Acrylic paint
An emulsion of pigment to form a fast-drying paint that is water-soluble but permanent after it dries; useful primarily for cold finishes.
See Cold finish
Air-brushing
Technique for applying a thin liquid slip, glaze or stain in nebulized form to the surface of a ceramic work by means of an air-spray device.
See Air-compressor, Glaze, Slip, Spraying, Stain
Air-compressor
Device for providing high-pressure air-spray through a jet nozzle for the purpose of applying nebulized liquid slip, glaze or stain to the surface of a ceramic work.
See Air-brushing, Glaze, Slip, Spraying, Stain
Altering form
After a clay piece has been formed on a potter’s wheel, its uniform shape and configuration can be modified by hand or with simple instruments. This process is called altering. An example is the formation of a pouring lip by pinching the clay at the rim of a vessel.
See Impressing, Incised decoration
Amaco velvet underglaze
A versatile semi-translucent, lead-free underglaze that yields two different finishes when left unglazed, velour or velvet. Colors intensify when subsequently covered with gloss glaze.
See Glaze, Gloss glaze, Overglaze, Satin glaze, Underglaze, Velvet glaze
Amorphous
Term applied to materials like glass which have no regular crystalline structure. Clay becomes amorphous when subjected to vitrification at very high kiln temperatures.
See Clay, Kiln, Vitreous, Vitrification
Anvil
See Paddling
Banding wheel
A rotating wheel for holding a ceramic work in place and rotating it while it is being decorated with a spray of thin liquid colored glaze. The wheel can circle around slowly or quickly depending on the artist's objective. The less the work is handled before firing, the better the piece will be because handling can stress the clay and smear the surface designs. The banding wheel has concentric circles on the head to allow for easy centering. The banding wheel is particularly useful for easily and consistently spraying a ceramic vessel while it spins around.
Baroque gilding
Gilding is the application of gold leaf to a surface. The gold can be burnished to a high gloss or left satiny without burnishing. Gilding is an ancient art, but grew more ornate and sophisticated from the 17h Century Baroque period and subsequently.
See Gilding
Bas-relief
See Relief
Bisque
A ceramic work that has been fired for the first time at high temperature to convert it from the greenware state to a hard condition, prior to glazing. The temperature to which it is exposed in the kiln is not enough to produce vitrification. Firing makes the piece hard and resistant, but it remains somewhat fragile and porous, although not as fragile as in the greenware state.
See Bisque firing, Drying, Firing, Greenware state, Leather-hard state, Kiln, Vitrification, Wet State
Bisque firing
Initial kiln firing in which clay hardens without vitrifying. It is porous, but no longer capable of softening in water.
See Bisque, Firing, Kiln, Vitrification
Bone dry
The driest state of raw clay in the sequence of wet, leather-hard and bone dry (also called greenware). In the wet phase, the clay is too soft and unstable to maintain its shape; in the leather-hard phase, it is wet enough for altering and other modifications; in the bone dry phase, it is too brittle to avert chipping, but ideal for safe kiln firing.
See Bisque, Drying, Greenware state, Leather-hard, Wet state
Calipers
An adjustable measuring instrument consisting of two curved parts joined at one end where they are hinged. It is used for measuring the internal or external dimensions of an object, such as the diameter of an opening for making a fitted lid.
Cast
See Mold, Slip, Slip cast molding, Slurry
Ceramic
Hard, porous and brittle heat-resistant material made by firing preworked clay in a kiln at high temperatures.
See Clay, Earthenware, Porcelain, Stoneware
Ceramicist
Artist who creates three-dimensional clay-based art works in the form of hard, permanent, durable ceramic creations.
Ceramics
A term of art for the technique of making objects with fired clay. While clay has been integral to fine art ceramics since prehistoric times, it also has a long history of use in decorative, industrial and applied arts.
China paints
Low-temperature colored glazes applied over previously fired high-temperature glaze. They provide greater detail and brighter colors, but are susceptible to surface abrasion.
