Intro to Ceramics
What is clay?

Made of alumina + silica + water (Al2O3 + SiO2 + 2H2O)
Clay is a compound of decomposed and weathered feldspathic rock consisting of various hydrated
silicates of aluminum along with non-plastics, such as quartz, and organic matter.
Methods for working in clay:
1.
Wheel Throwing (potter’s wheel)
-Typically used to produce functional ware: cups, bowls, plates, vases, etc.
-Can include sculpture from the wheel: using wheel thrown forms to construct sculptural
pieces.
2. Handbuilding
-Pinching (pinch pots)
-Coil building
- Slab Construction
- Modeling (carving and sculpting)
-Plaster Molds (slump and drape molds)
-Slip Casting (used plaster)
Clay (“Greenware”) Stages of Dryness:
1.
Slip: liquid clay that is the consistency of thick cream. Used when joining pieces of clay
together by “scoring and slipping”.
2. Soft “Plastic” Clay: Workable clay that is the ideal consistency for most ceramic
processes.
3. Leather Hard: the condition of raw clay ware when most of the moisture has evaporated
leaving it still soft enough to be carved or joined to other pieces but too firm to bend.
4. Bone Dry: the condition of unfired clay that has no absorbed moisture other than natural
humidity.
Greenware: All stages of unfired clay can be “recycled”. As long as the clay has not been bisque
fired it can be reused over and over again. Leather hard or bone dry clay can be added to a bucket
of water and will turn back into slip which can be “re-claimed” and mixed to create soft workable
clay.
Bisqueware: Clay that has been fired once. It is very porous and must be glazed in order to seal the
pores of the clay and make it food safe. After clay has been bisque fired it cannot be turned back
into clay. It is now ceramic.
Types of Clay Bodies:
1.
Earthenware (low-fire)
2. Terra-cotta (low-fire)
3. Stoneware (mid-range) * This is what we use
4. Porcelain (high-fire)
Temperature ranges for clay bodies: (bisque and glaze)
1.
Low-fire
2. Mid-range
3. High-fire
Wedging: The purpose of wedging is to eliminate air pockets, align clay particles and make the clay
more consistent and workable. Not wedging enough makes it difficult to center on the wheel and
could cause your work to explode in the kiln due to trapped air.
Grog: Bisque fired clay that has been ground into a fine particle and added to clay. It ranges from
fine to coarse and is used to reduce shrinkage, promote even drying, prevent warping and cracking
and increase durability.
Plasticity: Clay that is easily manipulated and can be worked without crumbling is called plastic.
Short: Clay that is not elastic and breaks or crumbles easily when worked.
Shrinkage: Clay shrinks! As clay dries it looses moisture and shrinks a very small amount. It also
shrinks a small percentage when it is fired in the kiln. (In total about 10%) Because clay shrinks
when it dries, it is not a good idea to add water to bone dry clay. It will act like a dry sponge. When
water is added it will expand and crack!
Porosity: The capacity of a clay body to absorb moisture.
Warping: Distortion of a clay shape caused by uneven stresses during shaping, drying or firing.