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Glossary

Absorption:  Is the amount of moisture that will soak into plaster when casting, or into bisque when glazing.

Accenting:  Is the process of emphasizing an area with lighter or darker colours by outlining or shading.

Acrylic Paint:  This is a product made from pigments and acrylic which is a type of plastic. Acrylics do not go in the kiln but they do go onto most craft surfaces such as Bisque, paper, fabric, terracotta plant pots and can be used to do brush strokes onto your house walls

Add Ons:  An “embellishment” that is added to the main piece.

Adherence:  Is the ability of a colour to stay in place on a given surface

Airbrushing:  Is the process of applying colour with the use of a small air gun. Used for shading and general decorating

Antiquing:  Is a decorating process in which you remove applied colour to accentuate detail

Appliqué:  Is a type of ceramic add on.

Banding:  Refers to applying colours to items in decorative bands. Usually done with the aid of a banding wheel.

Banding Wheel:  Usually refered to as a lazy jane. It is a hand operated turntable used for cake decorating.

Basecoat:  Generally an all over coat of colour on bisque on top of which decorating is done.

Batt wash:  A wash of refractory material painted onto kiln furniture to protect against glaze runs.

Biscuit/Bisque:  The first firing, converting clay to ceramic that cannot be reconstituted in water.  Bisque is used to describe a first firing that is higher than the subsequent glaze firing. Biscuit describes the reverse where the glaze firing is the higher, also the ware produced by these firings

Blistering:  Refers to the appearance of broken bubbles found on the glazed surfaces of fired ceramic pieces.

Casting:  Is the process of filling a plaster mould with casting slip (liquid clay) to create a clay object. Once the plaster mould is removed the clay object is called greenware or unfired clay.

Casting Slip:  A liquid clay used in the process of forming objects with plaster moulds, also refered to as slip.

Ceramic:  Clay that has been altered by firing to produce a hard substance that cannot be reconstituted in water.  The general name given to all fired clay ware.

Ceramics:  Clay forms that are fired in a kiln

China:  A term which usually refers to bone china also associated with white ware and porcelain

Clay:  Is a decomposed granite type rock that should be free of vegetable matter.

Clay Carbon Paper:  Is carbonless paper used for transfering designs onto greenware or unfired clay

Cleaning Greenware:  Also known as "fettling" is the process of removing mould seam lines and imperfections from unfired clay objects.

Coats:  Applications of ceramic colour by brush, sponge or spray which cover an entire piece or a specific area.

Coil:  This is the technique of building ceramic forms by rolling out coils, or ropes, of clay and joining them together with the fingers or a tool. (How to do this can be found at http:  //www.jhpottery.com/tutorial/coil.htm and http:  //www.jhpottery.com/tutorial/scoil.htm.

Cones:  Small pyramids of specially prepared clays formulated to bend at specific temperatures giving accurate measurement of heat work generated in the firing.

Cratering:  Refers to moon like craters that may apear on a glazed surface.

Crawling:  A glaze fault where the glaze has rolled back in the firing leaving a bare patch, caused by dirt, dust or grease on the pot before glazing and by the glaze being stiff, or applied too thickly and not flowing easily in the firing.

Crazing or delayed Crazing:  A network of small cracks in the glaze surface caused by a poor glaze fit.  The glaze contracts more than the clay and the resulting tension cause it to crack.  If a glaze contracts after firing more than the clay, the glaze being unable to stretch starts to crack under the tension.  The glaze will continue to crack until the tension is eased as crazing covers the surface and becomes finer.  Delayed crazing can occur days or even months after firing.  The most common cause of crazing is under fired biscuit.  If the clay does not reach its full maturing temperature either in the bisque or glaze firing, it will not contract sufficiently to fit the glaze. 

Decal :  A decal is a design printed with ceramic colour on special paper, which can be applied to the surface of ware and fired for permanency - a type of "pottery transfer".

Dipping:  Is a method of applying glaze by immersing piece in a container of glaze.

Dry footing:  Leaving the foot ring of a pot unglazed so that it can be fired standing on the kiln shelf without being stilted.

Drybrushing:  Is an effect achieved by applying non fired colours very lightly with an almost dry brush.

Earthenware:  A type of clay.  Typically it is clay that is lower fired ware (usually less than 1200°C). 

Element:  The heating coil of an electric kiln.

Enamel:  Coloured glasses used to decorate metal and ceramics, see On-glaze

Engobe:  Usually used to mean decorating slip.  A covering over the base clay not firing to a glassy finish.

Fettling:  Cleaning of cast ware, especially the removal of the seams produced by joins in the plaster mould.

Finger Sand:  The gentle rubbing of the glazed surface to remove ridges.

Fired Finish or Glazed Ware:  A finish that must be fired to produce proper colour and surface finish.