See Glaze
Chuck
A temporary device for holding a ceramic piece in place over a wheel while it is being tooled or trimmed. It is made of a thrown base of wet or bisque-fired clay, in the form of a cylinder open on both sides.
See Trimming, Wheel throwing
Clay
A naturally-occurring soft, earthy material formed from physical breakdown or chemical weathering of rocks. It is also made by crushing and pulverizing fine-grained rock, such as feldspar or granite. It is slippery and plastic when wet so it can be worked into art forms. Drying in air gives it a leather-like texture. It is converted to very hard rock-like consistency byfiring to high temperatures in a kiln.
See Ceramic, Earthenware, Leather-hard state, Porcelain, Stoneware
Clear glaze
Colorless, transparent glaze.
See Glaze, Gloss glaze, Matte glaze, Satin glaze
Cold finish
Application of various finishing touches to a ceramic work to complete it after the final kiln firing. It includes a wide variety of techniques including use of enamels, gilding, acrylics, colored waxes, colored pencils, pastel, beads, gemstones, and other materials.
Cone
A small slender pyramid made of clay and glaze intended to melt and bend at specific temperatures. It is used in a kiln to determine when the optimal kiln temperature for a given ceramic piece has been achieved. Cones are designed by mixing combinations of clay and flux materials so they respond to a narrow range of temperatures at which they reliably bend, making them accurate means for assessing kiln temperature. Also called pyrometer or pyrometric cone.
See Cone temperature
Cone temperature
In practice, three cones are placed within the kiln firing chamber within view at the peep hole. Each is expected to bend at a different temperature during firing, bracketing the optimal temperature for a given ceramic object. When the cone sensitive to lower temperature melts, it indicates that the kiln temperature is approaching optimal. When the optimal-temperature cone melts, the firing ends and the kiln is allowed to cool. If the cone that indicates temperature exceeding optimum should bend, it demonstrates that the piece has been subjected to excess heat in firing.
See Cone, Firing, Kiln, Peep hole
Crazing, Crackling
A network of fine hairline cracks in the glazed surface of a fired ceramic work. It can be intentional, as in Raku firing, or an adverse consequence of a thermal expansion mismatch between the glaze coating and the clay body during cooling. Crackling is the term usually reserved for desired crazing done deliberately for decorative effect; while crazing applies to faulty, unintentional fractures in glazing.
See Raku firing, Raku ware
Cut Stencil Silk-Screening
A silk-screening technique that uses a green film, called S3S Stay-Sharp Lacquer Film. A design is cut into the film. This is a laborious method that precedes application of the film to a silk-screen frame, allowing it to be used in a method similar to photo silk-screening. Ink is applied to the film surface and spread by means of a squeegee across the frame. The design on the film is transferred to flat slabs of clay placed under the frame.
A special modification of this technique, which I invented, permits application of a silk-screened image to an irregular surface. Because the application of silk-screening is limited to objects with a flat surface, a special procedure had to be devised. To achieve this, I make a cut stencil silk-screen and adhere it to the silk-screen frame with adhering fluid in the usual manner. But then I cut it right out of the frame with the film adhered into the silk-screen. I then cut it to precisely fit the flat part of a ceramic object, such as a plate or bowl. These cut segments are placed directly on a desired surface and, once in place, the silk-screen image is air-brushed on, rather than applied by using a squeegee.
See Air-brushing, Clay slab, Image transfer, Photo silk-screening, Silk-screening, Silk-screening on nonplanar surfaces
Decal
Image transfer is facilitated by embedding images on inorganic material, consisting of powdered ground glass, that fuses permanently with the surface of a ceramic work during kiln firing. Because decals are created in multiples, they can be used to embellish clay works without the need to repeatedly draw or paint the same design.
See Image transfer
Decoupage
A technique for decorating the surface of an object by gluing cut-outs of various flat materials, such as paper or fabric, and then applying multiple layers of varnish or lacquer. From the French decouper, to cut out; also called Japanning.
Dremel drill
A device for drilling tiny holes into ceramic surfaces, often arranged in intricately-designed patterns. It uses diamond-tipped drill bits which resist damage from the hard substance they have to pierce.
