Glossary of Terms



Degree of moisture that will soak into plaster when casting, or into bisque when glazing or decorating with nonfired colors.



Emphasizing an area with lighter or darker colors, by shading or outlining.



Greenware parts added to main casting. (Example:  handles to cups.) (See Stick-Ons)



Ability of a glaze, underglaze or nonfired color to stay in place on a given surface.



Letting newly mixed casting slip set, undisturbed, for several days. During this aging period, all the materials will become properly blended and produce the best casting qualities.



Small spray gun used for applying glazes, underglazes or nonfired colors. Also, used for shading and general decorating.


Alumina Hydrate

A mineral that, in a powder form, prevents porcelain or stoneware greenware articles that touch from fusing together during firing or adhering to kiln shelf.



Three colors that are next to each other in the color wheel; these color combinations can often be found in nature.


Antique Brass and Antique Bronze

Special Effect Glazes that produce polished metal-like surfaces.


Antique Glazes

Trade name of glazes with a frosted look and variance of color tones.



Removing applied color to accentuate detail.


Antiquing Gels

(See Water-Based Antiquing Gels)


Antiquing Solvent

A thinner for airbrushing nonfired oil-based colors and the cleaner and conditioner for brushes used with oil-based colors.



Applying material such as lace, string, grog, etc. to ware; name of a type of ceramic add-on.


Art Glazes

Trade name of glazes that produce a blend of colors within themselves.


Artisan Glazes

Trade name of glazes that replicate the cone 5-6 look with just a cone 06 fire.


Automatic Shut-Off Device

A mechanical device triggered by a small cone that shuts off the kiln.



Applying color to ware in decorative bands.


Banding Wheel

A hand-operated turntable used to apply or blend bands of color and to accomplish other types of decorating.


Bar, Pyrometric

(See Cone)



Material added to hold ceramic ingredients together, such as gum arabic.


Bisq-Stain® Opaques

Trade name of nontoxic nonfired acrylic colors for bisqueware. Can also be used for accenting pattern in Crackletone Glaze.



Fired, unglazed objects of clay. Hard bisque, witness cone 04 or higher; soft bisque, witness cone 06.



Broken bubbles on fired glaze surface.



A container, with agitator for mixing slip.



Term used to describe any formula of clay.


Bone China

Articles made from a clay body that includes bone ash for translucency and strength.



Term used to describe greenware that is completely dry, containing no free moisture.


Brush Cleaner

A cleaner and conditioner for brushes.



Term used to describe placement of two or more glazes in close proximity on the same piece. The second glaze is applied so that it comes within the width of a pencil-point line of the first glaze but does not touch it. If the glazes accidentally touch, the area is scraped clean with a cleanup tool, then retouched. The butting technique prevents glazes from flowing together during firing.



The process of filling a plaster mold with casting slip, thus creating a clay object.


Casting Slip

Liquid clay for mold casting.



Special type of high-fire clay body that has a translucent quality.


Clay Carbon

Carbonless paper for transferring designs onto greenware.


Cleaning Greenware

Removal of mold seam lines and imperfections from unfired clay objects. (See Greenware Preparation)


Cleanup Tool

A tool used to clean greenware.


Color Burst Crystal Chips

Trade name of dry glaze chips that can be mixed with glazes or applied on wet glaze to create vibrant bursts of color.



Colors directly opposite each other in the color spectrum, creating a strong contrast.


Concepts Underglazes

Trade name of a large underglaze family with light, bright and dark color values.


Cone or Bar, Pyrometric

Heat-measuring device used when firing a kiln. A bar or a three-sided pyramidal form made of ceramic materials which react to time and temperature in the same way ceramic ware does in a kiln.


Courtyard Art Glazes

Trade name of a line of self-antiquing matte-finish glazes.



Trade name of nontoxic opaque underglazes used for full color coverage. Also, used for decorative purposes.


Crackles Glazes

Trade name of glaze which has been especially formulated to produce a delicate “crazed” surface pattern.



Moon-like craters on a glazed surface.



Term used to identify a glaze defect in which the glaze pulls away or crawls from the bisque, leaving bare bisque areas.



Hair-like cracks which appear on a fired glaze surface. Often referred to as either immediate or delayed crazing.



A recessed area of greenware or bisque.



To apply second and third coats in a series of parallel strokes that intersect.


Crystals Glazes

Trade name of nontoxic, dinnware-safe glazes that produce bright flecks on a background of rich color when fired.


Debut Brushes

Trade name of Duncan Taklon brushes.



A picture or design, printed with ceramic colors (underglaze or overglaze) on special paper, which can be transferred to the surface of the ware and fired for permanency.


Decorating Wheel

(See Banding Wheel)



A process whereby a cut-out design is applied to ware after which the ware receives several coats of lacquer or sealer.



