Glossary
(What it means when they say;-)
All glossary terms are from published sources.
Additives - give colour to the clay, prior to working. Various coarse additives can also be added. Sands give the final product texture, and contrasting coloured clays and grogs result in patterns. Combustible particles can be mixed with clay or pressed into the surface, to give textures.
Agate – earthenware made to resemble the semi-precious stone agate creating a marling effect. It is created by building up and blending irregular layers of white, green, blue and brown clay.
Agateware - refers to pottery that is made with a mixture of colored clays. The name is derived from agates, which show bands of different colors.
Alkaline - various soluble mineral salts found in natural water and arid soils.
Amphora - used in Mediterranean countries, this pot was used for storing and transporting liquids. Typically two handles were linked from the neck to the body of the pot.
Anneal - to heat glazes and then slowly cool it to toughen it and reduce brittleness.
Annealing Temperatures - opals tend to anneal best several degrees lower than transparents, and hot colours (reds & oranges) are best annealed lower than opals. Ideal annealing temperatures are between 965 F (518 C) and 940 F (504 C). Annealing will still occur if you hold 20-30 degrees above or below the ideal temperature, it just takes more time to fire. If you hold at a temperature that is too far away from the ideal anneal temperature that is 40 degrees or more, you may never sufficiently relieve the internal stresses. It is also important to cool slowly down from the anneal point to the strain point. If the temperature throughout the project is not very similar, it is possible to create permanent stress.
Antiquing - a stain is applied and then gently wiped off, accentuating the detail of piece.
Anvil and Beater - An anvil is any material used to shape a pot. An anvil is used to shape the inside the pot and a beater (or paddle) is used on the outside. This thins the pot wall and shapes the pot. To assist the material to stretch without cracking, an anvil is often “pecked”, ie, it is covered with small holes or dimples.
Apparent Porosity - Relation between the volume of a mass and the volume of the water absorbed when the mass is immersed.
Arabesque - Ornamentation characterized by smooth running, linear designs of scrolls or leaves. The use of flowers and foliage in this style produce intricate patterns of interlaced lines.
Ark - a tank used for the storage of clay or glaze slips. There is often a continuous stirring that occurs mechanically that prevents the slip from settling.
Atelier – the studio of an artist or designer.
Atmosphere - the chemical make up of the volatilized vapours surrounding the pottery inside a pottery kiln, or within a post firing containment such as is frequently used in raku pottery.
Backstamp - A Backstamp is the mark found on items which help to identify the maker, country of origin and date the piece. Backstamps are also referred to as backmarks. It is the manufacturers mark, tradename and/or logo placed on the back of pieces, sometimes incorporating pattern numbers and dates or date codes.
Bagwall - The wall on the inside of a fuel burning kiln which deflects the flame from the wear.
Bisque Fire - First firing, without glaze. Slips can be used in a bisque firing.
Ball Clay - this is a general term used for many clays. Ball clay is actually blue. This is usually light in colour and highly plastic with a high dry strength. Unfortunately by itself, it is too slippery and fine for use, unless it is combined with sand, grog and coarser less plastic clays. Organic matter can also be present. It can also be a secondary clay taken from a parent. It is named after clay found in the English counties of Dorset and Devon where it was cut into balls that originally weighed 30 pounds.
Ball Mill - a grinder for reducing hard materials to powder.
Band - It is when a line is applied to the outside of a piece of pottery using any means of decoration that can be applied at any stage of manufacture. Banding is the process of marking a band.
Banding Wheel - A revolving wheelhead which sits on a pedestal base. It is turned by hand and used for finishing or decorating pottery.
Barbotine decoration - using a fine nozzle, thick slip is dragged along in streams hard pot.
Barnhard's Clay - is a high-fire slip which gives burnt metallic tones to the finished surfaces of pots to which it is applied.
Barbotine Decoration - a fine nozzle filled with thick slip is dragged along in streams onto a leather hard piece of pottery.
Bas Relief – a type of relief in which figures or shapes protrude only slightly from the background. ‘relief’ is a pattern that projects from a background surface rather than standing freely. A ‘bas’-relief is one in which the degree of projection is low. (‘bas’ from the Italian wordbassomeaning low in height).
Basalt – a type of hard, unglazed, black stoneware that is uniformly and densely grained. It was developed by Josiah Wedgwood around 1768 and refers to this very hard, unglazed stoneware stained with cobalt and manganese oxides.
Basaltware - stoneware that is black and unglazed. About 50% of the clay is vitrified and colored by 50% of iron and manganese oxides.
Batch - A mixture of weighed materials such as a batch of glaze or slip or a clay body.
Batt - A refractory kiln shelf used to support ware during firing.
Bats - are surfaces on which wet clay or pottery is carried or worked upon. Throwing bats are circular disks that can be fitted to the head of a pottery wheel so that finished pieces, particulary broad bottomed pieces such as plates or platters, can be easily lifted off the wheel. Bats can be made of Plaster of Paris, wood, or bakelite. Bats can be fitted to the head using clay or bat pins.
Batwash - kiln shelves become sticky from glaze droppings when heated. To prevent other pieces from sticking to the shelves during firing it is necessary to use bat wash on the shelves, which is a mixture of flint and water.
Bauxite - is the most important aluminium ore. It consists largely of the minerals gibbsite Al(OH)3, boehmite γ-AlO(OH), and diaspore α-AlO(OH), together with the iron oxides goethite and hematite, the clay mineral kaolinite and small amounts of anatase TiO2.
Beading - extreme crawling, which causes the glaze to roll back in on itself and form odd shaped raised globs on a bare piece of pottery.
Bentonite - volcanic ash clay that can absorb large amounts of water and swells many times it normal volume.
Biscuit - typically soft and porous, this term applies to pottery that has been fired only once without a glaze. Fired but not yet glazed ware.The first firing of clay. From the French “twice fired,” a reference to the preliminary firing involved in the production of the glassy frit used in French soft-paste porcelain.
Biscuit Firing - Biscuit Firing is where the greenware is fired for the first time. Bone China Biscuit ware is fired at 1250oc to 1300oc.Porcelain Biscuit bodies are fired at 800oc to 900oc.Biscuit firing hardens the clay in preparation for glazing. Some sculptural biscuit pieces are deliberately left unglazed and undecorated.
Biscuit Porcelain - Biscuit Porcelain is decorated Porcelain fired without a glaze.
Bisque - a greenware piece (unglazeded clay) used to make pottery that is fired at a high temperature and is porous; preliminary firing given to pots to render them hard enough for further work such as decoration and glazing.
Bisque Fire - First firing, without glaze. Slips can be used in a bisque firing.
Bisque Ware – ceramic pieces that have undergone their first firing. In this non-porous state, the ware will no longer dissolve in water and cannot be turned back into malleable material.
Bizen – glaze named after the Japanese city of Bizen produced by a long wood-firing, with resulting heavy ash deposits and other effects.
Blank - Pottery or porcelain left undecorated. Often sold from factory shops as white ware and are the base shape for many designs.
Bloating - Swelling of pottery during firing caused by the escape of gasses from the clay.
Blistering - appearance of broken bubbles found on glazed surfaces of fired ceramics and pottery.
Bloating- Distortion of the body caused by the evolution of gases during firing particularly when the firing has been too rapid and sinteringhas occurred before organic matter has been completely burned out. A swelling or expansion of body due to (a) over firing or irregular firing, (b) carbon trapped within a vitreous body, its appearance is of a bubble formation within the body.
Blue-and-White Ware – porcelain and other white ware that has a decorative blue pigment beneath the glaze. The pigment is derived from cobalt.
Blunge - mix water with clay.
Blunging - A process of mixing ceramic material in liquid by agitation.
Blunger Machine- for mixing water with clay. The clay is fed into a hopper and goes through a system of angled rotating blades to mix it with the water.
Bocarro - red unglazed stoneware which originated from 17th- century china. This term is now commonly used for any vitrified red ware.
Body-The bulk composition of a ceramic vessel, including clays. Name given to prepared clay. The name used to describe the physical composition of any type of ceramic ware, as opposed to its decoration or glaze.
Bone Ash - animal bones that have been baked and ground to a powder, used in the production of bone china.
Bone China – A soft paste porcelain made from a mix of dried bone, kaolin and putentse. Combines bone ash with the hard-paste porcelain ingredients kaolin and china stone, in a formula of 50% bone ash, 25% kaolin and 25% china stone. This formula is still used today. It produces a translucent, chip resistant lightness and soft colour body. Bone China is perceived as high quality china.
Bone Dry – describes raw clay that contains little moisture. At this stage, the clay cannot join other pieces and cannot be carved, but may be suitable for some other decorative processes and biscuit firing.
Bole - an impalpable powdery red clay. Found in eastern Mediterranean countries. It is used in the compounding of enamel colours and also as a pigment.
Borax Sodium Borate - a mineral salt found in alkaline deposits. A form of borax purified by calcination is used as a flux in glazes.
Boxing - rim to rim nestling of bowls or cups to prevent warping while drying and firing.
Bristolware - An imported British glaze used on hard wearing high usage potteries such as bottles.
Burning off - loose terminology for the simple removal of bound water in the ceramic change.
Burning out - this is where unwanted matter is removed by the use of heat in the kiln. An example would be, the creation of some colours using gums and oils. They would be convenient carriers of the colours when applied however they would need to be burnt out by oxidation at temps above red heat. If they were not burnt out, they would damage the glaze, body or colour by bubbling, blistering and possible discolouration.
Burning - firing pottery at a temperature of at least 1112 F (600 C)
Burnishing- A finishing technique, rubbing leather-hard vessel with hard tool, such as a stone or potsherd, to produce glossy surface, with irregular lustre and polishing marks visible.Polishing leatherhard clay by rubbing with a smooth stone or back of a spoon etc. This creates a polished look and reduces the piece’s porosity, making the clay more resistant to water absorption.
