Ceramics

Vocabulary Words Sgraffito Wash Glaze Slab Wedging Grog Slip Coiling Resist Trailing Scoring Underglaze

Bisque Firing Bisque firing refers to the first time the pots go through high- temperature heating. It is done to vitrify the clay pots enough that they won’t be harmed when glazes are applied, but not to such an extent that the glaze won’t adhere correctly. The bone-dry greenware is fragile and must be loaded into the kiln with a great deal of care. The kiln is closed and heating slowly begins. A slow temperature rise is critical. During the beginning of the bisque firing, the last of the atmospheric water is...MORE driven out of the clay. If it is heated too quickly, the water turns into steam while inside the clay body, causing the clay to burst.

Clay Transformation When a kiln reaches about 660 F, the chemically bonded water will begin to be driven off. By the time the clay reaches 930 F, the clay becomes completely dehydrated. At this point, the clay is changed forever; it is now a ceramic material. The bisque firing continues until the kiln reaches about 1730 F. At this temperature, the pot has sintered, making it less fragile while remaining porous enough to accept the application of glazes. After the desired temperature has been reached, the kiln is...MORE turned off. The cooling is slow to avoid breaking the pots due to stress from the temperature change. After the kiln is completely cool, it is opened and the newly created bisqueware removed.

Glaze Firing At this point, potters apply glazes to the bisqueware. After glazes are applied and have a chance to dry, the ware is carefully loaded into the kiln for the glaze firing. Pots cannot be allowed to touch at all or the glazes will melt together, welding the pots together. The kiln is heated slowly to the proper temperature to bring the clay and glazes to maturity and then slowly cooled again. Only after the kiln has cooled is opened and unloaded. The changes in temperature in the kiln cause a...MORE remarkable change in the clay and glaze. Pots change from a soft, fragile substance to one that is rock-hard, impervious to water and time.

More words to know Firing Pressing Wax Kiln Silicia Wet Cleaning Pinching Slacking Kiln Wash Stain Plasicity Vitreous

Clay Stages Greenware Finished leather hard or bone dry clay pieces not yet fired; raw ware Leatherhard AllCheesehard stage which clay reaches before being bone dry; stiff enough to support itself but can still be altered. Bisque Underglazed but FIRED ware, low temp firing prior to the glaze fire

Types of Clay Earthenware Stoneware Porcelain All ware with permeable or porous body after firing. Earthen ware is glazed fired to cone 04 (1950 degrees F). 10 to 15 % absorption. Stoneware Hard, dense, durable ware generally fired to 2150 degrees F or above. 0 to 5 % absorption. Porcelain Mechanically strong, hard, frequently translucent, fired clay body is the strongest of all clay (0% absorption)

Rules to know Floors impervious to water and easy to clean, such as concrete or linoleum Access to water (but NO CLAY should go down any drains!) Sturdy table a clay-won't-stick-to-it surface to work on (see below) sturdy shelving for drying pots Cover your clay in plastic

What to bring – Thursday – 8-17-17 Old Towel / Rags Sponges Spary bottle Found objects to make imprints (leaves, bottom of a shoe, small chains, bunch of paper clips, use your imagination!) Sketch ideas Old shirt *Optional – rolling pin -