Firing:  Is the process of maturing ceramic products by varying degrees of heat. Firing usually takes place in a kiln.

Firing Chamber:  The interior of a kiln.

Firing Cycle:  The system of gradually raising and lowering the temperature of the kiln to properly free the ware.

Flow:  Is the term used when referring to the running or moving qualities of a glaze.

Flowing:  Coat is used to describe applying colour with a well loaded brush

Food Safe:  A product that has been tested and determined to be safe for use on surfaces that come into contact with food.

Foot:  Refers to the base of any ceramic item.

Frit:  A fusion of soluble or harmful glaze materials in a glass that renders them insoluble and safe so that they can easily be incorporated in the glaze.

Glaze:  The glassy layer covering the surface of pots to provide a non-porous, decorative and usually smooth surface giving increased strength to the pot.

Glaze Brush:  Is a brush with long full hairs for the application of glazes and underglazes

Glaze Butting:  Is the term used to describe placement of two or more glazes in proximity on the same piece of work.

Glaze Trailing:  Refers to the use of a fine tip squeeze bottle to trail one glaze over another to create a design

Gloss:  A shiny gloss-like finish

Greenware:  Unfired clay ware

Handbuilding:  This term refers to the one of several techniques of building pots using the only the hands and simple tools rather than the potters wheel. The term used for creating pottery using the potter's wheel is "throwing".

Hard Spots:  Are areas that will reject colour and sometimes cause ware to have bare spots, commonly caused by improper greenware casting.

High Fire:  Refers to ceramic articles that are fired to witness cone 04 or higher, like stoneware or porcelain.

Hot Spot :  A section of the kiln that fires to a hotter temperature than the rest of the kiln.

Immature Bisque:  Is ware that has been fired cooler than witness cone 06.

Kiln:  Is a heating chamber for hardening and maturing clay and glazes.

Kiln Furniture:  These are implements used to make full use of the kiln's capacity, e.g. Shelves, posts and stilts.

Kiln Wash:  Is a coating used on the top of kiln shelves and kiln floors to protect them from glaze drippings.

Liner Brush: Is a brush used for fine lines and designer work.

Loading:  Refers to completely filling the brush with colour.

Lustre:  Precious metals in liquid suspensions that are applied to glaze fired ware and fired to low on-glaze temperatures to produce a metallic surface - an overglaze that imparts an iridescent surface to the ware.

Majolica:  Painted decoration of oxides or decorating colour applied to a white tin glaze before the glaze is fired.

Matt :  A soft finish with little or no shine.

Matured Bisque:  A bisque that has been fired at the proper rate of heating and cooling to produce an even state of hardness throughout.

Maturing Point:  Is the temperature needed to mature glaze or clay.

Mini Bars:  Pyrometric cones that are used to measure the firing temperature of a kiln.

Modelling Clay:  Is prepared clay used for hand modelling and using on a potter's wheel

Mould Or Mold:  Is a hollow plaster of paris from which articles are reproduced using slip.

Non Fired Finish:  A colour that is applied to bisque; these colours are never fired in the kiln.

Non Moving Glazes:  Are ceramic glazes that move or flow very little in the glaze firing.

Non Toxic:  Is the term used to describe paint products conforming to us standard astm d 4236 to contain no material in sufficient quantities to be toxic or injurious to humans.

Once-Fired:  Ware that has been fired once, i.e. glaze applied to greenware with glaze and body maturing together.

On-Glaze:  Colour decoration applied to fired glaze and fired again to between 680°C and 880°C

Opaque:  Refers to non transparent colour.

Overglaze:  Is a decorative finish applied over a fired glaze surface and made permanent by firing.

Palette Knife:  Is a flexible knife with no sharp point used for mixing or stirring colour.

Peeling:  See shivering

Pin Holes:  Small holes in the glaze surface.  These can be caused due to poor manufacturing or due to

Porosity:  The quality of fired ware to absorb water. Lower fired ware is generally more porous and absorbs water readily while ware fired to vitrification will have practically no porosity. The correct level of porosity is important in glazing where the rate of water absorption affects the thickness of the glaze layer.

Posts:  Are columns of refractory material used to support shelves inside the kiln.

Pouncing :  Is a technique in which you apply colour with a quick up and down movement with a brush or sponge.

Pour Holes:  A section at the opening of the mould used for pouring the slip into the mould cavity.

Pouring:  Is the process of filling plaster moulds with casting slip to create the clay objects. Once the plaster mould is removed the clay object is known as greenware.

Prop:  Another word for posts i.e. shelf risers.

Pyrometer:  Is am instrument that indicates temperature in the kiln.

Raku:  A method of firing where pots are removed from the kiln at maturing temperature. After removing from the kiln Raku pots are often enclosed in sawdust or other combustible material to create a reducing atmosphere where bright metallic colours can often be produced.

