porcelain in modern times. It’s the strongest kind of porcelain. It’s very resistant to chip damage and has great physical strength. It usually produces a white or translucent result. It contains kaolin, bone ash, feldspar, and phosphates.
Uses: kaolin clays are the least plastic clays and are therefore quite hard to work with. This means that porcelains are mainly used in wheel throwing and cast slipping to create tableware, vases, and other decorative objects.
Stoneware is a dense, strong, and impermeable clay that is normally only partially vitrified (fired to the point that it is not porous). Stoneware may be vitreous or semi-vitreous depending on the temperature it is fired to and is normally glazed.
Stoneware is fired at temperatures ranging from 2,000° to 2,400° F These high temperatures partially or completely vitrify the clay.
Unlike porcelain, which is almost always white, stoneware is usually colored gray or brownish because of impurities in the clay; potters can make stoneware with multiple different clay colors today.
Uses: This type of clay can be easily worked with and painted with underglazes, glazes, overglazes, enamels, etc. This makes stoneware clay a popular clay to use for tableware. Used mainly in hand-building and wheel throwing.
Other pottery clay types you might run across
Ball clay
Ball clays are the most plastic (stretchy) clays and contain very limited mineral impurities. They contain a large percentage of kaolinite and quartz, with around 10-25% mica. Ball clays occur naturally as sediments or deposits containing very fine minerals.
Ball clays vary widely in plasticity, particle size, raw color, and drying properties, but in practice, most are remarkably similar. Ball clays tend to lose most of their color during the firing. At the greenware stage, ball clays have a light brown or gray color. After firing, they obtain a light buff color. They produce a fine white color when fired right, making them popular among potters. Ball clay alone tends to be too fine and slippery for use. It can be used for wheel throwing when mixed with other clays but is mainly used in casting slip and as an additive to other clay bodies.
Uses: Because of the high plastic and high binding quality, Ball clays are commonly used for floor tiles, toilet bowls, vases, and tableware.
Egyptian paste
Egyptian paste is a self-glazing clay body suitable for small beads, sculptures and press-molded forms. Also called fritware, its history goes back thousands of years to ancient Egypt. Egyptian paste has a high silica and high soluble alkaline flux component and an abnormally low clay content. This mixture develops a film when drying that fluxes in the kiln to create the glaze on each piece. Egyptian paste is not plastic (stretchy and bendable) like normal clay mixtures.
Uses: Egyptian paste is used to make small statues, ornaments, and jewelry.