Glossary4

dry footing

A potters' term for removing all the glaze from the foot of a pot before firing.

high relief

A sculpture whose full contoursare almost detached from a flat background.

multiples

A series of identical objects usually referring to those formed in molds.

drape mold

A support (such as a stretched cloth, a woodem frame, or rope network) in or over which a clay slab is draped to shape as it stiffens. The term isalso sometimes used for a hump mold over which slabs of clay are stiffened.

luster (lustre)

A thin film of metallic salts usually, though not always, applied to a glazed surface, then refired at a low temperature in reduction. Modern luster mediums include a reducing material.

needle tool

A tool with a fine tip, like a needle. Used for cutting, scoring and trimming.

kaolin (also called china clay)

A white-firing natural clay that withstands high temperatures. An essential ingredient in porcelain.

latex

An emulsion of rubber or plastic material with water. Used in ceramics as a resist material in applying glazes.

glass former

An essential component of any glaze. The main glass former is silica.

mold

Any form that can be used to shape fluid or plastic substances. In ceramics, usually the negative form from which pottery or sculpture can be cast by pouring or pressing methods using either liquid slip or dampclay. Molds can be made in one piece orin multiple sections. See also hump mold.

glaze

Any vitreous coating that has been melted onto a clay surface by the use of heat. Made of fine-ground minerals that, when fired to a certain temperature, fuse into a glassy coating. Glazes may be matt or glossy, depending on their components.

dipping

Applying glaze or slip to the object by immersing the piece and shaking off excess glaze.

installation

Ceramic pieces (or any art medium) shown as one work, generally with an overall theme or statement.

fire clays (refractory clays)

Clays that withstand high temperatures. Used in kiln bricks and also as ingredients in stoneware bodies orin clay bodies for handbuilding or sculpture.

glaze stain

Commercial blends formulated with various coloring oxides that produce a wide range of colors when used in glazes or clay bodies.

local reduction

Creation of a reduction atmosphere in one section of a kiln or in a sagger through direct contact with combustible material.

grog

Crushed or ground particles of fired clay gradedin various sizes of particles. Added to the clay body to help in drying, to add texture, and to reduce shrinkage and warpage.

high-fire

Describes clays or glazes that are fired from cone 2 and up is usually considered to be stoneware.

kiln furniture

Heat-resistant shelves, posts, and slabs that support the ware in the kiln during firing. Kiln shelves maywarp in firing if they are not well supported.

firing

Heating pottery or sculpture in a kiln or open fire to bring the clayor glaze tomaturity. The temperatureneeded to mature a specific clay or glaze varies.

Flux

In ceramics, flux lowers the melting point of glaze. Oxides such as iron, sodium, potassium, calcium, zinc, lead, boric oxide, and others combine with the silica and other heat-resistant materials in a glaze, helping them to fuse.

mixed media

In ceramics, the combining of various media, such as metal, wood, paper, stone, with clay in potttery or sculpture.

maquette

In sculpture, a French term used for quick, small preliminary sketches.

enamels

Low-temperature opaque or translucent glazes that are usually painted over high-fired glazed surfaces. Most commonly called china paints.

overglaze

Often called enamel or china paint. A low-temperature ceramic enamel painted on a previously glazes and firedsurface, then fired for a second time at a lower temperature, usually as the final firing process used to obtain bright colors like red and orange that would burn out at high temperatures will be maintained in the lower firing.

engobe

Originally, the term referred to slip that is applied over the entire surface of a piece of pottery or sculpture to change the color and/or texture of the clay body. The term now often refers to slip used for decoration.

maiolica (majolica)

The Italian name for tin-glaze ware that was sent from Spain to Italy via the islandof Majorca. Later, local styles of decoration were developed in Italian pottery towns such as Faenza and Deruta. Now a general term for any earthenward covered with a tin-lead glaze.

fit

The adjustment of hte glaze composition to the composition of a clay body so that it will adhere to the surface of the ware.

neck

The area of a pot that narrows in near the top before it flares out to the opening.

