Advanced Ceramics Vocabulary

Types of Clay Bodies

  • Ceramics: Objects made of clay hardened by heat.
  • Earthenware: A low-fire clay body typically fired between cones 06-04. Examples include terra-cotta and low-fire white clays. Earthenware pieces remain porous after firing.
  • Air Dry Clay: A clay body that is soft and moldable but air dries to a hard state, requiring no baking or firing. It remains porous but can be painted.
  • Potter: A person who makes pots, plates, and vessels from clay, either by hand or on a potter’s wheel.
  • Primary Clay: Clay found close to where it was formed in nature; often white in color.
  • Clay: Rocks broken down by weather into tiny particles; water between these particles allows clay to be formed and shaped. When the water evaporates, it cannot be shaped further.
  • Secondary Clay: Clay found far from where it was formed in nature; it picks up other minerals (like iron) during its journey by wind and water. Secondary clays are often tan, buff, orange, or terra cotta colored and are frequently more plastic than primary clays.
  • Porcelain: A white high-fire clay body, a primary clay first discovered in China. Valued for its brightness, and if fired high enough, it can become translucent.
  • Ceramicist: A person who makes ceramics.
  • Pottery: Pots, plates, and vessels made from clay and fired in a kiln.
  • Stoneware: A mid to high-fire clay body fired between cones 5-7; high-fire stoneware is fired between cones 8-11. Stoneware clays contain fire clays that are refractory, meaning they can withstand high temperatures. These clays are fired to vitrification, which means they aren't porous after firing and won't absorb water, making them suitable for dinnerware and pots.
  • Plasticine: An oil-based clay body; the oil prevents it from drying out. Plasticine is reusable and will not fully harden.
  • Grog: Crushed, unglazed pottery or brick used as an additive to increase the clay’s strength.
  • Play Doughs: Soft and pliable clays made from various ingredients mainly for sensory play.

Stages of Clay

  • Slip: Liquid clay used to join pieces of clay together. It can be poured into molds or used for decorating.
  • Bone Dry: Clay pieces that have not been fired in the kiln.
  • Underglaze: Pigment mixed with a little bit of melter that is applied to raw clay or bisqueware to give it color. Underglazes are applied like paint and go underneath a glaze; a clear glaze is often applied over the underglaze.
  • Greenware: Clay from which as much water as possible has evaporated. If held to the cheek, it will seem dry instead of cold and damp. This clay looks and feels chalky and is very fragile. It is at this stage that clay pieces are fired in the kiln.
  • Glaze: A coating of glass that is applied to clay pieces, glaze can be brushed, dipped, or sprayed onto objects made of clay; when fired in a kiln, the glaze melts into a glass coating, turning it into a ceramic surface. Glaze forms a glossy or matte finish when fired to temperature.
  • Plastic: Clay that is wet enough that it can be shaped into forms by hand or on the wheel without breaking.
  • Leather Hard: Clay that has started to dry but has some flexibility. It can still be carved, cut, and joined together, but it is hard like a block of cheese.
  • Glazeware: A clay piece that has been fired twice - once in a bisque firing and a second time in a glaze firing; it has a glossy or matte glasslike finish and a smooth texture.
  • Matte Finish: A dull, flat finish without a shine; often used on sculptural ceramic pieces because it allows the form to be seen more easily.
  • Bisqueware: An unglazed clay piece that has been fired in the kiln once at a low temperature and is ready to be glazed.
  • Gloss Finish: A shiny finish that reflects light and looks like a layer of glass; often found on dinnerware.

Forming Techniques

  • Pinching: The process of squeezing a piece of clay between the thumb and forefingers to make a hollow shape; pinch pots are made by pinching.
  • Coiling: Rolling or extruding a cylinder of clay to create a long, snake-like form; coils can be stacked to create pots or sculptures.
  • Wedging: The process of pushing and pressing on clay to expel all air bubbles trapped in it and to bring the clay to a uniform, consistent moisture level.
  • Slab Building: Rolling clay into a flat sheet with either a rolling pin or slab rolling machine; clay slabs can be formed into pots or sculptures at the soft stage, or the slabs can be left to stiffen and assembled when leather hard.
  • Forming: The act of creating three-dimensional (3-D) forms.
  • Additive: The process of joining pieces to create a form.
  • Subtractive: The process of removing pieces to create a form; carving is an example of the subtractive process.
  • Hollowing: Removing the inside from a form.
  • Relief: A sculpture that projects from a flat surface.
  • Slump Molding: Draping a slab of clay into a form to shape it.
  • Hump Molding: Laying a slab of clay over the top of a form to shape it.
  • Extruding: The process of forcing clay through an opening in a die to give it a shape.
  • Slip Casting: Pouring liquid clay into a plaster mold to create a form.
  • Throwing: The process of creating a pot on the potter’s wheel using your hands and water.
  • Score/Scoring: Scraping small lines into a piece of clay to roughen the surface prior to joining two pieces together; slip is applied to the scoring lines, and the two pieces are then smoothed together.
  • Modeling: The act of creating three-dimensional (3-D) forms.

