Ceramics Vocabulary

 BEGINNER’S VOCABULARY LIST

 

  1. CLAY- Decomposed granite material that has been moved by erosion, glaciers, water, or wind.Impurities left can give rise to different characteristics in color, firing range and plasticity.

 

  1. PRIMARY CLAY- clay found in nature that was formed in place rather than transported by the action of water.Also called residual clay.  Kaolin is a primary clay.

Primary clay tends to be free of iron or other contaminants, have large particle size, and can be fired to high fire range.(cone 10)

 

  1. SECONDARY CLAY- Natural clay that has been moved by water or wind from its source and settled elsewhere in deposits. Secondary clays may vary in color due to impurities and have reduced particle size. This clay has a range of firing temperatures.

 

  1. PORCELAIN-High-fire clay with little impurities.  White or gray in color and vitreous. Developed in China. Matures above 2230 F. (Fired to cone 10)

 

  1. STONEWARE-Vitreous high-fire ware that is plastic due to its impurities, such as iron.  Matures at temperatures above 2195 F. (Fired to cone 10)

 

  1. EARTHENWARE-A low-fire, porous, reddish clay body, frequently containing grog or other temper.  Used throughout history for common, utilitarian ware; also used for sculpture.

 

  1. VITREOUS-Nonabsorbent qualities of a glaze or clay.  Can’t be penetrated by water

 

  1. GREENWARE-Pottery that hasn’t been bisque fired.

 

  1. LEATHER HARD-Unfired ware that still has enough moisture to either be carved or receptive to attachments.

 

  1. BONE DRY-Clay that has dried.  Clay that hasn’t been fired yet and still be reclaimed if slaked down.

 

  1. GROG-Fired clay that has been crushed and added to a clay body to “open” a clay, and reduce shrinkage, warping, and cracking.

 

  1. WEDGING-Kneading the clay to aid plasticity and removal of air pockets.

 

  1. BISQUE-Ware that has been through a preliminary firing to drive off all chemically combined water.

 

  1. GLAZE FIRE-The temperature when glaze melts to form a coating on the surface of the ware.  This is usually at the point of maturity for the clay body, and is usually much higher in temperature than the bisque fire.

 

  1. GLAZE-Liquid suspension of materials that form a glass-like surface when applied to the bisque ware and fired.

 

  1. EUTECTIC-A mixture of substances that melts at a lower temperature than the melting points of the individual substances.

 

  1. CRAZING- a glaze that contracts more than the clay body upon cooling from firing therefore leaving small cracks in finished glaze surface.

 

  1. CRAWLING- When a glaze pulls from surface during the firing leaving small beads of glaze and bare spots on surface of form. The cause can be from oil on the bisque before firing or too thick of glaze application.

 

  1. PINHOLING- Small holes through the fired glazed surface. They appear like popped bubbles and are from gases being released from ware during firing. The remedy can often be longer slower higher fired bisque. The gases will then be properly burned off ware for glaze firing.

 

  1. CONES-Small pyramids of ceramic materials formulated to bend over and melt at designated temperatures.  They measure time and temperature.

            15A.  Bisque firing-  range cone 08-06 (1751- 1852 F) for stoneware and

                                              earthenware. Porcelain is closer to 04  (1940 F).

            15B.  Glaze firing-  range cone 10 (2373 F) for stoneware and porcelain.

                                            cone 08-04 for earthenware.

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