CLAY VOCABULARY

WedgingKneading the clay by cutting and reforming it in order to expel air and blend all the ingredients.

Wedging

Clay BodyIt is possible to work with the clay as it comes from the earth, however it will not posses certain characteristics such as color, plasticity, strength, or fired density. By mixing two or more clays and adding other materials, these effects can be produced in what is called a clay body.

Pinch PotTo make a pinch pot begin with a ball of clay. Push your thumb into the center, and then pinch up the walls. Turn the piece as you pinch. This will help you keep the walls of the piece at an even thickness. Lightly push the bottom of the pot on a flat surface to create a flat spot that it will rest on when finished.

Pinch Pot

Banding WheelBanding Wheel: A portable turntable for rotating pottery being formed, decorated or otherwise worked

Banding Wheel

BatA disk or slab of plaster or other material such as wood used for drying clay for supporting clay forms while being worked

KilnKilns are thermally insulated chambers, or ovens, in which controlled temperature regimes are produced. They are used to harden the clay body.

Kiln continued… Kilns can be electric, natural gas, wood,

coal, fuel oil or propane. Materials used to heat the kiln can affect the work: wood ash can build up on the surfaces of a piece and form a glaze at high temperatures. Some potters introduce chemicals into the kiln to influence the effects of the firing.

Note: we use electric kilns

Electric Kiln

Coil Pot

Coil Pot - Examples

Coil PotsMade from ropes or coils of clay. Layered

one upon another to create the walls of the pot. Smooth coils or leave some coils exposed.

ScoringScoring clay is the method potters use to adhere two pieces of clay together. Simply use any pointed clay tool to make X shaped marks into the clay where you will be adhering another piece. This roughs up the surface area of the clay, which is needed for a good adhesion.

Scoring

SlipSlip is another name for clay glue. Slip is simply wet sticky clay. Slip can be applied by a paint brush or simply your finger. Do not use just water.

Slip

Score and Slip Cleanup

SgraffitoSgraffito. This is a decorating technique where a colored slip is applied to a leather-hard piece of clay and left to dry. Once the slip is dry a variety of different tools are used to carve into the clay to remove the slip and leave an embedded decoration behind.

Sgraffito

MishimaA Japanese decorating method of filling a design impressed or carved into the clay with a different colored slip.

Mishima: Comparison Example

Sgraffito on the Left

Mishima on the Right

Crazing The fine network of small cracks that occurs on glazes. The Japanese encourage crazing and will stain cracks with concentrated tea.

Crazing

Raku Pottery is fired normally but removed when it is red hot and the glaze is molten. It is then usually placed in a bed of combustible materials and covered, creating intense reduction resulting in irregular surfaces and colors.

Raku-Examples

Slab BuildingClay slabs are cut to shape and joined

together using scoring and wet clay called slip. Slabs can be draped over or into forms, rolled around cylinders or built-up into geometric forms. Large forms are difficult because of stresses on the seams and because the slab naturally sags. Some potters get around this by working fibers into the clay body. The fibers burn out during the firing, leaving a network of tiny holes.

Slab Boxes

The clay goes through stages of drying.

1.Wet, or raw clay.2. Leather hard

3. Bone Dry

Stages of Clay

GreenwareAny pottery that has not been bisque fired. The clay could be wet, leather hard, or bone dry.

Greenware-all stages of unfired clay

Leather hardClay has begun to dry out and can no longer be formed or molded but the surface can easily be carved

Leatherhard-can ‘t continue to remold but effective carving at this stage

Bone DryClay that has been completely air dried and is ready to go to the first firing (bisque)

Bone Dry-very brittle at this stage, ready for the bisque fire

There are two firings:1.Bisque2.Glaze

Firing the Clay

Bisque FiringThe first firing, without over glaze. However colored under glazes (slips) may be applied to the greenware and then bisque fired.

Bisque firing-load bone dry clay

Glaze Firing

The final firing, with overglaze.

Glazeware: finished glaze firing; ready to be unloaded

1.Greenware~Underglaze ~ Bisque fire2. Bisqueware~Clear Overglaze~Glaze

fire

OR1. Bone dry clay~Bisque fire

2. Overglaze applied~Glaze fire

Finishing the Pottery

UnderglazeColored clay slip used to decorate Greenware on leather hard pieces before bisque firing.

Apply underglaze to greenware

OverglazeA thin coating of glass. An impervious silicate coating, which is developed in clay ware by the fusion under heat of inorganic materials.

Overglaze: apply over bisqueware

GrogGrog is fired clay that has been crushed into granules which may be added to a clay body to increase strength, control drying and reduce shrinkage.

Grog

Pyrometric ConeA small triangular pyramid made of ceramic materials that are compounded to bend and melt at specific temperatures. The cone serves as a time-temperature indicator of heat work in the kiln.

Hand-building Wheel Thrown