Butterfly - a type of glaze crawl that leaves its place and folds back on itself leaving double thickness and a bald patch on a piece of pottery.
Calipers - A tool used to measure the diameter of round forms, for example calipers are used to get lids to fit just right.
Candling - is the initial firing of a kiln, can be anywhere up to 12 hours before firing to boil off the water from within the clay to prevent explosion.
Cane Clay - sand like in texture this is a refined fireclay, it is less refractory than fireclay. When fired, the colour of the pottery is that of straw or cane.
Caneware – unglazed, tan-coloured stoneware with a dry look, occasionally decorated delicately with light-blue enamel.
Carinate - this is a pottery shape that is made by the joining of straight inward shaped walls to a round base.
Casting - A manufacturing process in which clay slip is poured into plaster molds which contains a hollow cavity of the desired shape. After pouring is completed, the mold is allowed to solidify to form desired shape of a finished product eg: Teapots, Vases, Platters, Platters etc. The plaster draws moisture out of the clay so the pottery can be handled when it is unmolded, commonly called greenware.Forming pottery by pouring slip into a porous mould.
Celadon – range of green colours produced by firing an iron bearing glaze in a reduced oxygen atmosphere. Colours may vary from turquoise to olive depending on the amount and type of iron. Stoneware with a feldspathic glaze that gives it a bluish-green colour.
Centering - Technique to move the clay in to a symmetrical rotating axis in the middle of a wheel head so you can throw it.
Ceramic- may be sculptures, tiles, bricks or any object made from clay (or glass). Often it is the artist’s choice. Objects produced by a process of strong heating of clay; pottery. An object made by firing clay in a kiln at high temperatures. It is an inorganic, non-metallic solidprepared by the action of heat and subsequent cooling. An object made by the process of heat acting upon the silicates in the material used. Although both clay and glass are ceramics the term most commonly refers to objects made with clay. The temperature at which the clay is hardened determines the name given to the finished material such as raku (low fired at around 850c.), earthenware, terra cotta, stoneware or porcelain (high fired at up to 1400c.). The term ceramics is often used in an interchangeable manner they call themselves a sculptor or a potter. Ceramic is one of the oldest art forms, fired clay vessels have been found in the Middle East dating back to 8000 BC. Today artists often decorate the ceramic with glaze, a hard coating invented in Europe in 1283 which can both water proof as well as beautify a ceramic object. The surfaces of ceramics may also be textured or inscribed to produce a design (the earliest examples dating from 4000 BC in China).
The word “ceramic” is traced to the Greek term Keramos, meaning pottery or potter.
Ceramics is the craft of creating useful and/or decorative objects from clay.
Ceramic Change - the slow process of clay becoming ceramic. Clay which is exposed to heat 1112oF (600oC) loses its chemically bound water molecules and can no longer be broken down by water. Once this change has occurred it cannot be reversed.
Chamois - extremely smooth and soft leather that, when wet, can be used to soften sharp edges on wet to leather-hard clay pottery.
Chamotte - Grog. This is a fired fireclay. (Other types of refractory clay) Due to Scandinavian usage the term chamotte ware or chamotte also applies to artistic wares made up of coarsely grogged clay. Non plastic part of some ceramics. Made by high temperature firing and crushing to appropriate size of refractory clay.
Chattering - this is a rippling effect that appears when turning.
Cheese Hard - this stage of clay can be carefully handled without deformation, due to it being dried sufficiently from it’s plastic state. It is the softest stage at which pottery can be shaved, or turned on a lathe, or kickwheel. Further drying would make it the leather hard stage.
Chigger Bite- is a tiny chip that removes the glaze from a spot, but doesn’t go into the clay.
China - a term applied to high-quality porcelain or ceramic ware fired at very high temperatures. Ceramics are believed to have originated in China. China is sometimes referred to as ‘Porcelain’ or ‘Earthenware’, which is generally used for tableware. Porcelain is occasionally referred to as "china" in some parts of the world because until the 17th century, the Chinese were the sole producers of vitrified porcelain products. This actual term originates from the habit of naming imports by their countries. To potters the implication of this word is that of a translucent white body covered with a glaze fired lower in temperature than the body. A term commonly used to describe ceramic wares, named after the country of origin.
China Clay - this is the purest of all natural clay.
Chinese Export Porcelain – Chinese ceramics produced specifically for export to the West. During the 18th century, English potters duplicated the decorations of this type of porcelain, while the Chinese duplicated some European artwork, making it difficult to ascertain the origins of certain motifs.
Chip - A chip is a missing portion of the item, or a portion glued back into place (repaired chip). The missing portion includes some of the clay under body. Has a negative effect on value.
Chittering - A series of small irregularities on the outer edge or rim of pottery ware. Mainly caused by incorrect fettling.
Chuck - A piece used to aid the potter in trimming. A chuck is a form that can hold a pot upside-down above the wheel head while the potter trims it. Chucks are thrown and bisque fired clay cylinders which are open on both sides.
Chunk or Chunker- Is a chip but over 1/2″.
Cistercian ware - deep red clay that is thinly potted, it has a glaze that is dark and shiny, which contains iron and manganese oxides. This is earthenware that was made in some cases by Cistercian monks during the 16thcentury.
Clair-de-lune flush - this is a romantic term used in the 19th century to describe pale blue stripes (distinguishable from the surrounding colours--striations). This can be found in Chinese stoneware glazes.
Clay- Stiff, viscous earth found in many varieties in beds or other deposits near the surface of the ground or at various depths below it. With water it forms a paste that can be moulded into any shape that hardens when dried. It forms the material of bricks, tiles, pottery and earthenware.Clays are produced through two basic geological processes, either by: 1) the weathering of bedrock; or 2) the deposition of fine grained sediments in water. The particle-sizes are less than two-thousandths of a millimeter, and becomes plastic when wet. Clay is a by-product of the earth’s crust, resulting from the decomposition of aging rocks exposed to the natural elements. Formed from small crystal compounds it is made up of the mineral kaolin, which consists of silica (SiO2) and alumina (Al2O3). The elements, silicon, oxygen and aluminum are the most abundant in the earth’s crust. There are three main groups of clays: Kaolinite-Serpentine, Illite, and Smectite. Altogether, there are about thirty different types of "pure" clays in these categories, but most natural clays are mixtures of these different types, as well as other weathered minerals. The basic material for all ceramic ware is clay, a soft earth that is plastic, or may be molded with the hands, consisting of hydrated silicates of aluminum. It is the result of the wearing down and decomposition, in part, of feldspathic rocks containing aluminous minerals, such as granite.
Clay Body - a clay designed for a special purpose. It is created by blending different clays or by adding to clays other materials, such as feldspar and flint in order to produce a desired workability, maturing temperature, or finished result.
Clay Carbon - carbonless paper used to transfer designs onto greenware.
Clobbering – A derogatory term used when people add decoration to someone else’s already finished pottery, in the hopes of giving the item an added boost to increase the value of the piece.Porcelain that is originally white or blue and white that is touched up with various other colours.
Cobalt - cobalt creates a dark dense royal blue in most cases. The strongest colourants used are the oxides of cobalt (blue), iron (red or green depending on kiln atmosphere and titanium (tan to blue breaking into red like tongues of flame. Used in China as a painting pigment on blue and white wares. The blue pigment used in the decoration of blue-and-white ware.
Co-efficient of Expansion - A measure of the reversible volume or length change of a ceramic material with temperature.
Coggling - Using a wheel shaped tool (a Coggle-Wheel) to impress a pattern or decoration into the clay.
Coil - A piece of clay rolled like a rope, used in making pottery.
Coiling - a hand building technique used to make pottery. Long round strips of clay are used creating the walls of ceramic forms by melding together rolls of clay.
Colourant - any substance that will colour something else.
Combed Ware – clay objects decorated with dots or lines made by pressing a comb into damp clay or by dragging a comb across surface of the clay.
Commedia dell’Arte – this movement began as a disrespected, improvised form of street theatre in 16th-century Italy. It is best known for its high-spirited characters, including Harlequin, Columbine, Pantalone, Scaramouche and Pulcinella. These characters have been represented in porcelain sculptures, paintings and engravings for centuries.
Composite Pots - Pots that were thrown or hand built in separate pieces and then assembled.
Compress - Pushing the clay down and together, forcing the particles of clay closer.
Cones - pyrometric cones are composed of clay and glaze material, designed to melt and bend at specific temperatures. By observing them through a small peep hole in the kiln it is possible to ascertain the exact conditions in the kiln. Cones are a better indicator than temperature alone as the degree of glaze melt is a combination of time and temperature heat work. A fast firing needs to go to a higher temperature to get the same results as a slow firing to a lower temperature.
Cone Numbers - cones are numbered from cone 022 up to cone 42. Cone 022 is the lowest melting cone and requires the least amount of heat to deform or bend. During firing, a cone softens and melts as it is heated. Cones used on the kiln shelf bend due to the effects of gravity pulling the tip down. This bending indicates the cone and the piece of pottery has received a specific amount of heat. It typically takes 15 to 22 minutes for cones to bend fully once they start bending. Each higher cone number requires more heat to bend. A cone 01 needs less heat treatment than cone 1 and cone 020 needs less than 019. Although cones do not actually measure temperature, cone bending behavior and temperature are related. The faster the firing, the higher the temperature required to bend the cone and the slower the firing, the lower the temperature required to bend the cone. The 6 oclock position, 90 angular degrees, is considered the end point of cone bending.
