What is the difference between earthenware and stoneware clay?

Earthenware and stoneware are two types of clay used in pottery and ceramics, and they differ in their composition and firing temperatures. Here's a breakdown of the differences:

Composition:

• Earthenware Clay: Earthenware clay is typically composed of a higher percentage of impurities such as iron and other minerals. It tends to be more porous and has a lower firing temperature compared to stoneware clay.
• Stoneware Clay: Stoneware clay is usually made of a higher-quality, denser clay body that contains fewer impurities. It has a higher proportion of silica, which contributes to its strength and durability.

Firing Temperature:

• Earthenware Clay: Earthenware clay is fired at lower temperatures, typically between 1,800 and 2,100 degrees Fahrenheit (980-1,150 degrees Celsius). The lower firing temperature means the clay retains its porous nature and remains somewhat permeable, even after firing.
• Stoneware Clay: Stoneware clay is fired at higher temperatures, typically between 2,200 and 2,400 degrees Fahrenheit (1,200-1,315 degrees Celsius). This higher firing temperature vitrifies the clay, transforming it into a non-porous and more durable material.

Appearance and Characteristics:

• Earthenware Clay: Earthenware pottery often has a reddish or tan colour due to the iron content in the clay. It has a porous structure, making it more susceptible to absorbing liquids and may require glazing to be watertight. Earthenware is generally considered less durable than stoneware.
• Stoneware Clay: Stoneware pottery has a range of colours, from light grey to dark brown, depending on the clay and firing techniques used. It is non-porous and dense after firing, making it suitable for functional ware like plates, bowls, and mugs. Stoneware is known for its durability and strength.

Glazing and Decoration:

• Earthenware Clay: Earthenware pottery often requires a glaze to achieve a smooth and watertight surface. The porous nature of the clay can result in a softer, more matte appearance. Decorative techniques like majolica, where colourful glazes are applied over an unfired glaze, are commonly used with earthenware.
• Stoneware Clay: Stoneware can be left unglazed or glazed depending on the desired aesthetic and functional properties. Some stoneware may have a natural, earthy appearance, while others can be highly decorative with glazes that enhance the texture or colour of the clay body.

Overall, the choice between earthenware and stoneware depends on the intended use, aesthetic preferences, and firing capabilities of the potter or ceramic artist.