Pottery Vocabularypottery Vocabulary
Pottery Vocabulary
Bat - Any slab used as a base for throwing or hand-building clay: also applies
to a trough used to dry slurry clay to the plastic state: usually made of
plaster, press board, plywood, or other porous material.
Bisque, Biscuit – Unglazed, but fired ware, usually accomplished in a low
temperature firing prior to a glaze fire; also applies to unglazed ware fired
high, as in porcelain bisque.
Body – A combination of natural clays and non-plastics, especially formulated to
have certain workability and firing characteristics.
Burnishing – Polishing with a smooth stone or tool on leather-hard clay or slip
to make a surface sheen; the surface will not stay shiny at temperatures above
2000 F (1100 C)
Casting – Process of forming shapes by pouring deflocculated liquid clay slip
into plaster molds for repetitive production.
Centering – Pushing a mass of clay toward the center with the centrifugal motion
of a potter’s wheel.
Ceramics – Art and science of forming objects from earth materials containing or
combined with silica, produced with the aid of heat treatment at 1300 F (700 C)
or more.
Clay- Earth materials formed by the decomposition of igneous rock; when combined
with water, clay is plastic enough to be shaped: when subject to red heat or
above, it becomes dense and rock-like.
Coiling, CoilBuilding – Age-old method of constructing hollow forms by rolling
and attaching ropes of soft clay.
Cones – Pyrometric cones, Orton or Seger brand; pyramids made of clay and glaze
constituents that bend at specific temperature. Cones are placed in the kiln
during firing to indicate the final heat; they are classified by numbers coded
to their softening point.
Engobe – A liquid clay slip colored with metallic earth oxides or glaze stains
applied to wet or leather-hard ware for decoration. Engobe can be covered by
glaze or used alone.
Extrusion – Forcing plastic clay through and auger or form, mechanically or by
hand, to change its shape; can be solid or hollow.
Firing – Heating in a kiln to the required temperature for clay or glaze, at
least to red heat, 1300 F (700 C). Bonfiring in a pit or on the ground.
Foot – Base or bottom of a piece.
Glaze – Glassy melted coating developed by chemicals and heat on a clay or metal
surface. Glaze provides decoration and color, prevents some penetration of
liquids or acids, and yields a matt or glossy, functional surface.
Greenware – Finished leather-hard or bone-dry clay pieces not yet fired; raw
ware.
Grog – Crushed or ground-up fired clay, purchased commercially or made by the
potter; used to reduce shrinkage, it yields texture; aids in even drying and
firing.
Hand-Building – The process of forming pieces without the use of a potter’s
wheel. Examples are pinching, coil building and slab building.
Kiln – Furnace for firing clay, slumping glass, or melting enamels; studio kilns
can achieve temperatures up to 2500 F (1370 C). They can be fueled
carbonaceously, organically, or electrically.
Kiln Furniture – Refractory slabs, posts, supports (called setters) for holding
ware in the kiln, handmade or purchased.
KilnWash – Half clay, half silica, mixed with water to coat kiln shelves.
Leather-hard – Cheese-hard stage which clay reaches before being bone-dry; stiff
enough to support itself, but still can be altered.
Luting – A method of putting together coils, slabs, or other clay forms in the
wet or leather-hard stage by cross-hatching and moistening; the same as scoring.
Matt – Dull, non-reflective surface; in the case of glaze, due to deliberate
composition or immature firing.
Mold – Usually a plaster form, single or multi-pieced, which will be used to
reproduce any number of accurate copies of the original model in clay or
plaster.
Pinching – Moving and shaping clay with the fingers.
Plaster – The mineral gypsum, with the chemical composition of calcium sulfate,
used for clay/mold reproduction and as a work surface.
Plasticity – Workability; clay is the only mineral having real plasticity,
meaning the ability to form into any shape, and to get progressively harder in
the same shape on being fired to 1300 F (700 C) and above. Other materials, such
as talc, can be said to have claylike plasticity.
Pottery – A loosely used term; often means earthenware or just any clay piece
that has been fired.
Pressing – Forming plastic clay in a plaster mold or other form, by laying it
against the mold face.
Resist – Wax, varnish, latex, or other substance applied in pattern on a clay or
glaze surface to cover an area while the background is treated by another
material or color.
Scoring – A cross-hatch and moistening method of putting together coils and
slabs in the wet or leather-hard stage; the same as luting.
Sgraffito – A design scratched through one surface to another.
Shrinkage – Contraction of clays or bodies in drying and firing, caused by the
loss of physical and chemical water and the achieving of molecular density.
Slab – Flat piece of clay from which shapes can be fabricated.
Slip – A suspension of ceramic materials in water; generally refers to casting
slip for molds; can mean a liquid clay engobe for decorating or a glaze slip.
Slurry – Thick suspension of one or more ceramic materials in water; usually
refers to slushy clay.
Throwing – The process of forming pieces on a revolving potter’s wheel from
solid lumps of clay into hollow forms.
Trailing – A method of decorating with engobe or glaze squeezed out of a bulb
from a small orifice or poured from a narrow lip.
Translucency – Ability to transmit scattered light, not quite transparent.
Transparent – Clear, like window glass; can be colored or colorless. Texture or
decoration instantly shows through a transparent glaze.
Wedging – Kneading clay to expel air and make the mass homogeneous for hand
processes.