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HOBBY CERAMICS GLOSSARY OF
TERMS
When working with ceramics, it is advisable to become familiar with its
language. As with most any topic, there are terms relevant to ceramics that
may be unfamiliar or used differently for other subject matter.
Having a glossary of terms handy and becoming familiar with them, will ease you in reading about, talking about and actually working with ceramics.
Costly mistakes can be made by making
assumptions or through misunderstandings. So to help you as you your
exploration in the wonderful world of ceramics, please feel free to refer to
this listing of terminologies.
Airbrushing - the process of applying paints to an item using an air
compressor and a spray gun.
Antiquing - the process of applying a paint and wiping it off, leaving
varying amounts of color in the detail or design of an item.
Banding Wheel - a flat surface that sets on a revolving base used to turn
items easily while painting or decorating
Bisque - aka bisq - a clay item that has been fired to mature hardness which
removes all moisture from the piece creating an adequate surface to apply
glazes and paints.
Casting - aka slip casting - the process of pouring ceramic clay slip into a plaster mold and
then draining it to leave a formed item.
Ceramics - the art of creating items out of clay. Includes the field of
pottery.
Ceramist - any person dabbling in the practice of creating ceramic items.
China Paint - a concentrated paint/color pigment applied to fired, glazed
china or porcelain bisque which is then re-fired to harden and fuse to the
item.
Clay Puzzling - a technique of using ropes of extruded clay to create an
fretted look.
Cleaning - the process of removing seams and flaws from greenware.
Cone - specially formulated clay rods designed to melt at specific
temperatures. Used to control firing temperatures of kilns.
Crawling - a flaw in a fired glaze where the glaze pulls away from the
surface of the item leaving an area of bare bisque.
Crazing - a flaw where glazes have a web-like cracking in the surface of the
finished piece. Prevalent in vintage ware, though a continuing problem with
modern ceramists.
Decals - colored painted designs on a thin film like base which are applied
to fired glaze surfaces and then re-fired to fuse to the surface of the
item. The filmy base is fired away just leaving the design.
Deflocculant - a chemical such as sodium silicate or sodium carbonate which
reduces the amount of water needed to make slip fluid - consequently
reducing shrinkage after it is applied to the clay.
Drybrushing - The process of using a stiff bristled dry brush and small
amounts of paint to gradually add color to a base-coated item through
dragging the brush cross-wise over the raised details of the design, or by a
pouncing to create a softer cloth-like finish.
Dryfoot - the practice of leaving the bottom of a ceramic piece unglazed so
that it can be fired standing on the kiln shelf without being stilted. Some
molds are specifically designed to produce ware that can be dryfooted.
Stoneware and porcelain are always dry footed.
Earthenware - a low-fire blend of clay, usually porous, used worldwide for
domestic ware.
Engobe - a colored decorating slip, often opaque. Concentrated color is
added to liquid slip and then applied to greenware before firing. Many
underglazes are Engobes.
Extruder - a tool used to press clay into long strings or strips of varying
designs.
Fettling - trimming the spare clay from the mold pour area before removing
the greenware piece from the mold.
Fretting - the art of cutting intricate designs in leather hard
castings/clay leaving open cuts completely through the thickness of the clay
and covering the majority of the item.
Glaze - liquid composed primarily of silica which creates a glassy coating
that is fused onto the surface of the clay when fired. Glazes may be matte
or glossy, depending on their chemical makeup.
Glazing - the process of applying glazes to items and then firing them
Greenware - any unfired clay object.
High-Fire - the firing of a clay body to the range of cone 2 up to cone 13.
Ware fired at cone 2 and up is usually referred to as Stoneware.
Incise or Re-incise - the process of cutting into a clay body to create a
design or to refine already established details.
Kiln - the oven used to fire or bake clay or glass items.
Kiln sitter - the part of a kiln that holds the firing cones and gauges the
temperature then automatically shuts off the kiln
Lace Draping - the process of dipping cotton lace into slip and applying it
to an unfired item and then firing it. The lace burns away, leaving the
delicate clay design.
Low-fire - the firing of a clay body to the range between cone 015 and cone
1. Ware fired at low temperatures is usually referred to as Earthenware.
Majolica - a glaze technique of applying an opaque satin/matte glaze to
bisque, then colors are painted on this and fired to fuse the two together
and create a bright, colorful surface.
