Ceramics Vocabulary

Clay Bodies

Clay body: the actual clay mixture that is used in forming objects. It might only have one specific type of clay in it, but it is more likely to consist of a mixture of different types of clay.

  • Other additives may also be introduced into the mixture. Each specific ingredient used is included to give the clay particular attributes. For example, ingredients may be added to aid plasticity, to lower or raise the clay body's firing temperature, or change its fired coloration.
  • Clay bodies come in a wide spectrum of colors, from white, to red, to black, and many colors in between.

Classes of Clay

  • Clay can be divided into several classes, based on characteristics and at what temperature the clay must be fired to in order for it to become mature, or reach its optimum hardness and durability.
  • The three most commonly used clay bodies are earthenware clay bodies, mid-fire stoneware clay bodies, and high-fire stoneware clay bodies.
  • All three are available commercially in moist, ready-to-use form.
  • Clay bodies can also be produced by mixing dry clays and additives with water to create your own desired clay body.

3 Most Common Clay Bodies

1. Earthenware Clays

  • Earthenware clays were some of the earliest clays used by potters
  • The most common type of clay found.
  • porous – functional ware needs to be glazed
  • These clays are highly plastic (easily worked) and can be sticky.
  • Earthenware clays contain iron and other mineral impurities which cause the clay to reach its optimum hardness at between 1745°F and 2012°F (950°C and 1100°C).
  • Typical colors for moist earthenware clays are red, orange, yellow, and light gray.
  • Colors for fired earthenware includes brown, red, orange, buff, medium grey, and white.
  • Fired colors are in large part determined by the content of mineral impurities and the type of firing.

Stoneware Clays

Stoneware clays are plastic and are often grey when moist. Their fired colors range through light grey and buff, to medium grey and brown. Fired colors are greatly affected by the type of firing.

2. Mid-Fire Stoneware Clay Bodies

  • formulated to fire to maturity between 2150°F and 2260°F (1160°C and 1225°C).

3. High-Fire Stoneware Clay Bodies

  • fire to their mature hardness between 2200°F and 2336°F (1200°C and 1300°C).

Vitreous clays: become hard, non-porous material, whose particles meld together and become like glass when fired to high temperatures.

  • Glazing is used for aesthetic and hygienic qualities
  • Stoneware – used for functional ware and sculpture. May be gray, beige, or brown
  • Porcelain – fine quality white clay; can be translucent after firing if the walls are thin enough
  • Bone china – hard, translucent white clay body

Porous clays

  • Earthenware: very plastic; must be glazed to make non-porous
  • Can be used for glazed functional ware, and glaze or unglazed sculptures.
  • Terracotta: reddish-brown low-fire porous earthenware that is very strong after firing because of its high iron content.
  • Commonly used for pottery, sculpture, pipes, and flower pots.

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