Clay and Glaze 101

What Exactly is Clay?

Clay is found, in one form or another, in almost every region of the world. It is naturally formed over time as rock (feldspar) is broken down and washed down mountains where it is deposited in lakes, rivers and streams in the valleys below. As the rock washes down the mountain it is combined with different organics and minerals (i.e. iron, sodium, calcium…) along the way which give each regions clay, its own unique characteristics.

Technically speaking in it’s purest state clay is an aluminum silicate mineral kaolinite. Its property of being plastic arises from its composition of microscopic disk-shaped platelettes that give clay its ability to hold its shape when molded.

In early civilizations, potters would go down to the riverbeds where clay was deposited, dig it up, pick out the rocks and sticks and start making pots. Today the process is a little more refined. Clay manufacturers purchase the refined raw materials neccesary to make the clay bodies they offer. These raw materials are first mixed as dry materials, water is then added, and the mixed clay is de-aired in a pug mill where it then is extruded into bags and boxed. 

When dried clay is fired to temperatures between 1800°F and 2300°F, depending on the type of clay, it changes chemically into ceramic, and becomes rigid, durable, and permanent (no longer plastic and moldable).