LEXICON | Pottery and Ceramics terms

Ash glaze: A glaze made with ground ash, usually wood ash and sometimes mixed with other materials.
Ball clay: A sedimentary clay that will withstand high firing temperatures. Plastic in quality.
Baluster (form): A vase or other vessel that is slender above and bulging below.
Base (form): The solid support or bottom of any vessel.
Bat: A flat disk that sits on the potter’s wheel. Used for heavy pieces that would be difficult to separate from the wheel.
Beaker (form): A trumpet-shaped vase, having neither handle nor spout nor beak.
Belly (of a pot) (form): The widest outwardly or convexly swelling area of a pot.
Bevel (form): The edge of any flat surface that has been cut at a slant to the main area.
Bisque-firing (Biscuit): Pots that have been given a preliminary firing to render them hard enough for further work such as decoration and glazing. The higher the temperature of the bisque firing, the harder the pot will be.
Blisters: Blisters appear as large bubbles either just below or penetrating the surface, leaving sharp, rough edges. Also known as glaze pops
Blunger: Machine with angled, rotating blades for mixing water with clay.
Body (form): The belly, waist, and shoulder of a pot, taken together, are known as the body of the pot.
Bone China: A china made white and translucent by the addition of calcined animal bone to the body.
Bottle kiln: A large kiln, wide at the bottom and narrow at the top like a bottle.
Bottle (form: A vase with spheroidal body, long neck and narrow mouth.
Bowl (form): A low-walled vessel with a big opening.
Burnish (polish): To smooth the surface of a pot by rubbing it with a hard object to give a finish with a polished effect.
Cartouche (decoration): An oblong shaped panel surrounded by a border and acting as a frame, enclosing an entirely different decorative motif from the ground pattern.
Cast: To produce shapes by pouring fluid clay into moulds. The ‘negative’ moulds are usually of plaster of Paris, and made from a ‘positive’ so that when they wear out, new ones can be made.
Celadon glaze: A type of glaze, generally used on porcelain or stoneware. Celadon glazes can be produced in a variety of colors, including white, grey, blue and yellow, depending on the thickness of the applied glaze and the type of clay to which it is applied. The color is produced by iron oxide in the glaze recipe or clay body.
Chawan (O-chawan): A bowl used for preparing and drinking matcha (powdered green tea) in the Japanese tea ceremony. Also the standard term for bowls for rice. Common shapes include cylindrical, flat and round. Cylindrical bowls are called tsutsu-jawan, while shallow bowls are called hira-jawan.
Cheese-hard (see Leather-hard)
China clay (see Kaolin)
China (see Porcelain)
Chrome oxide: Used to produce yellow or green colours in glazes.
Chun glaze: A pale blue glaze used on stoneware.
Clay: Raw unprocessed clay consists of clay particles and undecomposed feldspar, usually combined with quartz, mica, iron-oxides and other materials. When moist it is soft and plastic; when fired becomes permanently hard.
Clay body: Apart from the coarsest earthenware which can be produced from clay as found in the ground, most pottery is made from special clays mixed with other materials (grog, feldspars, etc.) or ingredients to produce the desired results. The mixture is known as the clay body.
Climbing kiln: A multi-chamber kiln with each successive chamber at a higher level than the last.
Cobalt oxide: Used to produce a blue colour in glazes.
Coiling: Long strands of rolled clay which are laid on top of each other and joined through blending coil to coil.
Cone: Cones are test pieces inserted in the kiln to indicate to the potter when a certain temperature has been reached. They are made of various glaze materials of known melting point.
Copper oxide: Used to produce green colours in glazes. When used in a reducing atmosphere it produces a red colour.
Crackle glaze: Minute decorative cracks in the glaze that are often accentuated by rubbed-in coloring material.
Crawling: A defect that appears as irregular, bare patches of fired body showing through the glaze where it has failed to adhere to or wet the body on firing. The cause is a weak bond between glaze and body; this may result from greasy patches or dust on the surface of the biscuit ware or from shrinkage of the applied glaze slip during drying. Also called glaze skip or glaze crawls.
Crazing: A fine network of cracks in the glaze usually caused by uneven contraction and expansion of the body and the glaze during changes of temperature. In some pottery (Raku) this is a design feature rather than a fault.
Dunting: Cracking or breaking of pots when cold draghts are allowed to enter the kiln. Can also be caused by the free silica in the body being too fine.
Earthenware: Usually fired at low temperatures (1 000-1 200oC). Porous and not waterproof. To be functional, it needs to be glazed. The iron-content of the clay used for earthenware gives a colour which ranges from buff to dark red, or even cream, grey or black, according to the amount present and the atmosphere in the kiln during firing.