Drying
Act of allowing wet clay to dessicate over time so that it can be worked on in its leather-hard state or kiln fired in its bone dry state. Drying process can be accelerated by using a hot-air gun. Wet clay can be rolled out, bent, modeled, thrown, and otherwise worked into forms; in a somwhat drier state (but not yet leather-hard), its surface can be decorated with silk-screening; in its still drier leather-hard state, carving, incising, altering, joining and trimming can be done; in the bone dry or greenware state, the clay is ready for optimal kiln firing.
See Bisque, Bone dry, Greenware state, Hot-air gun, Leather-hard state, Wet state
Earthenware
A type of clay used for pottery since ancient times. It is of variable composition. It is fired at relatively low temperatures of 1,830-2,010°F (990-1,100°C) or cones 02-06. It is not as strong or resistant to chipping as stoneware, but has the advantage of being lower in cost and easier to work with. Because it is so porous, vitreous glazing is required to make it functionally water tight.
See Clay, Porcelain, Stoneware, Vitreous
Embossing
See Impressing.
Engobe
Decorative underglaze in the form of a slip containing less raw clay content for application to thoroughly dried greenware and bisque-fired clay. It is intended to reduce shrinkage during the drying period.
See Glaze, Overglaze, Slip, Underglaze
Extruded clay
Clay strips that are formed by an extruder in various designated lengths and shapes according to artistic need.
See Extruder
Extruder
A device that forces plastic raw clay through a die to produce extruded clay strips in a variety of shapes.
See Extruded clay
Fimo clay
A commercially available polymer modeling clay that can be baked to mature at kitchen oven temperatures of 265°F (130°C). It comes in a number of colors. When fired, it is hard in consistency and water resistant.
Firing
The process by which preworked clay is converted from its soft greenware state to its hard ceramic form by exposure to very high temperatures in a kiln.
See Ceramic, Greenware state, Refiring
Foot
Treatment of the undersurface of a ceramic plate or other object that serves to provide balance and stability to the work. Created by the process of trimming.
See Trimming
Gilding
See Baroque gilding
Glaze
Colored and clear silicate coating that forms a glass-like coating by fusion under high heat. It is a powdered ceramic material prepared in water suspension. It melts smoothly and bonds to the clay surface during kiln firing. It is a vitreous coating with added flux to lower its melting point and metallic oxides for color. It is impervious to damage from the high temperatures of the kiln. Glazes are applied to bisque for purposes of decorating a ceramic work or making it water tight.
See Bisque, Gloss glaze, Matte glaze, Satin glaze, Vitreous, Vitrification
Gloss glaze
Glaze that retains its shiny reflective glossy surface appearance after firing.
See Glaze, Matte glaze, Satin glaze
Glossification
See Vitrification
Greenware state
Clay that has been worked and allowed to dry in air beyond leather hard, but not yet fired. Clay is most fragile in this state. Green or greenware refers to bone dry, unfired clay with no moisture left.
See Bisque, Bone dry, Drying, Leather-hard state
Hand building
The process of forming plastic ceramic objects from raw clay by the artist’s hands alone or with simple tools, unassisted by use of the potter’s wheel. Techniques in hand building include altering, pinching, coiling and slab construction, among other types of modification of the clay structure.
See Slab building.
For illustrated details see also Technical notes: Hand building
Hollowing
A technique for removing the internal core of clay in the leather-hard state of drying for purposes of creating a cavity in a ceramic work and making the walls uniformly thick. This essential step is needed to prevent irreparable damage that is likely to occur from exposure to high temperatures during the kiln firing process.
See Drying, Kiln firing, Leather-hard state
For illustrated details, see also Technical notes: Hollowing
Hot-air gun
Device for accelerating the drying process by high-heat delivered by a hand-held heating unit.
See Drying
Image transfer
The process by which images are applied to clay. The image can be in any form, including drawing, photograph, painting, print, stencil, photocopy, among others. The image is transferred onto the surface of the clay by any number of techniques, such as press mold, silk-screen, photo silk-screen, stenciling, decals and mono printing.
