CERAMICS VOCABULARY (revised 4-9-12)
1) Clay: A decomposed granite-type rock. To be classified as clay, the decomposed
rock must have fine particles so that it will be plastic. (free of vegetable matter)
(alumina & silica & water)
2) Primary clay: Clay found at its original site where the parent rock disintegrated.
3) Secondary clay: Clay that has been transported by water, ice, and natural
occurrences.
4) Earthenware: Low fire pottery, usually red or tan in color. (below cone 03)
(Lots of iron)
5) Stoneware: a high fire ware (above cone 6) with very little absorbency.
6) Composite: A mixture of clays combining heat resistant and shrinkage qualities
of various clays
7) Grog: Hard fired clay that has been crushed or ground to various particle sizes;
used to reduce shrinkage in such ceramics products as sculpture and architecture.
8) Plasticity: The quality of clay that allows it to be manipulated and still maintains
its shape without cracking or sagging.
9) Short: Describes clay that lacks plasticity (not enough moisture).
10) Leatherhard: The condition of the raw ware when most of the moisture has left
the body but when it is still plastic enough to be carved or joined.
11) Bone Dry: Clay that is completely absent of moisture, and therefore ready to be
fired.
12) Greenware: Pottery that has not been bisque-fired.
13) Bisqueware: Unglazed ware fired to a temperature sufficient to harden
but not mature the body.
14) Wedge: Kneading plastic clay with the fingers and heels of the hands in a rocking
motion: Forces out trapped air pockets and develops a uniform texture.
15) Slip: A clay in liquid suspension.
16) Scoring: Scribing or roughing up the surface of the clay prior to joining two
pieces.
17) Burnish: Using a smooth object to polish the surface of leather hard clay.
18) Sgraffito: Decoration achieved by scratching through colored slip or a glaze to
show the contrasting body color beneath.
19) Incising: Engraving a decoration into unfired clay.
20) Paddling: Striking the seam between two joined pieces of clay using a flat piece
of wood.
21) Luting: Attaching two pieces of leather hard clay with slip
22) Firing: Heating clay in a kiln to a specific temperature
23) Kiln: A furnace made of refractory clay materials for firing ceramic products.
24) Kiln furniture: Refractory shelves and posts upon which ceramic ware is
placed while being fired in the kiln.
25) Kiln wash: A protective coating of refractory materials applied to the surface of
shelves and kiln floor to prevent glazes from fusing the ware to the shelves.
26) Refractory: The quality of resisting the effects of high temperatures.
27) Pyrometric cone: Small triangular cones made of ceramic materials compounded
to bend and melt at certain temperatures, thus allowing the potter to know the
firing is complete.
28) Vitrification:The process of becoming glass-like. This is the last step in the firing
cycle, and occurs at different temperatures with different clays.
29) Shrinkage:Contraction of the clay in either drying or firing.
30) 8%-12%: The amount of shrinkage from moist clay to fired clay.
31) Thermal shock: A heated ceramic piece is required to cool too quickly,
causing cracking and splitting.
32) Oxidation: The kiln chamber contains an ample supply of oxygen.
33) Oxide: When oxygen combines with another element. Metallic oxides are often
used as coloring agents in the glaze.
34) Reduction Firing: Removing oxygen during the firing of certain glazes
35) Raku: Glazed, groggy earthenware; originated in Japan. Used for tea ceremony.
36) Coiled pottery:
A hand method of forming pottery by building up the walls
with rope-like rolls of clay and then smoothing over the joints.
37) Slab: A handbuilding method in which forms are created by joining flat pieces of
clay.
38) Glaze: A liquid suspension of finely ground minerals that is applied by brushing,
pouring or spraying. Glaze ingredients will melt together during firing to form a
glassy surface coating.
39) Engobe: A combination of colored slip and glaze used in coloring greenware or
bisqueware.
40) Throwing: Forming plastic clay on a potter’s wheel.
41) Sagging:
The condition of clay when there is too much water.
42) Foot: The round base of a pottery piece.
43) Bat: A disk or slab of plaster of paris on which pottery is formed or dried. It is
also used to remove excess moisture from plastic clay.
44) Embossing: A form of decorating in which slightly raised forms are added to the
clay
45) Relief: A sculpural form that is raised on one side and flat on the other.
46) Impressing: Decorating a clay piece but pushing a textured object
into the surface of the clay while it is still fairly plastic
47) Flux: is an element or compound used in clay bodies or glazes which lowers the
melt temperature of that clay body or glaze.
48) Flange: a projecting rim or collar on a piece that serves to hold it in place or give
it strength.
49) Lug: handles that are a kind of flattened knob attached to the side of pottery.