Combined Water - The water driven off when a dry substance is heated. It should be distinguished from the moisture which is driven off below 110c, and which can be variable. The combined water is present in finite proportions.
Continuous Kiln - A continuous kiln is also called a ‘Tunnel Kiln’, which is a long tunnel structure in which only the central part is directly heated. For example, in the glost firing stage, the bodies are slowly transported through the entrance of the kiln where the temperature is slowly increased as it approaches the middle part of the kiln. In the middle part of the kiln the glaze fuses to the body of the porcelain. After this stage is completed the bodies move along the conveyor where the temperature is gradually reduced where it exits the kiln at near room temperature.
Coralene - A decorating technique which was popular during the Victorian Era from 1850 to the early 1900’s. Coralene technique was the application of tiny glass beads, which were shaped into a decorative design such as a tree, flower/s etc and then placed in a kiln and heated. Coralene technique can be found on glass, porcelain and pottery products. When a Coralene technique item was completed, the finished decoration resembled a beaded ‘marine coral like texture’. Coralene textured items are highly prized amongst some Japanese collectors.
Cornish Stone - a feldspathoid used as a flux but is also a major element in glazes. Contents include quartz, feldspar, mica, kaolinite with a small percentage of fluorspar. Melts at 2102 F to 2372 F (1150 C to 1300 C) and becomes a stiff glass that is opaque with suspended fine bubbles.
Crack - Is a fracture in the piece.
Crackle - This is just what it sounds like, if you were to take a piece of paper and crackle it up, crunch it up, upon straightening that paper out, you would end up with a similar look to a pot where the glaze has been crazed. With lines going every which way. The intentional creation of a fine network of cracks in the glaze on a clay surface, sometimes darkened for accentuation. Rakuware often has this feature. It is a glaze that intentionally has minute cracks in the surface finish which are caused by the uneven contraction of glaze and body. It gives the piece of pottery an interesting finished texture. Or
Craquelle - An intentionally crazed or cracked effect on art pottery, emphasised by rubbing colouring matter into the cracks and refiring the ware.
Cratering - moon-like craters that appear on a glazed surface.
Crawling – a part of the underlying clay surface that is exposed when the glaze separates from the body. When a glaze pulls apart from a continuous surface into many nearby sections with voids in between, a bit like spots on a leopard. This is sometimes done intentionally to give the surface of the piece of pottery increased texture and interest.Movement of glaze over the body surface during the glost firing stage, due either to dust or grease on the surface or over thick glazing or excessive colloidal material in the glaze.
Crazing - A network of cracks in the glaze caused by tensile stresses greater than the glaze is able to withstand, and may result from mis-match of the glaze with the body. A crackling effect in the glaze; A spidery type crackling effect–looks like crackle glass. Not detectable when you rub you fingernail over it. An effect similar to crawling, where the glaze cracks along many lines and into many pieces. Unlike crawling, these sections remain very close to each other and the lines in between them remain very thin, even hairline. This is caused by the glaze shrinking during cooling to a greater extent than the clay underneath shrinks. The outside glaze is too small for the clay which it covers. Because the glaze covering over shrinks, it cracks. This is also described as the glaze not fitting the clay. This is often used to create an interesting surface texture on pieces of pottery. Crazing can also occur as a consequence of poor handling procedures as a result of minimal use or subjecting the product to sudden hot and cold temperatures such as in dishwashing machines.
Crock – Old term for pot.
Crocker – Old term for potter.
Crockery – Term used still to describe pottery, now applied to domestic dinnerware.
Crystalline Glazes - most glazes have no easily visible crystal structure, but these have large and dramatic crystals up to about three inches across. A high alkaline low alumina glaze is vital for crystals to develop. Additions of zinc and titanium also help seed the crystals. An extremely slow cooling of the kiln is necessary, to allow the crystals to grow. Because of the low alumina content in crystalline glazes they are very runny and often pottery is supported in the kiln on stilts to avoid them adhering to the kiln shelves, the stilts can be broken off after the firing.
Creamware (or Queensware) – a type of earthenware developed in the 18th century that came to dominate western ceramic tastes during that time. This is the forerunner of English white earthenware today. It was developed in the 18th century by the Astburys, and later Whieldon and Wedgwood perfected it. The recipe is made up of 25% china clay, 25%ball clay, 35%flint and 15% Cornish stone.
Damper - a crude device, usually a refractory clay brick, used to block the flue of a kiln.
De Airing – A vacuum process to remove air from a slurry.
Decals -The term used to refer to the art of transferring designs in the form of a decorative sticker made from specially prepared paper, cloth or plastic material that has printed on it a design/pattern which is applied by hand to either china, glass, or a metal surface usually with the aid of heat or water. A decal or transfer once fired then becomes a permanent feature. The word is short for ‘decalcomania’. A picture or pattern applied, after soaking in water to release backing, to a piece of glazed pottery or ceramic. An image, usually multicoloured, printed using a copper plate on tissue paper. Images are soaked to remove them from a backing sheet and to transfer them to the ceramics, before the glazing process. This process is more commonly known as "Transfer Printing".
Decal Decoration - is always done by hand and is divided into three methods of application.
Over Glaze – This procedure is fired at 750oc – 900oc.
Under Glaze – This procedure is fired at 700oc.
Sink-In Glaze – This procedure is fired at 1200oc -1300oc.
Decals are first applied by hand to the top of the glost fired bodies which is called Decal Decoration Firing. Over-glazed products are fired at 750oc to 900oc. Sink-in products are fired at 1200oc to 1300oc.
Decoration Firing (Gold and Platinum Lining) - Gold and Platinum lining decoration firing occurs after each piece has been individual hand painted with a very fine film of liquid gold or platinum which is then fired at 750oc to 850oc.
Deflocculant - with the addition of very little water, this substance will act chemically on plastic clay giving it liquid characteristics. Sodium silicate and sodium carbonate will have this effect.
Deflocculation - The dispersion of clay slip or glaze by the addition of an alkaline electrolyte e.g. sodium silicate, dispex etc.
Delftware - made in Delft, Holland this English term is used to describe blue tin-glazed earthenware. Often this term is used to describe all blue tin-glazed pottery made in England.
Diatomaceous - consisting of diatoms or their skeletons.
Ding - see Nicks.
Dipping - is a process of covering a bisque body with a glaze by immersion in the liquid, either by hand or machine.
Dolomite - a magnesia rich sedimentary rock resembling limestone.
Dry Foot - practice of not glazing the bottom of a piece of pottery so it won't have to be stilted.
Dunting- Cracks or cracking caused by the too rapid cooling or heating of ware, and due to thermal stresses set up in the body.
Dusting - throwing a layer of dry ceramic or glass on a piece of pottery and firing it.
Earthenware- A moderately porous pottery body which is fired to a temperature somewhat below that required to produce a vitreous article.Ceramic vessels fired to temperatures of 700-1200° centigrade. It is generally opaque, porous, course ceramic and made from potash, sand, feldspar and clay. It is one of the oldest materials used in pottery. Classically, most earthenware has a red coloring, due to the use of iron rich clays. However, this is not always the case, and for the modern potter, white and buff colored earthenware clays are commercially available. It can be as thin as bone china and other porcelains, though it is not translucent and is more easily chipped. Earthernware is also less strong, less tough, and more porous than stoneware, but its low cost and easier working compensate for these deficiencies. Due to its higher porosity, earthenware must usually be glazed in order to be watertight.
Eflocculate - to disperse the particles in a slip so that less water is required to make the slip fluid.
Elutriation - this is the division of course clay and fine clay, by putting the clay in water. The fine clay will remain suspended in the water where as the larger particles such as stones and sand will sink. A mechanical device is used in this process to move the slurry upwards against gravity.
Embossed - pottery that has a raised or moulded decoration produced either in the mould or formed separately and applied before the first firing. Embossing occurred as part of the casting process but can also be formed separately and then applied before the firing process.
Enamel- is a form of low temperature glaze that is applied on top of an already fired higher temperature glaze. Enamels are often lead based and are a flux that works at a low temperature. Overglaze enamels are low-fired metallic oxides used to decorate ceramic wares. The frit, suspended in an oily medium, is painted on the glazed surface, and the suspension material is burnt away.
Engine Turning – a technique developed in 18th-century England in which a vessel in the leather hard or greenware state is incised with a decoration while rotating on a lathe.
Engobe – A white or coloured coating of slip applied to the clay before glazing for decoration.Liquid clay slip applied to the surface of a pot to give color, improve or add texture or provide a ground for further decoration. It may be applied to wet. leather-hard, dry or bisqued ware.Liquid clay slips that are applied to the surface of either wet clay, leather-hard clay, greenware or bisque ware. Its purpose is varied; it can be added to change the colour or texture of a piece or to prepare it for additional decoration.
Encaustic - decoration where the use of different coloured clays are inlaid into the body clay. These inlaid pieces are actually put into cut out portions of the body, though sometimes they are just rolled onto the body. Cistercian monks used this technique while producing paving tiles.
Eosine - this rainbow-hued finish is named after the Greek goddess Eos (same as the Roman Aurora), the goddess of dawn. Not the same as Eosin, the organic dye. Eosine is the finish found on Zsolnay pottery from world-famous Zsolnay Factory in Pécs, Hungary.
Eutectic – The lowest possible melting point of a mixture of two or more substances, from the Greek “to melt”.
Extruded - A process of forcing clay through an apurture to make handles or decoration.
Factory Flaw - In general, factory flaws are imperfections introduced during production. Examples include bubble bursts in the glaze, glazed over chips, "kiln kisses", and the like. "Old chips" cannot be considered factory flaws unless there is some portion of it glazed over. Hair- line cracks, crazing, dings and nicks and flakes are not factory flaws even though they may have occurred at the factory. The rule of thumb is: If you can't reasonably prove it happened at the factory, it didn't, and should be graded accordingly.