Embossing (decoration): A process of stamping, hammering or molding a material so that a design protrudes beyond the surface.
Enamel glaze: Low-fired coloured glazes.
Engobe (see Slip)
Faience: Tin glazed European earthenware, usually from France.
Feathering (decoration): Effect obtained by trailing a feather through wet slip decoration.
Feldspar (Felspar): A crystalline substance found in granite.
Fettle: The removal of unwanted blemishes, seams and flash from nearly dry pots prior to glazing and firing.
Firing: Clay is hardened by heating it to a high temperature, fusing the clay particles. Primitive pottery is usually fired on the ground or in pits with whatever flammable material is available. Kilns allow a more efficient use of materials and more control over the atmosphere during a firing. The two basic atmospheres, oxidation and reduction, affect the color of the final piece.
Flambé: A flame-like effect produced by a reduced copper oxide glaze.
Flatware: Plates, saucers, trays, etc.
Fluting (decoration): A repeated pattern of parallel concave vertical grooves, used as a decoration.
Flux: A substance mixed with a body or glaze to promote fusion. It effectively lowers the melting point.
Foot (form): Pots may or may not have a foot. When present, the foot is an area that is distinct from the body of the pot, and which is smaller in circumference than the body. The foot raises the pot up and away from whatever surface the pot is standing upon. Feet are generally viewed as giving a pot more elegance and “presence”; visually they make the pottery form read as lighter. Tactility they can make a pot feel more comfortable in the hand if the pot is small enough for the hand to cup around its base. An overly tall, spindly foot can make a pot look and often actually be unstable.
Form (Shape): Cylindrical, spheroidal (globular), ovoid (egg-shaped), pomiform (apple-shaped), puriform (pear-shaped), cubical, hexagonal, etc.
Fretwork (decoration): Interlocking geometrical designs used ornamentally.
Functional ware: Pots that are used for food and drink, including plates, bowls, mugs, goblets, pitchers, and teapots.
Galena glaze: An ore of lead sulphide used as a glaze.
Gilding (Bronze doré ) (decoration): An advanced technique utilizing metallic mixtures of powdered gold, silver, copper or platinum to achieve a range of colours and effects.
Glaze firing: The last firing of a pot when the glaze is applied.
Glaze: A coating of vitreous material applied to ceramics before firing that forms a glass-like surface to render it impermable to moisture. In addition to the functional aspect of glazes, aesthetic concerns include a variety of surface finishes, including degrees of gloss and matte, variegation and finished color. There are four main types of glaze: feldspathic, lead, tin and salt. Lead and tin are commonly used to glaze earthenware, while stoneware is usually salt-glazed.
Greenware: Pottery that has not been fired.
Grog: Gritty material added to clay to modify its behaviour in firing. It is usually ground clay that has already been fired, and can be course or fine depending on the type of work for which it is being used.
Guinomi: Guinomi is often called a miniature chawan. Every part of it, like the kodai (the foot), kuchizukuri (the lip), and koshi (the hips),
Gypsum (see Plaster of Paris)
Hakeme: Oriental technique of applying white slip with a brush made from straws, allowing the slip to be applied to the pot thickly.
Handbuilding: Constructing pots from pre-made parts. The components might be moulded, coiled or fashioned by hand.
Hollow ware: Cups, jugs, bowls, etc.
Impressed (decoration): Stamped into the leather-hard clay with a tool or die.
Impressed (mark): Stamped into the leather-hard clay with a tool or die.
Incised (decoration): Pattern cut into the clay with a sharp tool. The reverse of relief carving.
Incised (mark): Maker’s name, monogram or mark cut into the clay with a pointed tool.
Jar (form): Bowl with constricted lip opening.
Jigger (also Jolley): A mould or profile used when unform shapes have to be made repetitively on the wheel.
Jug (form): A container for liquid, with a handle and an opening for pouring or drinking from.
Kaolin: China clay. A white clay made from pegmatite.
Keshiki: “Landscape”. The keshiki is the name given to the design the fire makes on the clay surface and the design is governed by the pieces placed around and the flow of the flames.
Kiln: The furnace in which ceramics are fired. Kilns can be electric, natural gas, wood, coal, oil or propane. Materials used to heat the kiln can affect the end-result.
Kiln furniture: The various items made of refractory materials that are used in the kiln to support or protect the pots such as shelves, posts, stilts, saggars, etc.

Lattice (decoration): An openwork criss-cross pattern.
Lead glaze: A clear glaze containing a lead component, nowadays used in its non-poisonous bisilicate form.