An alkaline substance added slip to increase flowing qualities without increasing water content.


Designer Glazes

Trade name of glaze family with color breaks in the glaze to result with an appearance that emulates the look of fabric


Diamond Dust

Small granules of glass-like material that can be sprinkled over a wet Brush-On Sealer for a glittering “diamond” look.


Dinnerware Safe

Term used for a glaze that complies with the Food and Drug Administration’s safety requirements concerning lead and cadmium release when properly fired to witness cone 06.



Coating an object with liquid glaze by immersion in a container of glaze.


Discovery Brushes

Trade name of a line of Duncan brushes.



Effect achieved by applying color very lightly with an almost dry brush.



Leaving the bottom area of an article unglazed so stilting is unnecessary. Not recommended for low-fire ceramic utility items due to the porosity of the ware.



Breaking away of clay body during firing, due to trapped air or foreign substance.



Nonvitreous ware made from low-fire clays.



A high-temperature resistance wire wound in a coil that carries electrical current for heating kiln.


Elephant Ear

Fine-grained, thin sponge.



A raised design.


Enamelware Glazes

Trade name for a type of Crystaltone Glaze.



Colored slip or clay. Also, the term used when decorating an unfired clay object with colored casting slip or liquid clay.


Envision Glazes

Trade name of a full-range color line complete with translucent and opaque finishes.


E-Z Stroke®

Trade name of nontoxic premixed translucent underglaze colors for detail work, line work, color washes, etc.



Metal band of brush to hold hairs or bristles in place.


Fettling Knife

Tool used to remove excess clay from the outside of the mold and from the mold pour hole.



The process of maturing ceramic products by various degrees of heat.


Firing Chamber

Inside area of kiln.


Firing Cone

(See Cone)



The undesirable transference of a soft glossy sheen onto unglazed ware when high fired glazed and unglazed ware are fired together.



Shiny edges on ware which many low-fire glazes show when high fired.


Flash Casting

Cleaning a mold by making a thin casting with a different slip to pick up any traces of the last-used clay body.



The term used when referring to the running or moving qualities of a glaze.


Flowing Coat

A coat of glaze applied with a well-loaded brush, so that the brush does not drag against the surface of the ware.



Any substance added to clay or glaze to lower maturing temperature.



Bottom of ceramic item.



Shape with no uniformity.


French Dimensions

Trade name of nontoxic high-pile glazes for raised design effects over and under glazes, and over each other.



Articles necessary to use full capacity of kiln space. Shelves, posts and stilts.



A fired finish consisting of a prepared mixture of frit that produces a glass-like surface when fired.


Glaze Brush

A brush with long full hairs for application of glaze and opaque underglaze.


Glazes, Nonflowing

(See Nonmoving Glazes)


Gloss Glaze

Shiny glaze.


Gold Dust

A fine powder to be mixed with a nonfired acrylic and translucent color products to create colors with a metallic sheen or mixed with a Brush-On Sealer for a brilliant gold paint.



To create wood-grained effect by incising greenware or using thinned nonfired colors applied in a wood-grain pattern.


Granite Stone

Trade name of nontoxic nonfired water-based textured colors with sparkling flecks.



Unfired clay articles.


Greenware Drill

A small tool with a threaded point used for drilling holes in dry greenware. (See Ceramic Tools)


Greenware Preparation

Removal of mold seam lines and imperfections from unfired clay objects. (See leaning Greenware)


Greenware Saw

A small tool with a serrated edge used for cutting dry greenware. (See Ceramic Tools)


Grit Sponge

A square sponge with an abrasive surface on one side.



Ground-up bisque added to clay to reduce shrinkage and add strength. Sometimes changes texture and color.


Guard Cone

(See Firing Basics)


Guide Cone

(See Firing Basics)


Hard Bisque

Ware that has been fired to witness cone 04 or hotter.


Hard Spots

Areas that will reject color, and sometimes cause ware to have bare spots. Can be caused by over sponging greenware, but is generally caused by improper greenware casting.



The effect of combining colors that are pleasing to the eye and work well together.



Refers to ceramic articles or glazes that are fired to witness cone 4 or higher (stoneware and porcelain).


High-Fire Art Glazes

Trade name for Duncan nontoxic dinnerware-safe glazes created solely for use only on high-fire clay bodies and design to mature at witness cone 6.



Device to measure density of liquids.


Immature Bisque

Ware that has been fired cooler than witness cone 06.



Impenetrable; often used as another term for waterproof.



To cut clay surface to create design.


Incompatible Colors

Ceramic colors unsuitable for use together because of unbalanced chemical effects.




A clay used in certain clay bodies for whitening. Main ingredient in porcelain.



A heating chamber for hardening and maturing clay and glaze.


Kiln Furniture

(See Furniture)


Kiln Wash

A coating used on the tops of kiln shelves and kiln floor to protect them from glaze drippings.