See Cut stencil silk-screen, Decal, Photo silk-screen, Press mold, Silk-screen
Impressing
A method of decorating clay by pressing a textured or patterned material or object into the clay surface while it is still in its wet state. Also called Embossing.
Incised decoration
A method for treating the surface of a ceramic work by means of a sharp instrument to drag, cut or carve shallow lines into leather-hard clay in the greenware state. It is a technique in use since ancient times.
See Greenware state, Leather-hard state
Iridescent luster
Keraflex porcelain
A commercially available clay-like substrate for creating two- and three-dimensional ceramic art objects. It is manufactured in very thin sheets. The sheets can be cut, bent or folded, and used for hand building. The surface can be modified in various ways, such as embossing. When fired initially to cone 10, this material virtrifies to become a thin translucent porcelain-like structure. In this state it can be glazed and otherwise embellished just like porcelain clay. In another form, Keraflex Porcelain Canvas comes in various flat tile sizes. The tiles can be embellished by glazing. The glaze determines the kiln temperature needed for kiln firing. The canvas has to be warmed before glazes are applied; warming is facilitated by working with the material on a special warming tray. One of the special attributes of Keraflex tiles is that they do not warp the way porcelain tiles do.
See Ceramic, Clay, Earthenware, Porcelain, Paperclay, Stoneware
Kiln
A special oven or furnace used to fire clay at high temperatures. It consists of several parts: firebox, flue, dome and exhaust vent. Raw clay forms are placed in the firing chamber, kept separated from direct contact with the heat source. As contrasted with open firing, kiln firing uses hot gases to achieve its effect. While it is therefore slower and less economical, it is advantageous in allowing finer and more delicate works to be fired at much higher temperatures, giving the resulting ceramics a generally higher quality.
See Firing, Refiring
Kiln furniture
Prefired ceramic structures, made in a variety of sizes and shapes, that are placed within the kiln for purposes of supporting kiln shelves and for propping clay objects that are being fired. They are used to prevent the object from being damaged during the firing process. Kiln furniture can be fired up to cone 10.
Lace draping
A technique based on a lost art method, revived and refined for modern ceramic art work, in which cotton lace is dipped into thin slip and draped on a ceramic object during construction. When dried and fired to high heat in a kiln, the lace is incinerated, leaving the residual delicate clay structure in place.
See Firing, Kiln, Slip
Leather-hard state
The state reached after worked clay has been allowed to air dry to the point of stiff firmness, but not complete dryness. In this condition, it feels and behaves like leather. Most of the water content has evaporated, shrinking the work somewhat by compacting the clay particles. It is the state in which structural surface treatments, such as carving or incising or altering, can be done because the clay is still moist enough to permit them without chipping. Joining and trimming clay are done in this state as well as slip decoration. This is the best state of clay for slab construction because the stiff clay slabs remain structurally upright and do not bend as wet clay does.
See Altered form, Bisque, Greenware state, Impressing, Incised decoration, Slab building, Slip, Slurry, Wet state
Luster glaze
A metallic overglaze finish. It is painted on the surface of a ceramic piece in liquid form, as a metallic salt in an organic binder, over a previously-fired glaze. It can also be sprayed as a metallic salt dissolved in water into the kiln onto objects at low red heat during the cooling cycle or in a separate firing.
See Glaze
Majolica technique
Tin-glazed earthenware made opaque by the addition of tin oxide to lead glaze. The glassy dense white glaze developed by firing serves as a strong complementary ground for the overlying hand-painted surface decorations. A second firing makes the glaze interact with the metal oxides in the overglaze to create deep translucent colors typical of this form. The method has been in use to produce white lusterware pottery since the Italian Renaissance. Also spelled maiolica.
Mandala design
A concentric geometric art depiction symbolic of the universe, used for healing, self-discovery and personal transformation. It is of Hindu and Buddhist origin as an aid in meditation, Incorporating color, balance, repetition and symmetry.