foot

The base of a piece of pottery.

leather-hard

The condition of a clay body whenmuch of the moisture has evaporated and shrinkage has just ended, but the clay is not totally dry. Carving, burnishing, or joining slabs is often one at this stage.

lip (or rim)

The edge of the opening of a pot.

drying

The elimination of water from pots and sculpture. Insufficient drying before firing can result in a piece exploding in the kiln, while drying too fast can cause warping or cracking ofthe ware.

glaze firing (also called glost firing)

The firing during which glaze materials melt and form a vitreous coating on the clay body surface.

model

The original form in clay, plaster, wood, plastic, metal, or other material from which a mold is made.

firing chamber

The part of a kiln that holds the wares to be fired.

firebox

The part of the kiln into which fuel is introduced and where combustion takes place.

flues

The passageways in a kiln designed tocarry the heat from the chamber to the chimney or vent.

handbuilding

The process if building pots or sculpture without the use of the potter's wheel. This term includes pinching and coiling and building with slabs.

opening

The process of making a hole in a centered ball of clay while the wheel is spinning medium to fast. The first step is to make a hole in the clay dome 1 to 2 in. wide and 1/4 to 1/2 in from the bottom. The second step is to widen the opening by pulling the wall out.

low-fire

The range fo firing of clays and glazes in which the kiln temperature reached is usually in the cone 015to cone 1 range.

kick wheel

The traditional potter's wheel which is powered by kicking a lower wheel or by pushing a treadle back and forth with the feet.

lead

Until recently, when the solubility of lead in acid foods andliquids was understood, lead was used as a low-fire or medium-temperature flux in glazes. Potters now do not use lead in any glaze for containers that can be used for food orliquid.

extruder

A mechanical aid for forming moist clay by pressingit through a die. This causes the clay to take the shapeofthe die. Extruders can form clay quickly into many forms, from tubes to tils.

greenware

Unfired pottery or sculpture.

hump mold

A mold of plaster or terra cotta, or a found object such as a rounded rock, an upended bowl, or a bag of sand, foam padding, or crumpled newspaper over which a slab or clay can be laid to shape as it stiffens.

kiln wash

A coating of refractory materials (half flint and half kaolin) painted onto the kiln floor and the top side of shelves to keep the melting glaze from fusing the ware onto the shelves.

kiln sitter

A control that uses small pyrometric cones that slump when the desired temperature is reached and turn off power to an electric kiln by tripping a switch or in a gas kiln by shutting off the gas solenoid valve.

kiln

A furnace or an oven built ofheat-resistantmaterials for firing pottery or sculpture.

frit (fritt)

A glaze material formed when any of several soluble materials aremelted together with insoluble materials, cooled rapidly and splintered by immersion in cold water, then ground into a powder. This reders them less soluble andless likely to release toxic materials. Feldspar is a natural frit.

matt glaze

A glaze with a dull, nonglossy finish due to irs deliberate composition. Alumina added to the glaze, along with a slow cooling, assists the formation of matt glazes.

feldspar

A group of common rock-forming minerals containing silicates of aluminum, along with potassium, sodium, calcium, and occasionally barium. Used extensively in stoneware and porcelain bodies and in glazes as a flux.

downdraft kiln

A kiln designed so that the heat moves up throughthe firing chamber, down through the ware, then is vented into a stack (chimney) opening at the bottom of the kiln.

fettling knife

A long, tapered knife used for trimming ware and for cutting slabs.

opacifier

A material that causes a glaze to become opaque by producing minute crystals. Tin, zirconium, and titanium oxides are used as opacifiers in combination with various oxides.

earthenware

Pottey that has been fired at low temperature (below cone 2) and is porous and relatively soft. Usually red or brown in color. Used worldwide for domestic ware, glazed or unglazed.

maturing point (maturity)

Refers tothe temperature and time in firing at which a clay or glaze reaches the desired condition of hardness and density. Bothclays and glazes have differing maturing points, depending on their composition.

multipart mold

See piece mold