Lace Tool

Long, pointed tool for use in applying lace.



Term used to describe cast or hand-formed clay items that are damp but firm enough to handle without losing shape.


Liner Brush

A brush with long pointed hairs for fine lines and design work.


Liquid Pearls

Trade name of nontoxic nonfired pearlescent water-based colors.



To completely fill brush with color.



An overglaze that imparts an iridescent surface to the ware.


Majolica Technique

Underglazes applied in design over an unfired nonmoving glaze. After the glaze firing, the design is a permanent part of the glaze surface.


Mask ‘n Peel®

Trade name of water-soluble emulsion used to protect design areas on greenware or bisque. Must be removed before firing. Can also be used with nonfired colors.


Maturing Paint

Temperature needed to mature glaze or clay.



Repairing broken greenware or bisque.


Metallic Glazes

Trade name of a unique glaze line that create shiny to matte polished finishes.


Modeling Clay

Prepared clay for hand modeling.



A hollow plaster-of-paris form to which articles are reproduced through the use of liquid clay (slip).


Mold Keys

Matching parts on each mold section that align mold properly for casting.



Having only one color represented by different hues and tins.



Heat-conducting pieces of pipe around firing chamber of gas kiln.


Natural Touch® Drybrushing Acrylics

Trade name of nontoxic nonfired water-based acrylic colors formulated for all types of drybrushing, base-coating and detail work.


Natural Tint® Translucents

Trade name of nonfired oil-based antiquing colors that can be wiped back with water or Antiquing Solvent.



A heat-resistant type of wire.


No-Fire Snow

Trade name of a nontoxic product that creates realistic snow effects without firing.


Nonmoving Glazes

Glazes that move or flow very little in the glaze firing.



Refers to a ceramic product that conforms to the US standard ASTM D-4236 and is certified to contain no materials in sufficient quantities to be toxic or injurious to humans or to cause acute or chronic health problems.



Nontransparent color.



A decorative finish applied over a fired glaze surface and made permanent by firing.


Palette Knife

A flexible knife with no sharp point used for mixing or stirring color.



Gently touching color to desired areas of ware with brush, sponge or cloth, in an up-and-down motion.



Trade name of a mender for welding broken greenware or bisque.



Tiny holes penetrating a glazed surface. A glaze defect caused by underfired bisque, applying glaze to greenware, firing too rapidly or poorly deflocculated casting slip.



Pliability of modeling clay.


Pooling or Puddling

Fired glaze that has run to the bottom or puddled in detail or ware.



A vitrified clay body that matures at a high temperature and is translucent.



The permeability of fired or unfired clay.



Columns of refractory material used to support shelves inside the kiln. (See Furniture, Kiln)


Potter’s Wheel

Revolving wheel driven by foot or electric power, used in forming articles from clay.



Applying color to ware with quick up-and-down movements, using a brush or a sponge.



(See Casting)


Pouring Sprue

A term for the excess clay around a mold’s pour hole that is trimmed away before opening mold. (See Spare)



A nontoxic water-based primer for ceramic bisque, plaster and other craft surfaces.



Project Finishers

Trade name of Duncan mold accessories used to complete ceramic projects.


Pure Brilliance

Trade name of a clear glaze that offers a sparkling, protective finish to ware.



An instrument that indicates temperature in the kiln.



A nontoxic water-soluble medium used to create an antique wood or aged pottery effect.



A process of taking pots while they are still glowing red from the kiln, and placing them immediately into containers filled with combustible materials such as sawdust, dried leaves, newspaper, etc. causing a beautiful reaction to all glazed areas.



Heat-resistant material.


Renaissance Glazes

Trade name of premier mid-range glaze family that is specially formulated for cone 5-6 firings for one-of-a-kind color breaks.


Rolling Consistency

Consistency to which glazes are thinned for rolling inside ware:  milk consistency for 2-coat glazes; light-cream consistency for 3-coat glazes; cream consistency for 4-coat glazes.


Rolling Glaze

Method of covering inside area of ware, by rolling thinned glaze inside, then pouring out excess.



Refers to fluidity of a glaze at the point of maturity before cooling and hardening.


Safety Timer

A back-up shut-off device designed to turn the kiln off if the automatic shut-off device fails to do so.


Satin Glazes

Trade name of nontoxic glazes that produce a smooth, opaque matte finish and move very little in the firing.



To scratch tiny crisscross lines on areas of greenware that will be fastened together with Duncan’s Patch-A-Tatch or clay slip.



Applying initial priming coat of thinned opaque underglaze or glaze, or partially removing fired metallic overglaze from ware.



Spray or brush-on coatings for use over nonfired colors to protect the surface and enhance the colors.




Ridge formed in greenware where mold pieces join.



The leaking of fluids through fine cracks or openings.