Matte glaze
A glaze that is nonreflective with a dull, nonglossy surface when fired. A slow cooling period is usually required to prevent it from turning shiny and reflective.
See Glaze, Gloss glaze, Satin glaze
Mid-range stoneware
A form of stoneware clay that is optimally fired at moderate cone temperatures, as contrasted with low-range earthenware or high-fired porcelain clay.
See Clay, Cone temperature, Earthenware, Firing, Porcelain, Stoneware
Mold
A preformed object used in the hand-building process to create a shape or form. It is made of hardened plasters or latex. Clay can be impressed into it or slip cast can be poured in it to shape a structure. When set and dried, the cast becomes an exact negative replica of the mold.
See Hand-building, Slip, Slip cast molding, Slurry
Mother of pearl luster
Luster glaze made of an emulsion of nacre derived from a composite made from the inner shell of mollusks. It provides an iridescent coloration to a ceramic surface.
See Iridescent luster, Luster glaze, Opalescent luster, Pearlescent luster
Opalescent luster
A coating applied to a ceramic work to provide surfaces with shimmering milky iridescent reflections, similar to pearl, mother of pearl or opal. Also called pearlescent or iridescent luster.
See Luster
Overglaze
Any surface decoration applied over a glaze surface. It is usually an oxide wash applied over a raw glaze surface before glaze firing. It may also be a glaze application used at lower temperatures over a previously high-fired glaze surface.
Oxidation
Firing process that provides an ample supply of oxygen to the ceramic work in the kiln. Usually achieved in an electric kiln.
See Firing, Kiln, Reduction kiln
Paddling
Technique for shaping, thinning, flattening or smoothing leather-hard clay by beating it with a wooden paddle or beater. The paddle can be textured. The process often involves using an external paddle against the counterpressure of a rounded wooden or clay anvil placed internally.
Paperclay
A type of clay mixed with processed cellulose, often paper. The clay base can be of any variety, including earthenware, terra cotta, stoneware, porcelain or bone china. It is fired in the same way as other clays. Less shrinkage occurs in the drying stage than with conventional clay. Strong joinery is possible. Objects made with paperclay are stronger, more porous, easier to work with, and more resistant to breakage.
Patina
The tarnish that forms on the surface of bronze and similar metal works. It is produced naturally by oxidation or other chemical process affecting the surface over time. Patina is often deliberately added by artists to enhance the original design and decoration of an art piece or to simulate antiquity in newly-made objects.
Pearlescent luster
Peep hole
A small aperture in the wall or door of a kiln. It is used to observe the contents during a firing. Primarily used to determine the condition of the temperature cones so as to ensure optimum firing temperatures and to examine the state of the objects being fired. Also called spy hole.
See Cone, Cone temperature, Firing, Peep hole plug
Peep hole plug
A heat-resistant ceramic figure, often decorated, made to snugly fit the peep hole in a kiln. It is kept in place in the peep hole between observations during firings to prevent heat loss.
See Peep hole
Photo silk-screening
Adaptation of silk-screen printing technique in which a photographic image is used to create the stencil. The image is first transferred to clear acetate, which is laid over a screen (mesh) that has been treated with a light-sensitive material. Exposing the screen to strong uniform light reproduces the photographic image on the mesh. The mesh is then used as the stencil in the silk-screen process.
See Cut stencil silk-screening, Silk-screening, Silk-screening on nonplanar surfaces
For illustrated details, see also Technical notes: Photo silk-screening
Plaster
A white powder of mineral gypsum, calcium sulfate, mixed with water to form a paste that hardens quickly as it dries. It is used in ceramics to make work surfaces and molds for reproducing clay works. Also called plaster of Paris.
See Engobe, Mold, Wedging board
Porcelain
A form of white stoneware clay that is hard, fine-grained and nonporous. It is often translucent and white in its unglazed form. The mineral composition is kaolin, quartz and feldspar. It is fired to high kiln temperatures above 2,400°F (1,350°C) or cone 11.
See Ceramic, Clay, Earthenware, Keraflex, Paperclay, Stoneware
Potter’s wheel
A rotating device for making pottery forms from clay. It may be foot powered or electrically operated.
