Porous firebrick with insulating values much higher than hard brick.

An iron ore with significant titanium most often used in granular form to produce dark specks in clay or glaze. Higher iron concentration than in Rutile.

Decorating technique where textured or patterned material or object is pressed into clay surface.

Decorating technique where design is formed by cutting or carving shallow lines in clay surface.

Any particles or bubbles of material that remain suspended within the glaze-melt, affecting the glaze appearance.

Contact face between clay and glaze. On low-fired wares, primarily just a physical interlocking of glaze into pores in clay. In high-fired wares, an intimate interaction of clay and glaze, reinforced by mullet crystals, creating very strong bond.

A kiln that is loaded cold, brought to temperature, cooled and unloaded. See continuous kiln.

Most abundant coloring material on earth, responsible for brown and sometimes black color in natural rock and fired clays. In oxidation firings, the red ferric oxide remains very refractory, but in reduction firing and or at high-fire temperatures it transforms to the black ferrous oxide, a powerful flux.

FeCl₂—6H₂O soluble metallic salt fuming agent used to produce lusters on glazed surface. Highly toxic in inhalation and ingestion. 

FeO—Cr₂O₃ glaze colorant producing pink or red with tin, brown with zinc, gray with alkaline fluxes. Highly toxic in absorption, inhalation, and ingestion.

FeO reduced form of iron oxide gives same results as red iron in the firing, dependent on oxidation/reduction.

Fe₂O₃ powdered rust refractory red in oxidation, converts to black iron (flux) in reduction and/or high-fire. Low quantities in clear glaze produces celadon-green high quantities produce Temmoku black or saturated iron red powerful flux. More than 5% in a glaze significantly increases fluxing in reduction.

  See yellow ochre.