Foodservice Glossary

Alumina:
A major component of the chemical composition of clays, clay bodies and most glazes.

Alumina Oxide:
Used for its hardness & strength to increase the durability of chinaware.

Ball Clay:
Secondary clay moved from the parent rock, ball clay is often mixed with other clays and minerals, organic matter are frequently present. Ball clays commonly exhibit high plasticity and high dry strength.

Bisque:
Unglazed, white ceramic ware or porcelain that has been fired but not yet glazed.

Bone China:
Vitreous, translucent pottery made from a body of the following approximate composition: 45-50% calcined bone, 20-25% kaolin. 25-30% china stone.

Burnishing:
A form of chinaware treatment in which the surface of the pot is polished, using a hard smooth surface such as a wooden or bone spatula, smooth stones, plastic, or even glass bulbs, while it still is in a leathery 'green' state, i.e., before firing.

Casting:
Is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods

Crazing:
A glaze fault characterized by the cracking of fired glazes and due to high tensile stresses.

Earthenware:
A pottery created by low temperature firing.

Embossing:
Process for producing raised or sunken designs or relief for a chinaware pattern.

Feldspar:
A primary raw material in ceramics.

Firing:
The process of heating clay pottery in a kiln to bring the glaze or clay to maturity.

Glaze:
A coating that has been matured to the glassy state on a formed ceramic article, or the material or mixture from which the coating is made.

Greenware:
Unfired clay articles.

Holloware:
Tableware such as sugar bowls, creamers, coffee pots, teapots, soup tureens, hot food covers, water pitchers, platters, butter pat plates and other metal items that went with the china on a table. It does not include flatware. Holloware was constructed to last a long time. It differs from some other silver plated items in being made with thicker walls and more layers of silver-plate.

Jiggering:
A machine for the shaping of clay body into flatware by the differential rotation of a profile tool and mould. Also the process.

Kaolin: 
Otherwise known as china clay, white or off-white firing kaolinitic. Used to make porcelain.

Kiln:
A furnace for the firing of ceramics.

Mold:
Is a hollowed-out block that is filled with ceramic raw materials. The liquid hardens or sets inside the mold, adopting its shape. A mold is the counterpart to a cast.

Overglaze:
Coloured glass-like decoration applied to ceramic wares. Also called on-glaze decoration. Often made by mixing metal oxides with a lead-based flux

Porcelain:
A vitreous ceramic material. Traditionally considered to be white and if, of thin section, translucent.

Ram Pressing:
A machine that is used to press clay into molded shapes, such as plates and bowls. In operation, a slice of de-aired clay body is placed in between two shaped porous moulds, and vertical movement of the moulds presses the body into the required shape.

Reactive Glaze:
Reactive dinnerware often consists of two or more colors which blend together. For example a dark blue plate may fade to light blue at the edges. Since these are variegated glazes there is typically an under color that shows faintly through holes or cracks in the overlay color so that the dinnerware does not possess a "flat" color. The glaze undergoes a chemical reaction during firing, usually melting or oxidation, to produce a particular pattern or variegation.

Reduction Fire:
Firing in an oxygen starved environment.

Refractory:
Refers to heat resistant or clay that is fired at a high temperature.

Silica:
A primary raw material for ceramics.

Stoneware:
A vitreous or semi-vitreous ceramic material. Traditionally made primarily from non- refractory fire clay.

Thermal Shock:
Occurs when a thermal gradient causes different parts of an object to expand by different amounts. This differential expansion can be understood in terms of stress or of strain, equivalently. At some point, this stress can exceed the strength of the material, causing a crack to form. If nothing stops this crack from propagating through the material, it will cause the object's structure to fail.

Translucence:
Is the physical property of allowing light to pass through a material diffusely.

Underglaze:
Decoration applied to biscuit pottery and covered with a glaze.

Vitrification:
Process by which clay materials bond to become dense, nonabsorbent, and glassified after firing.

Water Absorption:
The mass of water absorbed by a porous ceramic material, under specified conditions, expressed as a percentage of the mass of the dry material. It is used as a common quality control test used for both ceramic raw materials and ceramic bodies.