See Wheel throwing
Press mold
Process by which raw clay is impressed into a preformed mold and allowed to set and air dry to the greenware state so as to create an exact negative replica of the shape of the mold.
See Greenware state, Mold
Pulling clay
Technique for producing a long strip or roll of clay, often for use as a teapot handle. A small mound of clay is shaped into an oblong and, with water added, it is carefully elongated by pulling, similar to pulling taffy, so that the clay gradually softens and stretches.
Pyrometric cone
See Cone
Raku firing
A low-temperature (about 1,800° F or 980° C) process of Japanese origin for firing raw-glazed earthenware ceramics. When the fired work reaches glowing hot maximum temperature, it is removed from the kiln with tongs and then placed in a combustible material such as paper or straw. The smoke and fire created by combustion reacts with the glaze to create unpredictable surface patterns.
See Crazing, Firing, Kiln, Reduction kiln, Raku ware
Raku ware
Ceramic works, usually fragile and porous, produced by Raku firing. After the piece is removed from the kiln, the interstices in the crazed glaze are enhanced by smoking during the cooling period to embed carbon black.
See Crazing, Raku firing
Reduction kiln
A fuel-burning furnace with an atmosphere containing insufficient oxygen to ensure complete combustion of the fuel, thereby exposing fired works to unoxidized carbon and hydrogen. Firing in a reduction kiln alters the appearance of both the clay and the glaze.
See Firing, Kiln
Refiring
Sequential technique for repetitive firing of a ceramic piece using progressively lower kiln temperatures to avoid altering or harming previously fired glazes.
See Firing, Kiln
Relief, Relief sculpture
A sculpture in which the modeled form is raised above (or lowered below) the flat background surface. Three forms include bas-relief (low-relief), which is a shallow projecting image, high-relief, the more prominently protruding work, and sunken-relief, the work lowered into the flat surface.
Satin glaze
A glaze with a degree of reflectance between dull non-reflective matte glaze and shiny fully reflective gloss glaze.
See Glaze, Gloss glaze, Matte glaze
Score and slip
Technique used for joining two pieces of leather-hard clay together. It consists of three steps: First, the sites to be joined or adhered are scored, that is, the edges are roughened. Second, the parts are slipped, that is, the sites to be joined are moistened with slip, used as if it were glue. Third, the pieces are pressed and held together.
See Greenware state, Hand building, Leather-hard state, Slab building, Slip, Slurry
For illustrated details, also see: Technical notes: Hollowing
Sculpting, Sculpture
Process of creating a three-dimensional work of art by various methods, including carving or modeling. In ceramics, sculpting is done primarily on clay in the wet or raw state, although it can also be further worked, by carving for example, in the drier greenware state. Sculpting is the most spontaneous and free-form method of constructing art objects in clay, beginning simply with a mound of clay and manipulating it with one’s hands to make forms and modifying it further with simple sculpting tools for more detail work. Bits of clay are added as needed. If the work becomes large and unwieldy, it can be divided so that each half can be individually carved out; the sections are then joined together by scoring and slipping method.
See also Altering form, Greenware state, Hand building, Mold, Paddling, Press mold, Relief, Score and slip, Slab building, Slip cast molding, Wet state
Sgraffito
A decorating method achieved by scratching or carving through a layer of previously-applied slip or glaze. It is done to expose the underlying contrasting clay coloration prior to firing. From the Italian scratch.
Silk-screening
A printing technique in which a finely-woven fabric, called mesh (originally of silk, but currently nylon or polyester), is stretched across a frame and used to support an ink-blocking impermeable stencil. The stencil is a negative of the image that is to be printed with open spaces where ink will appear. The open areas in the stencil allow transfer of ink or paint onto a substrate. A roller or squeegee is moved across the screen stencil forcing ink past the mesh threads onto the printing surface so as to print the desired image. Also called serigraphy or screen-printing.
