CERAMICS GLOSSARY
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 – 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.