Additives - give color to the clay, prior to working. Various coarse additives can also be added. Sands and other grogs give the final product texture, and contrasting colored clays and grogs result in patterns. Combustible particles can be mixed with clay or pressed into the surface, to give textures.
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. Two different colors of clay are lightly kneaded together, before being formed into a shape. Not all clays can be used because of differing rates of drying and expansion in firing. It is common to use a light colorless clay and add a colorant to part of it. A interesting design can also be made by pressing small blocks of colored clays together.
Alkaline - various soluble mineral salts found in natural water and arid soils.
Alumina - along with silica, a basic building block of clay and glaze. It doesn't melt at temperatures used for ceramics and glazes, reduces flow in glazes, and helps with strength.
Amphora - this pot was used in Mediterranean countries for storing and transporting liquids. Usually 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 colors (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 which 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.
Arabesque - ornamentation that is characterized by smooth running, linear designs of scrolls or leaves on pottery. The use of flowers and foliage in this style produce intricate patterns of interlaced lines.
Ark - a tank that is continuously stirred mechanically to prevent the slip from settling and is used for the storage of clay or glaze slips.
Atmosphere - the chemical make up of the volatilized vapors surrounding the pottery inside a pottery kiln, or within a post firing containment such as is frequently used in pottery.
Ball Clay - a term used for many clays. Ball clay is actually blue. This is usually light in color and highly plastic. Unfortunately by itself, it is too slippery and fine for use, unless it is combined with sand, grog and coarser less plastic clays.
Ball Mill - a grinder for reducing hard materials to powder.
Banding - It is when a wide line that is applied to the outside of a piece of pottery.
Barbotine Decoration - a fine nozzle filled with thick slip is dragged along in streams onto a leather hard piece of pottery.
Basaltware - stoneware that is black and unglazed. About 50% of the clay is vitrified and colored by 50% of iron and manganese oxides.
Bats - are surfaces on which wet clay or pottery is carried or worked upon.
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 - pottery that has been fired only once without a glaze and is soft and porous. Due to it’s porosity it is easier to get a glaze to adhere to it. The temperature range for firing is red heat 1562 F to 1832 F (850 C to 1000 C).
Bisque - a greenware piece of pottery that is fired at a high temperature and is porous and unglazed. The pottery is easier to handle due to the hardness and warping from shrinkage can be controlled a little easier by setting the pieces in sand during the firing.
Blistering - appearance of broken bubbles found on glazed surfaces of fired ceramics and pottery.
Bloating - is any general swelling, or increase in diameter of the piece of pottery.
Blunge - mix water with clay.
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 - referring to the color and composition of the clay. Keep in mind that the color of a piece of pottery can be in the body or on it.
Bole - a powdery red clay found in eastern Mediterranean countries that is used in the compounding of enamel colors and also as a pigment.
Bone Ash - animal bones that have been baked and ground to a powder, used in the production of bone china.
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 pottery bowls or cups to prevent warping while drying and firing.
Burning - firing pottery at a temperature of at least 1112 F (600 C)
Burning Off - removal of bound water in the ceramic change.
Burning Out - unwanted matter is removed from pottery by the use of heat in the kiln. An example would be the creation of some colors using gums and oils. They would be convenient carriers of the colors 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 color by bubbling, blistering and possible discoloration.
Burnishing - rub leather hard clay pottery with a hard object like a smooth pebble or back of a spoon and a polished appearance would occur.
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.
Calcine - the purifying of a material through the action of heating to red heat 1292-1382 F (700–750 C).
Cane Clay - sand like in texture this is a refined fireclay, it is less refractory than fireclay. When fired, the color of the pottery is that of straw or cane.
Carinate - this is a pottery shape that is made by the joining of straight inward shaped walls to a round base.
Casting - slip is poured into plaster molds. The plaster draws moisture out of the clay so the pottery can be handled when it is unmolded, commonly called greenware.
Celadons - a term used for oriental stonewares, and porcelains with green glazes. The color is acquired by the use of small amounts of iron in the glaze.
Ceramics - means the art of making any article of clay. As in its original and true meaning, Americans use the word to cover all the silicate industries where the burning process is essential in production.
Ceramic Change - the slow process of clay becoming ceramic. Clay which is exposed to heat 1112oF (600oC) losses 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, a fired fireclay. Other types of refractory clay. Due to Scandinavian usage the term chamotte pottery or chamotte also applies to artistic pottery made up of coarsely grogged clay.
Chattering - a rippling effect that appears when turning clay on a kickwheel that is too hard or soft, if a blunt or hard tool is used. Chattering can be used as decoration on pottery.
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.
China - it is a translucent white body covered with a glaze fired lower in temperature than the body.
China Clay - this is the purest of all natural clay.
Chuck - tube like form to hold a pot upside-down on the wheel for trimming the foot.
Cinerary Urn - pottery that was used primarily for the burial of cremated remains and has been found all over the world. They have been found in all sizes, some as small as 2 inches tall, to vessels as tall as 36 inches. The best example of this type of urn comes from the Middle Bronze age of South Wales, Britain, 1400-1000 B.C.
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