See Cut stencil silk-screening, Photo silk-screening, Silk-screening on nonplanar surfaces
Silk-screening on nonplanar surfaces
Silk-screening has been limited to flat surfaces heretofore. An innovation of mine permits silk-screening on surfaces that are not flat. The technique involves wetting the back of a clay slab upon which an image has been silk-screened in the stiff, almost-dry leather-hard state. Wetting serves to revert the piece to its more flexible and pliable wet clay state so it can be worked on by modifying its shape as the artistic design might require without damaging or distorting the silk-screen image.
See Cut stencil silk-screening, Photo silk-screening, Silk-screening
For illustrated details see also Technical Notes: Silk-screening on Nonplanar Surfaces
Sintering
Solidification process that occurs when clay is kiln-fired at relatively low temperatures. Particles within the clay stick together to form a hard mass. With still higher temperatures, the strength of the bond that forms between refractory particles increases, enhancing structural integrity, but still leaving the clay porous. Clay that is low-fired to bisque state are sintered but not vitrified.
See Bisque, Clay, Firing, Kiln, Vitrification
Slab
Clay piece that is pressed or rolled flat for use in hand building.
See Hand building, Slab building
Slab building
A hand-building technique that involves forming and joining flat slabs of wet clay to create a three-dimensional ceramic art object.
See Hand building, Wet state
For illustrated details see also Technical notes: Hand building
Slip
Clay mixed with water to a semiliquid viscid suspension, about the consistency of heavy cream. It is applied as a surface treatment for ceramic works in their leather-hard state for purposes of casting, decoration to affect color and texture, or functionality, such as sealing the surface to reduce permeability to fluids. It can be applied by dipping, pouring or painting. It can also be used by casting into plaster molds to create ceramic forms. Clay slip also serves as the glue for joining clay slabs in the process of scoring and slipping.
See Mold, Score and slip, Slip cast molding, Slurry
Slip cast molding
A technique for creating a three-dimensional mold from plaster. First, a complex plaster mold is made. Second, slip is poured into it. Finally, when the slip has set to a hard consistency, the two- or three-part mold is removed, leaving a finished solid or hollow ceramic piece.
See Mold, Slip, Slurry
Slumping
Collapse of a ceramic object during firing at very high kiln temperatures that exceed the temperature needed for the optimal vitrification process so that the work sags, sinks, melts, deforms or puddles.
See Kiln firing, Vitrification.
Slurry
Clay mixed with a small amount of water to form a very thick clay slip. It is often used for joining slabs of clay after the surfaces have been scored.
See Score and slip, Slab, Slab building, Slip
Soda firing
Atmospheric firing technique in which a solution of soda (sodium bicarbonate, called baking soda or soda ash) is introduced by spraying into kiln ports at high temperature of 2,350°F (1,290°C) or cone 6. The soda vaporizes to combine with the silica in clay so as to create a glaze on the surfaces of ceramic works loaded within the firing chamber.
See Firing, Glaze, Kiln
Soft-cut technique
A printmaking method originally using incised linoleum for the template. Commercially-available Soft-Kut was adapted by me after much experimentation for designing patterns in clay. It serves well as a medium for press mold because it is softer and easier to cut.
See Image transfer, Mold, Press mold
Spraying
Application of a liquid slip, glaze or stain using mechanized air-spray equipment. It provides a smooth glaze coating, but avoids pooling of glaze in surface recesses.
See Air-brushing, Air-compressor, Glaze, Slip, Stain
Spy hole
See Peep hole
Stain
A liquid ceramic colorant made of powder ground from fired oxides or combinations of oxides and opacifiers for use as transparent or opaque glaze, engobe, slip or color mix for clay. In water suspension, stain can serve for overglaze brushwork or as a patina on unglazed clay.
See Engobe, Glaze, Slip, Slurry
Stencil silk screening
See Cut stencil silk-screening
Stoneware clay
A type of clay that is fired at high temperatures to produce hard and durable ceramic objects. Fired at temperatures of 2,200-2,400°F (1,200-1,350°C), the equivalent of cones 5-11.