Faience- this term describes colorfully decorated earthenware or glazes. Today the style that is considered faience is the covering of surfaces with matt and shiny glazes that are often blended together. French version of tin-glazed earthenware that was popular in 16th, 17th and 18th century Europe. The name is derived from the northern Italian town Faenza, where maiolica was produced.
Famille – this is the French word for “family.” In the 19th century, French ceramic collector Albert Jaquemart divided the ceramics of the Qing Dynasty into categories based on their predominant colour. The categories are: famille verte (green), famille rose (pink), famille jaune (yellow) and famille noire (black).
Fat clay - highly plastic clay, long clay, that is often added to other clays to improve workability.
Feathering Effect- obtained by trailing a feather through wet slip decoration.
Feldspar - a naturally occurring mineral, aluminosicilate, formed by the decomposition of granite or igneous rocks. Composed of alumina and silicon oxides plus soda (sodium carbonate), potassium or calcium. Feldspars melt around 2150 F (1177 C) and tend not to run due to their high alumina content. It is one of the predominant naturally occurring fluxes used primarily in stoneware glazes. The three most commonly used feldspars are Potash, Soda, and Lithium. Feldspars can be the only flux present in a stoneware glaze although this is uncommon and additions of calcium usually supplement it. An abundant group of rock-forming, hard crystalline minerals containing potassium, sodium, calcium, silicates of aluminum and sometimes barium. It is used widely to produce stoneware, porcelain and glazes as a flux.
Feldspathic Glaze – used on hard-paste porcelains, this glaze is made of the same kaolin and petuntse as the body but in different proportions. It fuses into a type of natural glass when heated to a very high temperature.
Feldspathoids - though “feldspathoids” have similar properties tofeldspar, they are not true feldspars at all. They can be useful in glazes, but cannot be considered as true minerals due to the fact that they do not conform to unified chemical formulae.
Fettling - the removal or trimming away of excess clay, unwanted blemishes, seams and flash from nearly dry pots prior to glazing and firing. The removal of the seam left by the mould in greenware, by fettling knife and/or sponge.
Fire / Firing – to bake clay in a hot kiln or oven. To harden clay, the temperature must be high enough to fuse the clay particles. High firing (1200°–1400°C) is used for porcelain; moderate firing (1200°–1280°C) is used for stoneware; and low firing (800°–1100°C)
Firebrick - An insulation brick used to hold the heat in the kiln and withstand high temperatures.
Firing Range - The range of temperature at which a clay becomes mature or a glaze melts.
Fireclays – these clays contain a slightly higher percentage of fluxes than does pure clay. They usually fire to a grey colour and mature at between 1371º–1482ºC, which are higher temperatures than that typically used in firing pottery and glazes. Fireclay is often used to make muffle, firebrick and kiln linings. These are typically refractory clays and often used for firebricks. Pale buff or ‘almost’ white is the colour that appears when fired.
Firing- The process where clay is converted to ceramic. A temperature in excess of 550° C is required to drive off chemically combined water from the clay molecules and make them ceramic.
First red - when the temperature in a kiln reaches 600 C (1112 F) the pot that has been fired gives off an incandescent glow. This tells you that the point of dunting has been passed and the ceramic change is almost complete.
Fit- the act of clay and surface components shrinking at about the same rate.
Flake - Caused when a portion of glaze is lost from the piece. Often seen in conjunction with crazing. Has a negative effect on value. Flaking is caused by glaze being under excessive compression.
Flambé - means to flame or appears to flame.Made from copper, a crimson glaze, sometimes flecked with brown, blue or purple, and often resulting in a crackle glaze effect, due to the high temperature firing process.
Flash - undesirable transfurence of a softglossy sheen onto unglazed ware when high fired glazed and unglazed ware are fired together.
Flashing - shiny edges on pottery produced by overfiring; changes to colour and texture caused by the flow of flame over a piece during firing in a wood-fired or gas kiln.
Flatware - Any flat items on the table including plates and platters, more commonly used to refer to cutlery, particularly in the US and Canada.
Flea Bite- Is a raised bubble bump or a tiny nick. Sometimes you can’t see them well, but running your fingernail across the piece will pick up the flaw.
Flint - pure silica that contains less than 5% impurity. Its native colour is black which turns to white when heated. It is usually bought in the form of powder, which is added to clay and glazes. When added to clay it gives a whiteness and hardness to pottery and also adds a resistance to crazing.
Flocculate - to thicken.
Flux - means flow, and thus fluxes are materials that help glazes flow. They do this by lowering the temperatures at which other minerals would naturally melt. A substance that lowers the melting point of material in which it is present, either naturally or to which it has been added. It is a base oxide that lowers the melting point of vitrification, the fusion of particles that occurs in stoneware, porcelain and overglaze enamels. Fluxes include alkaline materials such as sea salt, feldspar, soda, potash, bones, ferns, seaweed and lead.
Foot ring – area at the base of a pot, separate from the body and sometimes left unglazed.
Fosted - if there is a hole, or slight air intake during the firing of a pot, one side may end up underfired, which will make part of the pot look lighter in appearance than the rest of the pot.
Frit - by heating two or more raw materials together, this is a manufactured glaze or body that is melted together to form a glass that is then shattered, usually by pouring into cold water. The shattered pieces are then ground into powder. A ceramic glass-like composition, melted or fused together. Used to render soluble constituents of glazes insoluble. Aglassy frit is composed of silica (found in sand or quartz), a flux (potash or soda) and metallic-oxide pigments. The mixture must be calcined (melted) and ground to a powder before being added to soft-paste porcelain or overglaze enamels.
Galena - this is lead ore, impure, used to make lead glazes. In the 10th to the 17th centuries Galena was dusted on newly thrown wet ware. This fused the upper layer of clay during the firing into a glaze.
Geochemistry – the study of the crust of the earth, its chemical composition, and the chemical changes that occur within it.
Gilding – the application of gold to the surface of an object for decorative purposes. An early technique was unfired lacquer gilding, in which a gold powder mixed with lacquer was painted on a glazed vessel, but the result was fragile and easily worn off. Honey gilding involved ground gold leaf mixed with honey, which was fired at a low temperature and could be chased and tooled. This was replaced with mercury gilding in the 19th century. Now used as a more generic term referring to gold, silver or platinum trims often appearing on the rims of plates, cups and dishes etc, and sometimes within the pattern itself. (see Lining)
Glaze - the glassy coating used to render ceramics impervious to liquid and smooth to the touch. A glassy coating fused with a ceramic body by firing, creating a water-tight surface. The glaze consists of silica, stabilizers (alumina) and various fluxes, the latter added to lower the required melting temperature. A layer of ceramic, flint, ground glass or other material that is applied to the surface of the clay object fused onto the surface of the clay of a pot or ceramic piece at a high temperature. Used to seal the piece, decorate it, or both.
Glaze/Body Fit - The relationship between thermal expansion of body and glaze. Ideally the glaze should have a lower thermal expansion than the body, so that on contraction the body puts the glaze into compression. This avoids crazing of the glaze due to tensile stresses in it.
Glaze Miss - A small spot on an item where the glaze did not cover. This is a factory flaw and treated differently for different potteries when it comes to value. For potteries with high quality control these may reduce the value as they would be a factory "second", also called a Glaze Slip.
Glaze Pop - A popped air bubble that burst at the surface of the glaze during firing.
Glazing- The process of coating the piece with a thin layer of a glassy material (often a mix of dolomite, frit, flint, feldspar, sodium borate, clay and whiting). This is important for functional earthenware vessels, which would otherwise be unsuitable for holding liquids due to porosity. Glaze may be applied by dusting it over the clay, or dipping or brushing on a thin slurry of glaze and water. Brushing tends not to give very even covering, but can be effective with a second coating of a coloured glaze as a decorative technique. With all glazed items, a small part of the item (usually on the base of the piece) must be left unglazed, else it will stick to the kiln during firing. Some of the strongest colourants used are the oxides of cobalt (blue),iron (red or green depending on kiln atmosphere), and rutile, a.k.a. titanium (tan to blue breaking into red like tongues of flame.
Gloss- a glaze which has a smooth, shiny surface.
Glost - Meaning glazed.
Glost Firing - Glost firing is where the glaze is applied to the biscuit bodies and firing for the second time. Bone China is glost fired at 1100oc to 1200oc. Porcelain glost firing occurs at between 1280oc and 1400oc.Fine China (Formal China) usually has gold or platinum trims.
Greenware – Hard clay objects that have not yet been fired. In this state, moisture can be added to turn the clay back to a malleable form. Despite its name, it may be grey, turquoise, yellow, or blue. Pottery that has been air dried but not yet fired. Unfired glazed clayware.
Grog - this is ground, already fired body that is added to clays. It can provide texture to a piece. It has many advantages in its usage. One being that since it has already been fired; it helps to cut down on the overall shrinkage. Ceramic material which has heated to a high temperature before use and predominantly inert. Usually made of fireclay or a comparable type of clay that has already undergone the firing process, grog is added to clay to diminish shrinking and cracking as the clay dries; to increase durability, workability and strength; to protect against thermal shock and to add texture. Grog is often added to wares such as Raku and flameware because of their vulnerability to thermal shock.
Hairline - A fracture in which the fragments do not separate because the line of break partially be present. A hairline facture may measure only a couple of millimetres in length.Hairline cracks usually show up as dark grey lines on the surface of a piece. These cracks go through to the inside where they also show up as dark lines. They are most often found near an edge. Sometimes called stress cracks or age cracks, they have a negative effect on value. They are often difficult to detect on pieces with dark glazes. Sometimes you can only hear a hairline crack and not see it (for the more experienced).