A method of creating a design by gently scratching through applied color to reveal the color or the clay body beneath it or to create carved designs.


Shelf Support

Same as posts. (See Furniture, Kiln)



Flat slabs of special high-temperature materials on which ware is placed inside kilns. (See Furniture, Kiln)


Shimmer Glazes

Trade name of an innovative glaze formula that offers sparkle and shine for beautiful and sheen finishes.



Occurs when the glaze or underglaze and the clay body are incompatible. The clay body shrinks more than the color, causing the color to peel or break away from the body after firing.



Reduction in size of a clay object as a result of firing.


Signature Brushes

Trade name of Duncan red sable or badger hair brushes specifically design for use on ceramics.


Silk Sponge

For decorating; recognizable by short hairs over entire sponge. Soft when wet.


Silver Dust

A fine powder to be mixed with nonfired acrylic and translucent color products to create colors with a metallic sheen or mixed with Gloss or Hi-Gloss Brush-On Sealer for a silver paint



Clay in liquid form.


Slip Trailing

Using slip in an applicator bottle to flow on design for a raised effect. Tinted slip can be used for contrasting details.



Graying or discoloration of a glaze, caused by underfiring.



A Special Effect Glaze formulated to create snow and fur effects.


Snow Accents

Trade name of a nontoxic product that creates realistic snow effects without firing.



Holding the temperature in the kiln chamber for a longer period of time than usual.


Soft Bisque

Ware that has been fired to witness cone 06-05.



A dissolving agent used in antiquing to clean brushes used with oil-based translucent colors.


Sparklers Brush-On Glitter

Trade name of nontoxic nonfired premixed glitter colors.



A term for the excess clay around a mold’s pour hole that is trimmed away before opening mold. (See Pouring Sprue)



Method of applying small flecks of color to ware, usually with a bristle brush.



Use of sponge instead of brush to apply colors directly to surface of ware or over a base coat.



To separate successive coats of glaze by fractions on an inch to prevent glazes from flowing together or from dripping off base of ware in firing.



Paper perforated with design through which color can be brushed or sponged onto a surface.



Greenware parts added to main casting. (Example: handles to cups.) (See Add-Ons)



Supports used to separate a glazed article from a shelf during firing. (See Furniture, Kiln)



A method of applying color by pouncing the tip of a brush loaded with color against the ware.



A heavily grogged clay body requiring a high firing to vitrify.


Stoneware Clay Tints

Nontoxic, dinnerware-safe tints that can be added to Duncan stoneware slip or low-fire ceramic slip to create beautiful decorator colors. Colors are more intense in low-fire slip than in stoneware slip.


Stoneware Dry Body

Duncan’s nontoxic stoneware clay in powdered form.


Stoneware Slip

Duncan’s nontoxic stoneware clay in liquid form.


Suspension Agent

Chemical added to keep glaze ingredients from separating.



A pattern or guide used in shaping a clay form.



Natural low-fired clay. Also, a color.



Planned surface finish or roughness produced for interest.


Thermal Shock

Subjecting the ware to abrupt changes from hot to cold or vice versa.


Thin ‘n Cast

Trade name for Duncan’s nontoxic stoneware accessory product that aids in the thinning of stoneware slip.


Thin ‘n Shade

A nontoxic water-based medium to be mixed with any Duncan water-based color. Also, used as a drying time extender.



To lightly apply diluted colors over a base coat or coloring a product with another product.




Touching tip of loaded brush with other colors for muted shading or accenting.



Transparent, allowing color underneath to show.


True Matte

Trade name of a glaze family with a smooth matte finish.



A ceramic color used under a glaze.


Utility Items

Dinnerware, cups, canister sets, lamps – functional rather than purely decorative items.


Ultra Metallics™

Trade name for nontoxic nonfired water-based metallic colors.


Vent Holes

Small holes made by piercing greenware when attachments have been made to allow trapped gases and moisture to escape from attachments during bisque firing.



Rate of resistance to flow.



Impervious surface (waterproof).



To become a stone-hard, impervious surface.



Color and water solution, used for shading and antiquing.


Water-Based Antiquing Gels

Nontoxic nonfired water-based colors for antiquing over all Duncan nonfired colors.



(See Impervious)


Water Smoking

The first part of firing, during which moisture is forced from the clay.


Wax Resist

A wax emulsion that repels underglazes and glazes applied over it. The wax is burned off in the firing.



To force air pockets and bubbles from modeling clay by rolling it back and forth and from side to side on a flat work surface, applying hand pressure at the same time. A professional wedging table equipped with a wire for cutting the clay to release air bubbles is often used by studios.



Sealing two clay surfaces together.



(See Potter’s Wheel)


Witness Cone

(See Cone)


Wool Sponge (or Sea Wool Sponge)

A sponge that has very open texture and is soft when wet.

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