Firing Process

  • Kiln: A furnace or oven for firing clay sculptures and pottery; some kilns are gas fired while others use electricity or burn wood, all giving different firing results. Kiln Types: electric, gas, wood, salt, raku, bonfire.
  • Reduction Firing: Typically happens in gas kilns. Oxygen is prevented from interacting with the glazes as they melt, by closing the damper on the chimney a bit to cause the fuel in the kiln to burn less efficiently. Glazes fired in reduction result in mottled, rich, earthy colors. Often the iron from the clay body shows through the glaze as speckles.
  • Firing: The process of maturing ceramics by heating them in a kiln; firing makes the clay objects permanent.
  • Cone: Pyrometric devices used to gauge heat-work during the firing of ceramic materials. The cones, often used in sets of three, are positioned in a kiln with the wares to be fired and provide a visual indication of when the wares have reached a required state of maturity - a combination of time and temperature.
  • Low-Fire: Ceramics fired in the cone 06-04 range are considered low-fire. Low-fire works are typically fired to less than 1950 degrees Fahrenheit. Examples of low-fire clays are terra cotta and low-fire white clay bodies. Low-fire ceramic objects are still porous and can absorb water.
  • Mid-Fire: Ceramics fired in the cone 5-7 range. The clay used in mid-fire ceramics is stoneware. Glazes fired in this range in an electric kiln often yield bright colors. If an appropriate midfire clay and glazes are used, the works produced will be vitrified and safe to use for dinnerware.
  • High-Fire: Ceramics fired in the cone 9-11 range. High-fire works are often fired in gas kilns. While firing at this heat in electric kilns is possible, doing so wears out the heating elements in the kiln more quickly, leading to more frequent replacement. Stoneware and porcelain are examples of clay bodies used in high-fire ceramics.
  • Vitrified: When a clay object becomes glasslike from being fired in a kiln.
  • Oxidation Firing: Typically done in an electric kiln but can also be done in a gas kiln. Oxygen is free to interact with the glazes when firing, resulting in glazes that are bright in color.

Decoration Techniques

  • Impressing: Pushing a clay stamp or textured object into a piece of clay to decorate it.
  • Trimming: Removing excess clay from a form that was thrown on the potter’s wheel.
  • Painting: Applying glaze or slip with a brush.
  • Glazing: Pouring, dipping, spraying, or applying glaze with a brush.
  • Oxides: Ground up metallic minerals, such as red iron oxide.
  • Stains: Pigments that come from minerals and oxides that have been ground into a powder.
  • Slip Trailing: Applying colored liquid clay with a bulb syringe to decorate a clay object.
  • Wedging: Process of pushing and pressing on clay to expel air bubbles and achieve uniform moisture.

Throwing Terms

  • Burnishing: Smoothing clay with a stone, plastic bag, or a finger to give it a smooth, polished finish.
  • Bat: A flat, removable disc attached to a potter’s wheel that allows a potter to throw and remove a piece from the wheel without distorting its shape.
  • Sgraffito: The act of carving through one layer of clay or underglaze to expose a different colored clay below it.
  • Centering: The act of pushing a piece of clay into the center of the potter’s wheel; this is done before the clay is opened and a wall is raised.
  • Incising: Decorating a clay object with a series of cuts.
  • Collaring: Act of narrowing the opening on a cylinder that is thrown on the potter’s wheel.
  • Carving: Using a tool to remove small clay pieces from a larger whole piece in order to create a form or finished artwork.
  • Neck: The thinner part of a vase, bottle, or pitcher that is located above the larger body or belly of the pot.
  • Piercing: Cutting or poking holes through a piece of clay.
  • Foot: The bottom of a pot, a foot is often trimmed into pottery when it is at the leather hard stage.

Miscellaneous Vocabulary

  • Shard: A broken fragment of pottery.
  • Base: The bottom part on which something rests or is supported.
  • Shrinkage: Clay objects get smaller in size throughout the drying and firing process; the average shrinkage rate for clay objects is 12.5 percent.
  • Dipping: Act of submerging a clay piece into a glaze or slip.
  • Wax Resist: Bottoms of pots are dipped into warm wax to repel glaze from sticking to the waxed areas; this keeps the bottom of the pot free from glaze so that it does not stick to the kiln shelf when fired. Wax resist can also be used for decorative purposes, if it is applied between layers of glaze.
  • Frit: A mixture of silica and fluxes melted at high temperature and then poured into water to cool, this mixture is then ground into a powder and used in glaze recipes; frits are often more consistent in their behavior in a glaze than the raw materials they are made from.
  • Flux: A melter; in a glaze recipe, the flux lowers the melting temperature of the glass, allowing it to melt at temperatures that can be reached in a kiln.
  • Refractory: The ability to withstand high heat without deforming; kiln bricks are refractory in nature.
  • Tiles: Flat pieces of fired clay used for various surfaces.
  • Mosaics: Art made by arranging small pieces of colored material.

Uses of Clay

  • Bricks
  • Roofs
  • Sculptures/Figurines
  • Pottery containers, plates, bowls, cups, mugs, serving dishes, teapots, jugs, planters, vases, urns, vessels

Tools and Equipment

  • Potter’s Wheel
  • Sgraffito Tool
  • Extruder
  • Wire Tool
  • Slip Brush
  • Sieve
  • Cones
  • Loop Tool
  • Knife
  • Pugmill
  • Rib Tool
  • Rolling Pin
  • Banding Wheel
  • Modeling Tools
  • Hole Piercer
  • Slip Trailer
  • Clay Cutter
  • Sponge
  • Scale
  • Stilts
  • Needle Tool
  • Paddle
  • Bat
  • Scoring Tool
  • Slab Roller
  • Kiln