Handle - By definition, a Ramekin without a functional handle is just a bowl. A handle makes contact with the body of the ramekin at one or sometimes two places on the same side of the body. The handle of a ramekin creates its point of difference and can be unique to a studio. The bowl of a ramekin is sometimes quite plain so the handle creates an opportunity for the potter to give visual balance or distinctive design to their work. A handle must be comfortable to use because a ramekin is, first and foremost, a functional object. Some potters uses other materials for their handles, ie wood, bamboo etc. ramekins do not. Ramekin handles are made from the same material as the bowl.
Handles are of two main types, those moulded during the making of the bowl, flowing from the lip, or a lug (either a knob, tab or a finger shape that is made separately then later attached to the bowl. Moulded handles tend to be smaller tab types that are usually flat and relatively the same thickness as the body of the bowl. Lug handles can be any size or shape, solid or hollow, round, tubular, flat (or strap).
Lug handles are attached to a section of scored area on the body, they are made separately and then applied to the body. The handle is first shaped to the potter's desired form. Before the handle dries, the ends of the handle and connecting spot on the body is scored and lightly moistened; a technique known as "scratch and slipping." The handle is pressed onto the bowl with just enough pressure to allow the potter to complete the attachment by smoothing the join. In rare cases, a handle is fixed to the body in a hole through the side of the bowl.
The most common form is a strap handle, made from a flat section of clay, then fixed to the bowl. Many strap handles are folded to form a loop, either horizontal (Duldig) or vertical (Wilton). Handles can be either solid (Ellis, Elischer) or perforated (Gluck, Warrandyte Pottery) so they can be hung on a wall hook. Some are extended down the bowl to give additional strength to the bowl at the join (Picton Hopkins).
Attached handles can be cut from a slab, rolled into a coil or pulled from a wedge of clay and are usually of a similar thickness to the body to reduce problems of shrinkage and expansion. For this reason, mass-produced ramekin handles are usually hollow and have a small hole to the underside to balance pressure during firing, especially those that are knob ended and closed at the outer end. Handles should be made and attached before the "Leather-Hard" stage is reached.
Hakeme – decoration technique in which a stiff brush is used to apply slip directly to the surface of a pot.
Handbuilding – creating ceramic pieces using only the hands and simple tools as opposed to the potter’s wheel.
Hard-paste Porcelain – “true” or Oriental-type hard-paste porcelain is made from white china clay (kaolin) and china stone (petuntse or feldspar, a silicate of potassium and aluminium). These two ingredients are fired together at a high temperature (1250º–1350ºC) to produce a glassy matrix.
Harlequin – In pottery terms it means multi coloured. When each ramekin in a set of ramekins of similar design have different colours, it is described as Harlequin. Named after the comic character in Italian comedy who wore a mask and multi-coloured clothes.
Heat Work - Energy input during firing, normally represented in terms of temperature and time. Cones indicate this.
Hausmauler – freelance artists who ran independent decorating studios in Germany, Holland and England. They painted on a variety of materials including porcelain from China, Meissen and Vienna.
High fire - pieces which are produced about 2305 degrees Fahrenheit (1263 Celsius) or cone 8. Typical stoneware and porcelain.
High Gloss - Indicates a high shine finish.
Holloware - A collective term for items that are hollow, ie; teapots, jugs, vases, pots, casseroles etc.
Hump Mould - The process of laying a slab of clay over a shape, the hump, or slapping, paddling or pounding an amount of clay over such a form.
Humper - this is a distorted plate, where the flat part has risen up in an unacceptable fashion. Usually found on pressed plates, and or plates that are glazed only on the top and sides.
Imari – A pottery region around Kyoto, also known as Arita Yaki.
Impress - A method of stamping semi-hard clay with a mark. Either a makers mark or decoration.
Incised Decoration - Marking leatherhard clay for decorative purposes.
Inglaze - A method of decorating ceramic articles, where the decoration is applied on the surface of the glaze before the glost fire so that it matures simultaneously with the glaze. the application of ceramic colors put (usually painted) onto an unfired glaze. The colors will sink into the glaze, and stain it.
Inlay - (or “Mishima”) – a decoration technique that involves pressing coloured or contrasting clay into incisions made on a clay object. The excess clay is scraped off when it has partially dried. A type of decoration where the surface of cheesehard clay is scored, and filled with a thick coloured slip.
Insizing – decorating by cutting designs or signatures into the semi-hard clay with a sharp tool or wire.
Intermittent Kiln - A kiln where the bodies are loaded into the kiln. The kiln is sealed and the internal temperature is increased according to a schedule for the particular firing cycle eg: glost firing. After the firing schedule is completed, both the kiln and ware are cooled.
Ironstone – a dense, durable, hard white pottery first produced in England during the 18th century. It contains a high percentage of clay and a low percentage of non-clay materials, and is fired at a high temperature.
Istoriato – an Italian term meaning story. Refers to imagery on ceramic surfaces that tells a story.
Ivory China - Ivory China is named because of its ivory colour look, whatever material it may be. Ivory China is created in three ways. Any of the following factors could make it Ivory China.Glaze, Combination of materials, Oxidation Firing (low temperature firing).
Jasper Ware – white or coloured, fine-grained, vitrified stoneware developed by Josiah Wedgewood in the 1770s. It was unglazed but was often stained with a variety of colours, typically blue, black, lilac and green.
Jiggering - Shaping of flatware, by means of a profiled tool at a fixed distance from the rotating surface of a plaster mould.
Jiggering Machine - A machine for the shaping of clay body into round shape products such as plates and cups.
Jolleying - Shaping of hollow ware by means of a profiled at a fixed distance from the rotating surface of a hollow plaster mould.
Jun - this is an opalescent pale blue stoneware glaze. The origin of this term is from a town in northern China. This was first made in the 11thcentury. The glaze needs to be applied in a thick manner, otherwise the body will show through, and it will seem almost transparent.
Jutland ware - The origin of this pottery is that of Neolithic times. (Nearing the end of the Stone Age) It was perfected early on and continued to be made until the mid-20thcentury. This was unglazed, peat-fired pottery.
Kaki - Japanese name for persimmon fruit, also the name for the rust colour that appears on the surface of stoneware glazes. This occurs when iron oxide crystals spread.
Kaolin – this very fine, pure, white-firing natural clay is used to make porcelain paste. Kaolin forms when the mineral feldspar decays, and is sometimes called “China clay” because of its prevalence in China.
Keuper marl - A high quality mudstone, from the Triassic Period. (a time characterized by the appearance of dinosaurs, time of high volcanic activity) It began as a desert dust. Though not consolidated it can be reconstituted as clay. High in clay content, iron, and lime. Brown and gray when raw but brown-burning.
Kick Wheel – a manual potter’s wheel that is powered by the artist’s foot, which kicks or pushes a stone or concrete base.
Kidney - a kidney shaped tool, which can be used for finishing thrown pots as well as smoothing and pressing clay in a mould. For use in finishing thrown pots, it is made of flexible steel. When used for smoothing and pressing clay, it is made of stiff rubber.
Kiln - simply put this is a structure that is built to maintain heat where clay is fired and turned into pots. It is an oven that is used for hardening, burning, or drying anything. Kilns have been used for converting wood into charcoal and are used to heat dried clay objects in order to make them hard and durable in a process referred to as firing. They have been made for as long as there has been pottery and items made of clay. The technology is thus very old. Most likely the first kilns where campfires or open bonfires. Early examples of kilns found in the United Kingdom, include those made for the making of roof-tiles during the Roman occupation. These kilns were built up the side of a slope, such that a fire could be lit at the bottom, and the heat would rise up into the kiln. There are many kinds of kiln types, but the major division is betweenfuel burning kilms andelectric kilns. Fuel burning kilns are usually known by the name of their fuel: such aswood fired kiln, gas kiln, etc. They can also be known by the particular type of pottery they're designed or dedicated for, such as a raku kiln or asalt kiln.They can be permanent, re-usable fixtures orone time kilns, for example, kilns built, fired and torn down, or kilns tailored to fit a specific monumental pieces of pottery, or a primitive sheep or cow dung dome kiln in which the fuel itself is the structure of the kiln and does not survive the firing. There's even talk of a solar kiln for ceramics. Kilns can be powered by electricity, natural gas, propane, wood, coal or fuel oil.
Kiln Batt Wash – A coating of refractory material applied to saggers, kiln furniture etc, to prevent sticking during firing.
Kiln Furniture - General term used to describe refractory pieces used to separate and support pottery during firing.
Kiln Kiss - Occurs when two pieces are fire in contact with each other. The resulting flaw often appears as a burn mark, and or large glaze bubble burst.
Kiln Spur –Usually a tripod support used to separate pieces and keep the shape of ceramics during firing.
Kiln Wash - Mixture of Kaolin, flint and water.. It is painted on one side of the kiln shelves to separate any glaze drips from the shelf.
Kneading - clay preparation, where a lump of clay is rolled in upon itself, while stretching and pulling to get out the air bubbles.
Kochi - this is Japanese Raku ware. A hard-fired biscuit is used.
Kutani - Kutani-yaki is a pottery region in Ishikawa prefecture dating back to the Edo Period, known for bold colours and designs.
Kwaart - to give a higher gloss and depth to colour, this technique was used by the Delft potters to imitate Chinese blue-and-white porcelain. To get this effect they used a clear transparent glaze over a white opaque glaze.
Lead Glaze - Long before chronic lead poisoning became a public health issue. lead was a popular constituent of ceramic glazes. Aclear glaze in which lead oxide serves as the principal flux. Lead glazes can be pigmented with a variety of metallic oxides.