Maturation Point - the firing point at which a clay body reaches its maximum
hardness and non-porosity.
Mold - a plaster form which is used to shape and model clay.
Opaque - solid color, not transparent in any way. (You cannot see through an
opaque color!)
Open Pour Mold - a one piece mold that can be used for casting slip or
pressing clay into it.
Overglaze - colored paint-like surface decorations which are applied on top
of a previously fired glazed piece which is then fired again at very low
temperatures. Most common are gold, mother of pearl, decals and china paint.
Oxidation firing - a firing process which takes place in an atmosphere of
ample oxygen in a kiln to produce complete combustion of the contents. This
allows the metals in clays and glazes to produce their oxide colors. Bright,
clear low-fire colors are associated with glazes and clays fired in an
oxidation atmosphere.
Peephole - the hole/s on the side of a kiln used to view the inside during
firing and to allow the exchange of oxygen and gasses during the firing
process.
Pinholes - a small pore in a glaze surface which is caused by escaping
gases.
Plasticity - the ability of damp clay to readily change shape without
cracking.
Polished Underglaze - the process of rubbing damp underglazes to a sheen
prior to firing them.
Porcelain - a blend of clay, usually white, which is fired to a high
temperature at which the clay body vitrifies and becomes translucent.
Pour gate - the opening of a plaster ceramic mold where the slip is added.
Press mold - a mold used by pressing clay into it.
Reduction firing - a firing process that reduces the proportion of gas to
oxygen, forcing the oxygen-starved flame to attack the oxides in the clay
and glazes of the ware. Color changes during the process because there isn't
sufficient oxygen in the kiln for complete combustion and carbon dioxide in
the kiln combines with the oxygen in the clay body and glaze.
Reverse Dry-brushing - the same as dry-brushing except color is built from a
dark base and each layer is increasingly lighter. The lightest color is the
last, top most layer.
Sculpt - the process of working with clay and creating objects without the
use of a casting mold.
Semi-Transparent - the ability to see through color slightly with some
distortion. In the case of glazes, color deepens in crevices and details of
item and is lighter on the high points.
Semi-Opaque - Dense color that has a very slight translucency
Sgraffito - the method of producing a design on ceramics by incising the
outer coating of slip or glaze to reveal the base of a different color. A
surface decoration drawing technique in which coats of contrasting
underglazes or colored slips are applied to clay, then scratched off with a
fine-pointed knife or stylus to reveal layers beneath the surface.
Slip - liquefied clay used for casting ceramic molds. A finely sieved
mixture of clay and water, either white or colored, which can be applied to
clay surfaces in one or more layers.
Slip Trailing - the method of decorating ware by squeezing thickened slip
from a bottle or nozzle onto the surface of the pottery to create raised
lines.
Spare - the clay waste which is trimmed from the pour gate of a mold before
the greenware is removed from the mold.
Spray fix - a clear spray used to give a protective finish to stained,
non-fired items.
Stain - most commonly referring to non-fired painting techniques.
Stoneware - a blend of clays, usually brownish in color, which is
characteristically fired to a high temperature at which the clay body
becomes vitrified and non-porous, but not translucent.
Terra cotta - a type of clay whose name translates as 'baked earth' ranging
in color from yellow to orange to red.
Transparent - clear or color you can see through. Transparent glazes
generally 'settle' into detailed areas, making them slightly darker and
bringing the detail to view.
Underglazes - a liquid containing a clay or chemical base with colored
agents which are used under a glaze. Most commonly indicates colors used to
decorate greenware and bisque before a protective clear glaze is applied.
Viscosity/viscous - the fluidity of ceramic slip.
Vitrification - the point at which a clay body or glaze reaches a glassy,
dense, hard and non-absorbent condition.
Wax resist - a wax emulsion especially created to repel underglazes and
glazes applied over them. The wax is burned off during firing, revealing the
designs protected from other paints applied around them.
Wet-brushing - similar to dry brushing only using slightly larger amounts of
paint, thereby enhancing the color at a faster rate resulting in filling in
the design details somewhat more than the drybrushing technique
Wetware - any clay item that is freshly removed from a casting mold or still
wet.