Leather-hard (Cheese-hard): Clay that has dried to the point where it is stiff enough to retain its shape but wet enough for further work to be done on it.
Limestone: Chalk. Used in lime glazes.
Lip (Rim) (form): The open upper edge of the pot.
Lug: A knob or extrusion on the side of a vessel.
Lustre: Metallic oxide film applied to pots after glazing and firing to produce pearly finish after a further firing in a reducing atmosphere.
Lute: To join two pottery surfaces together with slip.
Maiolica (Majolica): The technique of applying low fired tin-glazes with different oxides to produce multi-coloured effect.
Manganese oxide: Used to produce a purple or brown colour in glazes.
Mould: A concave shape made from Plaster of Paris for slip casting. Also the die used for press-moulding.
Mouth (form): Top opening of a round ware such as a bowl, jar or a vase.
Mouth-rim (form): Topmost edge of the neck of a round ware such as a bowl, jar or a vase.
Neck (form): Section part between mouth-rim and shoulder on a jar or a vase. In the bottle, flagon, and flask, the neck is of different length and form. The throat may be narrow or wide, inclining inwards or outwards, or even perpendicular.
Nickel oxide: Produces a brown, green or violet colours in glazes.
On-glaze decoration: Decoration applied after the pot has been glazed.
Ovenware: Any pottery that will be used in the oven or microwave must be very resistant to thermal shock.
Overglaze (decoration): A decoration applied over an already glazed finish.
Oxidation firing: A firing atmosphere with ample oxygen. An electric kiln always gives an oxidizing fire. In a wood or gas firing, the mixture of fuel and air is perfectly adjusted to give a clean burn.
Oxides: Metal oxides can be mixed with water and applied to the surface of clay. By varying the amount of material applied and rubbed off, the potter can achieve effects similar to stained wood. The most common stain is iron oxide (rust).
Peephole: Small hole in the kiln for the potter to see what is going on inside.
Peppering: Minute black specks of carbon that is sometimes seen in white or light coloured glazes.
Pinch pots: Starting with a ball of clay the potter opens a hole into the ball and forms a bowl shape through a combination of stroking and pinching the clay.
Pin-hole: A fault that is commonly the result of a bubble in the glaze when it was molten that burst but was only partially healed.
Plaster of Paris: Gypsum. Calcium sulphate. Used for making moulds for slip-casting.
Plasticity: Capacity of clay to be shaped or moulded.
Porcelain: Hard, fine, high-fired material made from kaolin, felspar and silica. It is white and translucent. Also known as hard paste. It can be worked as clay, but when fired properly reaches a state similar to glass.
Pot (Vessel): Usually (any) round and deep vessel appropriated to any of a great variety of uses; often with a handle and lid.
Potter’s wheel: A heavy horizontal wheel onto which clay is thrown and shaped. The weight of the wheel gives momentum to preserve continuity of speed.
Pugmill: Siimilar in operation to a domestic food mincer, The clay is put in at the top and comes out of the mouth at the bottom in the form of slices or wedges.
Pulling: Shaping a handle.
Pyrometer: A thermometer able to measure the very high temperatures found in kilns.
Quill: A pointed instrument - a porcupine quill, a thin piece of bamboo, a knitting needle, etc. - used in throwing.
Raku (Raku-yaki): A type of Japanese pottery that is traditionally and primarily used in the Japanese tea ceremony, most often in the form of tea bowls. It is traditionally characterized by hand-molding of the clay, low firing temperatures, lead glazes and the removal of pieces from the kiln while still glowing hot. It is then usually placed in a bed of combustible materials and covered, creating intense reduction resulting in irregular surfaces and colors.
Reduction firing: Reduction firing is when the atmosphere inside the kiln, full of combustible material, is heated up tremendously, eventually using up all of the available oxygen in the atmosphere of the kiln. This then forces oxygen from the glaze and clay to be taken out to continue the reaction and resulting in the metallic content in the glaze and clay to change colour.
Reeding (decoration): Converse of fluting; parallel, vertical pattern in the form of reeds.
Refractory: Capable of withstanding very high temperatures. The kiln furniture has to be able to remain stable at temperatures in excess of the normal firing temperature an must be made of refractory materials.
Rib: A shaped tool to facilitate the forming of pots.
Saggar: A fireclay box used to protect pottery while it is being fired.
Salt glaze: Created by adding common salt into the chamber of a hot kiln. The salt acts as a flux and reacts with the silica and clay in the clay body. A typical salt glaze piece has a glassine finish, usually with a glossy and slightly orange-peel texture, enhancing the natural colour of the body beneath it.