Lead Solubility - The solubility of lead glazes in particular in diluted hydrochloric acid.
Leather Hard - Particularly dried clay ware. The ideal stage for turning, fettling, sponging, etc.This is a stage midway between wet and dry clan which unfired pottery is firm enough to handle without being distorted, but pliable enough to add more clay.
Lining - The Technique when Gold or Platinum is applied to the edge of decoration. The Gold used is normally 14K, 18K or 22K. The liquid gold decoration is normally fired at approximately 750ox – 850oc. Lining is always done by hand.
Low-Fire Kiln – a kiln that heats to a temperature high enough to fuse the clay into a solid mass, but too low to make the clay totally non-absorbant.
Low Solubility - L.S. or low sol glaze. Defined by the Pottery Health Regulations as a glaze which does not release more than 5% of it's dry weight of soluble lead, when subjected to a specified test using hydrochloric acid.
Lug - Projections, either raised or applied,protruding from the sides of vessels and which may or may not be functional.
Lustre – the technique of applying an iridescent decoration to ceramics by depositing a metallic film onto the glaze. Oxides of silver, copper or gold are dissolved in acid, combined with an oily medium and painted onto the ware. The object is then fired in a reduction (oxygen-starved) kiln, causing a metallic film to adhere to the ceramic surface that becomes iridescent when burnished.
Lustres - An iridescent optical appearance, due to light reflections producing diffraction patterns on a glazed surface. Produced by very thin coatings of metallic substances fired onto the glaze.
Lusterware - A type of pottery or porcelain with a metallic glaze that gives the effect of iridescence, produced by metallic oxides in an overglaze finish, which is given a second firing at a lower temperature in a reduction kiln which excludes oxygen. A surface of seemingly changing colours like "mother of pearl". The effect is achieved using silver or copper metallic pigments.
Majolica - this is a general term used for Earthenware that has been glazed with an opaque tin glaze and painted over with oxides.In modern pottery, a soft opaque coloured glaze, firing temperature approx, 900 c - 1050 c. Originally named from the island of Majorca where it was first made in the 16th Century. Basically, similar to Delft.
Matte - A low shine finish, a glaze that has a surface that is not shiny, although it may have some sheen, ranging from dull to stony color with a slight sheen or patina.
Maturity – When ceramic firing is completed. Combined time and temperature effects on ceramic in a kiln. Maturing Point – the temperature and time during firing at which the clay or glaze attains its ideal state of solidity and density. The temperature at which the clay becomes hard and durable.
Mocha Ware – this glazing technique was first developed in 18th-century England. An acidic solution called “tea” was originally made of hops, herbs, and tobacco juices, with oxides added for colour. Small amounts of this solution are dropped onto an alkaline slip, forming a unique dendritic (treelike) pattern.
Modulus of Rupture. Maximum breaking stress applied to a material before fracture. It is a common quality control test used for ceramic raw materials and ceramic bodies.
Moisture Expansion - The extent to which a porous ceramic material will expand in size when it absorbs water or water vapour.
Monochrome pottery - this is pottery that is typically made in one colour. Where decoration is used the colour is one single contrasting colour.
Moriage Decoration - A style of decoration used by porcelain manufacturers during the late 1800s/early 1900s. It is the art of laying "beads" of porcelain on the item prior to firing in the kiln. Most typically it was decorated later in gold. Be careful purchasing Moriage decorated items as the beads have a tendency to be broken off.
Mould - Hand-building technique using permanent forms into or over which clay is impressed to shape vessels.
Mudstone - fine grained sedimentary rock whose original make up is clay or mud or both.
Muffle – a kiln or a compartment in a kiln in which pottery can be fired without exposure to direct flame or other contaminants.
Muffle Kiln – A kiln made to protect ceramics from direct contact with fire.
Nicks - A small impacted area where a very small portion of the glaze is missing. These areas often go undetected, and do not expose the clay under body. May have negative effect on value.
Once Fired- a piece of pottery that has undergone a single glaze firing. The glaze is applied directly on to the dry or leather hard pottery avoiding the bisque firing. The making, glazing and firing of ware in one operation.
On Glaze - A method of decorating porcelain products, where the decoration is applied after it has been glazed. When the ware is fired, or re-fired in the case of twice fired ware, the colours fuse into the glaze and so the decoration becoming durable. Because the decorating fire can be at a lower temperature with on-glaze decoration a more varied palette of colours is available than with underglaze decoration.
Opalescent- showing a milky iridescent color.
Opaque- Opaque Glaze – a non-transparent glaze that conceals the clay beneath it. A glaze which will not pass light, therefore blocking any color underneath it, whether of the clay, a decoration or another glaze. Glazes are typically made opaque by the addition of tin oxide or various zirconium compounds.
Open firing- A method of firing vessels without a proper Kiln structure. The most common methods are bonfires or pits.
Oven Safe - Most porcelain and Bone China are not safe to use in an oven, refer to backstamp.
Oribe - Oribe-yaki is a type of Japanese pottery known for it's use of green copper glaze and bold painted designs. From the Mino region (modern day Gifu prefecture.)
Overglaze- Over-Glaze - a technique where the decoration is applied on top of a layer of glaze and then fired. Overglaze methods include applying one or more layers or coats of glaze on the porcelain body. “Over-glaze” technique is less expensive than the “under-glaze” technique. “Overglaze” products may be more subject to scratching from vigorous utensil use. This technique required firing at 750oc to 900oc. Apartial or complete coating of one or more glazes, often clear or translucent, applied over previous layers of glaze or glazes, called an underglaze which may or may not be previously fired. The application of low-fire coloured glazes to clay pieces that have already been glazed and have usually already been fired.
Oxide- any element combined with oxygen.
Oxides – pigments derived from metallic oxides and used to decorate ceramic bodies and glazes. Pure metallic oxides include cobalt for blue, copper for green, iron for brown, manganese for purple, antimony for yellow and various other compounds to produce red and black. Metal-oxide pigments are called underglaze colours when painted over the glazed surface and refired. In-glaze pigments are painted onto the unfired tin-opacified lead-glazed ware, which fuse together during firing. Overglaze enamel colours provide the greatest range of colours because of their low-firing requirements.
Oxidation – a kiln firing in which the pottery is exposed to a full supply of oxygen. Electric kilns perform these firings, and oxidation occurs between 704º and 1149ºC. All pottery goes through an oxidation stage during firing, although it is called “oxidation” firing only when the complete process is fulfilled; otherwise, it is known as “reduction” firing.
Oxidized Pottery- Pottery in which the constituents in the paste have taken up as much oxygen as they can.
Paper Clay- Any clay that has had paper added to it. This makes the clay piece stronger and more pliable, and can be added to, cut apart, reassembled and mended even after it has dried.By the addition of paper pulp to plastic clay (proportions of 50% to the total) there is greater plasticity, a reduction of shrinkage and an almost glue like bonding that occurs. This is especially important to hand builders and sculptors when joining pieces together.
Parian - A fine white semi matt porcelain, so called because of it's similarity to the white statutory marble of the Greek Island of Paros.
Parian Body – this soft, translucent porcelain made from feldspar is commonly used for making statuettes and figurines. It is in the form of liquid clay, and has to be poured into moulds. Parian ware was especially popular in the mid-19th century.
Parian Ware - Soft porcelain (soft paste) composed of one part china clay and two parts feldspar, used for making statuettes.
Paste – Clay or mixture of clay and added materials that compose the clay body, exclusive of the glaze. Paste can be described as coarse, medium- or fine-grained and in terms of its porosity. Usually referring to porcelain.
Pate-sur-Pate – An elaborate and expensive style of decoration in which successive coats of porcellaneous slip are applied to a contrasting body, then carved to create a cameo-like, low-relief design. This technique was developed in the mid-19th century at the French factory Sevres.
Patina- thin layer of antiquing stain that is applied and wiped back leaving it only in the lines of the design on the piece of pottery or ceramic.
Pearlware – Refined earthenware containing a large percentage of kaolin, making it whiter than creamware. It was developed by Josiah Wedgwood in the late 18th century.
Peephole - A small observation hole in the wall or door of a kiln.
Peppering- Tiny black specks in the glaze, normally white or light colored glazes.
Petuntse – a type of feldspar that is sometimes mixed with kaolin to create Chinese porcelains.
Pigments - Any substance used as a colouring agent, particularly finely ground particles that constitute a paint. Most pigments are now manufactured but traditionally pigments have been made from plant, mineral and animal sources.
Pinch - Manipulate clay with you fingers in your palm to a hollow shape. Pinch pots are a popular beginners project.
Pinch Pot – a clay form created by manually pinching and manipulating a mass of clay into the desired shape.
Pinholes- tiny holes that penetrate a glazed surface cause by escaping gasses.
Pinpoint- Smaller than a fleabite, like the point of a pin. Most dealers consider this mint.
Plaster of Paris- or simply plaster, is a type of building material based on calcium sulfate hemihydrate, nominally (CaSO4)2. H2O. A large gypsum deposit at Montmartre in Paris is the source of the name. When the dry plaster powder is mixed with water, it re-forms into gypsum, initially as a paste but eventually drying into a solid.
Plasticity- The ability of moist clay to be moulded and maintain its shape.To be malleable and impressionable without cracking.
Porcelain – a white, translucent, vitrified clay body fired at a very high temperature (1250º–1450ºC) with vitrified bodies, usually white and mildly translucent (light shines through in thin sections). It can be decorated to provide colour.Porcelain is superior to Bone China in respect to glaze hardness and is cheaper than Bone China to produce.
Porcelaineous Stoneware – a high-fired white ware that is similar to, but not as glassy as, true porcelain.
