All About CLAY

What is Plasticity & Elasticity in Clay?

Clay plasticity refers to how flexible a clay or clay body is specifically ‘the quality or state of being plastic; especially: a capacity for being molded or altered’. Clay plasticity depends upon particle size, water content, and aging.

Clay elasticity is the clay’s ability to ‘assume a new shape without any tendency to return to the old

In general, it’s the ability of the clay to be kneaded, shaped, pushed, pulled and remain in that state. The more “workable” clay is, the easier it is to mold into your desired form and shape.

There are three primary groups of clay minerals and each one of them is formed with their own very distinct properties. They are: kaolin (perhaps the most well known), Illite and Montmorillonite.

What is the difference between Ceramics, Stoneware and Earthenware?

Ceramics or pottery refers to a process of forming, firing or baking, and glazing or decorating a mixture of clay and other materials, then refiring it to harden the glaze. The three ceramics are earthenware, stoneware and porcelain.

Stoneware

  • Mid-High fire: cone 4-10 (2160-2372 degrees).
  • Non-porous when fully vitrified (fired to maturity temperature recommended by clay company).
  • Widely used for dishware and functional items as well as sculpture and decorative pieces.
  • Range of shrinkage depending on specific clay composition, but your piece WILL get smaller when you fire it.

Stoneware, named after its dense, stonelike quality after firing, is tougher and more durable than earthenware. And unlike earthenware, stoneware is waterproof. Earthenware can be made waterproof by being coated with a vitreous (glasslike) liquid and refired.
UsesStoneware is made from a particular type of clay that is fired at high temperatures, generally between 2,012 and 2,372 degrees Fahrenheit. It was first produced in China, during the Shang Dynasty (circa 1,400 BC). The qualities of stoneware traditionally made it useful for dishes used for food, for drinking vessels and for storage. Today it is often used for cookware, bakeware and serving dishes.

Earthenware:

  • Low-fire: cone 06-3 (1850-2135 degrees).
  • Slightly porous, even when fired to maturity (water will soak into it if not glazed or sealed).
  • Low-shrinkage from wet to fired states.
  • Great for planters, oven steamers/garlic roasters, kids projects/art class and decorative items.
  • Not so great for dishware as it is not as sturdy as stoneware or porcelain and is prone to chipping and staining.