Stages of Clay

Learning Goal Students will be able to recall and identify the stages of clay. Michael T. Schmidt, Valdosta, GA

Physical Stages of Clay GREENWARE refers to unfired objects. Clay bodies at this stage are in their most plastic form. They are soft and malleable. Hence they can be easily deformed by handling. Wet Clay Leatherhard Clay Bone Dry Clay

Wet Clay In this stage clay can be easily manipulated and formed. Typically for methods of construction, pinch, coil, and slabs are all used in the Wet Clay stage. Clay is very malleable, with at least 80% moisture remaining.

Physical Stages of Clay LEATHER-HARD refers to a clay body that has been dried partially. At this stage the clay object has approximately 15% moisture content. Clay bodies at this stage are very firm and only slightly pliable. Trimming and handle attachment (putting pieces together) often occurs at the leather-hard state.

Physical Stages of Clay BONE-DRY refers to clay bodies when they reach a moisture content at or near 0%. You may not alter your piece once it gets to this phase. Your piece is ready to be bisque fired at this stage. Can you make Bone Dry clay Wet? Can you make wet clay Bone dry?

Physical Stages of Clay: Bisque BISQUE refers to the clay after the object is shaped to the desired form and fired in the kiln for the first time, known as "biscuit fired". This firing changes the clay body in in several ways. Mineral components of the clay body will undergo chemical changes that will change the color of the clay.

Physical Stages of Clay GLAZE FIRING is the final stage of some pottery making. A glaze may be applied to the biscuit form and the object can be decorated in several ways. After this the object is "glaze fired", which causes the glaze material to melt, then adhere to the object. The glaze firing may also harden the body still more as chemical processes can continue to occur in the body. Stephen Heywood, Jacksonville, Florida

Glaze a vitreous substance fused on to the surface of pottery to form a hard, impervious decorative coating Creates colors, decorations, and seals the clay Egyptians were the first to discover glaze (from over-firing Kilns)

Recycling Clay / Reclaiming Clay reclaiming has to be done when clay has dried too much, pieces have been made and not used because they are broken or cracked, bits are thrown off while working, they can still all be used again. There will be ‘Slip’ cans or buckets to put clay in that is too dry. If clay is only slightly dry or leatherhard, simply spray and place back into the clay bag. Until clay is bisque fired, it can always be reclaimed and reused.

Kiln A KILN is a thermally insulated chamber, or oven, in which a controlled temperature regime is produced. Uses include the hardening, burning or drying of materials. Kilns are also used for the firing of materials, such as clay and other raw materials, to form ceramics

Pyrometric Cone Equivalency We fire our bone-dry pottery to become bisque in a Kiln. The temperature we fire to is 1945 degrees Fahrenheit. The Pyrometric Cone Equivalency (PCE) Is CONE 04. (Bisque) We have glazes that fire to Cone 06 (1855) or Cone 05 (1911)

Graphic Organizer You are to create a Graphic Organzier with information for the Stages of clay and Ceramic terms: Greenware Wet Leatherhard Bone Dry Bisque Glaze Firing Firing Kiln Pyrometric Cone Equivalency (PCE)