Porous- anything which absorbs or leaks water. In pottery and ceramics this usually refers to a clay that has been dried but not fired or fired but not to a high enough temperature to glassify it, which makes it vitreous, so that it would be non-porous.
Porosity – the state of being porous. This is an important factor in the creation of ceramics. Clay can be too porous or not porous enough, which may result in cracking. Clay can be combined with flint, grog, or another type of clay to adjust its porosity.
Pottery- is made by forming a clay body into objects of a required shape and heating them to high temperatures in a kiln to induce reactions that lead to permanent changes, including increasing their strength and hardening and setting their shape. Refers to any type of ceramic ware or the workshop where ceramic ware is produced.
Potter’s Wheel – A flat, rotating disk used for throwing clay. Can be either electric or manual. A device with either a manual (foot powered) or an electric rotating wheel head used to sit at and make pottery forms.
Pouncing – a fine powder, such as powdered charcoal, that is sprinkled over a stencil to create a design on the underlying clay piece.
Pug / Pug Mill – To mix. A machine for mixing clay and recycling clay. A device for producing a cylinder of clay which is forced through a tapered tube, rather like an old fashioned mincer.
Punctuation- Holes drilled through the vessel wall to repair cracks. Holes would be drilled on either side of the crack and then laced with cordage.
Raku - A type of earthenware that originated in Kyoto, Japan, in the 16th century. Raku (meaning “pleasure”) has a rough, handmade and unpredictable appearance. The technique involves heating bisqued work to a red-hot temperature, removing it from the kiln and allowing it to burn in wood shavings, newspaper or a similar combustible material. A method of low-fire surface change produced commonly by putting a red-hot piece of pottery into a bucket called a sagger, which contains combustible material, typically sawdust, newspaper, leaves and even garbage. The temperature of the piece ignites the materials and they begin to smoke.
Raw- A glaze or clay that has not yet been fired. It may still be greenware or fully dried.
Raw glazed – process whereby the glaze is applied directly to the hardened clay body and the pot is then fired once only.
Reduction - A kiln firing in which there is an intentional absence of oxygen. This type of firing produces carbon monoxide, which functions to extract oxygen from the clay and glaze, resulting in colour changes to the piece.The atmosphere in a kiln that has insufficient air to support complete combustion. This will often cause smoke, which affects the surfaces of glazes and clays.
Redware - A type of earthenware made from clay that contains a large proportion of ferrous oxide, giving it a red color. The base clay is often the determining factor for how a piece of pottery is named. It is made from a clay with a high amount of ferrous oxide, which gives the body its red colour and usually has a lead glaze.
Refractory - Any material that melts at a very high temperature.
Relief - Protrusion of figures or shapes from a flat background.
Resist decoration - When a wax is painted onto a pot, that area will resist any coloring or glaze.
Rib - A rubber, metal or wooden tool used to facilitate wheel throwing of pottery forms.
Rockingham - Australian brown glazed household pottery mainly from the 19th Century
Rub - A small area where the glaze has been worn thin through use. May also describe an area of several small scratches.
Restoration - The act of making new or to repair to make look like new again, or to make a piece look like it did before it was damaged.
Restorer - A skilled worker who is employed to restore or refinish antiques and other damaged pieces.
Sagger - a clay pot or bucket in which pieces of pottery are placed while inside a kiln to protect them from the direct effect of flames.
Salt Glaze (or Soda Glaze) – a glaze formed on stoneware by throwing common salt into the kiln at peak temperatures, which vaporizes into sodium and chlorine. The sodium combines with the silicates in the clay stoneware to form a thin, colourless glaze that resembles the texture of orange peel. By throwing salt into a kiln during the glaze firing, a shiny gloss will occur as it vaporizes and combines with the silica in the body of the pottery. Once a kiln has been used for salt glazing it can only be used for that type of firing after that. The salt volatilises and fluxes with the silicas in the unglazed clay surface, creating a glassy translucent effect with a slightly ‘orange-peel’ texture. Brown, blue or purple salt glazes are the result of applying a thin wash of iron, cobalt or manganese oxide before firing.
Satin Glaze - A glaze with medium reflectance, between matt and gloss.
Satsuma - Satsuma-yaki is a pottery region in Kyushu.
Scratch Blue – a process whereby a design is incised into pre-fired stoneware clay and a blue pigment is rubbed into the incised design.
Soak - To maintain ceramic ware at a pre-arranged temperature in the kiln for a particular time.
Score- To score (verb) a pot or piece of clay means to scratch hatch marks into it. This is done prior to brushing on slurry and joining the pieces together. The process is often called "score and slip".
Scratch- Is a scratch.
Sgraffito - this is a design or decoration that can be made by scraping or scratching through a layer of slip or engove that has been applied to reach the contrasting colour of the clay body beneath.
Ramekins come in many colours shapes and sizes but consist of a bowl, having a hemispherical profile usually.but not always with a truncated base and a handle. Shapes are as follows;
Shapes -
Disc- Having a flat circular shape.
Cup- Shaped like a standard tea-cup.
Triangle- Three sided ramekin.
Straight -A cylinder where the vertical is at 90 degrees to the base from the base to the top rim.
Jar- Spherical bulbous base, with straightening sides angling upwards to top rim.
Bell- Having a wide mouthed top rim of a convex shape curving outwards from the base that resembles a bell, reversed.
Heart -More recent shape being straight sided with a styalized shape of a human heart
Round- Bulbous shape similar to a sphere that curves outwards from the base then inwards to the rim.
Lozenge - Like a donut, flat top and base with a rounded side bulging outwards.
Flower- Circular ramekin with flared lobes designed to resemble a flower.
Tumbler- Flat circular base with a conical wall rising up to the rim.
Drum- A shallow cylinder where the vertical is at 90 degrees to the base from the base to the top rim.
V or Vee - Conical cylinder, narrow at the base and wide at the rim.
Lidded- Having a separate lid moulded to fit the rim of the ramekin.
Rim -The shaped edge of the top of the ramekin
All my measurements are in millimeters.
1 The width of the bowl from the outside top width of the rim, unless the bowl bulges beyond the rim, in which case, it is the widest point opposite the handle.
2 The width of the base from the outside of the footring.
3 The height of the bowl from the bottom of the footring to the top of the rim, not including the depth of the interior of the bowl or the depth of the cavity under the footring.
4 Measurement of the horizontal maximum length of the ramekin, incorporateing the width of the bowl as measured to the external opposite edge of the ramekin to the handle irrespective of angle of handle. No handle width is included.
Shards - pieces of broken pottery.
Shelling - flaking or peeling. A glaze or glaze and slip defect in which the glaze falls from the body in flakes. It is caused by insufficient bond between glaze and body, usually the result of under firing.
Shigaraki - Shigaraki-yaki is a pottery region in Shiga prefecture.
Shino – decoration technique in which a thick white feldspar glaze is allowed to run down and crackle around the clay body, sometimes enhanced with oxide brushwork under or over the glaze. Modern shinos may include flashing, beaded or crawled surfaces. Iron-rich clays added to the glaze produce brilliant orange colours and pigments may be added for other colour effects.
Shrinkage - the decrease in the size of clay pottery due to drying and firing.
Silica - a basic material of glaze and clay. In nature this is also known as quartz. In a glaze, promotes flow (fluxing).
Sintering - is a method for making objects from powder, by heating the material below its melting point until its particles adhere to each other.
Skip- Is a factory flaw where the glaze is lighter or did not cover the entire piece.
Slab - Pressed or rolled flat sections of clay used in hand building.
Slab Built Pottery- pottery constructed wholly or mostly from sections of clay slabs without the use of a wheel.
Soda glazed – chloride-free alternative to salt glazing developed in the 1970s, whereby sodium carbonate or bicarbonate is added to the kiln at the end of firing to create soda-vapor. The effects are similar to salt glazing but aesthetically different, with a higher potential for flashing.
Soluble - capable of being dissolved in water.
Slake - to moisten dry clay with water.
Slip - A slurry of clay used to cast objects in a mould. Slip is poured into a mould and and allowed to set up on the outside (slip cast). The still liquid centre is poured off leaving a hollow clay object. Coloured slip is often used like paint to decorate clay objects.
Slip Casting - Slip casting involves pouring a liquid solution of clay, called 'slip', into a plaster mould that absorbs the water, leaving a layer of clay adhering to the mould's surface. The clay would shrink, allowing the mould to be removed and leaving the piece ready to be dried and fired. The moulds were frequently made of Plaster of Paris, as they were highly absorbent and cheap to make, and would be held together with ball and socket projections and rubber bands, sometimes made from old car tyres. This reduces the water content in a slip to that of most plastic clays, around 30% of total weight.So long as the detail in the moulds was maintained, they are able to be cleaned and dried for reuse. A specially formulated glaze was then applied to the slipware either by hand sponging, dipping by hand, or by using a hand-held spray gun.
Slipware – a decorative technique using slip, a liquid mixture of fine clay and water. The slip can be coloured with oxides or coloured clays and applied to the vessel by dipping or painting, or trailed on like icing on a cake.
Slumping - firing a piece of pottery or ceramic to a very high temperature which causes the piece to drop or sink, and basically melts.
Slurry - thick slip.
Soda glazed – chloride-free alternative to salt glazing developed in the 1970s, whereby sodium carbonate or bicarbonate is added to the kiln at the end of firing to create soda-vapor. The effects are similar to salt glazing but aesthetically different, with a higher potential for flashing.
Soft-paste Porcelain – sometimes referred to as “artificial” porcelain, soft-paste porcelain is made without kaolin. France was the first to successfully manufacture this type of porcelain in the 17th century.
Spalling - The flaking, cracking or other disintegration of ceramics when subjected to sudden temperature changes.
