- Slides: 19
Where does clay come from? • Clay comes from the ground, usually near areas where there is water. – Topsoil is top layer of ground, clay found below topsoil – Clay found near lakes, rivers, and reservoirs – Can also be found in dry areas in powdered form – Clay is mined in Wisconsin
How does clay get from the ground to PHS? • Clay is mined from the ground • Raw materials are added to clay and mixed • Clay is filtered to remove unwanted material • Extra water is removed from clay • Air is removed from clay • Clay is formed into blocks and shipped to schools, businesses, and artists
Different types of clay • Clay gets its color from elements and materials in the ground. Traditionally red, grey, and white. • Earthenware – low fire clay, easy to work with, needs glaze to hold water • Stoneware – medium fire clay, very hard and durable, holds water without glaze • Porcelain – high fire clay, difficult to work with, very strong
Important Clay Terms • Wedge – process of blending clay to remove air bubbles • Plasticity – how flexible the clay is, depends on the moisture of the clay • Porosity – how much water the clay can absorb • Shrinkage – how much clay shrinks as it dries, is fired, and is glazed
Important Clay Terms • Greenware – clay that has been shaped, but not fired in the kiln, very fragile • Leather hard – clay is dry, but not all the way • Bone dry – clay is all the way dry, nothing can be added at this point • Bisque – clay has been fired once and is hardened, but not glazed or painted
Greenware, before being fired in a kiln Bisque pottery
Clay Processes • Pinchpot – Pinching a ball of clay into a functional bowl • Coil building – Rolling and stacking coils on top of each other to create a cup, bowl, vase, etc.
Pinch pot Coil building
Clay Processes • Slab building – Rolling slabs of clay to usually create boxes or vases • Throwing – Using a potters wheel to create perfectly circular cups, bowls, plates, etc.
Throwing on a wheel Slab building
Clay Processes • Scratch and slip – Used to attach clay to clay. Placing small scratches on the surface of the clay and using slip (clay glue) to hold clay together.
Scratching clay Clay slip
Clay Decorating • Glaze – Used to add color to finished clay pieces. Traditionally painted over bisque fired clay, then fired again to reveal colors and patterns • Paint – Acrylic, latex, and watercolor can be added to the surface or bisque fired clay. (Room temperature glaze)
Glaze after kiln Glaze before kiln
Glossy and matte glaze
Clay Decorating • Kiln – Clay oven that operates at extremely hot temperatures – Usually around 1400 – 2500 degrees F – Used to turn brittle, dry clay (greenware) into strong, durable clay – Used to alter dry, unattractive glaze into colorful, attractive glaze
Man made brick kiln Modern electric kiln
Clay Tools • • • A A. Fettling knife B. Sponges C. Ribbon or Loop tools D. Rib Tool: used to smooth out the surface of clay pots E. Banding wheels: used for hand building, coiling, and decorating C E D B