Rolling Glaze:  Is a method of covering the inside area of ware by rolling thinned glaze inside.

Score:  Refers to the process of scratching tiny criss-cross lines on areas of greenware that will be fastened together with a repair solution or slip.

Score and Slip:  Score and slip refers to a method of joining two pieces of clay together. First, score the clay; this means that you make scratches in the surfaces that will be sticking together. Then you slip it; that is you wet the surface with some slip, using it like glue. Next, you press the two pieces together. It is very important to always score and slip clay that is leather hard. If you do not, the pieces will likely pop apart when they are fired.

Sealers:  Are spray or brush on coatings for use over non-fired colours to protect the surface and enhance the colours.

Seam Lines:  Are formed on greenware where mould pieces join.

Semi Matt:  A satin like surface which has a semi-sheen to it.

Semi Opaque:  Colours which generally only allow dark colours to show through.

Sgraffito:  Decorating technique involving scratching through a slip or glaze layer.  A method of creating a design in wares by gently scratching through applied colour to reveal the colour or clay body beneath it or to create a carved design

Shelf Cone:  Temperature the cone temperature that is fired on the shelf of the kiln. The amount of heat the ware actually receives.

Shelling:  See shivering.

Shelves:  Are flat slabs of a special high temperature material on which ware is place inside the kiln.

Shivering:  A glaze fault occurring when the body contracts at a greater rate than the glaze, putting the glaze under compression and causing it to separate from the body and flake and peel off, particularly on edges of pots. Shivering is the opposite fault to crazing.

Shrinkage:  Is the reduction in size of a clay object as a result of the firing.

Slip:  Clay in a liquid form for casting or decorating.

Slip Casting:  Method of reproducing shapes in clay by moulding liquid slip in plaster moulds. The plaster absorbs water from the slip leaving a coating of clay next to the mould surface taking the shape of the mould.

Slip Trailing:  Is the process of applying slip in an applicator bottle to flow on a design for a raised effect.

Slop:  The name given to a glaze after it has been mixed with water ready for glazing.

Soak:  Holding the temperature for a given time during the firing to enable the kiln temperature to even out and to allow glazes to become smooth while molten without over firing.

Soaking Cycle:  Is the process of holding a certain temperature in the kiln chamber for an extended period.

Soft Bisque:  Is ware that has been fired to witness cone 06 05.

Solvent:  Is a dissolving agent used in antiquing and to clean brushes with oil-based paints.

Spattering:  Is a method of applying small flecks of colour to ware usually with a bristle brush

Sponging:  Refers to the use of a sponge to apply colour directly to the surface of a piece of ware.

Spray Gun:  See air brush.

Sprigging:  Embossed decoration on clay ware, usually press moulded shapes applied to the pot to give a raised decoration.

Stencil:  Refers to the process of using paper perforated with a design through which colour can be brushed or sponged onto a surface.

Stilts:  Are supports used to separate glazed articles from a shelf during firing.

Stippling :  Is a method of applying colour by pouncing the tip of a brush loaded with colour against the ware.

Stoneware:  Ceramic ware and the clays and glazes from which it is made. Stoneware is fired high enough to produce a low porosity body. Usually taken to be ware fired above 1200°C. Stoneware is also characterised by the integration of the glaze and the body. 

Terracotta:  Is a natural low fired clay. Terracotta is also a colour name.

Thermal Expansion:  The expansion that occurs in glazes and clays when heated in a kiln.

Thermal shock:  Sudden change of temperature in a fired pot that creates stress due to expansion and contraction. Ovenware must be made of clay that withstands the thermal shock of repeated cooking. 

Thermocouple:  An instrument for measuring temperature in the kiln.  Thermocouples are the ceramic probes that protrude into the kiln.  Wires inside the thermocouple generate a small current that is measured by a Pyrometer that displays the temperature.

Throwing:  The forming of round pots by rotating clay on a potters' wheel.  The clay is driven through the potters' hands by the force of the wheel and the position of the hands determines the shape of the pot.

Transfer:  See decal.

Translucent:  Refers to transparent colour, allowing colour underneath to show

Underglaze:  Decoration applied to pots that are subsequently glazed with a transparent glaze.  Underglaze colours are protected from wear by the glaze layer on top of them.

Venting:  Allowing the escape of gasses both from the kiln during firing and the kiln room. It is important that all kilns and kiln rooms are vented adequately to prevent the build up of harmful gasses.

Viscosity:  The opposite of fluidity, the stiffness of a slip or a molten glaze. Viscous slips pour slowly and viscous glazes move very little in the firing.

Wax Resist:  A decorating technique where liquid wax is used to create areas of pattern that repel a covering colour or glaze. Wax resist can be applied in several layers, each layer blocking out more of the original colour. The wax is burned away during firing.