Spatterware – a crude, inexpensive pottery that is spattered or sponged with colour and decorated freehand with brightly coloured designs. Found on creamwares and sometimes ironstone.
Spongeware - is where the designs are produced through the application of paint or glaze with a sponge. This produces a mottled effect. Increasingly, sponges create elaborate shapes and sometimes, quite specific prints, for example leaf designs.
Sprigging - this is a technique used by Wedgwood, where relief-moulded decorations are applied to a leather hard pot.
Spit Out - Rapid desorption of absorbed moisture during the enamel firing resulting in small craters or bubbles being blown in the glaze.
Spur Marks - the marks left by the stilts used to support pottery in the kiln. Usually seen as three dots in the form of a triangle.
Stacking - Load a kiln to hold the maximum number of pieces.
Stains - a suspension of metallic oxides, clays and other materials with water used to add color to the surface of clay and glaze.
Staining- When a piece is stained or cloudy.
Static or Electric Cycle Pressing - Static pressing involves placing a kerosene and wax lubricated piece of clay between two steel spinning dies which are compressed to create the desired shape. These presses can apply up to 40 tonnes of pressure. Each press has a variety of die shapes that can be changed as necessary. Each die is very costly so it is essential that each shape is commercially viable before being converted into a steel die shape. New designs are generally made by hand until they prove their commercial viability and are then converted to machine dies for commercial manufacture. Presses vary in scale and pressure and take different die sizes.
Stilts - ceramic bars or circles with high heat wire protruding, that pottery is set on so it won't adhere to the kiln shelf when firing glazes.
Stoneware – a dense, fine-grained, non-translucent, vitrified clay body that is impervious to liquids and fired at a high temperature (1200º–1350ºC). The clay contains significant amounts of aluminum silicates.Stoneware has partially vitrified bodies and most often are brown, grey or white. An opaque ceramic containing a naturally vitrifying clay e.g., a stoneware clay or a suitable ball clay. Sometimes a non-plastic constituent and a flux are added. Stoneware is known for its colour glaze as it is inferior to porcelain in whiteness. Stoneware bodies are heavier than Porcelain and Fine Bone China and are not transparent and is usually made of local clay. Stoneware is less expensive than both Bone China and Porcelain products.
Tapestry Technique - A process using a coarse gauged fabric material placed in porcelain slip (liquid porcelain) and allowed to absorb/soak in the porcelain heavy bodied material. Once full absorption was achieved the artisan would ensure that fabric was evenly coated. He or she then affixes porcelain soaked material to the area of the object the ‘Tapestry Technique’ is to appear. Once the area has been shaped the object is allowed to dry and then placed into a kiln for a bisque style of firing, (First Firing). During the firing process the fabric is incinerated leaving the fine detail of the gauze and the outline of the shape. After firing, the artisan then proceeds to paint a design onto the now ‘Tapestry area’ and the remainder of the object. The object then goes to the decoration kiln and fired. It may then be followed by a glost firing depending of the function the object takes.
Tempering- is the addition of grit that helps the clay resist shrinkage and thermal stresses during drying and firing.
Tenmoku – iron oxide rich glaze resulting in an intense black surface. A range of effects is associated with tenmoku, including oil spots, hare’s fur, tortoiseshell, pig’s skin, tea dust and rust-coloured breaks where the glaze is thin.
Terra Cotta - clay that is baked to become hard and compact (from the Italian meaning "cooked earth") is a hard, semi-fired and absorbent clay used for both decorative and construction products. The colours can range from grayish to dark reddish-orange, light to medium reddish-brown, or strong brown to brownish or deep orange. A lightly fired, unglazed earthenware usually reddish in colour. It has frequently been used by sculptors and modellers to produce models or studies for more finished pieces in other materials.
Terra sigillata – very smooth, lustrous coating of clay made by syphoning off the thin milky layer from a mixture of clay and water that has been left to sit for a day or so. The sub-micron size particles of clay align when the surface is polished, creating a silky effect.
Thermal Shock - The disruption of a ceramic article by stresses set up due to differences in temperature in different parts of the article.
Thermocouple - A device for the measurement of temperature based on the voltage generated when two dissimilar conductors are heated in contact e.g. copper/constantan , chrome/alumel, platinum/rhodium etc.
Thixotropy - The ability of certain clay suspensions to thicken up on standing; characteristic of partially or over-flocculated slips.
Throwing - to make pottery by hand on a kickwheel, or
Thrown - Process of making a piece with the use of a potter's wheel.
Tin Glaze – a decorative technique invented in ninth century Mesopotamia for use on low-fired earthenware. Already-fired biscuit vessels are covered in a clear lead glaze with tin added as an opacifier to create a smooth white surface, imitating porcelain after a second firing.This is white and opaque glaze, made this way by the addition of tin oxide to the glaze.
Tobe - Tobe-yaki is a pottery region in Shikoku characterised by cobalt blue hand painted designs on white porcelain.
Trailing – a decoration technique in which lines or dots of coloured slip are dribbled on the surface of a clay body.
Trailed glaze – glaze applied as a trail over the clay body or another glaze.
Transfer Print – The process of soaking decals (images) to remove them from the backing sheet and transfer them to unglazed ceramics before firing. It is an economical method of mass-producing intricately decorated earthenware. A pattern is etched into a copper plate, and the plate is then coated with a coloured enamel glaze. The excess glaze is printed onto thin paper, and the paper is trimmed to fit particular vessels. The wet paper is applied to the vessel and rubbed lightly, resulting in the transfer of the enamel pattern to the vessel. The vessel is then fired to set the enamel. A method of decoration where a pattern or picture is printed onto the gelatin coating of paper and then, when wet, is slid onto the surface of a pot.
Translucent – Permitting diffused light to shine through.
Transparent - capable of transmitting light so objects on the other side can be seen clearly.
Transparent Glaze - Transmits light clearly.
True Porosity - The sum of open pores as determined by water absorptions plus the volume of those pores that are sealed by vitreous matter and therefore closed to water.
Turning - Trimming thrown pots in the leather hard state.
Underglaze - A technique of decorating porcelain products the decoration is applied to the surface before it is glazed. The glaze will subsequently cover it such decoration is completely durable, but because the subsequent glost firing is at a higher temperature than used in on-glaze decoration the range of available colours is more limited. This technique is used on pottery suitable for use in Microwave Ovens and Ovens. The firing temperature was around 700oc. This technique had limited use and was more expensive to produce. A decorative technique in which one or more colored glazes are applied to pottery then an overglaze of one or more clear or translucent glazes are applied over them either before or after the first glaze firing.
Unglazed - a piece of pottery that is fired but no finish is fired on the out side.
Underglaze Decoration – colour that is applied to greenware or bisqueware before it is glazed or fired.
Viscosity - The resistance to flow offered by a liquid. The opposite of fluidity.
Vitreous - As applied to ceramics means glassy, having extremely low or no porosity.
Vitrification – the conversion of clay into a hard glass-like substance by firing it at a high temperature. The temperature that occurs during this process varies with each different clay. During firing, vitrification is simply the fusion of a clay body. The formation of a glass and the stage in firing at which the clay particles actually begin to form glassy melts. The progressive fusion of a material or body during the firing process. As vitrification proceeds the proportion of glassy bond increases and the apparent porosity of the fired product becomes progressively lower.
Vitrified - means a process where ‘the starting material is solid, vitrification usually involves heating the substances to very high temperatures. Many ceramic products are produced in such a manner’.
Ware- Class of pottery characterized by similar technology, material, and surface treatment.
Waster- A vessel damaged during manufacture, in particular during firing.
Water Absorbtion – A quality control measure of the percentage volume of water absorbed by a ceramic body.
Wax Resist – a decoration technique in which warm wax is applied to pottery or to the pottery’s glaze so that subsequent layers of glaze do not adhere to the waxed areas. Used as a masking medium for application to areas on which no glaze is required. Water-soluble wax emulsions used to resist glazes, under glaze, stains, etc on foot rings, lid flanges and lids or for masking specific areas of a piece for multi-layered glazing techniques. Once applied, wax cannot be removed except by firing off in the kiln.
Wedging - to knead or mix plastic clay by hand. A hand process used to homogenize the clay and remove air bubbles, thus making it workable. A method of de-airing and dispersing moisture uniformly by hand in a piece of clay. The lump of clay is repeatedly thrown hard onto the work bench, turned over and occasionally cut through and re-joined.
Wheel-thrown- The term used to describe vessels that have been made on the potter's wheel. Such vessels are usually, though not always, flat-based. They can be recognized by the presence of rilling as revealed in thin sectionand by X-radiography, and frequently, by the presence of cheese-wire marks on the base.
Wheel Throwing (or Throwing) – using a potter’s wheel to produce pottery. A mass of clay is placed in the exact centre of the wheel head, forming an opening in the centre of the clay. The size of the opening gradually enlarges as the artist uses his or her hands to manipulate the clay into the desired form.
Whiteware - is pottery or porcelain with a white body, so called to distinguish it from redware or yellowware. Usually a higher quality tableware.
Wreathing - Ripples or waves on the outside surface of a cast body caused by variations in the casting rate. Also referred to as hesitation lines.
Yellowware - the earthenware body colour varies in hue from ecru to mustard and is made from a naturally occurring clay. Early yellowware was so named because of the lead content in the glaze.
Zinc Oxide - generally used as a flux in high temperature glazes, zinc oxide lends opacity and encourages crystal growth when used in large amounts. A common constituent of matt glazes, it also has a marked effect on colorants, promoting brilliance with copper and dulling iron and chrome. Zinc oxides can assist in reducing crazing of glazes. Not recommended for use with some ceramic stains.
