types of clay
Stoneware, earthenware, porcelain oh my... what do these terms mean when you're shopping for ceramics? Read on to learn about these different clay types; how to tell them apart and their different uses.
This post is an excerpt from pondercraft.ca, CCBC's educational website.
Earthenware clay is either red-brown or white in colour, becoming opaque once fired. A fairly brittle and lightweight clay, earthenware is notably soft in that when left unglazed, it can be scratched with a knife.
Earthenware is fired at the lowest temperature among clay types, at about 1000°C or 1830°F. However, this also means while it can withstand oven temperatures, after a few heatings, eventually it will crack. Due to earthenware’s coarse and porous texture (meaning it absorbs liquids easily), it requires a glaze to be appropriate for spaces such as the kitchen. Since it is non-vitreous, glazing provides both water and heat resistance, as well as overall strength and durability.
Earthenware is most commonly recognized as the basic, rusty orange outdoor planting pot found in your garden. However, earthenware is also used for tiles and building bricks. Today, fine earthenware makes up most of your contemporary tableware, subject to proper glazing.
Stoneware is a fine-grained denser clay, often feeling dense for its size. While opaque, it can be any colour ranging from white, grey, brown or even black.=
Stoneware is fired to ‘maturity,’ between 1100-1300°C or 2010-2370°F – this creates a sturdy and chip resistant material. Due to stoneware’s extremely hot initial firing, the material is able to handle cast temperature changes making it oven, microwave, dishwasher and refrigerator/ freezer safe. Unlike earthenware, stoneware is non-porous, vitrifying after a single firing. This means it does not need a glaze to be functional but is often glazed anyways for further durability and ornamentation.
Known for its durability, stoneware is perfectly suited for your kitchen tableware, serving guests or even in the garden. More traditionally, stoneware’s have been used as baking stones because of its dense, supportive nature and ability to withstand the rapid heating of the pizza oven. Stoneware is popular for functional pottery and utilitarian wares because of its high quality and versatility.
In addition to its whiteness, porcelain is known for its smooth surface. A great test for identifying porcelain is simply to hold the work up to a light, as it is notably translucent compared to other clay materials. Porcelain is sometimes called china or fine china, signaling its introduction to Western culture from China.
Porcelain is fired at the highest temperature of all the clay materials, between 1200-1400°C or 2190-2550°F, resulting in a high resistance to chemical attack and thermal shock. Its primary material is Kaolin, a very fine, soft white clay. Porcelain is non-porous, having low permeability and elasticity even before glazing. It is completely vitrified, making it exceptionally hard and tough and thus able to produce very thin, delicate objects.
Porcelain’s ability to combine well with paints and glazes and ease of modeling makes it a popular choice of material for decorative treatments in tableware, pottery and figurines – Chinaware being one of the most obvious
Learn more about clay and other craft mediums at ponder craft and design, CCBC's educational website.
cover image: May Fan Leung