Glossary Terms (Simple)

Fluorspar

CaF2—limited use as flux. As with Cryolite, fluorine reacts w/silica at high temperatures, can cause pinholing, blisters. Useful in special-effect crater-glazes. Highly toxic in inhalation and ingestion. 

Source: Clay: A Studio Handbook

Flue

Passages in kiln for flames or exhaust gases. 

Source: Clay: A Studio Handbook

Flocs

Commercial flocculant used in glazes—1/4 tsp. per gallon of glaze. 

Source: Clay: A Studio Handbook

Flashing Slip

Slip that is painted or dipped onto wares in order to promote flashing effects in the firing. 

Source: Clay: A Studio Handbook

Flashing

Color change in fired clay or slip due to direct flame contact and residual ash deposition in wood firing, or due to variable currents of vapor deposition in salt and soda firing. Flashing can occur on almost any light-colored clay body, but is most dramatic on porcelain bodies and slips. 

Source: Clay: A Studio Handbook

Flameware

Wares made to stand stove-top heat. Explosions from trapped moisture, and resulting lawsuits have caused studio flameware to disappear from the domestic market. 

Source: Clay: A Studio Handbook

Flame Flashing

Surface effects caused by direct flame contact on wares. 

Source: Clay: A Studio Handbook

Firing Ramp

The profile or schedule for temperature change in a kiln-firing, often including both the heating and cooling ramps. 

Source: Clay: A Studio Handbook

Firing Down

Maintaining some heat input after maturation, to slow down the cooling process, or to maintain reduction atmosphere during cooling. See reduction cooling. 

Source: Clay: A Studio Handbook

Firebox

The part of a fuel-burning kiln where fuel gases combust before contacting wares. Gas kilns need little if any firebox, whereas wood and oil kilns produce long hot flames whereas require a large firebox unless flame-flashing and ash-slagging (with wood) effects are sought. 

Source: Clay: A Studio Handbook

Fire Clay

Highly refractory secondary clays with minimal fluxes and usually fairly coarse particle size—low shrinkage, buff-color, often non-plastic. 

Source: Clay: A Studio Handbook

Fettling Knife

Long tapered knife useful for trimming cast or pressed pieces, and for separating mold components. 

Source: Clay: A Studio Handbook

Faience

Widely used (and misused) term referring to any earthenware pottery glazed with an opaque glaze (usually white) and overglaze decoration. 

Source: Clay: A Studio Handbook

Faceting

Decorating technique involving cutting or paddling flat facets in the clay surface. 

Source: Clay: A Studio Handbook

Eutectic

Chemical phenomenon where two materials in combination melt at lower temperature than either material by itself.

Source: Clay: A Studio Handbook

Ergonomics

The science of comfortable and effective utility, determining how well a functional object or device works with the human body. 

Source: Clay: A Studio Handbook

Epsom Salts (Magnesium Sulfate)

MgSO4—water soluble, rarely used as magnesium source in glazes. Most often used as flocculant for slips and glazes. Often added to porcelain and porcelaineous stoneware bodies (1/2 of 1% of dry materials weight) to counteract deflocculating alkalinity released by kaolins or fluxes. 

Source: Clay: A Studio Handbook

EPK: Edgar Plastic Kaolin

Al2O3×2SiO2×2H2O—pure white kaolin, less plastic than Tile-6 kaolin, frequently used in glazes. 

Source: Clay: A Studio Handbook

Element

Any of a group of slightly over 100 substances on earth that may exist as individual atoms, and from which all materials on earth are composed.

Source: Clay: A Studio Handbook

Egyptian Paste

A self-glazing clay body in which soluble alkaline fluxes effloresce to the surface as the piece dries, and subsequently form a thin glassy coating in the firing. 

Source: Clay: A Studio Handbook