Sang-de-boeuf: Ox-blood. Used to describe deep red colours in glazes.
Sedimentary clay: Clay formed by the decomposition of igneous rock.
Senchawan: Small porcelain cups used for fine-quality steeped green tea.
Sgraffito (scratching, carving) (decoration): The technique of scratching through a coating of slip to reveal the contrasting colour beneath.
Shino glaze: A generic term for a family of pottery glazes,ranging in color from milky white to a light orange, sometimes with charcoal grey spotting, known as “carbon trap” which is the trapping of carbon in the glaze during the firing process.
Shoulder (form): Outward projection of a vase under the neck or mouth.
Single-fire process: In the single-fire process, glaze is applied to ceramic ware while the clay is still raw (unfired). After drying, clay and glaze then are matured together in the intense heat of the kiln at the same time.
Slabbing: Clay 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.
Slip: Fluid clay in a creamy texture used for decorating, joining and as a material for casting. Applied to the surface of a vessel prior to firing. Slip fills in pores and gives uniform color.
Slip decorating: The application of slip (often combined with glazes) to a pot. This can take the form of an all-over or partial coating, or a trailed, feathered, combed or brushed design to achieve decorative effects.
Slip trailing: Method of decoration where slip is trailed onto a pot through a fine nozzle.
Slipware: Slip-decorated earthenware pottery.
Slurry: Slip with a thick consistency
Sprigging (decoration): Application of small low-relief, mould-case ornaments onto the body and attached by thin slip to pot when it is leather hard
Spur marks: The marks left by the stilts used to support pottery in the kiln. Usually seen as three dots in the form of an equilateral triangle.
Stacking: Loading a kiln with pots.
Stoneware: Called stoneware due to its dense, stone-like character after being fired, this type is impermeable (waterproof) and usually opaque. In its natural state stoneware clay is grey but the firing process turns it light-brown or buff coloured and different hues may then be applied in the form of glazes. Stoneware is usually fired at temperatures between 1 100-1 300oC. It is more durable than earthenware, and capable of resolving finer detail.
Tenmoku glaze (Temmoku, Temoku): A Japanese name for a dark Chinese glaze with a surface that resembles oilspotting. It is made of feldspar, limestone and iron oxide.The more quickly a piece is cooled, the blacker the glaze will be. Tenmoku glazes can range in color from dark plum (persimmon), to yellow, to brown, to black.
Terracotta: A brownish-orange to red earthenware clay body. Usually unglazed.
Throw: To make a pot on a potter’s wheel. The wheel revolves and maintains a fairly constant speed as would a flywheel. The clay is thrown onto the centre of the wheel and the potter shapes it by hand to the desired form.
Tin glaze: White opaque glaze containing tin oxide.
Transfer printing: Method of decoration where a pattern or picture is printed onto the gelatin coating of paper and then, when wet, is slid onto the surface of a pot.
Tunnel kiln: A kiln made in the form of a tunnel, with the highest temperature in the middle. The pots move slowly through on trucks, and the effect is similar firing in a normal kiln with a heating and a cooling period. Tunnel kilns burn all the time, allowing greater throughput.
Underglaze (decoration): A decoration applied to a biscuit or once-fired pot for subsequent covering with a transparent glaze.
Urn (form): Usually a vase furnished with a foot or pedestal, employed for different purposes, as for holding liquids, for ornamental uses, for preserving the ashes of the dead after cremation, etc.
Vase (form): A pot taller than it is wide, often decorated, adapted for various domestic purposes and anciently, for sacrificial uses.
Vessel (see Pot)
Vitrification: To change to a glassy state.
Volatilize: To cause to evaporate. Volatilized oxides can migrate from one part of the kiln to another.
Waist (form): When present, the waist on a pot is an area in which the form is collared inward. Pottery waists may consist of a strong demarcation between the upper and lower regions, or be a gentle concave curve between the outward swelling of the upper and lower areas it joins together.
Wax-resist (decoration): Wax applied to a pot to prevent adhesion of slip or glaze and produce a decorative effect.
Wedging: The cutting of clay into wedges in the process of mixing and kneading it to an even consistency.
Well (form): The hollow interior bottom of a bowl, plate or dish.
Wheel-thrown: The term for placing a piece of clay on a potter’s wheel head which spins. The clay is shaped by compression while it is in motion.
Yunomi (Unomi): Literally, cups for hot water. Handle-less cups on a raised foot of smaller diameter than the body, used for drinking regular steeped tea.

The Pottery Studio glossary of terms and abbreviations


Encyclopedia of Irish & World Art: 2011

The Free Library

Basics of Thrown Pottery Forms