See Cone, Cone temperature
Tagboard template
A template made of tagboard, a strong form of cardboard, for use as a guide in making clay slabs into prefigured shapes.
See Template
Teabag
Designation of Meryl Ruth’s ceramic works in which functional teapots are created in the form of handbags.
Teapet
Coined word for Meryl Ruth’s ceramic art pieces that incorporate pets and other animal forms as an integral design element.
Template
Master mold or pattern cut in cardboard or other material with a prefigured shape. It is used as a guide for rolling out clay and cutting it into the desired pattern. Also called pattern piece.
See Tagboard template
Terra cotta
A form of low-temperature ceramic clay that is used primarily for making pottery and tiles. Products made of terra cotta are durable, but porous. Terra cotta fires to a red-brown color because of its high iron content. From the Italian baked earth.
Terra sigillata
Ultrarefined clay slip that provides a soft sheen to the surface of a ceramic object to which it is applied. It can also be polished or burnished while damp to give it a high gloss. Its long history reflects use in ancient times.
See Glaze, Slip, Slurry
Throwing
See Wheel throwing
Tooling
See Trimming
Trimming
The process by which the bottom of a plate or vessel is finished on the potter’s wheel. After the piece has been thrown, it is allowed to dry somewhat to set up to the leather-hard state. It is returned to the wheel face down, where trimming tools are used to carve off excess clay on the bottom to shape and reveal a lovely foot that matches the structure of the ceramic object.
See Ceramic, Leather-hard state, Potter’s wheel, Wheel throwing
For illustrated details, see also Technical note: Trimming
Trompe l'oeil
A style of highly realistic, detailed painting in which the senses are tricked into perceiving the flat two-dimensional image as a three-dimensional illusion. From the French for “deceives the eye.” Although the technique was revived in Baroque times and more recently popularized (by a wide range of artists from Tiepolo and Peale to Dali, Harnett and Magritte, and latterly to Latzke and Orosz, among many others), it actually originated in ancient Greek and Roman painting and mosaic works. Synonymous with photorealism.
Underglaze
Colored slip that is applied to thoroughly dried greenware or bisque-fired objects. Formulated to have low shrinkage on drying. A wide palette of colors is available for low-fire use. Many will survive high-fire exposure as well. Underglazes can be applied for decorative effects directly to bare bisque-fired clay surfaces where they will fuse when fired again.
See Engobe, Glaze, Overglaze, Slip, Slurry
Velvet glaze
A matte finish glaze that imparts the look of velvet to the surface of a ceramic work.
See Glaze, Gloss glaze, Matte glaze, Satin glaze
Vitreous
The glassy amorphous state of clay, as contrasted with its crystalline state, achieved by firing to very high temperatures in a kiln.
See Firing, Vitrification
Vitrification
Process by which clay is converted from crystalline to a glass-like amorphous solid, accomplished by heating in a kiln to very high temperatures, well above the temperature needed for sintering. It decreases the porosity of the clay work so that it becomes impermeable to liquids, that is, water tight. Also called glossification.
See Firing, Sintering, Vitreous
Wedging board
A smooth, sturdy surface area, usually of wood, stone, slate, marble or canvas-covered plaster, for use in wedging (kneading) raw clay to a homogeneous workable state free of hidden air pockets and devoid of any stiff dry areas or soft moist areas. Wedging makes clay easier to work with and decreases the chances of damage while drying or firing.
Wet state
Raw clay before it is allowed to dry. It is in this state that clay can be rolled into slabs, shaped, thrown, bent or molded prior to drying or firing. If allowed to dry partially, before it becomes leather-hard, it can be printed upon by silk-screening or photo silk-screening. The proper degree of wetness or drying for a particular manipulation takes control and experience. Other clay states besides the wet state include leather-hard (greenware), bisque and glazed.
See Bisque, Clay slab, Glaze, Greenware state, Leather-hard state, Molding, Photo silk-screening, Silk-screening, Throwing
Wheel
See Potter's wheel
Wheel throwing
The process of creating a ceramic form from raw clay on a potter’s wheel.
See Potter’s wheel
