Terms that describe various clay bodies, states of completion, techniques, etc.

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Ceramic Terms

Ceramic Terms0
Ceramic is a broad term that encompasses all forms of fired clay bodies. The most common type of ceramic bodies that are used are: Slip is a liquid form of any clay body.  Slip is merely clay that has sufficient water to be in a liquid form.  Casting Slip, however, has the addition of a defloculant to make it more fluid and reduce shrinkage and cracking due to shrinkage on drying.

Defloculant A chemical that when added to the slip causes the particles of slip to repel each other so there is more space between them in the mixture.  This makes the mixture more fluid, while requiring less water.  Consequently the cast item will shrink less on dehydration and will be less likely to crack.

Greenware is any clay object that has not been fired.  The term greenware is often applied to slip cast items (even after they have been fired) that have been purchased this is not accurate other than the fact that pieces of this type are usually sold in the greenware state.  Greenware has nothing to do with the origin of the design or the technique used to create it.  It only refers to the state of the clay body, ie. UNFIRED

Bisque  A clay body that has been fired to the point it is no longer clay and will not melt, but not glazed.  Bisque can be fired anywhere from just hot enough to transform it from clay to ceramic (so it won't melt in water)  all the way up to the maturity temperature of the clay.  For example Porcelain Dolls are generally bisque.  They have been fired to the maturity of the porcelain but not glazed.

Glaze A product that is applied to the surface of a clay body that will melt when fired in most cases creating a non-porous finish.  Glaze can be matte or shiny or anything in between.  It can be clear or contain colors.  It can do unusual things like have metallic areas or bubbly areas.  Glaze is most often applied to a bisque surface, although some people do apply it to greenware, a technique which can result in lot of problems because it tends to seal in gasses that are released from the clay body as it matures by melting in whole or in part before the clay has finished outgassing.

Underglaze These are a group of products that are mineral based colorants that are usually painted onto the surface of greenware or bisque and then fired.  They are usually meant to be glazed over, thus the name underglaze.  However, it is not imperative that they be glazed over and when applied to the higher fire ceramic bodies such as porcelain and stoneware some of the underglazes will tend to vitrify and will become somewhat shiny on their own.

Overglaze This is a group of products that includes China Paint, Enamels, Lusters, Metallics, and Textures which are applied most often over a glazed surface.  Most can be applied to porcelain or stoneware fully fired Bisque, however.

Slip Trailing is a method of decoration where colored slips are applied to a Greenware item to create a raised decoration.  The Japanese are well known for their Moriage Dragonware which is an example of a slip trailed decoration.